The dust diffusion times take an average reduction rate of 15.7%, with the increase of return air velocity. The recommended return air velocity is greater than 1 m/s for large slope tunnels. When the slope changes from 0° to 9°, the hindrance rate of slope on dust diffusion is 2.88462%, 8.65385%, and 16.34615% respectively. Dust diffusion efficiency will be reduced as the tunnel slope changes from 0° to 9°, The growth rate of slope on dust diffusion is − 0.96154%, − 2.88462%, and − 6.73077% respectively.In this paper, a 1:21 model experiment was conducted to discuss the dust diffusion efficiency and liner trolley obstruction effect inside the tunnel at − 9% to 9%, the effect of different initial dust concentrations on dust diffusion and liner trolley obstruction effect at 6% slope, and the effect of different return air velocity on dust diffusion at 6% slope, the reliability of the results is verified by computational fluid dynamics simulations. The results show that as the slope of the tunnel changes from 0 to − 9%, the average dust diffusion time decreases by 3.7% at the working face and the dust concentration difference between the front and rear of the trolley is improved by 2.7%. When the slope of the tunnel changes from 0 to − 9%, the average dust diffusion time increases by 7.2% at the working face and the dust concentration difference between the front and rear of the trolley is improved by 17.9%. With each 100 mg/m In the technical background of the traditional drill and blast method as the main boring process, large slope tunnels and spiral tunnels are mostly used to solve the problem of large driving detour distances and slopes between high-altitude areas and low-altitude areas6. According to the current specification, the slope of the tunnel main tunnel is generally bounded by 3%7, while in recent years some tunnel cross passage and inclined shaft projects have extremely large slope cases such as − 14° and 38° 9. When in large slope tunnel and tunnel construction, the buoyancy and gravity of the smoke will no longer be perpendicular to the ground, which makes the buoyancy and gravity become an additional driving force for the smoke to spread in the tunnel, which has an important impact on the pollutant concentration distribution. Construction ventilation, as the main way of air purification in underground space operations, is one of the key indispensable technical aspects of tunnel construction11. At the same time, if the exhaust gas, toxic gas, dust, and other pollutants generated from drilling, blasting, slurry spraying, slagging, and other operational processes cannot be discharged from the tunnel in time, it will seriously threaten the physical and mental health and life safety of the tunnel workers13.With the effective depth of the “Western Development” policy, the continuous promotion of infrastructure construction in the western region of China, and high-speed railroad construction in western China in an orderly manner15. Some of these scholars have mainly used numerical simulations and field tests to study slope tunnel construction ventilation. Kong et al.16 used ANSYS to establish the ventilation model for tunnels with different slope changes, the flow field characteristics near the jet fan and the effect of tunnel slope on the ventilation efficiency were studied; Zhang et al.17 simulated the smoke diffusion effect of the shaft under the influence of longitudinal ventilation and slope to study the change in the rate of smoke emission from the shaft in the tunnel; Li et al.18 carried out a field test in an underground sloping tunnel and the results showed that the temperature decreases in the form of exponent; Rafael et al.19 learned influence of the slope in the ventilation semi-transversal system of an urban tunnel; Song20 studied the influence of slope and radius of curvature of the spiral tunnel on the diffusion pattern of pollutants.At present, the research on the construction ventilation of long tunnels has achieved considerable results. These studies mainly focus on dust diffusion characteristics, temperature variation characteristics, optimization of ventilation parameters21 investigated the wind-driven natural ventilation and dust suppression effects of coal sheds equipped with windbreak gables that have a porous structure. The investigation is conducted using a combination of wind tunnel experiments and computational fluid dynamics (CFD) numerical simulation; Guo22 used the virtual point source method, established the theoretical distribution model of the curved intersection tunnel to explore the distribution of dust that can be inhaled during the construction of drilling holes; Hou et al.23 developed an air-dust coupling model using the Euler–Lagrange method to study the dust migration law under various air conditions and the dust control mechanism in the large eddy, to address the challenging issue of dust diffusion pollution in tunnel excavation; Liu24 built an in-depth analysis of the effects of an air curtain generator’s radial and axial pressure airflow rate and a dust removal fan’s exhaust airflow rate on the diffusion and pollution behaviors of dust. In response to a large amount of dust generated during excavation in a large tunneling project, Ralf Irmler and Julian Buchner25 monitored whether certain geotechnical parameters of the rock could affect the quality and quantity of the dust, and the results showed that there was a correlation between water content and the quality and quantity of the dust; Liu26 used the numerical simulation method combined with field measurements to study the dust pollution diffusion law in a tunnel under different air suction volumes; Guo27 used the Ohl-Lagran method to simulate the combined motion of air and dust, and studied the time-spatial evolution of dust and inhalable particles that exploded under ventilation within 100 s of the explosion.At the same time, many scholars have also carried out a lot of research in the field of dust dispersion during underground construction through modeling tests, numerical simulations, field testing, orthogonal tests and so on. Su et al.However, few studies are carried out on the construction ventilation of large slope tunnels, and few studies on the effect of large slope on the change of diffusion of pollutants distribution using model experiments. Therefore, because of the complex construction environment of sloped tunnels, an in-depth study of the spatial and temporal distribution of pollutants during the construction period, the investigation of their transport characteristics and derivative development mechanisms under the coupling effect of wind and flow fields, and the formulation of the effect of slope on the transport efficiency of pollutants to achieve efficient and safe construction with green construction as the core concept are the key issues that need to be solved in tunnel construction today.In this paper, a 1:21 model experiment was conducted to discuss the dust diffusion efficiency and liner trolley obstruction effect inside the tunnel at − 9° to 9°, the effect of different initial dust concentrations on dust diffusion and liner trolley obstruction effect at 6° slope and the effect of different longitudinal return air velocities on dust diffusion at 6° slope. The results were validated by CFD numerical simulation.Generally speaking, the airflow in the tunnel is a complex three-dimensional turbulent flow. Still, the length of most tunnels is much larger than the hydraulic diameter of the tunnel. It can be considered that the airflow parameters approximately evenly distribute on the tunnel section, that is, the parameters such as airflow pressure, velocity, and density regard as constants in the same section. The following continuity equations and governing equations are used to calculate the airflow.ρ Is the air density, t is the time, uJ is the air velocity in XJ direction, μ is the dynamic viscosity coefficient, μe is the equivalent dynamic viscosity coefficient, Si is the generalized source term of momentum conservation equation; κ is the turbulent motion energy, ε is the energy dissipation rate of turbulent flow.where 29.Similarity experiments are based on the principle of similarity, according to a certain scale to make a model with a similar scale to the prototype for experimental studies, in order to predict the flow phenomenon that will occur in the prototype, the core of the modeled similarity experiments is to reproduce the physical nature of the phenomenon of motion. In the case of experimental conditions, the model experiment is more effective instead of theoretical calculationsL], [M] and [T], respectively. There are 7 main similarity parameters can be derived according to similarity criterion and basic equations of flow dynamics10:Stk is expressed as the ratio of the inertial force of dust particles to the resistance of the airflow, δ is the dust particle size, ρ is dust particle density, λ is the relative velocity of gas–solid two-phase flow, l is characteristic length(e.g. hydraulic diameter), v is fluid velocity;St is a similarity criterion for characterizing flow nonstationarity, t is time;Eu is the characteristic number describing the momentum transfer, p is the pressure difference; ρ1 is the volumetric massl;Fr is the characteristic number describing the relative magnitude of fluid inertia force and gravity force, g is the acceleration of gravity;Ma is the characteristic number describing the degree of compressibility of the fluid, a is the speed of sound;Pr is the characteristic number describing the interaction of energy and momentum transport processes in a fluid, μ is dynamic viscosity coefficient, k is the coefficient of thermal conductivity, cp is the isobaric specific heat capacity;Re is a characteristic number describing the flow of a fluid.The gas–solid two-phase flow analysis is used to describe the movement of dust particles in the airflow in the tunnel, and the length, time and amount of material (force) are often taken as the basic quantities in the mechanical analysis, which are [31.In practical terms, attaining entire equality among comparable quasi-numbers is both unfeasible and unattainable, leading to inevitable conflicts between similar principles. Given that each similarity criterion is associated with a distinct physical interpretation, and these interpretations reflect different emphases among the criteria, it is possible to disregard certain subordinate criteria that have minimal impact on the phenomenon by examining the experimental requirements and the physical meanings of each criterion. Given the low Mach number of the airflow velocity in this particular model, the ambient temperature being constant, and the interior airflow exhibiting a consistent flow throughout lengthy ventilation, the parameters Ma (Mach number), St , and Pr (Prandtl number) are not taken into considerationΛ) and the Reynolds number (Re).To ascertain the most appropriate similarity criterion, it is imperative to establish the flow state of the airflow within the tunnel. Consequently, the Nicholac curve is employed for the purpose of quantification. Nikolausz conducted artificial rough tube flow studies to establish the correlation between the along-track drag coefficient and the Reynolds number and relative roughness. The experimental data was partitioned into five distinct regions, including the laminar flow region, crucial transition region, turbulent smooth region, turbulent transition region, and turbulent rough region. Figure Λ in the turbulent roughness region is related to Δ/d rather than Re. In the modeling experiments, if both the prototype and the model are in the drag square region  is needed, not Re, to automatically achieve drag similarity. That is, by designing the model according to the Froude criterion, the viscous force similarity can be automatically realized without the need to satisfy the Reynolds similarity criterion.The experimental curves for the six tube flows in the figure have six different horizontal lines, indicating that Ret is the range of the square area of resistance to wind flow in the tunnel, dt is the hydraulic diameter of the tunnel, ∆t is the absolute roughness of