Development and verification of PWR-core fuel management calculation code system NECP-Bamboo: Part II Bamboo-Core

As the core calculation component of our fuel management calculation code system NECP-Bamboo, Bamboo-Core provides all functions required by fuel management calculation. Compared with existing PWR core codes, its features can be summarized into three items. (1) The generalized cross section parameterization module provides an opportunity for users to design their own parameterization form. (2) It is the first time to employ the Variational Nodal Method (VNM) as the neutron diffusion solver in PWR core calculation. Compared with the currently widely employed transverse integration based nodal methods, two advantages can be guaranteed due to the elimination of the technique in VNM. Firstly, the three-dimensional continuous nodal flux distributions can be obtained once the VNM solution is be obtained, which can eliminate the large error in pin-power reconstruction due to the fact that only transverse integrated fluxes in three directions. Secondly, the heterogeneous node can be handled directly by extend the VNM from homogeneous to heterogeneous, which can fully eliminate the control rod cusping effect. (3) The critical boron concentration search module by using the newly proposed neutron balance equation converges faster than the legacy one based on linear extrapolation. Verification cases chosen for this code in this paper is the BEAVRS problem. Numerical results, including critical boron concentration, radial power distribution, axial power distribution and detector response rate, agree well with the reference calculations at both HZP and HFP conditions from the begin of life (BOL) to the end of life (EOL).