Research on burnable poison in micro gas-cooled reactor
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摘要: 为分析气冷微型堆可燃毒物布置策略,分别建立长寿期(15 MW-20 a)、短寿期(5 MW-1 a)、较长寿期(5 MW-3~10 a)不换料堆芯模型,利用通用蒙卡程序,研究气冷堆中常用可燃毒物核素种类、可燃毒物布置方案对堆芯反应性、寿期等特性的影响。研究结果表明:长寿期堆芯中,整体型Er2O3可以有效控制堆芯剩余反应性,但在寿期末会造成一定的反应性惩罚;整体型B4C可以较好地控制堆芯剩余反应性,并在寿期末几乎不会造成反应性惩罚,通过分区布置还可以优化功率分布;分离型B4C可以使燃耗特性曲线在寿期初和寿期中变化很平坦。短寿期堆芯中,分离型Gd2O3毒物棒可以很好地控制剩余反应性且不会缩短堆芯寿期;常见的B4C布置方式并不合适,但B4C弥散在堆芯石墨内可以起到较好的毒物效果。较长寿期堆芯中,分离型Gd2O3毒物棒不仅可以有效控制剩余反应性,还可以保证堆芯具备仅依靠温度负反馈实现自动停堆的固有安全性。研究结果将为后续气冷微堆型号研发提供指导。Abstract: To analyze the characteristics of burnable poisons used in the micro gas-cooled reactor, this paper investigates how the kinds and layout of burnable poisons influence the reactor characteristics, such as reactivity and lifetime, based on the long-lifetime core (15 MW-20 a) model, short-lifetime core (5 MW-1 a) model and longer-lifetime core (5 MW-3−10 a) model, using Monte Carlo procedure. The results show that, as for the long-lifetime core, the monolithic type Er2O3 can reduce the core excess reactivity effectively with a certain reactivity punishment at the end of lifetime, and the monolithic B4C can reduce the core excess reactivity excellently with a better power distribution if an inhomogeneous distribution layout of B4C is applied, and the separated type B4C makes the characteristic curve of burn-up flatter. As for the short-lifetime core, the separated type Gd2O3 is an appropriate choice while the B4C with usual layouts is not, but it has a good behavior if the B4C disperses in the core graphite as the burnable poison. As for the longer-lifetime core, the separated type Gd2O3 not only can control the core excess reactivity effectively, but also can guarantee the core have the inherent safety of automatic shutdown only by the negative temperature feedback. These results will instruct the follow-up development of micro gas-cooled reactor devices.
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表 1 几种可燃毒物核素特性
Table 1. Properties of several burnable poison nuclides
material absorber nuclide natural abundance/% 0.0253 eV absorption cross-section/(10−28 m2) melting point/℃ density/(g·cm−3) Gd2O3, Gd2O3 155Gd, 157Gd 14.71, 15.68 60 799, 254 070 2350 7.40 B4C 10B 19.8 3839 2350 2.52 Er2O3 167Er 22.87 646 2355 8.64 Sm2O3 149Sm 13.83 40719 2325 8.35 CdO 113Cd 12.26 20192 1427 8.15 Eu2O3 151Eu 52.18 9172 2050 7.30 -
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