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Criticality Consequence Analysis Involving Intact PWR SNF in a Degraded 21 PWR Assembly Waste Package

John A. McClure
James R. Worsham, III
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The purpose of this analysis is to evaluate the transient behavior and consequences of a worst case criticality event involving intact pressurized water reactor (PWR) spent nuclear fuel (SNF) in a degraded basket configuration inside a 21 PWR assembly waste package (WP). The objective of this analysis is to demonstrate that the consequences of a worst case criticality event involving intact PWR SNF are insignificant in their effect on the overall radioisotopic inventory in a WP. An internal WP criticality is modeled in a manner analogous to transient phenomena in a nuclear reactor core. The light water reactor (LWR) transient analysis code, RELAP5/MOD3, is used to calculate the time evolution of the power level and other characteristics of a criticality involving PWR SNF. Reactivity tables based on changes in k-eff from a baseline configuration must be included in the RELAP5 input. The Monte Carlo N-Particle computer program, MCNP4A, is used to calculate a baseline k-eff for criticality safety evaluations and to determine the change in reactivity from one configuration to another.

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