the tunnel wall, in accordance with the general situation of smoothing the selection of 0.1 m, Ret0 is the reynolds number of airflow inside the tunnelBased on the above theory, the present prototype tunnel section is calculated. The calculation object includes the airflow state in the tunnel:Therefore, the Reynolds number of the airflow inside the tunnel is larger than the minimum value of the resistance square region, the flow state has entered the resistance square region, similar to the model in the Reynolds number criterion can be disregarded.Re are in the same region as the prototype dust Re. The Euler number characterizes the action of surface forces and is the ratio of pressure to inertial forces, and two flows with equal Euler numbers indicate similar pressures. The Froude number characterizes the ratio of inertial force to gravity. Two flow response Froude number is equal, it means gravity is similar. Although the tunnel ventilation WIND FLOW by gravity is often negligible, but the blasting of soot settlement and diffusion by gravity is more significant. And when the flow of the main forces for viscous force, gravity and pressure, because the pressure is usually a strain, as long as the viscous force, gravity is similar, the pressure will be similar on its own, that is to say: when the Reynolds number, the Froude number is equal, then the Euler number by itself is equal. Therefore the similarity of the tunnel model follows the Stokes number and Froude’s criterion.The Stokes criterion Stk, which is expressed as the ratio of the inertial force of dust particles to the resistance of the airflow, must be satisfied for dust diffusion tests. When the modeled dust reynolds number Π is usually determined according to the requirements and scope of the test, taking into account the experimental site, modeling and measurement conditions.After determining the flow state of the airflow inside the tunnel and the selected similarity criterion, it is necessary to determine the composition of the model and the similarity ratio. The model similarity ratio The operational area for tunnel construction utilizing the drill-and-blast method primarily encompasses the span between the working face and the lining cart, which is illustrated in Fig. 2. According to the size of the experimental site, the test method and the tunnel prototype, the length similarity ratio Πl is selected as 1:21.The tunnel model refers to the standard section of a double-line railroad tunnel, and the scaled-down model is constructed within 250 m of the construction section, with a proposed prototype section area of 150 mTo achieve better observation effect, the experimental model is made of 2 mm thick transparent acrylic plate custom splicing, the length of single section model is 1.2 m, a total of 10 sections, the total length of the model is 12 m, using a 0.5 m high platform to support the placement. The specific dimensions of the section are shown in Fig. In order to maintain comprehensive airtightness throughout the experiment, the perimeters of each individual section of the model were effectively sealed using aluminum foil tape. The schematic diagram illustrating the construction of the model is presented in Fig. The ventilation system of the model experiment adopts a small axial fan of SF4-4R type, meanwhile, in order to ensure the ventilation effect, on the basis of not exploring the air leakage of the pipe and its form on the overall impact of the experiment, it is proposed to use 1 mm thick PVC rigid pipe as the WIND FLOW path of the whole model experiment (i.e. the prototype pipe), with 1800 mm diameter pipe as the prototype to build the model, with an inner diameter of 85 mm, and the air supply system through canvas At the same time, SZ-J/0.75G-A2 fan velocity control switch is used to control the axial fan velocity to obtain the predetermined return air velocity in the tunnel with 0.75 kW power; the air pipe outlet distance from the palm surface is 0.95 m (20 m for the prototype), and the model ventilation system is shown in Fig. Λ is only related to Δ/d but not to Re in the square region of turbulent resistance. Therefore, in the modeling experiment, if both the prototype and the model are in the drag square region, then the drag similarity  can be achieved as long as the geometrical similarity is satisfied without the need for Re to be equal. In other words, by designing the model according to the Froude criterion, viscous force similarity can be achieved automatically without having to satisfy the Reynolds number similarity criterion at the same time. Therefore, the ventilation resistance similarity needs to pay attention to the absolute roughness of the material to satisfy the similarity ratio, and the calculated need to control the roughness is about 0.009 m, while the acrylic plate roughness is generally controlled in the 1 μm or less, which meets the demand.According to the Nikolaus experiment, Ret0 > 2 × 105 in the original tunnel, the Reynolds number Rem of the model for the check:From the previous section, it is known that the Reynolds number In essence, the hydrodynamic perspective establishes a similarity rule between the Reynolds number of the experiment and the Froude number in the flow field between the experimental and actual tunnels. In a similar vein, the Stokes number provides evidence supporting the validity of the similarity rule in elucidating the behavior of dust particles in both scenarios.The applicability of the similarity criterion for dust particle size is limited to dust flows consisting of particles of a single size. However, it should be noted that the dust particle size distribution in the actual project differs from this ideal scenario. In situations where the particle concentration is very low, such that particle collisions are not readily apparent, it is possible to simplify the representation of multiple-sized particles by employing a single characteristic size. This characteristic size can be determined as the biggest particle size within the system. In situations where the concentration of particles is relatively low, such that there is minimal occurrence of particle collisions, it is possible to simplify the representation of multi-sized particles by using a single characteristic size. In this case, the characteristic size can be determined as the biggest particle size.33.In the construction of the drill and blast method, drilling, blasting, slag transportation, shotcrete, and other construction processes will generate a large amount of dust, according to the source is divided into the original dust, blasting dust and process dust, blasting dust and process dust is 80% to 90% of the total dust production. The dust generated by blasting is mainly the dust formed by the rock being broken, accompanied by the dust caused by the huge blast force; the source of dust from slag transportation is mainly the transfer of slag and dust from operating machinery; the dust generated by shotcrete is mainly generated by the diffusion of concrete powder, the collision between high-speed concrete and tunnel walls and mutual collision. Tunnel blasting dust particle size is generally 0–75 μmThe standard port 50 ml constant pressure funnel with tetrafluorine piston valve is used as a dust generator to circumvent the disturbance of its initial distribution field morphological characteristics during the large-scale non-uniform intake of dust particles and restore the original state of blasting floating dust after stagnation as much as possible. To simulate the initial dust concentration field of different scales during the experiment, the sieved dust was introduced into the constant pressure funnel, the piston was opened, and the dust particles entered the model tunnel at a uniform velocity and in equal amounts. The ventilation dust concentration monitoring device is placed at the front of the tunnel model, and when the concentration near the palm surface reaches the predetermined experimental working condition, the ventilation system is turned on and the experimental monitoring is carried out. Experimental dust disposal progress and equipment are shown in Fig. In order to examine the distribution pattern of dust under the influence of coupling effects, the experiment employs return air velocity and dust as the primary monitoring parameters. Real-time monitoring is conducted on the return air velocity and dust volume concentration. The XZ4451D-500MT-05088 type hot film return air velocity sensor is utilized to measure the return air velocity within a range of 0–5 m/s, with a precision of 3%, thereby determining the velocity in the specified section. The experimental apparatus is depicted in Fig. The experiment intends to explore the key factors affecting the dust migration characteristics during the tunnel construction period, taking the dust particle size, initial concentration, return air velocity, and second lining step as the main research objects, and measuring the spatial and temporal distribution of dust at different particle sizes, different sizes of initial dust concentration fields, different return air rates and different second lining steps. The monitoring contents and working conditions are listed in Table 3, 200 mg/m3, 300 mg/m3, and 400 mg/m3 is used as the initial dust concentration variables in this study.According to current specifications and engineering examples, the slope of tunnels, auxiliary passages, and inclined shafts generally does not exceed 3%, and there are few cases of large slopes. In this study, to investigate the extreme cases, we set the slope of ± 3%, ± 6%, ± 9%, and 0% as the tunnel slope variables, where positive and negative represent the downhill and reverse slope cases, with 7 control groups. Also, for the field measurement results of relevant long-drawn railroad tunnels, subject to various unfavorable factors in the actual ventilation system deployment and implementation, and the cross-sectional area is relatively large, the cross-sectional return return air velocity of long-drawn tunnels is generally less than 2 m/s and maintained at 0.4–0.8 m/s level. Therefore, 0.5 m/s, 0.8 m/s, 1.0 m/s, 1.5 m/s, and 2.0 m/s are taken as the return air velocity variables, and a total of 5 sets of working conditions are set. The dust concentration after tunnel working face blasting is determined by the construction environment, surrounding rock conditions, explosive type, dosage, etc. The initial dust concentration of 100 mg/m3, controlling the model internal return air velocity of 1.0 m/s by adjusting the transformer. The variation of dust concentration with ventilation time at the location of the monitoring point was recorded and is shown in Fig. To investigate the effect of different slopes on the dust diffusion law, the experiment was designed with seven groups of comparison conditions, and the tunnel slopes were 0%, ± 3%, ± 6%, and ± 9% for a total of seven different particle size ranges of dust for the control experiment, ensuring the same initial concentration of 200 mg/mAs shown in the Fig. Comparing the changes in dust concentration with time at each slope, it can be seen that the effect of different tunnel slopes on dust diffusion is mainly manifested by the increase of dust peak and the increase of time required for dust discharge with the increase of slope. Under various working conditions, the concentration of monitoring surface 1 has a small local rebound. The above situation is because as the slope of the model becomes larger, the dust is more likely to gather in the tunnel during ventilation, making it difficult for some of the dust to settle inside the tunnel or be discharged under the action of gravity. According to the comparison of the concentration data of the two supervisory surfaces at the front and rear ends of the trolley, the lining trolley has a significant hysteresis effect on dust diffusion. By processing the test data of the two monitoring points, the average dust concentration difference and dust diffusion lag time comparisons for each slope in Table 3 respectively, there is no major difference between the operating conditions. The dust concentration at each monitoring section near the working face