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Strategies and decisions to protect emergency responders, the public, and critical infrastructure against the effects of a radiological dispersal device detonated outdoors must be made in the planning stage, not in the early period just after an attack. This contrasts with planning for small-scale types of radiological or nuclear emergencies, or for a large-scale nuclear-power-type accident that evolves over many hours or days before radioactivity is released to the environment, such that its effects can be prospectively modeled and analyzed. By the time it is known an attack has occurred, most likely there will have been casualties, all the radioactive material will have been released, plume growth will be progressing, and there will be no time left for evaluating possible countermeasures. This paper offers guidance to planners, first responders, and senior decision makers to assist them in developing strategies for protective actions and operational procedures for the first 48 hours after an explosive radiological dispersal device has been detonated.

One of the key issues in the aftermath of an exploded radiological dispersal device from a terrorist event is that of the contaminated victim and the concern among healthcare providers for the harmful exposures they may receive in treating patients, especially if the patient has not been thoroughly decontaminated. This is critically important in the event of mass casualties from a nuclear or radiological incident because of the essential rapidity of acute medical decisions and that those who have life- or limb-threatening injuries may have treatment unduly delayed by a decontamination process that may be unnecessary for protecting the health and safety of the patient or the healthcare provider. To estimate potential contamination of those exposed in a radiological dispersal device event, results were used from explosive aerosolization tests of surrogate radionuclides detonated with high explosives at the Sandia National Laboratories. Computer modeling was also used to assess radiation dose rates to surgical personnel treating patients with blast injuries who are contaminated with any of a variety of common radionuclides. It is demonstrated that exceptional but plausible cases may require special precautions by the healthcare provider, even while managing life-threatening injuries of a contaminated victim from a radiological dispersal device event. Copyright © 2005 Health Physics Society.

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In support of the Cassini Mission Final Safety Analysis Report (FSAR), Sandia National Laboratories (SNL) was requested by Lockheed Martin Corporation (LMC) to investigate for various scenarios, the distribution of aerosol and particulate mass in a stabilized buoyant plume created as a result of a fireball explosion. The information obtained from these calculations is to provide background information for the radiological consequence analysis of the FSAR. Specifically, the information is used to investigate the mass distribution within the ''cap and stem'' portions of the initial fireball plume, a modeling feature included in the SATRAP module in the LMC SPARRC code. The investigation includes variation of the plume energy and the application of several meteorological conditions for a total of seven sensitivity case studies. For each of the case studies, the calculations were performed for two configurations of particle mass in the plume (total mass and plutonium mass).

Uncertainty distributions for specific parameters of the Cassini General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) Final Safety Analysis Report consequence risk analysis were revised and updated. The revisions and updates were done for all consequence parameters for which relevant information exists from the joint project on Probabilistic Accident Consequence Uncertainty Analysis by the United States Nuclear Regulatory Commission and the Commission of European Communities.

A series of two-dimensional hydrodynamic calculations using the two-dimensional Second- order Hydrodynamic Automated Mesh Refinement Code (SHAMRC) developed by Applied Research Associates, Inc. (ARA), was made with the objective of understanding the behavior of aqueous foams in the presence of a C4-generated blast wave. A full three-phase water equation-of-state was incorporated in the first calculation. Comparison of the results of the first calculation with experimental data collected by Sandia National Laboratories (SNL) indicated that the interaction was much more complicated than could be represented by a mixture of detonation products, air, and water in local temperature and pressure equilibrium. Other models were incorporated in the code to examine the effects of thermal non-equilibrium between water and the gases and allowed for two-phase flow. The water droplets were allowed to slip relative to the gas velocity, providing non-equilibrium for the velocity distribution. These models permitted heated liquid droplets to be accelerated at high pressures and transported through and ahead of the decaying shock front. The droplets then exchanged momentum and energy with the foam ahead of the shock and preconditioned the medium through which the shock was propagating. This process had the effect of diffusing the shock front and its associated energy. These relatively high resolution calculations develop numerical representations of the Rayleigh-Taylor instabilities at the detonation products/foam interface. This unstable interface plays in important role in understanding the behavior of the interaction of the detonation products with the foam. Figure 4 clearly shows the developing instabilities at the interface and an inward facing shock at a radius of 25 cm. The results of the calculations using the various models can be edited to provide the total energy exchanged between materials, the fraction of water vaporized, and the extent of detonation products as a function of time.

