Validation and Verification for Nuclear Design Software Package TORCH V2.0 of Pressurized Water Reactor

Abstract

A conventional two-step approach of a transport calculation and a nodal diffusion calculation, such as CASMO/SIMULATE, APOLLO/SMART, was used in the light water reactor core design for decades. A new PWR core nuclear design software package named TORCH V20 was developed by Nuclear Power Institute of China (NPIC), and many advanced methodologies were implemented in TORCH V20 to enhance accuracy and performance. Based on the twostep calculation scheme, TORCH V20 mainly contains lattice physics code for assembly homogenization, link calculation code for fewgroup constant parameterization and core simulation code for fewgroup core calculation. The onestep direct heterogeneous calculation code KYLIN V20 based on finegroup structure was employed. KYLIN V20 was used to generate the homogenized parameters, including homogenized crosssection, diffusion coefficients, discontinuity factors and so on. Considering the fact that a certain state required by the reactor core calculation may be different from the ones provided by KYLIN V2.0, a process was required to provide a table between those neutronics few-group constants and state parameters based on the discrete points provided by lattice calculations. The code named PACFAC was used to provide the table for the core simulation code CORCA3D. The neutron diffusion equation would be calculated for core fuel management in CORCA3D. The calculation modules of each code were already verified against various benchmark problems, whereas the work presented in this paper focuses on the verification and validation (V&V) of linked code system TORCH V20 for the core design of pressurized water reactors (PWRs). The measured values of reactor startup physics test and nuclear power plant operation from six PWR NPPs (Daya Bay NPP, Ling’ao NPP, Fangjiashan NPP, Qinshan NPP, Hainan Changjiang NPP, Fuqing NPP) were utilized to do the comparison and analysis for V&V. Part of the reactor startup physics tests and a total of 85 cycles of 14 NPP units were simulated by TORCH V2.0. However, the content of the reactor startup physics tests varies in different cycles. Compared parameters of reactor startup physics test contain critical boron concentration, control rod integral value, boron differential value and isothermal temperature coefficient. Compared parameters of nuclear power plant operation contain critical boron concentration, assemblywise power distribution, hot spot factor and nuclear enthalpy rise factor. With the exception of very few results of critical boron concentration for some deep operation cycles, all the results of compared parameters are in good accordance with the measured values, which are agreed with the industrial acceptance criteria. The results show that the software TORCH V20 has reliable calculation ability and is applicable to the PWR nuclear power engineering design which is based on square fuel assembly. In the future, the uncertainty analysis of TORCH V20 would be carried out for the comprehensive verification and validation.

Keywords

• core nuclear design
• startup physics test
• nuclear power plant operation data
• validation and verification