gradually rises with time until the peak under the coupling effect of the wind flow field and then decreases with a decreasing trend of decreasing rate, and the monitoring section concentration at the working face under the slope of − 9%, − 6%, − 3%, 0%, 3%, 6%, and 9% working conditions reaches the specified threshold value with return air velocity increments of 350 s, 370 s, 370 s, 390 s, 400 s, 440 s, 480 s respectively. It can be found that from 0 to − 9%, the dust diffusion rate is partially increased, with a maximum difference of 50 s and an average growth rate of 3.7%; while from 0 to 9%, the dust diffusion rate is significantly reduced, with a maximum difference of 90 s. The average reduction rate is 7.2%.From the Fig. 3, 200 mg/m3, 300 mg/m3, and 400 mg/m3, for a total of seven different particle size ranges of dust for the control experiment, controlling the tunnel slope as 6% by adjusting the support frame and return air velocity of 1 m/s by adjusting the transformer. The variation of dust concentration with ventilation time at the location of the monitoring point was recorded and is shown in Fig. To investigate the effect of different slopes on the dust diffusion law, the experiment was designed with seven groups of comparison conditions, and the tunnel slopes were 100 mg/m3 increase in the initial dust concentration, the lining trolley obstruction time increases by 23.33 s on average. Under different initial dust concentrations, the overall change pattern of dust concentration with time gradient did not change significantly, and it showed a short time rise to the peak with the increase of time, and then the rate decreased. The initial dust concentration affects the peak concentration of the cross-section, which shows that the initial dust volume rises, the peak concentration rises, and the time of the peak concentration then lags, and the time used to reduce to the maximum allowable concentration lags accordingly. To further explore the effect of the initial dust volume on the dust diffusion efficiency of the tunnel, the following: monitoring point 1 and monitoring point 4 were selected to compare the variation of dust concentration in the internal section with time at different initial concentrations.The effect of initial dust concentration on dust diffusion mainly shows that the concentration peak rises with the increase of concentration field, the dust spreading rate decreases, and the lag degree of monitoring section position increases before and after the trolley, with each 100 mg/mIt can be seen from the Fig. 3, controlling the tunnel slope as 6% by adjusting the support frame. The overall trend of dust concentration with time gradient in each monitoring section under the coupling effect of the wind flow field is: rising to the peak within a short time, and then gradually decreasing with time in a power function-like trend, i.e., the rate of decrease is first fast and then slow and gradually decreasing.To investigate the effect of different slopes on the dust diffusion law, the experiment was designed with seven groups of comparison conditions, and the return air velocity were 0.2 m/s, 0.5 m/s, 1 m/s, and 2 m/s, for a total of 4 different particle size ranges of dust for the control experiment, ensuring the same initial concentration of 200 mg/mThe key characteristics of monitoring point 1 and monitoring point 4 are compared and analyzed under different return air velocity, see Fig. Figure In Fig. η is mainly expressed in the experiment as the length of dust discharge time and the time of maximum dust concentration appearance, also compares dust diffusion efficiency at 0%. When η is a positive number means that it hinders dust diffusion while a negative number means that it has a positive effect on dust diffusion. Therefore, in order to explore the relationship between the tunnel slope α and η, the relationship equation of η is defined as follows: tx is the time of maximum dust concentration; Tx is the total time for dust diffusion in the lining trolley section.To specifically quantify the effect of tunnel slope on dust diffusion efficiency, select data for different slopes at monitoring point 4, and the dimensionless number η is defined to represent the dust diffusion influence factor. ti and Ti at each slope are brought into Eq. , simulation of dust sprayed from the working surface, after the release of dust, turn off the injection source and start the fan to start the dust diffusion. The important relevant parameters are set as shown in Tables After the ventilation commenced, the computational cloud diagram of the working face is illustrated in Fig. The results of the numerical simulation of each working condition are brought into Eq.  for calcFrom the Figure, it can be seen that the numerical simulation results are in overall good agreement with the model test results. It is evident that the numerical simulation exhibits a satisfactory agreement with the model test outcomes, with an average discrepancy of 8.69%, when the slope is less than zero. Conversely, when the slope exceeds zero, the numerical simulation consistently yields lower results compared to the model test outcomes, particularly evident in the 9% condition where the error reaches 21.78%. Furthermore, the average error in this scenario amounts to 14.99%. The numerical simulation findings exhibit a tendency towards linear trends rather than curved patterns.The discrepancy between the error of numerical simulation results and model test results is commonly attributed to the boundary conditions employed in the numerical simulation. Specifically, the boundary conditions in the simulation solely account for reflection from the wall, whereas in reality, the wall also captures a portion of the dust particles. Consequently, the numerical simulation results exhibit a greater number of dust particles being reflected by the wall and subsequently diffusing further within the tunnel, leading to a reduction in efficiency. The roughness of the wall in the model test will be augmented by the diffusion of dust particles, however the numerical simulation fails to accurately capture this phenomenon, resulting in a discrepancy between the simulated and actual outcomes.As the slope of the tunnel changes from 0 to − 9%, the dust diffusion efficiency in the tunnel improves. The average dust diffusion time decreases by 3.7% at the working face and the dust concentration difference between the front and rear of the trolley is improved by 2.7%. When the slope of the tunnel changes from 0 to 9%, dust diffusion in the tunnel is significantly lagging. The average dust diffusion time increases by 7.2% at the working face and the dust concentration difference between the front and rear of the trolley is improved by 17.9%.3 increase in the initial dust concentration, the dust diffusion time at the working face and the tunnel exit increases by 9.15% and 8.17% on average, and the lining trolley obstruction time increases by 23.33 s on average.When the tunnel slope is 6%, the initial dust concentration affects the time of the peak concentration then lags, and the time used to reduce to the maximum allowable concentration lags as the initial dust concentration increases. With each 100 mg/mWhen the tunnel slope is 6%, with the increase of return air velocity, the dust diffusion times take an average reduction rate of 15.7%. The dust diffusion efficiency is significantly improved while the return air velocity is 1 m/s and 2 m/s with the dust diffusion efficiency improved by 14.4% and 24.7% respectively. The recommended return air velocity is greater than 1 m/s for large slope tunnels.The dust diffusion influence factor η represents the influence of the slope of the tunnel on the diffusion of dust to the exit. The results show that when the slope changes from 0 to 9%, the hindrance rate of slope on dust diffusion is 2.88462%, 8.65385%, and 16.34615% respectively. Dust diffusion efficiency will be reduced as the tunnel slope changes from 0 to 9%, The growth rate of slope on dust diffusion is − 0.96154%, − 2.88462%, and − 6.73077% respectively.The Dust diffusion efficiency formula is verified by numerical simulation, and the two results are well fitted, when the slope is < 0%, the numerical simulation fits well with the model test results with an average error of 8.69%, and when the slope is > 0% the average error also reaches 14.99%, and the numerical simulation results are more inclined to a straight line rather than a curve.This paper reveals the understanding about the influence of longitudinal slope on airflow-dust migration behavior after tunnel blasting. A series of model tests with a scale of 1:21 are carried out to investigate the effect of the different slopes, initial dust concentration and return air velocity in the tunnel on the dust diffusion efficiency. The main results are as follows:


We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about  High-precision measurements in fundamental physics, using particles, nuclei, atomic, or molecular systems, require exquisite temporal stability and spatial uniformity of many environmental parameters to control systematic effects and fully exploit their statistical sensitivity. The control of the magnetic field is of particular importance in those experiments sensitive to the coupling of the magnetic field to the spin of the system through its magnetic moment. For example, experiments searching for permanent or variable electric dipole moments (EDMs), signals of dark matter fields, neutron-antineutron and mirror-neutron oscillations, Lorentz invariance violation, or new forces –5. Most Since the 1980s, numerous active shields have been built for different applications –12, coveIn this paper, we report on the design-path, implementation, and initial performance characterization of a dedicated AMS for the n2EDM experiment –18, currThe specifications for the n2EDM internal magnetic field are discussed in detail in Ref. . AlthougFor the same reason it is crucial that the average magnitudes of the magnetic fields in the two UCN storage chambers  do not differ by more than this 10 pT, corresponding to a vertical magnetic-field gradient smaller than 0.6 pT/cm.Variations of the magnetic field will also be detected by the quantum magnetometers, and a field change larger than 25 fT over 180 s will be seen in the precession signals of the mercury co-magnetometer. While it would be desirable to reach this extreme stability level of 25 fT, this is not a sine-qua-non condition for the experiment, compare Tab. 4 of  Ref. .Due to the quasi-static shielding factor of the MSR of ppressed . Thus, aThe task for the AMS in n2EDM is thus to provide a magnetic field around the MSR that is stable to within a few mentclass2pt{minim(i)The magnetic fields over the complete volume occupied by the entire experimental apparatus were mapped before setting up the n2EDM experiment and are described in Sect. (ii)A method was developed to design optimal coils for specific magnetic fields when constraining the current-carrying wires to a predetermined, irregular grid on a surface around the volume of interest , 24, des(iii)A scaled-down prototype was developed and served as a proof-of-concept system, see Sect. (iv)A scheme to systematically simplify the individual, optimal, full-scale coils was developed to ease practical construction of the AMS without sacrificing the specified performances  Sect. 5. This in(v)The system was constructed with careful quality control during assembly of the system with more than 55 km of cabling, as described in  Sect. (vi)Current sources were developed and implemented Sect. . An arra(vii)The commissioning of the full AMS system was successfully completed with various performance studies, as described in Sect. This paper describes the design and implementation of the AMS system for the n2EDM experiment see , 18) and and18]) The n2EDM experiment is located at PSI in UCN area South. Before setting up n2EDM, its predecessor nEDM was disassembled and the area cleared. Figure Before designing the AMS system, the magnetic field of the experimental area was extensively mapped , 18 to dFigure Several strong superconducting magnets at 10–50 m distances contribute with fields in the tens of The superconducting magnet shown in Fig. The reproducibility of maps taken under similar conditions was of the order of a few We concluded that the AMS needed only coils to compensate homogeneous fields in the three independent spatial directions, and five independent first-order gradients. Therefore, a system could be designed using only eight independent coils.Concerning field strengths, it was found that a range of In a volume with no magnetised parts, any magnetic field can be generated by the correct current distribution on the surface of this volume. The currents on the surface can thus be chosen to exactly counteract the effect of any external field, stabilising the field inside. In a practical realisation, there is a finite number of coils on the surface, and the field is measured only in a finite number of points. Figure k is the number of coils . For example, choosing elementary currents as , a loop with a current of In order to change the magnitude of the field generated by a system of loops, all loop currents in the system need to change proportionally to the design current. Thus, the set of loops for a specific target field can be connected in series, creating one n correspond to higher-order gradients. The advantages of this decomposition are that the polynomials are orthogonal and each basis state satisfies Maxwell’s equations. This method was initially considered by Wyszynski [The described method of coil design for an AMS offers advantages over approaches using simple geometric coils, namely in two areas. 