全超导非圆截面托卡马克中性束注入窗口材料活化研究

Materials Activation Study on the EAST Neutral Beam Injection Port

中性束注入加热为全超导非圆截面托卡马克(EAST)主要辅助加热方式之一。伴随着中性束注入加热,等离子体中子出射强度可达到10^(14) n/s。由于中性束注入窗口具有较大的开口尺寸,窗口泄露的大量中子可能影响系统的安全稳定运行。本文基于EAST中性束二维模型和蒙特卡洛程序MCNP与材料活化程序FISPACT,研究EAST两条中性束夹角112.5°时,中性束关键部件材料SS304和铜活化情况,并研究材料活化所导致的停机剂量率,最后利用高纯锗能谱仪测量活化核素的γ能谱。研究表明,理论模拟与实验测量结果吻合较好。中长寿命核素^(51)Cr、^(58)Co、^(54)Mn等为SS304主要活化核素。EAST停止运行5 min后,停机剂量率已经降低到国际热核聚变实验堆计划(ITER)设计的剂量率限值10^(-5) Sv/h。本研究可为研究聚变堆中性束注入窗口的材料活化和停机维护方案设计提供指导。

Neutral beam injection heating system is one of the main heating methods to improve the operating parameters of EAST plasma physics.However,the neutron emission intensity can reach up to 10^(14) n/s.Because of the neutral beam injection(NBI)with a larger open size,the neutrons stream along the NBI duct.That may affect the safe and stable operation for NBI.In this paper,by using Monte Carlo program MCNP and activation program FISPACT,the material activation of the NBI key components has been researched based on EAST neutral beam two-dimensional geometric model when the angle between the reverse beam and the coaxial beam is 112.5 degrees.The theoretical simulation results are in good agreement with the experimental measurements.The results show that ^(51)Cr,^(58)Co and ^(54)Mn with medium and long life have obvious peak value of gamma energy spectrum,which indicate that those nucleus are the main active nuclides of SS304 and copper.When EAST stopped operating for 5 min,the shut down dose rate generated by activated gamma photon had been reduced to the dose rate limit designed by International Thermonuclear Experimental Reactor.This work could provide a preliminary exploration for material activation and shutdown dose rate analysis of the fusion reactor neutral beam injection port.