The US Nuclear Regulatory Commission (USNRC) and the European Commission (EC) have conducted a formal expert judgment elicitation jointly to systematically collect the quantitative information needed to perform consequence uncertainty analyses on a broad set of commercial nuclear power plants. Information from three sets of joint US/European expert panels was collected and processed. Information from the three sets of panels was collected in the following areas: in the phenomenological areas of atmospheric dispersion and deposition, in the areas of ingestion pathways and external dosimetry, and in the areas of health effects and internal dosimetry. This exercise has demonstrated that the uncertainty for particular issues as measured by the ratio of the 95th percentile to the 5th percentile can be extremely large (orders of magnitude), or rather small (factor of two). This information has already been used by many of the experts that were involved in this process in areas other than the consequence uncertainty field. The benefit to the field of radiological consequences is just beginning as the results of this study are published and made available to the consequence community.

The purpose of this discussion is to introduce the session on the Progress on the Resolution of Severe Accident Issues. There has been much work in the area of resolution of severe accident issues over the past few years. This work has been focused on those issues most important to risk as assessed by comprehensive studies such as NUREG-1150. In particular, issues associated with early containment failure have been analyzed. These efforts to resolve issues have been hampered by the fact that {open_quotes}issue resolution{close_quotes} has not always been well defined. The term {open_quotes}issue resolution{close_quotes} conjures tip different images for the regulator, the accident analyst, the physicist, and the probabalist. In fact it is common to have as many different images of issue resolution as there are people in the room. This issue is complicated by the fact that the uncertainty in severe accident issues is enormous. (When convolved, the quantitative uncertainty in an integrated analysis due to severe accident issues can span several orders of magnitude.) In this summary, hierarchy is presented in an attempt to add some perspective to the resolution of issues in the face of large uncertainties. Recommendations are also made for analysts communicating in the area of issue resolution.

The development of two new probabilistic accident consequence codes, MACCS and COSYMA, was completed in 1990. These codes estimate the risks presented by nuclear installations based on postulated frequencies and magnitudes of potential accidents. In 1991, the US Nuclear Regulatory Commission (NRC) and the Commission of the European Communities (CEC) began a joint uncertainty analysis of the two codes. The ultimate objective of the joint effort was to develop credible and traceable uncertainty distributions for the input variables of the codes. Expert elicitation was identified as the best technology available for developing a library of uncertainty distributions for the selected consequence parameters. The study was formulated jointly and was limited to the current code models and to physical quantities that could be measured in experiments. Experts developed their distributions independently. To validate the distributions generated for the wet deposition input variables, samples were taken from these distributions and propagated through the wet deposition code model. Resulting distributions closely replicated the aggregated elicited wet deposition distributions. To validate the distributions generated for the dispersion code input variables, samples from the distributions and propagated through the Gaussian plume model (GPM) implemented in the MACCS and COSYMA codes. Project teams from the NRC and CEC cooperated successfully to develop and implement a unified process for the elaboration of uncertainty distributions on consequence code input parameters. Formal expert judgment elicitation proved valuable for synthesizing the best available information. Distributions on measurable atmospheric dispersion and deposition parameters were successfully elicited from experts involved in the many phenomenological areas of consequence analysis. This volume is the first of a three-volume document describing the project.

This paper briefly describes an ongoing project designed to assess the uncertainty in offsite radiological consequence calculations of hypothetical accidents in commercial nuclear power plants. This project is supported jointly by the Commission of European Communities (CEC) and the US Nuclear Regulatory Commission (USNRC). Both commissions have expressed an interest in assessing the uncertainty in consequence calculations used for risk assessments and regulatory purposes.

In this study, a discrete element technique was used to simulate drop breakup in two dimensions. A series of simulations in which the drop breakup occurred in the presence of a flow field was performed. The density ratio of the flow field to the drop in the simulations was comparable to many of the isothermal liquid/liquid drop breakup experiments performed to investigate hydrodynamic breakup during Fuel Coolant Interactions (FCIs). The randomly directed internal kinetic energy of the drop increased rapidly at the beginning of the interaction between the drop and the flow field due to momentum transfer from the flow field to the drop. After the initial increase in internal energy of the drop, the momentum transferred from the flow field to the drop in the form of translational kinetic energy of the center of mass of the drop. It was also observed that the drops simulated in the presence of a flow field required higher internal kinetic energies to fragment than did the drops observed in the simulations performed in the absence of a flow field.