Robert J. Budnitz

Recommendations for probabilistic seismic hazard analysis: Guidance on uncertainty and use of experts

Probabilistic Seismic Hazard Analysis (PSHA) is a methodology that estimates the likelihood that various levels of earthquake-caused ground motion will be exceeded at a given location in a given future time period. Due to large uncertainties in all the geosciences data and in their modeling, multiple model interpretations are often possible. This leads to disagreement among experts, which in the past has led to disagreement on the selection of ground motion for design at a given site. In order to review the present state-of-the-art and improve on the overall stability of the PSHA process, the U.S. Nuclear Regulatory Commission (NRC), the U.S. Department of Energy (DOE), and the Electric Power Research Institute (EPRI) co-sponsored a project to provide methodological guidance on how to perform a PSHA. The project has been carried out by a seven-member Senior Seismic Hazard Analysis Committee (SSHAC) supported by a large number other experts. The SSHAC reviewed past studies, including the Lawrence Livermore National Laboratory and the EPRI landmark PSHA studies of the 1980`s and examined ways to improve on the present state-of-the-art. The Committee`s most important conclusion is that differences in PSHA results are due to procedural rather than technical differences. Thus, in addition to providing a detailed documentation on state-of-the-art elements of a PSHA, this report provides a series of procedural recommendations. The role of experts is analyzed in detail. Two entities are formally defined-the Technical Integrator (TI) and the Technical Facilitator Integrator (TFI)--to account for the various levels of complexity in the technical issues and different levels of efforts needed in a given study.

Exploring the Competitive Potential of Magnetic Fusion Energy: The Interaction of Economics with Safety and Environmental Characteristics

The Senior Committee on Environmental, Safety, and Economic Aspects of Magnetic Fusion Energy (ESECOM) summarizes its recent assessment of magnetic fusion energys (MFEs) prospects for providing energy with economic, environmental, and safety characteristics that would be attractive compared with other energy sources (mainly fission) available in the time frame of the year 2015 and beyond. Accordingly, ESECOM has given particular attention to the interaction of environmental, safety, and economic characteristics of a variety of magnetic fusion reactors, and compared those fusion cases with a variety of fission cases. Eight fusion cases, two fusion-fission hybrid cases, and four fission cases are examined, using consistent economic and safety models, to permit exploration of the environmental, safety, and economic potential of fusion concepts using a wide range of possible materials choices, power densities, power conversion schemes, and fuel cycles.

Radon-222 and its daughters. A review of instrumentation for occupational and environmental monitoring

The techniques which have been developed for measuring /sup 222/Rn and its daughters in vanious media are reviewed. The main emphasis is on measurements for surveillance and protection in occupational and environmental situations. Measurements in specialized research applications are not treated in detail. Overviews are first provided of the physical characteristics of /sup 222/ Rn and its daughters; of the sources of and typical levels of concentrations in the natural environment and in occupational exposures; and of the radiation guides. The various measurement techniques are then discussed. (auth)

Tritium instrumentation for environmental and occupational monitoring--a review.

The techniques developed for measuring tritium in various media are reviewed. The main emphasis is on measurements for surveillance and protection in environmental and occupational situations. Tritium measurements in specialized research applications are not treated in detail. Overviews are first provided of the physical characteristics of tritium; of the sources of and iypical levels of tritium concentrations in the natural environment; and of the radiation protection guides. The various measurement techniques are then discussed. (auth)

Plutonium: A Review of Measurement Techniques for Environmental Monitoring

An overview is provided of the techniques for measuring plutonium in various media. The emphasis is on measurements for surveillance and protection in environmental and occupational situations. Overviews are first provided for the characteristics of, sources of, and typical levels of plutonium concentrations. The various measurement techniques are then discussed.

Current status of methodologies for seismic probabilistic safety analysis

Abstract This report is a review of the methodology for conducting a seismic-probabilistic safety analysis (PSA) at a nuclear power station. The objective of this review is to provide an up-to-date review of the state-of-the-art of the various sub-methodologies that comprise the overall seismic-PSA methodology for addressing the safety of nuclear power stations, plus an overview of the whole methodological picture. In preparing this review, the author has had in mind several categories of readers and users: policy-level decision-makers (such as managers of nuclear power stations and regulators of nuclear safety), seismic-PSA practitioners, and PSA practitioners more broadly. The review concentrates on evaluating the extent to which todays seismic-PSA methodology produces reliable and useful results and insights, at its current state-of-the-art level, for assessing nuclear-power-station safety. Also, this review paper deals exclusively with seismic-PSA for addressing nuclear-power-station safety. Because the author is based in the U.S., it is natural that this review will contain more emphasis on U.S. experience than on experience in other countries. However, significant experience elsewhere is a major part of the basis for this evaluation.

