Monte Carlo Simulation On The Semi-Panorama Reference Radiation

Area dosemeters is a kind of common and necessary monitoring and early warning instrument for nuclear facilities,nuclear technology application equipment and other nuclear sites,to ensure nuclear safety and radiation safety.It can be seen that the working condition of area dosemeters,the accuracy of measurement data and so on will directly affect nuclear safety and radiation safety.Therefore,the ISO-4037 series standard stipulates that periodic calibration should be carried out for such monitoring instruments.However,most area dosemeters are equipped with separate probes and divided meters,so that they cannot be completely disassembled for calibration.At the same time,the current Standard Reference Radiation(SRR)also cannot calibrate such instruments.In order to solve the problem of in-situ calibration of gamma ray area dosemeter for radiation protection,it is a feasible solution to reduce the size of the current Standard Reference Radiation to build a non-standard reference radiation,reduce its weight and volume,and make it easy to move to the site of the gamma ray area dosemeter,and to carry out the calibration process.In this paper,Semi-Panorama Reference Radiation(SPRR)is proposed,which is employed for the study of the in-situ calibration technology for gamma ray area dosemeters.Compared with Standard Reference Radiation,the SPRRs' application environment is more complex.How to accurately calibrate the dose value at the point of test in complex application scenarios is the key to achieve in-situ calibration based on SPRR.In this paper,the Monte Carlo method is used to systematically study the characteristics of the SPRR radiation field,and the influence of the scattered gamma ray produced by the probe to be calibrated and the changing of the scenarios on the calibration process.Through theoretical calculation,the influence of the four main factors(the size of the probe,the wall surface,the ceiling and the obstacle)is analyzed.When the bottom radius of the probe to be calibrated is 120 mm,the influence rate of the generated scattering rays on the dose rate at the point of test is 4.73%,which is higher than the other three factors.By extracting the characteristic gamma ray spectrum of the SPRR radiation field,the results show that the impact of the wall surface and the probe size is significantly higher than other factors.With the change of various factors,the influence of the Semi-Panorama Reference Radiation field is increasing or decreasing regularly.In particular,the probe,the distance between the point of test and the wall surface,and the existence of the obstacles are all responsive to the characteristics peak of the gamma spectrum at the scattering monitory point,which provides a basis or way for the use of the gamma spectrum at the scattering monitory point to characterize the impact factors that affect the SPRR.In addition,through the study of the radiation effect of the Semi-Panorama Reference Radiation field,the results indicate that,under the condition of the specific wall thickness,the radiation environment of the dose rate generated by the 3.7GBq radiation source on the wall can basically meet the safety requirements of radiation protection.