1) The size of the coil system can be decreased relative to the size of the sensitive volume. A loss of performance, e.g., in the homogeneity of a given volume, can always be counteracted by choosing a denser grid. (2) The method allows construction of a coil for any field and the grid geometry that can be chosen almost arbitrarily. In particular, we have chosen to construct coils that produce orthogonal fields. The magnetic field is described as a superposition of orthogonal, cartesian harmonic polynomials: The sizeyszynski . We usedBefore applying the simple-coil method to design and construct the AMS system for n2EDM, we studied a smaller-scale prototype , 18 at EThe prototype consisted of the eight types of coils as intended for the AMS system. Similar in specifications, the system was designed to compensate target fields of x-, y-, and z-directions, respectively, providing a grid of squares as shown in Fig. y-direction and centered in x and z, as shown in Fig. The prototype was built on an aluminum-profile frame of 1.3 m The mu-metal cube in the prototype served as the emulation of the MSR of n2EDM concerning the fields on its outside. Its purpose was not to be an efficient magnetic shield but rather to provide a mu-metal surface to affect the fields between the mu-metal and the coil cage. It can be demagnetized using a set of demagnetization coils wound through the cube.The design method restricted the wires of the coil system to take paths on the grid, similar to the ones shown in the right panel of Fig. y-component of the magnetic field produced by the homogeneous y-field coil of the prototype in the As an example, Fig. Validation of the AMS fields We built a mapper robot carrying a movable three-axis fluxgate sensor to automatically measure the magnetic field in a large part of the volume inside the coil cage. In a first characterization, the static performance of the prototype was assessed by comparing the predicted and the measured fields for each coil. As an example, Fig. mentclass2pt{minimDynamic field stabilisation As a next step, we implemented a dynamic field stabilisation to actively suppress variable magnetic-field perturbations. This mode is based on continuous monitoring of the magnetic-field changes by fluxgate sensors with  modules , was use modules .The dynamic mode of operation relies on the quality of the feedback matrix mentclass2pt{minimnt}M Eq.  of the fIt was found that sufficiently stable performance can be reached with eight sensors placed close to the corners of the mu-metal. This fits well the intuitive understanding of the effects of mu-metal. Close to the surface of the mu-metal, field components parallel to the surface will be small while the orthogonal component remains. As the fluxgate magnetometers used for feedback are three-axis devices, this would mean that a fluxgate aligned near a large flat surface can measure the orthogonal field well with one axis, while two axes provide relatively little useful information. Thus, positioning fluxgates closer to mu-metal edges and corners turns out to be more informative.With the fluxgates mounted at their optimal positions, the feedback matrix was determined by measuring the magnetic-field components while scanning each coil current separately over the whole available range. For fields up to Shielding performance of the AMS prototype The obtained feedback matrix was used to operate the AMS in dynamic-stabilization mode. To test this regime, magnetic-field perturbations can be generated using a coil placed at some location around the setup. For this measurement, the square excitation coil with sides around 1 m was used. The coil was oriented perpendicular to the x axis and placed at about y, z coordinate of the center of the sensitive volume. The current source for the coil was modulated with a waveform generator to produce sinusoidal fields, with an uncompensated, maximal amplitude of about S, defined as the ratio:The AMS shielding performance was characterized by a shielding factor S and its frequency dependence up to 1 Hz. The measured shielding factor stays stable around 12 in the low-frequency range. The decrease of the shielding factor above 100 mHz is from the limited response of the system caused by the inductance of the coils on the aluminum frame of the cage. The frequency dependence of the shielding factor stays the same for similar measurements with the coil positioned at other locations. However, the magnitude of S strongly depends on the distance and orientation of the excitation coil. This can be understood qualitatively, as the magnitude of the higher order gradients of the fields within the sensitive volume depends on distance and orientation of the coil, and cannot in principle be compensated by a first-order AMS. Also, this was quantitatively confirmed using a COMSOL simulation of the system.Figure In summary, we successfully demonstrated an implementation of the method of simple coil design with the prototype AMS system, achieving the expected static and dynamic performance. The prototype design with an open-side demonstrated that this approach is capable of handling irregular grids, which is important to account for doors and other openings at the n2EDM experiment. Based on this feasibility demonstration, confidence was gained for the design and construction of the much larger AMS for n2EDM.Given the experience with the prototype and the requirements resulting from the mapping of the experimental area, the AMS system for n2EDM was designed. Compared to the prototype, the definition of the grid structure was more constrained by the needs of n2EDM and the available space, much more ampere-turns were necessary for similar field strengths, mechanical stability was more important, and much improved quality control was needed for the construction process.The design of the AMS coil system involved several steps, with iterations: (i) the choice of a surface and a grid on which the coil system could be constructed around the MSR, taking into account all constraints from experimental needs, equipment and area; (ii) finding the currents on the grid structure to create the target homogeneous and first-order gradient fields; (iii) organization of the currents in loops and coils as well as simplification of the optimal solution by the exclusion of (simple loop) currents contributing negligibly within the specified uncertainties.Grid design Placing the grid structure as far away as possible from the surface of the MSR ensures better field homogeneity. The main limitation was the size of the experimental area. Similarly, the whole experiment, and the MSR in particular, benefits from a clean, temperature-stabilized environment. The n2EDM experiment therefore must be separated from the main experimental hall and requires a thermal enclosure. The solution was the construction of a wooden house (‘thermohouse’), similar in principle to the one of the nEDM experiment [periment . The AMSThe possibility to fix the AMS to the walls and the roof of the thermohouse simplified its construction, given the mechanical stability of the structure, which was designed to carry the additional, substantial weight of the coils.Figure The process of designing the grid was mainly heuristic and required several iterations. The density of the grid mesh was optimized  to achieGiven the irregular layout of the experimental area and the thermohouse, the AMS tiles located at the kink in the wall see Fig.  into a sAn example of the Choice of optimization volume A shell of 20 cm thickness around the outer layer of the MSR was chosen as the volume of interest for the optimization  and EL4134 (16 bit DACs) operating at 1 kHz. The readings from all fluxgate channels are stored in the array While the performance is satisfactory already, potential improvements will be studied once commissioning of other n2EDM subsystems, which it would interfere with, is completed. A more detailed simulation model with improved utility for various numerical studies is being deployed, additional fluxgate sensors are being installed, and further optimization of sensor positions and feedback algorithms pursued.After the installation and the commissioning of all AMS coils and power supplies, we validated the static magnetic-field generation and measured the shielding performance of the AMS, as described below.As the MSR was installed in the experimental area before the AMS system, the actual magnetic fields generated by the AMS coils are not the simple homogeneous and first-order gradient fields as designed, but are modified by the MSR.Thus, after the quality control described in Sect. As the experimental area around the AMS was already partially occupied by other equipment after its completion, magnetic-field measurements around the MSR had to be done in a sampling mode rather than in form of full field maps (as described for the empty area in Sect. The magnetic fields created by individual coils were measured in some selected, easily accessible areas, usually along a straight aluminum profile with one fluxgate, and compared to the simulation. Figure y. While the non-existent The result of the measurement agrees with the simulations, and the behaviour of the magnetic-field components is as expected for this example. The design field at the sampled positions without MSR would only have a Commissioning measurements of the dynamic AMS shielding were performed outside and inside the MSR during ramps of the superconducting high magnetic-field facility ‘SULTAN’ . Magnetsz-axis, the most relevant for nEDM measurements, and the other one was oriented along the direction of the largest SULTAN perturbation. A second QuSpin sensor, installed close to the first one, was used to ensure that field changes could be identified as such and readings of one sensor were not simply due to sensor drift.The magnetic fields outside the MSR were measured by the eight 3-axis SENSYS fluxgates  involvedFigure entclass1pt{minimaH until saturation effects set in. It is therefore very important to describe the excitation field when quoting a shielding factor. For this particular example, the MSR of n2EDM has a quasi-static shielding factor of The measurements with the QuSpin sensor, shown in Fig. location . This isWhen the AMS system is in dynamic mode, the QuSpin sensor measures a more attenuated signal, see Fig. Nevertheless, we can deduce the approximate shielding factor for the combined system of the AMS and the MSR for large and slowly changing perturbations (here a one-hour ramp to Another interesting observation from the comparison between Fig. The AMS system was designed and built to compensate homogeneous and first-order gradient external magnetic-field changes around the MSR of the n2EDM experiment. It was developed using a novel method of coil design. After successful prototyping at ETH Zurich, the AMS system was constructed and commissioned at the n2EDM experiment at PSI. First performance measurements demonstrated its ability to suppress magnetic-field changes of about


