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熔盐堆作为第四代反应堆论坛推荐的6种候选堆型之一,具有输出温度高、能量密度高、无水冷却等特点。固态钍基熔盐堆(Thorium Molten Salt Reactor with Solid Fuel,TMSR-SF1)堆芯大部分结构材料为石墨,冷却剂杂质及石墨材料中的13C和杂质N、O易被活化产生14C。14C半衰期较长,同其他稳态核素12C、13C一样广泛参与各种复杂的生物循环,在反应堆中受到关注。TMSR-SF1中的14C广泛分布于冷却剂、堆芯石墨结构材料和燃料元件。本文采用输运燃耗耦合方法,应用SCALE6.1的TRITION控制模块对反应堆各区域的14C放射性活度进行计算分析,结果表明,反应堆在正常运行工况下一回路每年产生的14C放射性活度为0.34 TBq,满足现有的压水堆、重水堆管理限值要求。向环境释放的14C主要来自于一回路熔盐中N杂质的活化。
As one of the six candidate reactor types recommended by the 4th Generation Reactor Forum, the molten salt reactor has such features as high output temperature, high energy density and no water cooling. Most of the structural materials of the solid core thorium-based molten salt reactor (TMSR-SF1) are graphite. Coolant impurities and 13C and N, O in graphite materials are easily activated to produce 14C. 14C has a long half-life and is involved in various complex biological cycles as well as other steady-state radionuclides 12C and 13C, attracting much attention in the reactor. 14C in TMSR-SF1 is widely distributed in coolant, core graphite structure materials and fuel elements. In this paper, the transport burnup coupling method was used to calculate the 14C radioactivity in each region of the reactor by using the TRITION control module of SCALE6.1. The results show that the 14C radioactivity generated in the first cycle of the reactor under normal operating conditions is 0.34 TBq, to meet the existing pressure water reactor, heavy water reactor management limits. The release of 14C to the environment is mainly due to the activation of N impurities in the molten salt of the primary circuit.