State-of-the-Art Reactor Consequence Analyses (SOARCA) Project: Sequoyah Integrated Deterministic and Uncertainty Analyses (NUREG/CR-7245)

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Publication Information

Manuscript Completed: November 2017
Date Published: October 2019

Prepared by:
Severe Accident Analysis Department
Sandia National Laboratories
P.O. Box 5800 MS-0848
Albuquerque, NM 87185-0748

S. Tina Ghosh, NRC Project Manager

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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The U.S. Nuclear Regulatory Commission initiated the state-of-the-art reactor consequence analyses (SOARCA) project to develop realistic estimates of the offsite radiological health consequences for potential severe reactor accidents. The SOARCA analysis of an ice condenser containment plant was performed because its relatively low design pressure and reliance on igniters makes it potentially susceptible to early containment failure from hydrogen combustion during a severe accident. The focus was on station blackout accident scenarios where all alternating current power is lost. Accident progression calculations used the MELCOR computer code. For scenarios leading to an offsite release of radioactive material, SOARCA analyzed atmospheric dispersion, emergency response, and potential health consequences using the MELCOR Accident Consequence Code System (MACCS). The analysis included hundreds of MELCOR and MACCS simulations to account for uncertainty in important accident progression and offsite consequence input parameters. This analysis reinforces the results of past analyses of ice condenser containments showing that successful use of igniters is effective in averting early containment failure. Even for scenarios resulting in early containment failure, the calculated individual latent fatal cancer risks are very small.

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