Burnup lib compression method based on pseudo decay nuclides definement
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摘要: 燃耗数据库的构建决定了燃耗和衰变热计算的准确性,评价核数据库中的燃耗信息过于复杂,导致燃耗矩阵规模大,刚性强,计算效率低。从燃耗数据库的基本组成出发,考虑燃耗数据库中,各核素及其转化关系对中子学计算精度和重要核素核子密度计算精度的影响,并作为燃耗库压缩的依据。对于因裂变产物压缩而损失的衰变热计算精度,通过非线性最小二乘优化算法拟合衰变释热函数,构造伪衰变核代替裂变产物衰变热计算,以保持衰变热的计算精度。验证结果表明,原精细燃耗库中有超过1 500种核素,经压缩后保留不足200种核素。压缩后的燃耗数据库在有效增殖因子计算和核子密度计算中并未引入明显偏差。在衰变热计算方面,伪衰变核对于衰变热计算精度有显著的复原效果,对总功率贡献的计算偏差小于0.5%,满足衰变热计算精度的需求。Abstract: The construction of the burnup lib determines the accuracy of burnup and decay heat calculations. The evaluation of burnup information in the nuclear lib is complex, leading to a large, rigid, and inefficient burnup matrix. This paper begins with the basic composition of the burnup lib, considering the impact of each nuclide and its transformation relationships on the accuracy of neutronics calculations and target nuclide nuclear density calculations, which serves as the basis for the compression of the burnup lib. To address the decay heat calculation accuracy loss caused by the compression of fission products, a nonlinear least squares optimization algorithm is used to fit the decay heat release function, and pseudo-decay nuclides are constructed to replace the fission product decay heat calculation, thereby maintaining the accuracy of decay heat calculations. Verification results show that the original detailed burnup lib contains more than 1 500 nuclides, which are reduced to fewer than 200 nuclides after compression. The compressed burnup lib does not introduce significant deviations in the calculation of the effective multiplication factor and nuclear density. In terms of decay heat calculations, the pseudo-decay nuclides significantly restore the decay heat calculation accuracy, with the contribution of decay heat to total power having a calculation deviation of less than 0.5%, meeting the required accuracy for decay heat calculations.
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表 1 VERA_1A燃料栅元初始材料明细
Table 1. Specification of initial load materials in VERA_1A
material nuclides atom density/(1024 cm−3) fuel (3.1%) U234 6.11864 E-06U235 7.18132 E-04U236 3.29861 E-06U238 2.21546 E-02O16 4.57642 E-02moderator 565 K O16 2.48112 E-02H1 4.96224 E-02B10 1.07070 E-05B11 4.30971 E-05表 2 最终选取的目标核素
Table 2. Final selected target nuclides
target nuclides actinides fission products U-235 U-236 U-238 Kr-85 Sr-90 Y-90 Mo-95 Tc-99 Ru-101 U-239 Np-237 Np-239 Rh-103 Pd-105 Pd-108 Xe-131 Xe-135m Cs-133 Pu-238 Pu-239 Pu-240 Cs-134 Cs-134m Cs-137 Ba-137 Nd-145 Pm-147 Pu-241 Pu-242 Am-241 Pm-148m Pr-141 Nd-143 La-141 Sm-147 Sm-149 Am-243 Cm-242 Cm-244 Sm-150 Sm-151 Sm-152 Eu-153 Eu-154 Eu-157 Cm-246 Gd-155 Pm-150 表 3 压缩燃耗数据库明细
Table 3. Specification of the compressed burnup lib
burnup lib ${\varepsilon _1},{\varepsilon _2}$ number of
nuclidesnumber of fission
productsnumber of decay
channelsnumber of neutron
reaction channelsfine_lib 1547 1137 1341 1626 VERA_36H179 1E-6, 1E-3 179 142 138 364 VERA_36H151 5E-6, 1E-3 151 114 122 324 VERA_36H138 1E-5, 1E-3 138 101 119 298 VERA_34H133 1E-5, 1E-2 133 98 113 292 表 4 有效增殖因子计算偏差的最大值与均方根
Table 4. Maximum value and root mean square (RMS) value of keff deviation
maximum keff deviation/10−5 RMS of keff deviation/10−5 fine_lib VERA_36H179 VERA_34H133 fine_lib VERA_36H179 VERA_34H133 VERA_1A 202.07 201.79 200.77 93.72 93.64 92.40 VERA_1B 280.45 281.39 280.30 109.65 108.88 107.94 VERA_1C 273.52 274.47 273.39 115.27 114.90 113.87 VERA_1D 290.05 293.17 292.35 123.77 124.16 123.13 表 5 目标核素核子密度计算误差均方根值
Table 5. Root mean square (RMS) value of target nuclides densities deviation
RMS/% fine_lib VERA_36H179 VERA_34H133 0.8
GWd/tHM20.0
GWd/tHM60.0
GWd/tHM0.8
GWd/tHM20.0
GWd/tHM60.0
GWd/tHM0.8
GWd/tHM20.0
GWd/tHM60.0
GWd/tHMVERA_1A 1.77 1.69 1.97 1.14 1.12 2.91 1.33 1.35 5.46 VERA_1B 1.74 1.72 2.00 1.37 1.40 3.15 1.52 1.54 5.85 VERA_1C 1.74 1.71 1.98 1.49 1.52 3.24 1.65 1.66 5.86 VERA_1D 1.72 1.74 2.01 1.60 1.63 3.28 1.67 1.69 5.71 表 6 计算内存开销与计算时间
Table 6. Calculating memory overhead and computation time
calculating memory overhead/MB computation time/ms fine_lib 4.060 160 VERA_36H179 0.535 16 VERA_34H133 0.407 12 表 7 衰变热对功率的贡献
Table 7. Decay heat contribution to the power
decay heat contribution/% fine_lib VERA_36H179_16 deviation fine_lib VERA_36H179_16 deviation fine_lib VERA_36H179_16 deviation 0.8 GWd/tHM 20.0 GWd/tHM 60.0 GWd/tHM VERA_1A 6.37 6.00 −0.37 6.14 5.79 −0.35 6.16 5.69 −0.47 VERA_1B 6.39 6.01 −0.38 6.39 6.01 −0.38 6.18 5.70 −0.48 VERA_1C 6.40 6.02 −0.38 6.40 6.02 −0.38 6.16 5.70 −0.46 VERA_1D 6.40 6.02 −0.38 6.40 6.02 −0.38 6.16 5.70 −0.46 -
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