Analysis of the use of thorium in the GFR2400 gas-cooled fast reactor

Abstract

In this work the utilization of thorium in a gas cooled fast reactor was investigated. The study is based on the reference concept proposed by the French CEA (Commisariat à l'Energie Atomique et aux Energies Alternatives), with a thermal power of 2400 MWth (GFR2400). The Monte Carlo Serpent code, version 2.1.29, and the JEFF-3.1 cross section library was used to design a detailed 3D heterogeneous model of the GFR2400 reactor core. The calculations were performed for the reference fuel, uranium plutonium carbide (U, Pu)C and the proposed one, thorium plutonium carbide (Th, Pu)C. The effective multiplication factor for both models was calculated at beginning of life, as well as the neutron spectrum and the neutron flux and power distributions. A safety parameters assessment such as the Doppler constant, the depressurization reactivity effect, the control rods worth and the reactor shutdown margin was also performed. Kinetic parameters such as the effective delayed neutron fraction and the neutron generation time were also determined. The keff variation and the fuel evolution were analyzed for an operation time of 1450 effective full power days. The results show that under a single batch irradiation scheme, the breeding of 233U of our proposed (Th, Pu)C model can be high enough as to enlarge the operating cycle without degradation of the main steady-state neutronic parameters, which remain close to those of the (U, Pu)C reference core.