Engine oil forms a complex system with a number of features. These features consist of hydrocarbons, various natural, or synthetic polymers. The irradiation of polymers becomes an integral part of modern industry. The lubrication, charge, thermal and cleaning requirements, which engine oils are expected to meet, are often chemically contradictory and manufacturers have to decide to compromise. Electron accelerators are widely used to enhance polymer properties. By applying radiation technology, it is possible to increase the desirable properties of polymers while leaving other properties at their original value. The paper focuses on combustion engine oil modified by e-beam. The assessed engine oil has a hydrocarbon base, which, from the chemical point of view, is processed as a polymer during the irradiation process. In this paper we have compared selected properties of the conventional and the irradiated engine oil during two exchange intervals. We have examined appropriate dose, dose rate, irradiation volume and a container on a single accelerated electrons energy. The examined oil properties were of a physical and physico-chemical nature, and included mainly kinematic viscosity, viscosity index, the total base number, soot content, oxidation, sulfation, significant chemical elements and wear particles. Every oil attribute is compared with its original value. The main objective of this paper is to demonstrate that the application of e-beam is an adequate method used to enhance engine oil properties to achieve cleaner engine running, and extend engine oil lifetime. Particle accelerators represent modern technologies used for various applications in science and industry. Electron accelerators belong to the most used in industry. Accelerated electron applications have recently recorded a dynamic increase in polymer production and development. The mentioned technology, however, has not been commonly used in the oil industry despite its significant potential.1. The most of the engine wear occurs while the engine warms up. The combustion engine oil properties of the utmost importance include friction coefficient, chemical stability, and optimal kinematic viscosity as the engine starts, so it could flow in a shorter time through critical engine parts. The second most important factor is a higher viscosity index, so the engine oil kinematic viscosity should be more independent of temperature. There are many significant properties of engine oil because engine oil is undoubtedly the most technologically complex oil product whose properties are given by a number of often conflicting technical requirements. All kinds of combustion engine oils have inhibitors and additives for various reasons. Most of these oil enhancements are methods of chemical way to raise the engine oil classification. The aim of this paper is to focus on the possibility of physical modification in addition to subsequent chemical additivation. The irradiation of oils is also dealt with in the article2, where the effect of irradiation on the change in oil quality has been manifested. The authors achieved the results which demonstrate that oil irradiation led to oxygen incorporation, the formation of oxygenated hydrocarbons, and higher oil viscosities. Oil irradiation was associated with decreased dispersant efficacy, of the efficiency falling from 80 to < 50% in the baffled flask test after more than 3 days of irradiation.Nowadays, combustion engines continually push the boundaries of technology and engineering. They are smaller and more efficient, characterized by the lowest possible performance loss.. Advanced combustion engines challenge the oil with increasing pressure. These intense pressures cause greater friction, which can lead to the loss of up to 10% of the performance of the combustion engine2O3 are found within the used oil, suggesting the presence of debris from the anti-wear film of lubricated motor parts in the used oil3.The increase in photo-oxidation-induced viscosity seems to lead to the decrease in dispersant effectiveness. The detailed analysis of the measured data demonstrates that substantial differences are detectable in the spectra of fresh and used oil. Our results manifest that the Zn–S bonds of the ZDDP are decomposed during the operation, resulting in Zn–O bonds instead. Furthermore, six-fold Fe–O bonds similar to those of Fe4 includes an attempt to link different techniques such as laser and X-ray fluorescence (XRF). Engine oil samples were irradiated with laser and X-rays, which were later diagnosed and analyzed. The X-ray fluorescence technique was used to analyze and determine the concentration of various nanoparticles in engine oil. The paper focuses on investigating data for e-beam radiation applied to combustion engine oil. It is necessary to know the basics of electron radiation in relation to the objectives of the experiment. The presented work addresses a relatively unexplored topic—the theoretical part I takes into account the irradiation of polymers as a whole which behave in the same way as liquid hydrocarbons in the discussed issue. Radiation treatment of polymer properties is a common method in technical practice. Despite the information mentioned above, the irradiation of engine oils is an unexplored area. There are certain published works, however, which introduce the explored issue7.The introduced publication9 and other theoretical knowledge12 are a great prerequisite for achieving the highest efficiency of treatment of the given engine oil with electron radiation in the 10–60 kGy range.It is necessary to create a priority list of properties that we will focus on during the gradual research and modification of lubricating media. In relation to the theoretical assumptions and technical possibilities of the current production of engine oils for internal combustion engines, we determined a sequence of priorities focused on the viscosity index, taking into account the type and the number of particles released into the lubricating medium during engine operation and the alkaline reserve during mileage in the experimental measurement in operation. While setting the radiation modification of the lubricating medium, the stated properties of the engine oil will have a higher priority than other monitored quantities. Ptasinsky's resultsThe presented study is carried out with the commercially available Castrol EDGE engine oil, having the SAE 5W-40 specification, ACEA C3, API SN/CF, VW 505.01. The replacement interval of the mentioned engine oil according to the manufacturer's recommendations is 15,000 km. The data on the mentioned engine oil are shown in Table 13.The UELR-5-1S linear electron accelerator was used for the preparation of the experiment. The mentioned accelerator ’s nominal energy of accelerated electrons is 5 MeV, and a maximum dose rate is 0.2 kGy/s. In order to detect the absorbed dose of ionizing radiation, we used a dosimetry system based on B3 radiochromic foils for which the manufacturer declares a measurement accuracy of 3% in the range of 3–100 kGy. If the value exceeds 100 kGy, it is possible to evaluate the dose with accuracy of 5%17, it is possible to determine the radiation dose of 28 kGy. Figure Before irradiating the engine oil, which is part of the experiment in this article, it is necessary to determine a suitable irradiation container, depth profile, dose profile, and dose rate of electron radiation for the examined engine oil. Following the results of the four parameters mentioned above, it was possible to determine the optimal absorbed dose, irradiation parameters and geometry with respect to the maximum possible volume that can be irradiated in a certain container. Taking into account the results of previous experimentsFollowing the previous measurements, the radiation geometry is determined in a glass Petri dish of a 30 mm wall height and a 200 mm diameter into which 540 ml of engine oil is poured. The mentioned volume is reached at an 8 mm height which guarantees homogeneity of the absorbed dose in the oil volume in the range of up to 10%. The Petri dish is placed in a steel crate with a length of 550 mm, a width of 400 mm and a wall height of 100 mm, located on a conveyor belt 48 cm from the accelerator window. The accelerator parameters were set at accelerated electron energy of 5 MeV, a dose rate of 0.2 kGy/s, an electron cluster frequency of 240 Hz, a scanning frequency of 1 Hz with a width of 40 cm, a conveyor belt speed of 2.2 mm/s, and a beam current of 145 ± 3 μA. With the given settings, the samples were irradiated to a value of 23.7 kGy. The engine oil under examination was irradiated at a volume of 6 L, due to the necessary filling and topping of the engine during the exchange interval.The engine oil capacity for the given internal combustion engine is 4.5 L. The rest of the irradiated oil was stored in the original motor oil container. The dates of the irradiation and measurement of the samples are shown in Table Engine oil samples were taken at intervals of 2000 km of the raid. The exact sampling intervals for conventional engine oil are shown in Table The experiment was carried out for over two years, during the same seasons, from spring to fall. The beginning of monitoring of both conventional and irradiated engine oil was planned for the end of February which is almost the end of the winter period. The addition of the engine oil level after the low OBD was carried out twice during the technical life of both compared engine oils. The topping up was done during almost the same run-in. The date, mileage and amount of engine oil topping up are shown in Table During the entire experiment, the same filters of MANN-FILTER producer were used. The oil, air, fuel and cabin filters were changed before starting the experiment with both compared engine oils. We used filters from the given manufacturer which were compatible with the designated internal combustion engine. The filters used were oil filter HU 726/2X, fuel filter WK 853/3X, air filter C 27 192/1, and cabin filter CU 3037. No additives were applied to engine oil or fuel during the entire experiment, not even during the winter period when a new conventional engine oil of the same brand, type and kind was temporarily applied. Fuel was pumped mainly at Shell gas stations with the Shell FuelSave Diesel label.The evaluation of kinematic viscosity was performed by the laboratory semiautomatic viscometer SpectroVISC Q300. Viscosity index is evaluated from kinematic viscosity by EN ISO 2909:2002 standard. Soot content, sulphation, oxidation, total base number and water content were measured by the portable fluid condition monitor FluidScan Q1000. The measurement of the content of chemical elements was carried out by the atomic emission spectrometer with rotation disc electrode Spectroil Q100. FTIR analysis was performed by the laboratory FTIR analyser apparatus Spectro-FTIR Bruker Alpha Q410. The total number of particles and statistical processing of the classified wear particles were evaluated by the automatic laser particle counter Spectro LNF-C Q200.In this chapter, the measurements are made of the reference and investigated (irradiated) Castrol EDGE engine oil. Figure 2/s. In the Figure, it is possible to see relatively large changes after the first 1000 km of both conventional and modified engine oil. As the following graph shows, the irradiated engine oil has a more stable kinematic viscosity for the next engine oil samples. This is also evidenced by the linear regression equation which has a parameter × closer to the zero value. During the first change of engine oil, a decrease in kinematic viscosity is observed, and, on the contrary, during the second change, a slight increase is observed.It is desirable that the value of the kinematic viscosity