Study On Induced Radioactivity And Its Effects Of High Intensity Heavy-ion Accelerator Facility

As one of China’s major science and technology infrastructure during the 12 th Five-Year Plan period,High Intensity heavy-ion Accelerator Facility(HIAF)is designed and constructed by the Institute of Modern Physics,Chinese Academy of Sciences.It is capable of full particle acceleration from proton to uranium.It has the characteristics of wide energy range,high beam intensity,large scale and complex operation mode.During the operation of the accelerator,the beam and the secondary radiation generated by its losses interact with the accelerator components and the surrounding environmental materials to produce induced radioactivity,which poses a threat to the radiation safety of workers,the public and the environment.Therefore,it is essential to perform a study on induced radioactivity of HIAF,analyze its generation mechanism,change rule,distribution and potential radiation influence,and implement relevant protection designs accordingly.In this paper,FLUKA was used to compare the induced radioactivity of accelerator components and environmental materials,which produced by several typical beams of HIAF.The results indicate that the induced radioactivity induced by 12 C is the strongest,and the types and activity ratios of radionuclides induced by different particles in the same medium are generally similar.Next,the induced radioactivity of accelerator components and vacuum pipes was studied.The results show that the residual dose rate around the highly activated components such as Beam dump and slit,is very high,making manual operation unfeasible.Taking into account the characteristics of each component,the radiation protection designs were implemented using the protection strategy of "compact shielding" or "embedded Beam dump".Additionally,the thermal design of the component with ultra-high power beam loss was carried out.The activation of vacuum pipe may result in a high level of residual dose rate in the tunnel,necessitating dose interlocking to prevent personnel from entering the tunnel when the residual dose rate is high.At the same time,strict access management and realtime individual dose monitoring must be carried out for personnel who need to enter the tunnel.Finally,the induced radioactivity of environmental materials,including cooling water,air,concrete,soil and groundwater,was studied.The results show that the activated cooling water can contribute to a certain level of residual dose rate in the working environment of the water station.Corresponding protective measures are proposed according to the characteristics of the source term.Simultaneously,the collection and discharge of radioactive wastewater are analyzed and designed.The expected cumulative dose of radioactive exhaust emissions to the public was 0.0259 m Sv/y,which was lower than HIAF management target limit for the public.The activity concentration of radionuclides in the concrete shielding does not exceed the exempted level.However,its total activity passes the exempted level.Analysis of four radionuclides(3H,22 Na,45Ca and 54Mn)produced in soil and groundwater for environmental migration shows that the activity concentrations of these four radionuclides in groundwater are below the relevant guidelines for drinking water,even in conservative models.The research results of this paper hold significant importance in ensuring the radiation safety of HIAF during and after its operation.The relevant research methods and conclusions can serve as valuable references for similar facilities.