Reduced seismic loads for temporary conditions

A new methodology, developed under an EPRI Tailored Collaboration Project, to calculate and apply reduced seismic loads (RLSs) for evaluation of temporary conditions (TCs) in nuclear power plants using design-basis (DB) allowables is described. The methodology, which was submitted to Nuclear Regulatory Commission (NRC) through the Nuclear Energy Institute (NEI), calculates load reduction factors based on an allowed limit for time-averaged increase in seismic core damage frequency within the duration of a refueling cycle. For this allowable in the range 5 × 10 - 6 to 1 × 10 -5 per reactor year, substantial reduction relative to DB seismic load is possible. The methodology is equally applicable to plants with and without seismic probabilistic risk analysis model.

A methodology for analyzing precursors to earthquake-initiated and fire-initiated accident sequences

This report covers work to develop a methodology for analyzing precursors to both earthquake-initiated and fire-initiated accidents at commercial nuclear power plants. Currently, the U.S. Nuclear Regulatory Commission sponsors a large ongoing project, the Accident Sequence Precursor project, to analyze the safety significance of other types of accident precursors, such as those arising from internally-initiated transients and pipe breaks, but earthquakes and fires are not within the current scope. The results of this project are that: (1) an overall step-by-step methodology has been developed for precursors to both fire-initiated and seismic-initiated potential accidents; (2) some stylized case-study examples are provided to demonstrate how the fully-developed methodology works in practice, and (3) a generic seismic-fragility date base for equipment is provided for use in seismic-precursors analyses. 44 refs., 23 figs., 16 tabs.

Recent extensions to seismic margin review methodology

Abstract Two seismic margin review methodologies — one by USNRC and the other by EPRI — have been developed in the last four years. The focus is on assessing the capability of existing nuclear power plants to withstand earthquakes larger than the design basis earthquakes. The methods restrict the analysis to a selected few systems and components using the insights from past seismic PRAs, seismic analysis and qualification results, and earthquake experience data. The objective of this paper is to describe recent and on-going studies in extending the NRC seismic margin review methodology. Specifically, three topics are discussed: (1) extension of the HCLPF capacity to analyse radiological releases and importance of human factors and non-seismic failures; (2) importance of BWR plant systems and functions to seismic margins; and (3) extensions of seismic margin review results to obtain seismic risk estimates.

Sodium fast reactor safety and licensing research plan. Volume II.

Expert panels comprised of subject matter experts identified at the U.S. National Laboratories (SNL, ANL, INL, ORNL, LBL, and BNL), universities (University of Wisconsin and Ohio State University), international agencies (IRSN, CEA, JAEA, KAERI, and JRC-IE) and private consultation companies (Radiation Effects Consulting) were assembled to perform a gap analysis for sodium fast reactor licensing. Expert-opinion elicitation was performed to qualitatively assess the current state of sodium fast reactor technologies. Five independent gap analyses were performed resulting in the following topical reports: (1) Accident Initiators and Sequences (i.e., Initiators/Sequences Technology Gap Analysis), (2) Sodium Technology Phenomena (i.e., Advanced Burner Reactor Sodium Technology Gap Analysis), (3) Fuels and Materials (i.e., Sodium Fast Reactor Fuels and Materials: Research Needs), (4) Source Term Characterization (i.e., Advanced Sodium Fast Reactor Accident Source Terms: Research Needs), and (5) Computer Codes and Models (i.e., Sodium Fast Reactor Gaps Analysis of Computer Codes and Models for Accident Analysis and Reactor Safety). Volume II of the Sodium Research Plan consolidates the five gap analysis reports produced by each expert panel, wherein the importance of the identified phenomena and necessities of further experimental research and code development were addressed. The findings from these five reports comprised the basis for the analysis in Sodium Fast Reactor Research Plan Volume I.