United States Nuclear Regulatory Commission - Protecting People and the Environment

MELCOR Best Practices as Applied in the State-of-the-Art Reactor Consequence Analyses (SOARCA) Project (NUREG/CR-7008)

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Publication Information

Manuscript Completed: June 2014
Date Published:
August 2014

Prepared by:
Kyle Ross*, Jesse Phillips*, Randall O. Gauntt*,
Kenneth C. Wagner**

*Sandia National Laboratories
Albuquerque, New Mexico 87185
Operated for the U.S. Department of Energy

**dycoda, LLC

Jonathan Barr, NRC Project Manager

Prepared for:
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code N6306

Availability Notice


The modeling approach used in the State-of-the-Art Reactor Consequence Analyses (SOARCA) project to characterize the release of radionuclides to the environment accompanying a postulated severe (core damage) accident is based on plant-specific applications of the MELCOR computer code. MELCOR is a state-of-the-art computational model developed by Sandia National Laboratories for the U.S. Nuclear Regulatory Commission. Due to large uncertainties in many aspects of severe accident behavior, MELCOR provides the code user a wide spectrum of options for modeling uncertain physical phenomena and characterizing plant response to beyond design basis accident conditions. The selection and exercise of the available modeling capabilities are an important aspect of the overall modeling approach.

This document describes the specific manner in which MELCOR modeling capabilities were used to represent important, and in some cases uncertain, aspects of severe accident behavior in the SOARCA project. This description includes choices made among alternate modeling ptions offered through code input, changes to selected input parameters from those offered as ‘default’ values, and in some cases, user-generated ‘models’ to represent features of plant response to a severe accident that are not directly available in MELCOR. Collectively, these features represent the "SOARCA best practice" guidance for using MELCOR to calculate severe accident behavior in operating nuclear power plants.

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