Analysis of transient fission gas behaviour in oxide fuel using BISON and TRANSURANUS

Abstract

The modelling of fission gas behaviour is a crucial aspect of nuclear fuel performance analysis in view of the related effects on the thermo-mechanical performance of the fuel rod, which can be particularly significant during transients. In particular, experimental observations indicate that substantial fission gas release (FGR) can occur on a small time scale during transients (burst release). To accurately reproduce the rapid kinetics of the burst release process in fuel performance calculations, a model that accounts for non-diffusional mechanisms such as fuel micro-cracking is needed. In this work, we present and assess a model for transient fission gas behaviour in oxide fuel, which is applied as an extension of conventional diffusion-based models to introduce the burst release effect. The concept and governing equations of the model are presented, and the sensitivity of results to the newly introduced parameters is evaluated through an analytic sensitivity analysis. The model is assessed for application to integral fuel rod analysis by implementation in two structurally different fuel performance codes: BISON (multi-dimensional finite element code) and TRANSURANUS (1.5D code). Model assessment is based on the analysis of 19 light water reactor fuel rod irradiation experiments from the OECD/NEA IFPE (International Fuel Performance Experiments) database, all of which are simulated with both codes. The results point out an improvement in both the quantitative predictions of integral fuel rod FGR and the qualitative representation of the FGR kinetics with the transient model relative to the canonical, purely diffusion-based models of the codes. The overall quantitative improvement of the integral FGR predictions in the two codes is comparable. Moreover, calculated radial profiles of xenon concentration after irradiation are investigated and compared to experimental data, illustrating the underlying representation of the physical mechanisms of burst release

Modeling Benchmark for FeCrAl Cladding in the IAEA CRP ACTOF: FeCrAl-C35M Material Models and Benchmark Cases Specifications

“…Finally, performing calculations for analogous cases with Zircaloy-4 cladding instead of FeCrAl cladding is suggested in order to obtain useful comparisons and additional insight. The models used in INL's code BISON for UO 2 fuel, Zircaloy-4 cladding and fuel-to-cladding gap are summarized in previous publications [26][27][28][29][30]. Nevertheless, for these standard materials and fuel performance aspects, it remains understood that other participants will apply their own codes' models.…”

INL/US DOE Participation in the Coordinated Research Project FUMAC: Final Report

“…In addition, BISON's model of fission gas swelling and release in UO 2 was extended to include a specific treatment of the burst release effect during transients. This transient model was originally developed based on power ramp data [8,9] and has not been re-calibrated and validated yet for LOCA transients. However, it has been applied with some success to RIA design basis accident simulations [6], and can potentially be adapted and applied to the improved simulation of FGR during LOCA transients.…”

Summary of BISON Development and Validation Activities - NEAMS FY16 Report

“…The transient model has been validated against several LWR fuel rod irradiation experiments. Details of model characteristics and validation are presented in [50]. A short summary is given hereinafter.…”

“…The micro-crack healing process is also accounted for. Model characteristics and equations are discussed in detail in [50].…”