Research and Validation of the Monte Carlo-based Multi-cycle Neutronic Calculation Methodology for High Flux Research Reactor
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摘要: 针对高通量研究堆内的燃料辐照考验,以建立多循环高精度中子学计算方法为目的,本研究基于蒙特卡罗中光子输运-燃耗耦合程序,掌握了堆芯全局环境和考验装置局部环境中不同粒子产生、输运、泄漏、沉积的物理过程,建立了能够描述全堆芯多回路各物理过程的能量沉积高保真计算模型,考虑了高通量研究堆运行过程中燃料燃耗、控制棒棒位的动态变化及其与粒子输运过程的耦合关系,实现了包含多种类型燃料和可燃毒物的全堆换料和燃料管理计算。使用了不同燃耗步下实际临界棒位、辐照考验件功率、点燃耗测量值进行了验证,计算结果表明堆芯中子有效增殖因数(keff)计算误差小于1200pcm(1pcm=1×10−5),辐照考验件功率、点燃耗计算值与实测值的平均相对误差小于10%,验证了多循环中子学计算方法的准确性。Abstract: This paper focuses on the irradiation test in the high-flux research reactor. Based on the Monte Carlo neutron-photon transport-burnup coupling code, the physical processes of the generation, transport, leakage, and deposition of different particles in the global core environment and the local test device environment are studied, and a high-fidelity calculation model of energy deposition that can describe the physical processes of multi loops throughout the core is established based on the repetitive geometric structure. Taking into account the dynamic changes of fuel burnup, control rod position, and their coupling relationship with the particle transport process during the operation of the high-flux research reactor, the whole reactor refueling and fuel management calculations are realized, including multi-type of fuels and burnable poisons. Validation is performed using actual critical rod position, irradiation test assembly power, and point burnup measurement values under different burnup steps. The calculation results show that the error in the core neutron effective multiplication factor (keff) is less than 1200 pcm, and the average relative errors between calculated and measured values for irradiation test assembly power and point burnup are both less than 10%, verifying the accuracy of the multi-cycle calculation method.
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Key words:
- High Flux Research Reactor /
- Multi-Cycle /
- Monte Carlo method
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表 1 高通量研究堆堆芯RMC建模主要改进
Table 1. Major Improvements in RMC Modeling of High Flux Research Reactor Core
改进项目 原模型 改进模型 建模逻辑 直接描述 重复几何+层级结构 燃料元件 燃料元件不分区 燃料元件径向分6区,轴向分10区 铍块 未考虑 考虑反射层铍块、控制棒跟随体铍燃耗,且径向分2区,轴向分5区考虑铍杂质影响[5] 元件中孔、铍中孔 未考虑 考虑元件中孔、铍中孔靶件影响 核热耦合 未考虑 考虑多温截面、热化截面影响 停堆衰变 未考虑 全堆衰变计算考虑毒物积累 表 2 HFETR第一炉段辐照实际临界棒位下堆芯keff及反应性偏差
Table 2. Core keff and Reactivity Deviation at Actual Critical Rod Position for HFETR's First Cycle Irradiation
燃耗时刻/
EFPD实际临界棒位 keff 反应性
偏差/pcm(1,2)SB (3,6)SB (4,7)SB (5,8)SB 0 0 29.9, 30.5 100 0 1.0087 862.50 0.20 17.8 100 100 0 1.0050 497.51 2.00 42.2 100 100 0 0.9963 −371.37 5.00 50.5 100 100 0 1.0099 980.30 10.00 63.0 100 100 0 1.0058 576.66 14.00 88.0 100 100 0 1.0050 497.51 18.00 100.0 100 100 19 1.0114 1127.15 24.00 100.0 100 100 42.5 1.0017 169.71 28.75 100.0 100 100 65 1.0044 438.07 SB—手动控制棒;(1,2)—1号和2号控制棒为一组棒,其余小括号相同。 表 3 不同炉段实际临界棒位下堆芯keff及反应性偏差
Table 3. Core keff and Reactivity Deviation at Actual Critical Rod Position for Different Burnup Step
辐照炉段 keff 反应性偏差/pcm 1 0.9963~1.0114 −371.37~1127.15 2 0.9972~1.0117 −280.79~1156.47 3 0.9911~1.0100 −897.99~990.10 4 0.9922~1.0115 −786.13~1136.93 5 0.9912~1.0075 −887.81~744.42 6 0.9903~1.0085 −979.50~842.84 7 0.9904~1.0074 −969.31~734.56 8 0.9923~1.0102 −775.98~1009.70 9 0.9999~1.0099 −10.00~980.30 10 0.9928~1.0099 −725.22~980.30 11 0.9933~1.0034 −674.52~338.85 12 0.9931~1.0093 −694.79~921.43 13 0.9969~1.0106 −310.96~1048.88 14 0.9914~1.0073 −867.46~724.71 表 4 辐照装置A功率计算值与实测值比较
Table 4. Comparison between Calculated and Measured Power Values for Irradiation Device A
辐照装置 炉次(燃耗时刻) keff (热功率计算值/测量
值相对误差)/%辐照装置A 1(10 EFPD) 1.0058 6.10 2(10 EFPD) 1.0072 5.53 表 5 辐照装置A样品点燃耗测量值与计算值比较
Table 5. Comparison between Measured and Calculated Sample Point Burnup Values for Irradiation Device A
样品号 235U/238U相对误差/% 236U/238U相对误差/% 1 7.24 −3.26 2 11.27 −3.93 3 10.03 −4.19 4 10.96 −6.58 5 4.35 −7.26 均方根误差 9.16 5.28 -
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