Publications

Abstract not provided.

Abstract not provided.

The State-of-the-Art Reactor Consequence Analyses (SOARCA) project for the Peach Bottom Atomic Power Station (the pilot boiling-water reactor) and Surry Power Station (the pilot pressurized-water reactor) represents the most complex deterministic MELCOR analyses performed to date. Uncertainty analyses focusing on input parameter uncertainty are now under way for one scenario at each pilot plant. Analyzing the uncertainty in parameters requires technical justification for the selection of each parameter to include in the analyses and defensible rationale for the associated distributions. This paper describes the methodology employed in the selection of parameters and corresponding distributions for the Surry uncertainty analysis, and insights from applying the methodology to the MELCOR parameters.

Abstract not provided.

This paper describes the MELCOR Accident Consequence Code System, Version 2 (MACCS2) dose-truncation sensitivity of offsite consequences for the uncertainty analysis of the State-of-the-Art Reactor Consequence Analyses unmitigated long-term station blackout severe accident scenario at the Peach Bottom Atomic Power Station. Latent-cancer-fatality (LCF) risk results for this sensitivity study are presented for three dose-response models. LCF risks are reported for circular areas ranging from a 10-to a 50-mile radius centered on the plant. For the linear, no-threshold, sensitivity analysis, all regression methods consistently rank the MACCS2 dry deposition velocity and the MELCOR safety relief valve (SRV) stochastic failure probability, respectively, as the most important input parameters. For the alternative dose-truncation models (i.e., USBGR (0.62 rem/yr) and HPS (5 rem/yr with a lifetime limit of 10 rem)) sensitivity analyses, the regression methods consistently rank the MACCS2 inhalation protection factor for normal activity, the MACCS2 lung lifetime risk factor for cancer death, and the MELCOR SRV stochastic failure probability as the most important input variables. The important MELCOR input parameters are relatively independent of the dose-response model used in MACCS2. However, the MACCS2 input variables depend strongly on the dose-response model. The use of either the USBGR or the HPS dose-response model emphasizes MACCS2 input variables associated with doses received in the first year and deemphasizes MACCS2 input parameters associated with long-term phase doses beyond the first year.

This paper describes the MELCOR Accident Consequence Code System, Version 2(MACCS2), parameters and probabilistic results of offsite consequences for the uncertainty analysis of the State-of-the-Art Reactor Consequence Analyses unmitigated long-term station blackout accident scenario at the Peach Bottom Atomic Power Station. Consequence results are presented as conditional risk (i.e., assuming the accident occurs) to individuals of the public as a result of the accident - latent-cancer-fatality (LCF) risk per event or prompt-fatality risk per event. For the mean, individual, LCF risk, all regression methods at each of the circular areas around the plant that are analyzed (10-mile to 50-mile radii are considered) consistently rank the MACCS2 dry deposition velocity, the MELCOR safety relief valve (SRV) stochastic failure probability, and the MACCS2 residual cancer risk factor, respectively, as the most important input parameters. For the mean, individual, prompt-fatality risk (which is zero in over 85% of the Monte Carlo realizations) within circular areas with less than a 2-mile radius, the non-rank regression methods consistently rank the MACCS2 wet deposition parameter, the MELCOR SRV stochastic failure probability, the MELCOR SRV open area fraction, the MACCS2 early health effects threshold for red bone marrow, and the MACCS2 crosswind dispersion coefficient, respectively, as the most important input parameters. For the mean, individual prompt-fatality risk within the circular areas with radii between 2.5-miles and 3.5-miles, the regression methods consistently rank the MACCS2 crosswind dispersion coefficient, the MACCS2 early health effects threshold for red bone marrow, the MELCOR SRV stochastic failure probability, and the MELCOR SRV open area fraction, respectively, as the most important input parameters.

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The objectives of this study are to identify and evaluate alternative protective action recommendations (PARs) that could reduce dose to the public during a radiological emergency and to determine whether improvements or changes to the federal guidance would be beneficial. The emergency response strategies considered in this study are the following: (1) standard radial evacuation; (2) shelter-in-place followed by radial evacuation; (3) shelter-in-place followed by lateral evacuation; (4) preferential sheltering followed by radial evacuation; and (5) preferential sheltering followed by lateral evacuation. Radial evacuation is directly away from the plant; lateral evacuation is azimuthally (around the compass) away from the direction of the wind. Shelter-in-place is a protective action strategy in which individuals remain in their residence, place of work, or other facility at the time that a general warning is given. Preferential sheltering involves moving individuals to nearby, large buildings, e.g., high-school gymnasiums or courthouses, that afford greater protection than personal residences. This study shows that there are benefits to sheltering if followed by lateral evacuation. However, if the lateral evacuation strategy cannot be implemented, then early radial evacuation is often preferable. The most appropriate PAR depends on the evacuation time estimate (ETE) and, therefore, it is desirable to reduce the uncertainty associated with the ETE. Nuclear Regulatory Commission (NRC) guidance to commercial power plants currently allows for sheltering and/or evacuation as an emergency response to a serious nuclear accident. Frequently, however, licensees and states default to evacuation strategies and do not consider sheltering. Here we evaluate several alternative strategies to determine if standard radial evacuation is best or if other options could reduce the overall risk to the public. We consider two source terms based on the NUREG-1150 study. These involve a rapid release of radioactive material into the atmosphere and a more gradual release. Two variations in timing have also been investigated, but are not reported here. The evaluation was performed for a generic site, which uses a uniform population distribution and typical Midwest meteorological data (Moline, IL). Additional parameters that are varied in the study are the ETE (4-, 6-, 8-, and 10-hour ETEs are considered) and the duration of sheltering (2-, 4-, and 8-hr sheltering periods are considered). Additional sensitivity studies were performed to investigate nonuniform evacuation speed caused by traffic congestion, the time needed to reach a preferential shelter, and the effect of adverse weather conditions as opposed to favorable weather conditions. Adverse weather conditions are those for which precipitation occurs before the leading edge of the plume exits the 10-mile emergency planning zone (EPZ). Ultimately, emergency response strategies are ranked by their potential to reduce adverse health effects for residents within the EPZ. © 2006 by ASME.

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The deployment of the Joint Technical Operations Team (JTOT) is evolving toward a lean and mobile response team. As a result, opportunities to support more rapid mobilization are being investigated. This study investigates three specific opportunities including: (1) the potential of using standard firefighting equipment to support deployment of the aqueous foam concentrate (AFC-380); (2) determining the feasibility and needs for regional staging of equipment to reduce the inventory currently mobilized during a JTOT response; and (3) determining the feasibility and needs for development of the next generation AFC-380 to reduce the volume of foam concentrate required for a response. This study supports the need to ensure that requirements for alternative deployment schemes are understood and in place to support improved response activities.