Study On Radiation Characteristics Of Prototype Of Negative Ion Based Neutral Beam Injection System For CFETR

Negative ion based Neutral Beam Injection(NNBI)is one of the important auxiliary heating and current drive methods for the China Fusion Engineering Tester Reactor(CFETR).In order to support the construction of CFETR,a verification prototype of CFETR NNBI system is required for the purpose of key technology research and physical experiment research,providing technical support and experience accumulation for the development of future NNBI system.Furthermore,it can reduce the technical risk for the development of CFETR NNBI.The NNBI system will generate radiation during operation,which has a certain impact on equipment and operators.Therefore,it is necessary to analyze the radiation dose and design radiation shielding to protect the researchers from radiation,and support the experimental research on verification prototype of CFTER NNBI.This paper investigates the domestic and international development status of NBI systems.At the same time,the radiation types generated by the NNBI system when operated with hydrogen and deuterium were analyzed according to the basic principle of the NNBI system and the classification of the radiation type.When NNBI operates with hydrogen,the influence of electron(bremsstrahlung)on the radiation intensity of the NNBI system was analyzed.And when NNBI operated with deuterium,the influence of neutron(neutron radiation)on the radiation intensity was also studied.Meanwhile,according to the dose theory and the working conditions of CFETR NNBI prototype,the main radiation source of the prototype was determined.Based on this research,a two-dimensional geometric model of the CFETR NNBI prototype was established and the Monte Carlo method was used to simulate the radiation dose with two operating modes.The radiation dose generated by the NNBI prototype at different key positions with different operating modes were simulated.According to the operation requirements of CFETR NNBI prototype and the standard for the radiologic safety,the radiation shielding design of the CFETR NNBI prototype is carried out.The simulation results of the radiation dose distribution at key locations with radiation protection design was presented.The results shown that the radiation dose generated by the CFETR NNBI prototype is lower than the standard for the radiologic safety,which no harm to staff and the surrounding environment.The radiation simulation analysis and shielding design of the CFETR NNBI prototype will give the technical supports of radiation analysis and protection design for NNBI system.