at the temperature of 40 °C be as low as possible, thus closer to the value of the kinematic viscosity at the temperature of 100 °C. Figure 2/s. The trend line shows a lower dependence of kinematic viscosity on raid, which is just as desirable as for kinematic viscosity at 40 °C. The viscosity value of the irradiated engine oil increases rapidly in the first 1000 km, which may be the reason for the mixing of the conventional residual engine oil left in the crankcase and in the turbocharger lubrication pipe during the engine oil change. During the first topping up of engine oil, a steady value of kinematic viscosity is observed, and during the second topping up, a rapid increase is observed for the irradiated engine oil. It should be noted that the values of kinematic viscosity at 100 °C during the raid for conventional engine oil are more stable than for irradiated oil, which is also proven by the linear regression line.Figure The differences in viscosity indexes are not significant, as can be seen in Fig. Soot is classified as mechanical impurities that are created in the combustion chamber of an internal combustion engine, especially during the combustion of diesel fuel. Soot is a product of incomplete combustion of diesel fuel. Most of the soot is pushed out of the combustion chamber with the exhaust gases. A small percentage of the soot enters the crankcase together with the exhaust gases. Soot and exhaust gases come into contact with engine oil in the crankcase and affect its properties. In the case of incorporating the exhaust gas recirculation system into the combustion engine concept, part of the exhaust gases is directed back into the intake pipe of the combustion engine, which increases the amount of soot in the combustion chamber. Engine oil is therefore more burdened by soot content. Figure Sulphur in engine oils occurs only in small percentage of weight. It is contained in engine oils and fuels as an impurity during their production. Sulphur compounds and sulfur oxides or sulfates are acidic products that have a negative effect on the alkaline reserve, oxidation, and kinematic viscosity of engine oils. Figure Figure The course of the total base number of conventional and irradiated engine oil is shown in Fig. According to the measured values, the beginning is almost identical, and the first 1000 km were decisive, where a striking difference can already be seen. Subsequently, throughout the course, the regression lines are almost parallel with a high coefficient of determination, which in both cases is above the level of 0.92 taking into account the sample of engine oil before pouring into the crankcase. With two oil level top-ups of both monitored oils, the stabilization of the TBN value is observed.Figure The graphical course of the hydrogen content in the examined oils is shown in Fig. Carbon is present in the base of engine oils and fuels, which are made up of hydrocarbons, and it is also one of the structural elements of steel. The amount of carbon also affects the combustion of diesel fuel, where soot is formed due to incomplete combustion. The amount of soot reaches approximately 0.8% in conventional and 0.5% in irradiated engine oil. The stated values do not have a significant impact on the total value of the carbon content. Paradoxically, with irradiated engine oil, the concentration of soot is lower, and in Fig. 1, it is possible to assume a lower content of wear particles during the technical life of the engine oil. The course of the iron content in engine oil is shown in Fig. Iron is the main structural element of the metal parts of the internal combustion engine. Iron is usually found in bearings, piston pin, piston rings, working cylinder, it can also be found in the cam from the camshaft and tappets. Due to the lower value of the friction coefficient of similar irradiated engine oilsCopper belongs to the structural metals of combustion engines. Copper is usually found in rolling and plain bearings, bronze parts, valve tappets and piston pin bushings. The copper content during the experiment is shown in Fig. Chromium also belongs to the structural metals of combustion engines. Chromium is usually found in parts where it is necessary to provide a hard surface layer, such as piston rings, piston pin, cylinders and liners of some internal combustion engines, etc. The chromium content during the experiment is shown in Fig. Aluminium alloys have their great justification in the construction of internal combustion engines. Aluminium alloys are often used in constructions where it is necessary to reduce the weight of the part, whenever possible and justified. Aluminium has an order of magnitude higher thermal expansion than construction steel and is also a very significant wear element. For this reason, sliding sleeves made of lead or tin composition, or bronze, pressed into the aluminium body are used in the moving parts. Pistons and heads of internal combustion engines are usually made of aluminium, some roller and plain bearings have admixtures of aluminium as well as certain types of bushings. The aluminium content during the experiment is shown in Fig. Silicon is a hard metalloid that dust particles are made of. Silicon in higher concentrations and compounds causes severe abrasive wear of friction pairs. Pollution in the form of dust occurs in the engine oil as a result of manufacturing imperfections of air and fuel filters, and penetrates into the engine oil through the leaks in the combustion chamber. However, silicon in the form of silicon oxides can also be found in the construction materials of working cylinders of an internal combustion engine, in camshaft bearings, and in some antifreeze liquids there is silicon used as an additive. The silicon content during the experiment is shown in Fig. −1, where a small indistinct peak can be seen. This fact was indicated in Fig. −1 to 2838 cm−1, the first intense absorption band can be seen together with four other strong absorption bands with a peak at the wave numbers 1468 cm−1, 1454 cm−1, 1377 cm−1 and 722 cm−1 which indicate a high content of alkanes with different vibrational states. The peak at wave number 2964 cm−1 indicates the asymmetric ν stretching of the CH3 group of n-decane C10H22, the peak at wave number 2925 cm−1 indicates the asymmetric ν stretching of CH2 group of n-decane C10H22, and at wave number 2865 cm−1 it indicates the symmetric ν stretching of the functional group CH3 of n-decane C10H22. The peak at wave number 2850 cm−1 indicates the symmetric ν stretching of the CH2 groups. For the above-mentioned n-decane, it is possible to observe a peak at wave number 1468 cm−1, which indicates the σ symmetric deformation of CH2 group. The opposite is the absorption band at 1454 cm−1 indicating the σ asymmetric deformation of CH3 group, and the absorption band at 722 cm−1 indicates alternating fluctuation of CH3 groups.The graphic evaluation of the FTIR analysis of conventional oil through the replacement interval is shown in Fig. −1 it is possible to see the absorption band indicating the oil oxidation and the presence of aldehydes and carbonyls. The presence of aldehydes is commonly visible in the regions of 2900–2680 cm−1 and 1740–1660 cm−1. The absorption band in the region of 1605 cm−1 indicates the presence of carbonyls. Wave numbers 1605 cm−1 together with 1377 cm−2 determine the content of polymers with the functional group N=O, respectively O–N=O and other nitrogen compounds. A less pronounced absorbance peak at a wavelength of 1230 cm−1 detects the presence of detergent-dispersant additives. A significant depletion of detergent additives and a decrease in the concentration of zinc dialkyldithiophosphates ZDDP can also signal a decrease in TBN. The concentration of ZDDP as phosphorus additives occurs normally in the range of 0.1–2.5%, and in IR spectra it is manifested at wave numbers of 950–1050 cm−1. The absorption band at wave number 1159 cm−1 determines the amount of contained sulphates and sulphate detergents, and the almost negligible peaks at 815 cm−1 and 750 cm−1 indicate only a minimal fuel content in the engine oil.In the region of 1680–1750 cm−1, where a lower absorbance value is observed. The three peaks of the absorption bands in the region of 700–550 cm−1, i.e., at the limit of the MIR spectroscopy measurability, have a lower absorbance value and are located towards lower values of the wave number.The graphic evaluation of the infrared analysis of the irradiated oil after the replacement interval is shown in Fig. A graphic comparison of the total number of wear particles with the distribution according to particle size is shown in Fig. The number of particles and the basic statistics of wear particles with respect to the type of wear is shown in Table The correlation coefficients R reached high values for almost all the observed samples, which also indicates using appropriate sampling method, appropriate methods of measurement and processing of results. With a new engine oil, it is necessary to take into account the impossibility of obtaining objective results due to the content of large molecules that wrap smaller functional groups, thus preventing the measurement of certain properties and elements. The above stated applies in particular to the measurement of detergent and dispersant additives.Considering the measured values of the observed properties of conventional and irradiated engine oil, the effect of electron beam irradiation on their properties is obvious. The influence of radiation on the kinematic viscosity and thus also on the viscosity index is not as striking as it was assumed. However, it should be noted the possible effect of storage conditions on kinematic viscosity and viscosity index. Taking into account the measured values in the experiment, the positive influence of the second filling in the engine on the viscosity index is obvious.18. Oil oxidation and TBN belong to the basic evaluation elements used for determining engine oil change intervals. The measured values during the oil raid indicate a positive influence of electron radiation on the indicated values. With the results of kinematic viscosity, which show comparable values of chemical stability, it is possible to express the partial suitability of electron radiation for the modification of engine oils of internal combustion engines. Partly due to the conditional suitability of the modification and the complexity of engine oils, it is necessary to evaluate all aspects affecting the tribological system.As can be seen in Tables 1, it is possible to assume lower wear in the used engine oil at the chosen dose of radiation, which is also confirmed by the measured amount of iron. Throughout the experiment, the iron content is lower than that of conventional engine oil, which is an important indicator for assessing the suitability of radiation treatment of engine oils. The first 1000 km oil raid are crucial, where the iron content of conventional engine oil has almost tripled. The following course of iron content is almost constant for both monitored engine oils. Copper content is another similar key indicator of the impact of wear. Copper is an important wear metal associated with wear, especially the wear of bearings and bushings which are heavily stressed in diesel combustion engines. An internal combustion engine with pump-nozzle injection has a higher load on the crankshaft and camshaft bearings due to the order of magnitude higher pressures in the working space compared to internal combustion engines using fuel injection by the help of a rotary pump. Despite the higher operating pressures of the combustion engine, the observed oil did not lose its lubricating properties during the radiation modification. The course of the content of copper as well as chromium and aluminium increases almost linearly from the beginning of the experiment, but the increase is more pronounced in the case of conventional engine oil.The course of the soot content shows a clear decrease in both the percentage share in irradiated engine oil and the measured sulphation values. The author evaluates the results of the mentioned two properties as a clearly positive effect of the e-beam