基于CENDL-3.2的宽群屏蔽数据库开发与验证

为开展反应堆屏蔽计算研究，使用NECP-Atlas和NECP-Shield程序，基于我国最新的评价核数据库CENDL 32开发了宽群屏蔽数据库NECL CP29，该数据库的中子能群结构采用基于粒子群算法优化的29群结构。为验证该数据库，使用国际屏蔽基准题库SINBAD中包括Iron 88、ASPIS NG和HBR 2等在内的屏蔽基准题进行了计算，计算结果不仅与实验测量值进行了比较，而且与国际主流屏蔽数据库BUGLE B7和BUGLE 96的计算结果进行了对比。验证结果表明，NECL CP29数据库的计算值与测量值吻合较好，计算精度整体上优于BUGLE B7和BUGLE 96，且优化的能群结构有效提升了计算效率。

Development and Validation of Broad-group Shielding Library Based on CENDL-3.2

The neutron and photon shielding is an important part of the reactor design for safety of people and facilities. CENDL-3.2 is the latest Chinese evaluated nuclear data library released by China Nuclear Data Center (CNDC) in 2020. Many nuclides were improved with new evaluation techniques and experimental data. Thanks to the high calculation efficiency, broad group shielding libraries are widely used in shielding calculation. To carry on the research on reactor shielding calculation, the codes NECP Atlas and NECP Shield were applied to develop the broad group shielding library NECL CP29 based on CENDL 32. Generating a broad group shielding library needs three stages. Firstly, NECL CP199, a fine group library with 199 neutron groups and 42 photon groups, was produced using NECP Atlas and NECP Shield. When producing the fine group library, the neutron weight function consists of a 1/E spectrum, a fission spectrum and a thermal Maxwellian spectrum. The photon weight function consists of a 1/E spectrum at the middle energies. At the high and low energy, the spectrum goes down. Secondly, a typical 1D PWR model used in producing BUGLE libraries was calculated using NECL CP199 to obtain the fine group flux distribution in the model. Before calculating the model, the nuclides were self shielded using several different models, including a PWR pin cell model for the core, an iron water model for the down comer, a concrete model for the concrete, a carbon steel model for the pressure vessel and a stainless steel model for the baffle and barrel. Lastly, the fine group fluxes in core, down comer, pressured vessel and concrete were chosen to collapse fine group cross sections of self shielded nuclides to generate a broad group library. Moreover, the fine group flux in concrete was applied to collapse the fine group infinite diluted cross sections of all nuclides from NECL CP199. The energy group structure has an important influence on the accuracy and efficiency for shielding calculation. To obtain an improved broad group structure for better accuracy and efficiency, particle swarm optimization (PSO) was used. The research on application of PSO in optimizing the energy group structure for shielding calculation was performed, including the combination of PSO process and the generation of the broad group library, the mapping of PSO variables and the construction of fitness function. A 29 group structure was optimized using PSO. NECL CP29 with the optimized 29 group structure was generated. To validate NECL CP29 broad group shielding library, some benchmarks in SINBAD, the international shielding benchmark library, were calculated, including Iron 88, ASPIS NG, and HBR 2. The calculated results were compared with the measured results. Moreover, the results of BUGLE B7 and BUGLE 96 which are famous international broad group shielding libraries were also used for comparison. The numerical results show that the calculated values using NECL CP29 agree well with the measured values. Compared with BUGLE B7 and BUGLE 96 whose numbers of neutron groups are all 47, the calculation accuracy of NECL-CP29 is better. Especially in calculating the reaction rate of 197Au(n,γ) in Iron 88 benchmark, the results given by NECL CP29 are much closer to the measured values than BUGLE B7. Thanks to the optimized energy group structure with less neutron energy group number, the computational efficiency is obviously improved.