次锕系核素在铅冷快堆中的嬗变性能

乏燃料中大部分次锕系（minor actinides, MA）核素半衰期较长，对环境具有长期放射性危害。分离 嬗变技术将次锕系核素从高放废液中分离出来，并通过反应堆嬗变为短寿命或稳定核素，从而消除其放射性危害。为研究次锕系核素与燃料均匀混合、制成嬗变棒和做燃料芯块镀层装载方式下在铅冷快堆中的嬗变特性，采用MCNP和SCALE程序进行模拟计算。结果表明，三种方式下²³⁷Np、²⁴¹Am、²⁴³Am和混合次锕系核素使有效增殖因数k_eff降低，而²⁴⁴Cm和²⁴⁵Cm使k_eff升高，且²⁴⁵Cm可使k_eff大幅度增加。不同质量的混合次锕系核素装载后，三种方式下堆芯k_eff都随装载量的增加而降低，降低幅度由小到大分别为嬗变棒、均匀混合和镀层。不同次锕系核素装载量以均匀混合方式在堆芯经过550 d辐照后，²³⁷Np、²⁴¹Am和²⁴³Am嬗变率均为正值，其中²⁴¹Am嬗变率最大，而²⁴⁴Cm和²⁴⁵Cm嬗变率均为负值，²⁴⁵Cm增加明显，总的次锕系核素嬗变率为14%，可为次锕系核素在铅冷快堆中嬗变性能评价提供参考。

Transmutation Properties of Minor Actinides Nuclide in the Lead-cooled Fast Reactor

The half-life of most of minor actinides in spent fuel is longer and has long-term radioactive hazards to the environment. Partitioning-transmutation technology can eliminate radioactive hazard by separating minor actinides from the high level waste and transmuting into short-life or stable nuclide in the reactor. MCNP and SCALE are used to simulate transmutation characteristics of minor actinides in lead-cooled fast reactor. The three loading methods are as follows, the homogeneous mixing of minor actinides with fuel, forming transmutation rods and fuel pellets coating. The results show that²³⁷Np ,²⁴¹Am,²⁴³Am and mixed minor actinides make thek_eff decrease, simultaneous loading of ²⁴⁴Cm and²⁴⁵Cm makek_eff increase, and²⁴⁵Cm significantly increase k_eff. After loading mixed minor actinides with different mass, the core k_eff decrease with the increase of loading, and the decreasing range from small to large are transmutation rod, uniform mixing and coating, respectively. The loading of different minor actinides is irradiated by uniform mixing in the core after 550 days, ²³⁷Np,²⁴¹Am and²⁴³Am transmutation rate are always positive, the ²⁴¹Am transmutation rate is the largest, while²⁴⁴Cm and²⁴⁵Cm transmutation rate are negative,²⁴⁵Cm increases significantly, the total transmutation rate of minor actinides is about 14%. It can provide reference for minor actinides transmuted in the lead cooled fast reactor.