modification. Taking into account the measured values of the friction coefficient for similar engine oilsThe number of wear particles shown in Table 8. In the initiation stage, two cases can occur: ionization and excitation of atoms and molecules. In the case of ionization, the polymer is ionized and immediately after the interaction, the ionized molecule dissociates into a radical. During excitation, the irradiated atom passes from an equilibrium state to an excited state. When returning to the equilibrium state, the electron emits energy in the form of X-rays. Alternatively, the second possibility occurs in which the excited molecule dissociates into a radical. The mentioned chemical reactions complete the initiation stage and the second phase—propagation begins. The two radicals formed at the initiation stage return to a stable state by binding to another molecule by removing an electron, which creates another radical. Radicals formed on primary carbon are more reactive than radicals on secondary carbon. The terminal stage occurs in the case of a reaction between two radicals. In this manner, the radical returns to a stable state by binding to another suitable radical in sufficient proximity. By the mentioned mechanism, the reaction cycle of the propagation stage is interrupted and the chain reaction is terminated. Terminal steps rarely occur, as the concentration of radicals at any given moment is very low.The investigation of the influence of radicals is a complex process during which the attention must be paid to the amount and type of radicals. The reactivity of radicals is influenced by a number of factors that contribute to the formation of other radicals. The mentioned factors include the diversity of chemical elements and their concentrations, chemical bonds by which they are connected into molecules. The concentration of elements determines the probability with which they can further bind. A substantial part of the radical reactions takes place in the order of milliseconds to units of seconds during the irradiation. Based on the experiment, it is possible to express some conclusions by examining the influence of radicals on a theoretical level. It is generally accepted that the process of radical reactions is accompanied by three stages: initiation, propagation and termination−1, 1460 cm−1 and 720 cm−1 compared to the baseline. Alkanes are used in engine oils in conjunction with base oils. The content of alkanes forms a significant part of the fundamental property of oils—lubrication. The quantity and quality of alkanes together with additives used for optimizing lubricity properties are directly related to the friction coefficient of the tribological system of which they are part. The absorbance band in the region of 1377 cm−1 indicates the compounds of alkanes with nitrogen. However, nitration of engine oil can also occur during the natural run-in of engine oil by replacing the hydrogen atom with the nitro group by NO2, which is most often manifested on primary carbons. Nitrogen oxides NO2 are created by incomplete combustion of fuel in the combustion chamber of an internal combustion engine. The increased content of aldehydes can be observed by absorption bands at wave numbers of 2727 cm−1 and 1706 cm−1. The physical properties of aldehydes directly depend on the molar mass. The higher number of carbons in aldehydes is directly dependent on the boiling point. The reactivity of aldehydes is relatively high but decreases with increasing length of the chemical chain. The reactivity of aldehydes is caused by the presence of a carbonyl group which causes a higher electronegativity of oxygen in the functional group. It should be noted that in addition to the mentioned reaction mechanism of radical reactions in the process of irradiation with high-energy electrons, the occurrence of pericyclic reactions is also possible, affecting the entire process of modifying the properties of engine oils.Related to the amount of contained hydrocarbons and additives added to the engine oil, a large number of radical reaction products are formed. Following the comparison of the IR spectra shown in Figs. The influence of electron radiation on engine oil was described by the selected monitored properties during the engine oil change interval. Considering the extent of the work, there were more monitored properties, however, only the most significant ones have been listed in the article. A significant step has been achieved in the research of viscosity index, oxidation, TBN and the number of particles of internal combustion engine wear.Evaluating the optimization quality of radiation-modified engine oil is difficult, as there are currently no values for the appropriate absorbed dose of electron radiation for the monitored properties and the chosen type of oil. In light of these facts, it will be necessary to perform further numerous experiments and measurements of engine oils properties and evaluate the obtained information by comparative methods with conventional engine oils. In order to create an effective procedure with the application of ionizing radiation in the development of engine oils, it is necessary to meet a number of prerequisites, which include: a source of ionizing radiation with high accuracy of transverse and longitudinal homogeneity of the beam, creation of a suitable conveyor system for liquids with regard to ensuring uniform flow during irradiation at each point of the cross-section of the flow, a reliable and accurate dosimetric system, operation of a number of test rooms and tested combustion engines in laboratory conditions as well as vehicles in real operation for thorough statistical evaluation, regular collection of the examined oils samples at specified intervals, measurement of all examined oils immediately after taking the sample, creation of data database for various combustion engines and engine oils, examination of engine oils from the point of view of their origin (type of base oil) and additive package, evaluation of different storage conditions and their effect on the properties of engine oils. Subsequently, it will be possible to create models of the suitability of modified oils for different types of combustion engines which are significant in terms of the absorbed doses of radiation and added additives in base oils. Based on the results of the research, it could be concluded that the selected method is suitable for modifying the properties of lubricating oils of internal combustion engines.


Thyroid cancer is a very damaging disease. The most common treatment for this disease includes thyroidectomy and then using radioactive iodine (RAI). RAI has many side effects, including a decrease in salivary secretions, followed by dry mouth and oral and dental injuries, as well as increased inflammation and oxidative stress. Selenium can be effective in these patients by improving inflammation and oxidative stress and by modulating salivary secretions. So far, only one clinical trial has investigated the effect of selenium on thyroid cancer patients treated with radioiodine therapy (RIT) conducted on 16 patients; considering the importance of this issue, to show the potential efficacy of selenium in these patients, more high-quality trials with a larger sample size are warranted.This is a parallel double-blind randomized controlled clinical trial that includes 60 patients aged 20 to 65 years with papillary thyroid cancer (PTC) treated with RAI and will be conducted in Seyyed al-Shohada Center, an academic center for referral of patients to receive iodine, Isfahan, Iran. Thirty patients will receive 200 µg of selenium for 10 days (3 days before to 6 days after RAI treatment) and another 30 patients will receive a placebo for the same period. Sonographic findings of major salivary glands, salivary secretions, and sense of taste will be evaluated before and 6 months after 10-day supplementation.Due to its anti-inflammatory and antioxidant effects, as well as improving salivary secretions, selenium may improve the symptoms of thyroid cancer treated with radioactive iodine. In past studies, selenium consumption has not reduced the therapeutic effects of radiation therapy, and at a dose of 300 to 500 μg/day, it has not had any significant side effects in many types of cancer under radiation therapy.IRCT20201129049534N6. Registered on 16 September 2021.Iranian Registry of Clinical Trials The online version contains supplementary material available at 10.1186/s13063-023-07470-2. The order of the items has been modified to group similar items (see Thyroid cancer (TC) is more common than other endocrine malignancies and its incidence is increasing worldwide , 2. TC iOne of the most important causes of thyroid cancer is environmental factors such as ionizing radiation, toxic chemical compounds, and halogenated pesticides. The amount of consumed iodine is also effective on the probability of contracting it, so both deficiency and excess consumption of iodine can lead to an increase in the probability of contracting thyroid cancer , 6. SomeCurrent treatments for thyroid cancer include thyroidectomy , tyrosine kinase inhibitors (TKI), and radioactive iodine (RAI). Among these, one of the most common methods includes thyroidectomy followed by the use of radioactive iodine –13. The Selenium is one of the essential minerals, the largest amount of which per gram of tissue is present in the thyroid gland and it affects thyroid health through its role in the structure of selenoproteins –31. Selen = 16) [Recently, a clinical trial study investigated the effect of selenium on thyroid cancer patients undergoing RIT therapy, which reported that 300 μg/day of selenium from 3 days before to 6 days after RIT can help maintain salivary gland function . This isn = 16) , so thisWe aim to investigate the effects of selenium supplementation on sonographic findings of salivary glands in papillary thyroid cancer (PTC) patients treated with radioactive iodine. If this trial confirms our hypothesis, selenium supplementation may be used to improve the effects of existing treatments.A randomized, parallel, two-arm, double-blind, and placebo-controlled superiority clinical trial will be implemented.Our study will be performed at Seyyed al-Shohada Center, an academic center for the referral of patients to receive iodine, affiliated with Isfahan University of Medical Sciences, Isfahan, Iran.Age between 20 and 65 yearsDiagnosis of PTC with pathological findings of thyroid tissue biopsy.Treated with radioactive iodineSuffering from sialadenitis Suffering from Sjogren’s syndromeSubjects with severe side effects after thyroidectomy who were not possible for RITCollagen vascular disease involving the salivary glands.Any surgery on the salivary glandsPregnancy and breastfeedingLack of patient permissionConsumption of food supplements in the last 3 months .Suffering from special diseases such as diseases caused by congenital diseases, immune system defects, etc.Report any adverse effects after taking supplementsIf there is a significant change in any of the patient’s treatments during the period of intervention by the relevant doctorConsumption of less than 80% of selenium supplements by the patient.In this study, after providing written and oral explanations about the objectives and method of conducting the research, written informed consent will be obtained from the patients if they wish to cooperate in the study.The consent form received from the patients includes their agreement to use the data in related future studies. Of course, patients can only agree to the current study and not accept future studies.While receiving standard treatment, patients will be placed in one of two groups receiving a selenium supplement or placebo. The treatment group will receive one selenium capsule containing 200 µg of selenium per day and the control group will receive one placebo capsule containing 200 µg of maltodextrin per day for 10 days (3 days before to 6 days after radioactive iodine treatment).The reason for choosing 200 µg is that a dosage of 200 µg/day per extra-dietary supplementation of selenium is generally considered safe and adequate for an adult of average weight . In