Finite volume method for fission gas release modeling

Bernard, L.; Bonnaud, Etienne

doi:10.1016/s0022-3115(96)00720-9

Cited by 17 publications

(9 citation statements)

References 23 publications

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“…where B 1 , B 2 , B 3 , and B MIN are all adjustable parameters of the incubation threshold calculation in the model and T B is the parameter of the incubation threshold calculation. Its values are taken from previous literature [44]. In this case, Parameters are given in this calculation:…”

Section: The Incubation Thresholdmentioning

confidence: 99%

Extended Development of a Fission Gas Release Behavior Model Inside Spherical Fuel Grains for LWR Reactors

Guo,

Cheng,

Wang

et al. 2023

Applied Sciences

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Fission gas plays a significant role in fuel rod performance following accidents. The amount of fission gas increases dramatically under accidental conditions. This leads to a subsequent rise in the fuel rod internal pressure and temperature due to aggravated gap conductance between the fuel pellet and cladding. As a result, fuel rod performance degrades. Therefore, studying fission gas behavior is crucial for accident assessment and evaluating fuel rod performance. Minimizing the Impact of fission gas on fuel rods is essential for maintaining their integrity and safety within nuclear reactors. One important aspect of ensuring safety is predicting fission gas release (FGR). In this study, we presented an extended model to be used in light water reactors (LWRs). The FGR can be modeled using COMSOL Multiphysics with the finite element method. This modeling approach considers both normal and abnormal conditions, with the latter categorized as Class-II type incidents. The model assumes that the gas diffusion inside a spherical grain varies over time. By examining perfect sinks with gas production, perfect sinks without gas production, and imperfect sinks under steady-state conditions, different initial and boundary conditions are set. To validate the accuracy and universality of expressions used in the model, input parameters from other models and experiments are utilized. By comparing the model’s results with these inputs, the accuracy and applicability of the expressions can be confirmed. This validation process ensures that the model provides reliable predictions for fission gas behavior in fuel rods under both normal and abnormal operating conditions. Based on our findings, it is evident that the FGR fraction displays an upward trend as diffusion coefficients and temperatures rise. Conversely, larger grain sizes and higher linear heat generation rates are associated with a reduction in the FGR fraction. Notably, enhanced resolution leads to a postponed onset of FGR. Furthermore, the influence of the diffusion coefficient on the FGR fraction primarily stems from the interconnected effects of temperature and linear heat generation rate.

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Section: The Incubation Thresholdmentioning

confidence: 99%

Extended Development of a Fission Gas Release Behavior Model Inside Spherical Fuel Grains for LWR Reactors

Guo,

Cheng,

Wang

et al. 2023

Applied Sciences

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“…Three regimes for the retention at grain boundaries are modeled: complete retention, partial retention, saturation with no retention. For UO 2 the critical saturation: According to Bernard et al (1997) the surface specific energy J J/m 2 ,r b =0.5 Pm, fc = 0.25, and with R= 8.31E-6 m 3 •MPa•K í1 •mol í1 we obtain:…”

Section: Determination Of the Steady State Gaseous Fission Product Comentioning

confidence: 99%

Improved Prediction of the Temperature Feedback in TRISO-Fueled Reactors

Ortensi¹,

Ougouag²

2009

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The Doppler feedback mechanism is a major contributor to the passive safety of gas-cooled, graphite-moderated, high-temperature reactors that use fuel based on Tristructural-Isotropic coated particles. It follows that the correct prediction of the magnitude and time-dependence of this feedback effect is essential to the conduct of safety analyses for these reactors. This report presents a fuel conduction model for obtaining better estimates of the temperature feedback during moderate and fast transients. The fuel model has been incorporated in the CYNOD-THERMIX-KONVEK suite of coupled codes as a single Tristructural-Isotropic (TRISO) particle within each calculation cell. The heat generation rate is scaled down from the neutronic solution and a Dirichlet boundary condition is imposed as the bulk graphite temperature from the thermal-hydraulic solution. This simplified approach yields similar results to those obtained with more complex methods, requiring multi-TRISO calculations within one control volume, but with much less computational effort. An analysis of the hypothetical total control ejection in the Pebble Bed Modular Reactor (PBMR)-400 design verifies the performance of the code during fast transients. In addition, the analysis of the earthquake-initiated event in the PBMR-400 design verifies the performance of the code during moderately slow transients. These analyses clearly depict the improvement in the predictions of the fuel temperature, and consequently, of the power escalations. In addition, a brief study of the potential effects of particle layer de-bonding on the transient behavior of high-temperature reactors is included. Although the formation of a gap occurs under special conditions, its consequences on the dynamic behavior of the reactor should be analyzed. The presence of a gap in the fuel can cause some unusual reactor behavior during fast transients, but still the reactor shuts down due to the strong feedback effects.

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“…In combination with the perfect sink boundary condition, the solutions are obtained by adding the resolution flux to the source term. On the other hand, the diffusion equation under the resolution flux is also solved by adopting an imperfect boundary condition [4,5,9]. Rearranging Eq.…”

Section: Fission Gas Release Under Irradiation-induced Resolution Conmentioning

confidence: 99%

“…As for purely numerical methods [6,7,9], the gas concentrations at nodal points are calculated in advance. The gas accumulation on a grain boundary and the fractional release are obtained by integrating the profile of a gas concentration.…”

Section: Time-varying Conditionmentioning

confidence: 99%

“…Even with these semi-analytical solutions, it is necessary to obtain their responses through several iterations when time-varying histories are considered. On the other hand there are several numerical solution methods for which the gas concentrations are calculated at nodal points in advance: finite difference method [6], finite element method (FEM) [7,8], and finite volume method [9]. These numerical attempts are more attractive in the sense that they are rather easily extended to versatile situations such as the modification of a boundary condition, time-varying problems, etc.…”

Section: Introductionmentioning

confidence: 99%

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