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Atmospheric Transport Results for Fukushima Daiichi Units 1, 2, and 3

Bixler, Nathan E.; Clayton, Daniel J.

Many of the BSAF participants provided source terms to be evaluated by Sandia National Laboratories by applying HYSPLIT [2,3,4,5] to treat atmospheric transport and dispersion (ATD). The objective was to estimate the deposition pattern that would have resulted from the predicted source term. For the participants who provided results for all three units, the overall deposition pattern can be compared with the observed deposition pattern; for the participants who submitted source terms for one or two units, the results can only be compared with each other. Atmospheric transport calculations were performed for a single isotope, Cs-137. It is the primary isotope of concern for long-term contamination and it is relatively easy to measure the strong gamma signal produced from its short-lived decay product, Ba-137m. All the atmospheric transport calculations used the actual location of each of the three units; the releases were not presumed to emanate from the same location. Also, when they were provided, release energies were accounted for in the analysis, so plume lofting was considered. Finally, aerosol size distribution data were considered for purposes of estimating deposition. In some cases, aerosol size distribution can significantly influence deposition patterns.

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TYPE Other Report YEAR 2018
DOIOSTI

SecPop Version 4: Sector Population Land Fraction and Economic Estimation Program: Users? Guide Model Manual and Verification Report

Weber, Scott; Bixler, Nathan E.; McFadden, Katherine L.

In 1973 the U.S. Environmental Protection Agency (EPA) developed SecPop to calculate population estimates to support a study on air quality. The Nuclear Regulatory Commission (NRC) adopted this program to support siting reviews for nuclear power plant construction and license applications. Currently SecPop is used to prepare site data input files for offsite consequence calculations with the MELCOR Accident Consequence Code System (MACCS). SecPop enables the use of site-specific population, land use, and economic data for a polar grid defined by the user. Updated versions of SecPop have been released to use U.S. decennial census population data. SECPOP90 was released in 1997 to use 1990 population and economic data. SECPOP2000 was released in 2003 to use 2000 population data and 1997 economic data. This report describes the current code version, SecPop version 4.3, which uses 2010 population data and both 2007 and 2012 economic data. It is also compatible with 2000 census and 2002 economic data. At the time of this writing, the current version of SecPop is 4.3.0, and that version is described herein. This report contains guidance for the installation and use of the code as well as a description of the theory, models, and algorithms involved. This report contains appendices which describe the development of the 2010 census file, 2007 county file, and 2012 county file. Finally, an appendix is included that describes the validation assessments performed.

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TYPE Other Report YEAR 2018
DOIOSTI

Sequoyah SOARCA uncertainty analysis of a STSBO accident

PSAM 2018 - Probabilistic Safety Assessment and Management

Bixler, Nathan E.; Dennis, Matthew L.; Brooks, Dusty M.; Osborn, Douglas M.; Ghosh, S.T.; Hathaway, Alfred

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 and offsite consequence analyses were performed with MACCS. The analysis included more than 500 MELCOR and MACCS simulations to account for uncertainty in important accident progression and offsite consequence input parameters. Consequences from severe nuclear power plant accidents modeled in this and previous SOARCA analyses are smaller than calculated in earlier studies. The delayed releases calculated provide more time for emergency response actions. The results show that early containment failure is very unlikely, even without successful use of igniters. However, these results are dependent on the distributions assigned to safety valve failure-to-close parameters, and considerable uncertainty remains on the true distributions for these parameters due to very limited test data. Even for scenarios resulting in early containment failure, the calculated individual latent fatal cancer risks are very small. Early and latent-cancer fatality risks are one focus of this paper. Regression results showing the most influential parameters are also discussed.

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TYPE Conference Poster YEAR 2018
OSTIScopus
Results 26–50 of 121
Results 26–50 of 121