Application of Boron Carbide as Burnable Poison in Sodium Fast Reactors
Application of Boron Carbide as Burnable Poison in Sodium Fast Reactors
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DOI：
10.1080/00295450.2019.1620054
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发表时间：
2019-11-02
影响因子：
1.5
通讯作者：
Rimpault, G.
中科院分区：
文献类型：
--
作者：
Guo, H.;Sciora, P.;Rimpault, G.
与目前的反应堆相比，第四代反应堆预计将显示出显着的安全改进。在钠冷快堆（SFR）中，应避免瞬态过功率（TOP）期间的燃料熔化，因为这被认为是相对频繁的事故。在这些TOP事故中，控制棒抽出（CRW）事故是最有可能发生的，其影响取决于插入反应性的大小。本文介绍了不同堆芯设计所需的过量反应性以及通过使用可燃毒物（BP）来降低CRW瞬态过程中插入的反应性的方法。在对各种候选材料进行评价后，低浓缩度碳化硼与氢化锆慢化剂组合似乎是钠快谱堆中最有前途的BP。可燃毒物位于特定组件的销钉中，这些销钉在整个燃料循环中处于堆芯的固定位置。带有BPs的堆芯设计在整个燃料循环过程中表现出较低的反应性损失，因此限制了堆芯所需的初始过量反应性，以通过控制棒进行补偿。另一个约束来自堆芯功率分布，该功率分布在整个燃料循环过程中应保持几乎稳定。这种堆芯功率分布可以通过适当加载BP组件来修改。然而，由于它们的位置在整个燃料循环中是固定的，它们只能补偿局部通量倾斜的一部分。这些BP堆芯设计略微改善了反应性反馈系数，因为它们含有使中子减速的轻质材料。最后表明，CRW瞬态与BPs显着降低了最大燃料中心线温度相比，没有BPs的设计和CRW瞬态过程中的燃料熔化是避免在大型SFR核心。
Generation IV reactors are expected to exhibit significant safety improvements compared to current ones. In sodium-cooled fast reactors (SFRs), fuel melting during transient over power (TOP) should be avoided as this is identified as a relatively frequent accident. Among these TOP accidents, a control rod withdrawal (CRW) accident is the most likely to happen and its impact depends on the magnitude of the inserted reactivity. This paper presents the required excess reactivity for different core designs and the way to reduce the reactivity inserted during a CRW transient through the use of burnable poisons (BPs).After evaluating various candidate materials, it appears that a low-enrichment boron carbide combined with a zirconium hydride moderator is the most promising BP for use in sodium fast spectrum reactors. Burnable poisons are located in pins of particular assemblies, which are in fixed positions in the core over the entire fuel cycle.Four core designs with different loading schemes and BPs are investigated. Core designs with BPs display low reactivity loss over the fuel cycle and thus limit the required initial excess reactivity of the core to compensate with control rods.Another constraint comes from the core power distribution, which should remain almost stable through the fuel cycle. This core power distribution can be modified by a suitable loading of BP assemblies. However, as their positions are fixed over the fuel cycle, they can compensate only part of the local flux tilt. These BP core designs slightly improve the reactivity feedback coefficients as they contain light materials slowing down neutrons. It is finally shown that a CRW transient with BPs reduces significantly the maximal fuel centerline temperature compared to a design without BPs and that a fuel melting during a CRW transient is avoided in the large SFR core.