Development of analysis method for sodium void reactivity of step type FBR cores by using group-wise Monte Carlo code

• Published in: Annals of nuclear energy Vol. 38; no. 6; pp. 1382 - 1388
• Main Authors: Yokoyama, Tsugio, Endo, Hiroshi, Ninokata, Hisashi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2011
• Subjects: Diffusion; FBR; Fluxes; GMVP; Leakage; Mathematical analysis; Monte Carlo method; Monte Carlo methods; Perturbation methods; Perturbation theory; Sodium; Sodium void reactivity; Step type core; Voids; Perturbation theory; Monte Carlo method; GMVP; Step type core; Sodium void reactivity; FBR
• ISSN: 0306-4549; 1873-2100
• DOI: 10.1016/j.anucene.2011.01.033

► The total sodium void reactivity of the step type FBR core is found to be negative. ► Component analysis of reactivity was conducted by group-wise Monte Carlo method. ► The ratio of leakage term to non-leakage term is about −0.5 for 90 cm height core. A new method is proposed to separate the sodium void reactivity of step type FBR cores to components including non-leakage terms and a leakage term by using a newly developed perturbation code MCPERT where fluxes and adjoint fluxes are derived from a group-wise Monte Carlo code. The step type FBR core is a core where the height of the inner core is smaller than that of the outer core and a large sodium plenum region is located above the core so as to decrease the sodium void reactivity. The conventional diffusion perturbation method cannot treat such a large void region due to the diffusion approximation, while the Monte Carlo code can treat it exactly. In this study, a group-wise Monte Carlo code GMVP with a 70-group constant set JFS-3-J3.3 is employed to evaluate the neutron fluxes and adjoint fluxes which are used as inputs to the MCPERT code to evaluate the non-leakage terms. The leakage term is derived from the difference of the total sodium void reactivity evaluated by the direct calculation of GMVP and the summation of the non-leakage terms. It is found that the proposed method can provide the result approximately consistent to the ratio of the reactivity components derived from the conventional method.