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DOE OSTI · 1897618

Validating Intra-Plate Power Distributions in the Advanced Test Reactor

Bays, Samuel E.·Nielsen, Joseph·Cogliati, Joshua·Wemple, Charles
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Abstract

We report that the neutronics software, HELIOS, was validated in 2015 for performing core reload design and safety analysis of the Advanced Test Reactor. However, when HELIOS was benchmarked against historic fission-wire measurements (i.e., zero-power full-core measurements) a statistically resolved calculation-to-measurement bias was discovered. The azimuthal power along each fuel plate computed by HELIOS has consistently shown to under-predict measurements made by fission-wires in historic zero-power tests near the fuel element side-plates. It was hypothesized during the HELIOS software validation work, that this bias is attributable to local moderation in coolant vents in the side-plates axially just above and below the fission-wires on the fuel-plate edges. This work used detailed MCNP and MC21 models of the side-plate vents to test this hypothesis. By comparing the average azimuthal biases between HELIOS, and 2D and 3D MCNP models, and a 3D MC21 model, it was found that the HELIOS azimuthal bias is not due to the measurement.

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21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTSHELIOSMC21MCNPadvanced test reactorfission wireverification and validation

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Bays, Samuel E., Nielsen, Joseph, Cogliati, Joshua, Wemple, Charles. 2021-11-15. Validating Intra-Plate Power Distributions in the Advanced Test Reactor. https://doi.org/10.1080/00295450.2021.1980320

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