GET-based time-dependent lattice homogenization using a global-local approach

Schwanke, Peter; Nichita, Eleodor

doi:10.1016/j.anucene.2019.06.032

Cited by 1 publication

(4 citation statements)

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“…A recently developed GET-based time-dependent homogenization technique [1] that updates the nuclear parameters and the leakage-corrected DFs for every node at each time step is used to model the partial voiding of a 1D, 2G PHWR core. The core model consisting of 22 fuel nodes with two reflector nodes at either end to which vacuum boundary conditions are applied.…”

Section: Discussionmentioning

confidence: 99%

“…The time-dependent homogenization technique in [1] updates the nuclear parameters for every node in the PHWR model in response to the changes in the local flux occurring within each node at each time step. The DFs are also updated for every node at every time step by accounting for the changes in the boundary conditions that occur for each node due to the global variation in the flux across the core.…”

Section: Time-dependent Homogenizationmentioning

confidence: 99%

“…where ‫ݔ‬ ‫)ݐ(‬ and ‫ݔ‬ ‫)ݐ(‬ are as defined for eqn. (1) and N is the total number of nodes. The RMS percent differences in Fig.…”

Section: Figure 8 Time-dependent Discontinuity Factors and Assembly Discontinuity Factorsmentioning

confidence: 99%

“…A new technique was recently presented [1] that extends Generalized Equivalency Theory (GET) [2] to time-dependent problems by determining homogenized nuclear parameters and discontinuity factors at each time step using a global-local iterative scheme. The technique was applied to a one-dimensional (1D), twoenergy-group (2G), seven-assembly, boiling-water reactor (BWR) benchmark in which a step-reduction in the absorption cross sections was introduced in two of the assemblies.…”

Section: Introductionmentioning

confidence: 99%

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Time-Dependent Homogenization for Pressurized Heavy-Water Reactors

Schwanke

Nichita

2021

EPJ Web Conf.

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A new time-dependent homogenization approach that accounts for inter-assembly leakage has recently been proposed. The new technique extends Generalized Equivalence Theory (GET) to transient simulations through the use of time-dependent, leakage-corrected discontinuity factors that are calculated at each time step by means of a global-local iterative approach to account for the effect of neighbouring nodes so that highly heterogeneous cores are more accurately modelled than when employing single-node, zero-node-boundary-current Assembly Discontinuity Factors (ADFs). The technique has been previously tested for a one-dimensional, two-energy-group, BWR-like benchmark. The present work expands the analysis to a one-dimensional, two-energy-group, Pressurized Heavy-Water Reactor (PHWR) configuration. The PHWR configuration consists of 22 fuel nodes bounded on either side by two nodes of heavy-water (D2O) reflector. Each fuel node spans 28.575 cm and is a one-dimensional stylized representation of a 37-element, natural uranium fuel bundle with D2O coolant residing in a pressure tube that in turn resides in a calandria tube surrounded by D2O moderator. A simple transient induced by instantaneous half-core voiding of the D2O coolant is studied. Three types of calculations are performed: A reference, heterogeneous-node, fine-mesh calculation, a standardly-homogenized-node calculation and a GET-homogenized-node (using ADFs) calculation. The root-mean-square percent errors introduced by standard homogenization and ADF-based homogenization for kinetics calculations in PHWR cores are found to be 4% and 5%, respectively, after 0.5 s. This suggests that the use of a time-dependent homogenization method is desirable, and its use is shown to reduce the RMS errors to a maximum of 0.003% over the course of the transient. The conclusion is that although PHWR cores are not extremely heterogeneous, the accuracy of transient modelling for PHWRs is improved when using time-dependent homogenization over conventional ADFs and that the newly-developed time-dependent homogenization method promises to offer substantial improvements in accuracy for transient results with particular relevance to safety analyses.

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Section: Discussionmentioning

confidence: 99%

Section: Time-dependent Homogenizationmentioning

confidence: 99%

“…where ‫ݔ‬ ‫)ݐ(‬ and ‫ݔ‬ ‫)ݐ(‬ are as defined for eqn. (1) and N is the total number of nodes. The RMS percent differences in Fig.…”

Section: Figure 8 Time-dependent Discontinuity Factors and Assembly Discontinuity Factorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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