addiBoth treatment and placebo groups will be treated with radioactive iodine. The treatment group will receive one selenium capsule containing 200 µg of selenium per day for 10 days (3 days before to 6 days after radioactive iodine treatment). The control group will receive a placebo capsule containing 200 µg of maltodextrin per day for 10 days (3 days before to 6 days after radioactive iodine treatment). Selenium capsules are purchased from 21st Century company and the placebo is prepared by the Faculty of Pharmacy of Isfahan University of Medical Sciences. During the intervention, the type and dosage of the drugs used by the patients will not be changed, and the patients will receive all their usual treatments according to the previous routine , and receiving selenium or placebo is merely a supplement to the common treatments they receive.Each participant will be allowed to withdraw from the study at any time. Also, the reasons for each individual’s withdrawal from the study will be explained in detail in the study results.Selenium and placebo tablets will be delivered to the patients by the researcher (M.G) and during ten days of supplementation, the patients will be reminded to take the tablets by phone call. Also, patients will return the empty can of the supplement after ten days.The patient will receive all the usual care and treatment under the supervision of a specialist doctor. There will be no change in receiving standard care during the study. Patients only received selenium supplements or a placebo in addition to receiving routine treatments.All standard treatments will be continued after the study, but selenium or placebo supplements will only be received for 10 days during the study.In general, the variables evaluated in this study will include demographic variables, assessment of disease severity, and evaluation of changes in sonographic findings of major salivary glands .Demographic variables  will be collected from all participants by completing a general information questionnaire.Before and 6 months after the 10-day intervention with selenium or placebo, sonography was taken from parotid and submandibular salivary glands and according to sonography, these salivary glands will be evaluated in terms of echogenicity, size, margin, and contour.Huang et al.’s study including 446 patients with thyroid carcinoma, reported that the side effect of radioactive iodine on salivary glands occurs after a few months . Also, LThe level of taste sensation and secretion of salivary glands will be evaluated by the evaluation questionnaire of the level of sialadenitis . This quBefore and 6 months after the 10-day intervention with selenium or placebo, 10 ml of blood will be taken from the patients and collected in plastic tubes. A centrifuge will be used to separate the serum samples. Then the serum will be poured into 0.5 ml microtubes. The samples will be stored in a freezer at − 70 °C. To reduce the error in the measurements, all blood samples will be taken at 8–10 am in the fasting state.CRP will be evaluated at the beginning and end of the study, and if there will be no budget restrictions, we will also evaluate total antioxidant capacity (TAC) and superoxide dismutase (SOD).The study flow diagram is according to Table Since our study is the first in its kind, we calculate the sample size base on CRP as one the most important parameters of this study. Based on a previous study using selenium supplementation on patients with inflammation to reduce inflammatory factors such as CRP , and conA total of 60 subjects  would be required.Patients will be selected according to the entry and exit criteria from the patients who refer to Seyyed al-Shohada Center, an academic center for referral of patients to receive iodine, Isfahan, Iran.https://www.sealedenvelope.com/simple-randomiser/v1/lists” and using a block size of four based on age and sex using the website https://www.sealedenvelope.com/simple-randomiser/v1/lists, with the ratio of 1:1. Sample patients will be 20 to 65 years old. Therefore, the age threshold of 20 to 65 years will be considered. For the randomization, the stratification factors are age  and sex .After meeting the entry criteria, each patient will be randomly assigned to one of the two supplemental groups with selenium or placebo using the reliable random number generator website “Completely identical packages of selenium and placebo tablets with blinded labels A or B will be provided to the researcher without specifying the type of supplement. Researchers and patients will not know the type of supplement on each label until the end of the statistical analysis.An independent reviewer will assign the participants to the intervention or control group, and also the generation of the allocation sequence of the patients will be monitored by the second researcher (B.I).This will be a double-blind study, so the researchers and the subjects will not know which group they will enter. Also, selenium and placebo supplements will be produced in the same way in terms of shape, color, size, and smell, and they will have the same packaging.The disclosure of the label of the supplements will only take place at the end of the study after the completion of the statistical analysis. In case of any unblinding during the study, it will be reported in detail in the Iranian Registry of Clinical Trials and the final results of the study.Major salivary glands  will be examined by sonography before and 6 months after the 10-day intervention with selenium or placebo.A questionnaire evaluating the degree of dry mouth and its effects on the daily life of patients will be used to evaluate the sense of taste and secretion of salivary glands.To encourage patients to cooperate as much as possible, it will be explained about the possible effects of selenium supplementation on the reduction of complications caused by the treatment of thyroid cancer patients with radioactive iodine.The data will be carefully recorded and protected by a blind researcher. After completing the data, the result set will be reviewed.The ethical principles of confidentiality of the names and identification details of the patients will be fully maintained. The researchers will only mention the results of the study without mentioning the names and identification details of the patients, so the patients will not be identifiable under any circumstances.After separating the serum from the collected blood samples, they will be immediately placed in a freezer at − 70°C until the tests will be performed. If the patient agrees, the blood sample will be stored for future studies. Genetic tests are not related to the present study.t-test and between-group analyses will be performed using independent t-test and ANCOVA. The distribution of qualitative variables will be compared between two groups using the chi-square test. SPSS version 22 software will be used to analyze the data with a significance level of P < 0.05.In this study, the number of quantitative variables will be reported as mean (standard deviation), and qualitative variables will be reported as number (percentage). The evaluation of the normality of the distribution of quantitative variables will be done using the skewness index and the Q-Q plot diagram. Intra-group analyses will be performed using paired The primary results of this study include the evaluation of CRP and changes in sonographic findings of major salivary glands , and the secondary results include the evaluation of the level of taste sensation and secretion of salivary glands by the questionnaire to assess the level of sialadenitis .Not applicable.No subgroup analyses are planned.The analysis will be done in an intention-to-treat format so that the data from excluded patients are also mentioned in the results. The reason for each patient’s withdrawal, especially the presence of any side effects, will be mentioned in detail. A sensitivity analysis will also be done. Missing data will be checked by multiple imputations.If there will be logical requests for data in the direction of the present protocol, the corresponding author will send the data set. Otherwise, all information will remain confidential.The performance of the researchers and all stages of the study will be under the supervision of the Ethics Committee and the Vice-Chancellor of Isfahan University of Medical Sciences, so that if there is any contradiction with the ethical principles, the preservation of the patient’s health and also the preservation of his human values, the corrections or the termination of this study will be applied.Data monitoring will be done by the academic committee of Isfahan University of Medical Sciences, which includes impartial and continuous monitoring.Any side effects, whether significant or minor, will be reported in full detail though previous studies have reported no adverse effects of selenium supplementation in several types of cancer treated with radiation therapy , 44.The present study will be supervised by the Ethics Committee of Isfahan University of Medical Sciences. Unexpected inspection of the accuracy and correctness of the study and the correct performance of the researchers will be done at least twice during the study.https://irct.ir/.If there is a need for any changes in the study protocol, the changes will be made under the supervision and with the approval of the Ethical Committee of Isfahan University of Medical Sciences. All changes will be reported in detail at Final data and results will be presented in official publications.Thyroid cancer is a common disease worldwide , 2. InflSelenium is an essential mineral that affects the metabolism of thyroid hormones, the antioxidant system, and the inhibition of thyroid neoplasm , 34, 36.Selenium exerts part of its anticancer effects by controlling redox stimuli and thus modulating the redox process . A recenA review study in 2020 showed that supplementation with 300 to 500 μg/day selenium for a period of 10 days to 6 months without reducing the effectiveness of radiotherapy can reduce the side effects of this therapeutic strategy in several types of cancer treated with radiation therapy. This study did not report any side effects from selenium supplementation .Another review study reported that selenium supplementation reduces ageusia (loss of taste) and dysphagia and diarrhea caused by radiation therapy in various cancers. This supplement did not inhibit the therapeutic effects of radiation therapy and had no side effects .n = 60).Recently, in a clinical trial study, it was reported that selenium supplementation in thyroid cancer patients treated with radioactive iodine can help maintain salivary gland function. But this study only had 16 patients as a sample size. Also, the effect of selenium on oxidative stress and inflammation has not been investigated . TherefoThe main limitation of our protocol is that, due to ethical issues, we will not be able to stop the patients' other medications and study the effect of selenium alone. The solution we have thought of for this limitation is that we will carefully examine all the drugs received by the two groups (selenium receiving group and placebo group) at the beginning and end of the study. Then, if there is a significant difference between the two groups, we will adjust the results.Another limitation is that due to a lack of funding, it is not possible to consider selenium blood biomarkers to assess adherence to supplements. To control this limitation, the patients will be closely monitored in such a way that the patients will be reminded daily by phone call to take the supplement during the ten days of the intervention. Also, patients return the empty can of the supplement after ten days. In addition, the potential benefits of the current research for patients are described in detail so that patients can cooperate better.If the present study observes the effectiveness of selenium on thyroid cancer, selenium may be used as a safe supplement with a high potential in improving the symptoms of these patients in the near future.Version 1, September 2021 Recruitment will be started in February 2023 and approximately will be completed in September 2023.Additional file 1.