Date of Award

3-2023

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

John W. McClory, PhD

Abstract

The 2022 Russia-Ukraine War marks the first time in modern history of conventional military forces targeting and seizing control of an operational nuclear power plant. Power supply and operational cooling systems are critical to avert reactor loss-of-coolant accidents (LOCA) in the event of emergency shutdown, or SCRAM. A wartime non-design based reactor accident causing loss of reactor power and coolant supply would require an emergency heat exchange via coolant to mitigate reactor core heat. At present, the military does not have a well-defined model which characterizes this requirement for operational planning should such an event occur. SCALE 6.2.4 is used to determine the spent fuel decay heat for two reactor models – an experimental 5 MWe Magnox GCR and a commercial VVER-1000. Assumptions are made to account for the transient state of the reactor during the full time-span of the LOCA event. Following SCRAM and full LOCA, the spent fuel decay heat rate is shown at 24 hours to be on average 96.3 kW ± 0.83% and 9.17 MW ± 0.67%, at full core equivalents of the GCR and VVER-1000, respectively. This corresponds to 0.38% and 0.31% steady thermal power levels – matching ANS 5.1 (1973) approximations. Upon an emergency arrival 24hrs post-SCRAM, average volumetric flow rates of 287 gpm and 330 gpm for the GCR and VVER are estimated to achieve the decay heat-transfer necessary for fuel temperature abatement from 2847 ◦C to 400 ◦C. These rates are shown to decrease exponentially as a function of time, as expected. Advanced accident analytical codes should be used in future work to improve the modeling of LOCA progression after SCRAM and to develop radiological exposure and release metrics for comparative studies. This study may serve as a base model for the benefit of DoD organizations such as the 20th CBRNE Command.

AFIT Designator

AFIT-ENP-MS-23-M-093

Comments

PA cleared, 88ABW-2023-0156

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