Fission product model for BWR lattice calculation code.

Abstract

A benchmark calculation of full fission product was performed for thermal reactor application using an isotope transmutation code DCHAIN based on 185 nuclides with revised nuclear data library. The fission product model for BWR lattice calculation was studied and tested with the benchmark results, and a model containing 45 explicit nuclides and one pseudo nuclide was selected as a reasonably best model to predict the burnup reactivity with high precision for practically all types of fuel and reactor operating conditions. The evaluated thermal cross section and resonance integral for the pseudo nuclide are o2.2oo=2.6 b and RI = 10.6 b, combined with the pseudo fission yield values of 1.3898, 1.3233, 1.3675 and 1.2773 for fissions from 286 U, 288 U, 239 Pu and 241 Pu, respectively. The present results are believed as equally applicable to PWR lattice calculation.

OECD/NEA Burnup Credit Calculational Criticality Benchmark Phase I-B Results

“…Data library: Energy-group structure: GAM-type 68 groups for fast and epithermal range, THERMOS-type 30 groups for thermal range Data source: 235 U, 238 U, 239 Pu, 240 Pu -ENDF/B-V 241 Pu, 242 Pu -ENDF/B-IV All other actinides -JENDL-3 Fission products -mostly ENDF/B-IV Fission product chain: 45 explicit fission products plus 1 lumped pseudo-fission-product model. 5 Note: 95 Mo is not treated as an explicit fission product in this fission-product model, while it has been taken into account as one of the major contributors to the pseudo-fission-product poisoning as described in ref. 5.…”

“…5 Note: 95 Mo is not treated as an explicit fission product in this fission-product model, while it has been taken into account as one of the major contributors to the pseudo-fission-product poisoning as described in ref. 5.…”

“…Such reliance on the reduced reactivity of spent fuel for criticality control is referred to as 6burnup credit. 5 However, before such an approach can be approved by licensing agencies, it is necessary to demonstrate that the available criticality safety calculational tools are appropriate for application to spent or partially burned fuel systems. Toward this end, a suite of calculational benchmarks related to burnup credit criticality analysis has been conceived and proposed by the Nuclear Energy Agency (NEA) of the Organization for Economic Cooperation and Development (OECD) and analyzed by numerous participants.…”

Analysis of Reactivity Coefficients of Chernobyl Reactor by Cell Calculation

“…Linear heat generation rate was kept constant during burn-up. As for fission product (FP) chain model, Iijima model( 2 ) was taken which includes 45 explicit nuclides and one pseudo FP. Table 2 shows the composition of actinide nuclides at several burn-up steps.…”