Impact of new evaluated nuclear data libraries on core characteristics of innovative reactor designs

Abstract

The impact of new evaluated nuclear data libraries (ENDF/B, JENDL and JEFF) on core characteristics of thermal and fast spectra innovative reactor designs was investigated. The innovative reactor design with thermal neutron spectrum is represented by small-sized, long-life CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy producing reactors) HTGRs (High Temperature Gas-cooled Reactors) with uranium and thorium fuel cycles, while the one with the fast neutron spectrum is represented by compact, sodium-cooled BBRs (Breed-and-Burn Reactors). The CANDLE HTGR core characteristics (i.e. kinf, keff, discharge burnup, burning region moving velocity, core life time and axial power peaking factor) were evaluated by a dedicated deterministic neutronics and depletion code based on few-group neutron diffusion theory in 2-D RZ geometry, while the required microscopic cross sections were prepared by using SRAC2006 with JENDL-4.0, ENDF/B-VI and JEFF-3.1 based new SRAC2006 libraries. The BBR core characteristics were evaluated using a continuous energy Monte Carlo neutron transport code, SERPENT, with JENDL-4.0, ENDF/B-VILO, ENDF/B-VII.1 and JEFF-3.1.1 nuclear data based new libraries. The impact of new evaluated nuclear data libraries for innovative CANDLE HTGR core characteristics was found significantly larger for thorium fuel cycle than the one for uranium fuel cycle, especially in the discharge burnup, burning region moving velocity which affected the core life time significantly. The findings indicated the needs of more accurate nuclear data libraries for nuclides involved in thorium fuel cycle. The impact of new evaluated nuclear data libraries for innovative BBR core characteristics was found in a slightly large variation for keff evolution during burnup which in turn affected the estimated core life time. However, a good agreement within the statistical error on the integral kinetic parameters, Doppler reactivity coefficients, coolant density reactivity coefficients, axial and radial expansion reactivity coefficients, power density distributions can be observed among the libraries. In addition, the buildup of fission products and minor actinides were also similar.