自然循环铅冷快堆无保护瞬态分析研究

Transient Analysis on Unprotected Transients of A Natural Circulation Lead-Cooled Fast Reactor

基于系统分析程序ATHLET建立了100 MW小型自然循环铅冷快堆一回路主冷却系统分析模型,对超功率(UTOP)、失热阱(ULOHS)和超功率叠加失热阱(UTOP&ULOHS)这三类典型无保护事故分别进行了研究.结果显示:对于UTOP,燃料芯块和包壳的温度均先增大后减小,峰值温度小于安全限值并于700 s后达到新的稳态,反应堆热工安全裕量较小.对于ULOHS,反应堆在事故后400 s内实现了自动停堆,燃料芯块和包壳温度均远低于设计限值.对于UTOP和ULOHS叠加事故,反应堆的响应特性在事故初期与UTOP相似,在事故后期与ULOHS相似,且包壳最终稳定温度较UTOP更高,反应堆热工安全裕量最小.

In order to investigate the inherent safety features of the natural circulation leadcooled fast reactor,the primary cooling system analysis model for a natural circulation lead cooled fast reactor named SNCLFR-100 was established with ATHLET code.Unprotected transient overpower（ UTOP）,unprotected loss of heat sink（ ULOHS）,unprotected transient overpower and loss of heat sink（ UTOP ULOHS）,the three typical unprotected transient condi-tions were selected and analyzed. The analysis showed that,during the UTOP process,though the temperatures of fuel pellet and cladding increases first and then decreases,they are still below the safety limits and stabilize again after 700 s,and the safety margin is small.As for the ULOHS,the reactor shuts itself down with the help of various types of core negative feedback,fuel pellet and cladding temperatures are far below the design limits.With regard to the UTOP ULOHS,the response characteristics of the reactor are similar to UTOP at the beginning of the transient,and similar to ULOHS at the end of the accident,but the final stable temperature of cladding is higher than UTOP,the safety margin of the reactor is minimal.