Robert A. Bari

A MARKOV MODEL APPROACH TO PROLIFERATION-RESISTANCE ASSESSMENT OF NUCLEAR ENERGY SYSTEMS

A Markov model approach is developed for the evaluation of proliferation resistance (PR) of nuclear energy systems. The focus of this study is to create a high-fidelity probabilistic assessment model that better represents nuclear energy systems. Both extrinsic and intrinsic barriers associated with the energy systems are considered. Modeling uncertainty and safeguards false alarms, composite safeguards approaches, concealment, and human performance are particularly discussed in detail and incorporated in the Markov model. These features are anticipated to have significant impacts on PR assessment. The Markov model approach is adapted to a hypothetical example sodium fast reactor (ESFR) system using physically meaningful parameters that can be obtained from physical processes. Development of metrics for six PR measures is discussed. Computation of the PR measures using the Markov model of the ESFR system is illustrated. The results obtained in this study demonstrate applicability and effectiveness of the Markov model approach in the PR assessment.

Primary pipe rupture accident analysis for the Clinch River Breeder Reactor

Analyses of primary pipe rupture accidents in the Clinch River Breeder Reactor were carried out with Brookhaven National Laboratory-modified versions of the DEMO code. The thermal transient responses of the core and radial blanket were calculated for a large number of initial conditions and plant configurations. These include studies of variations of pipe break size and operating power. Pipe ruptures commencing from two-loop initial operating conditions are presented. The sensitivity of the thermal response to variations in particular parameters within the estimated ranges of their uncertainties has been studied. Conditions under which sodium boiling in the core occurs are delineated.

Proliferation Resistance and Physical Protection Evaluation Methodology: Objectives, Accomplishments, and Future Directions

An overview is presented of the objectives, accomplishments, and potential future directions of the program on the evaluation methodology for proliferation resistance and physical protection (PR&PP) of advanced nuclear energy systems. The PR&PP Working Group of the Generation IV International Forum developed the methodology through a series of demonstration and case studies. The results of the evaluations performed with the methodology are intended for three types of users: system designers, program policy makers, and external stakeholders. During the past few years, various national and international groups have applied the methodology to nuclear energy system design as well as to developing approaches to advanced safeguards. We suggest some future applications of the methodology in this paper.

Relative Proliferation Risks for Different Fuel Cycle Arrangements

Abstract The purpose of this study is to evaluate the proliferation resistance characteristics for different fuel cycle arrangements in the context of a global nuclear energy system using a Markov approach, which is capable of modeling complex systems and providing probabilistic measures. A technique that groups a set of reactors similar to each other and yet captures major fuel cycle features for proliferation study is proposed as an enhancement to the Markov approach to reduce the modeling complexity. In evaluating impacts on proliferation, both the amounts of total materials around the world and the amounts of materials that are used by the host state are considered. Proliferation concerns are represented based on the proliferation resistance measures of fuel cycles. In addition to representing proliferation impact in terms of proliferation success probability, a measure of proliferation risk is also introduced by using a product of the proliferation success probability and the material type index that represents the consequence of the proliferation. Sensitivity analyses are performed by varying the scale of the nuclear energy system owned and operated by a host state.

Guidelines for the Performance of Nonproliferation Assessments

The National Nuclear Security Administration (NNSA) established a Nonproliferation Assessment Methodology (NPAM) Working Group, comprised of representatives from the Department of Energy (DOE) laboratories and academia, to develop guidelines for the practical application of Nonproliferation Assessment Methodologies (NPAM). The purpose of these methodologies is to address questions and issues related to the proliferation of nuclear weapons and weapons-useable nuclear materials and related technologies, as input to policy analysis. This document presents the guidelines developed by the Working Group.

Advanced neutron source enrichment study

A study has been performed of the impact on performance of using low enriched uranium (20% {sup 235}U) or medium enriched uranium (35% {sup 235}U) as an alternative fuel for the Advanced Neutron Source, which is currently designed to use uranium enriched to 93% {sup 235}U. Higher fuel densities and larger volume cores were evaluated at the lower enrichments in terms of impact on neutron flux, safety, safeguards, technical feasibility, and cost. The feasibility of fabricating uranium silicide fuel at increasing material density was specifically addressed by a panel of international experts on research reactor fuels. The most viable alternative designs for the reactor at lower enrichments were identified and discussed. Several sensitivity analyses were performed to gain an understanding of the performance of the reactor at parametric values of power, fuel density, core volume, and enrichment that were interpolations between the boundary values imposed on the study or extrapolations from known technology. Volume 2 of this report contains 26 appendices containing results, meeting minutes, and fuel panel presentations. There are 26 appendices in this volume.

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.

A consistent and cost-effective quantification of containment performance criteria

Containment performance criteria (CPC) are derived systematically, given top level safety goals related to public risk. The main focus is on the relationships between the top level safety goals and lower level design objectives, and the way in which the latter are determined. A set of CPC is identified in terms of the reliabilities of the systems that perform various containment functions. The multiobjective optimization approach is used as a method for deriving a finite manageable set of self-consistent relations between the top level safety goals and specific containment performance. As a global set of measures of plant performance or objective functions, acute and latent fatalities and the total reliability cost are chosen. The latter is included because it represents both technical and economic limitations in achieving a certain level of the first two members of the global set. A specific application is made to a large dry containment. A set of noninferior solutions (optimized solutions in a multi-objective optimization problem) is shown and discussed.

Decision making and probabilistic risk assessment

Abstract Several questions have been posed, in advance, to members of a panel on Decision Making held at the International Post-Conference Seminar on the Role of Data and Judgment in Probabilistic Risk and Safety Analysis, (SMiRT-8, August 1985). The relationship between probabilistic risk assessment and decision making is discussed with emphasis on: the role of judgment; verification of results of probabilistic risk assessments; the review process; safety goals and standards.

Interpretation and Use of the Results of Proliferation Resistance Studies

Proliferation resistance (PR) evaluations of nuclear energy systems provide a structured approach for assessing the value of both intrinsic and extrinsic barriers to proliferation. Ultimately, PR studies allow an evaluation of proposed safeguards, an identification of potential weaknesses or alternative safeguard approaches, and a basis for improving and enhancing safeguards. To facilitate understanding and sharing of results, PR evaluations should be carried out following a standardized approach that has international acceptance and that provides consistent results independent of the analysts carrying out the evaluation. Proliferation assessment methodologies such as those being developed under the Generation IV International Forum (GIF) and IAEA’s International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO) provide the technical platforms for supporting overall evaluations, but their findings are unlikely to be directly used by decision makers. This situation arises because although all PR evaluation approaches develop valuable information about the proliferation resistance of a nuclear energy system, a significant effort is still required to make results of PR evaluations usable and understandable to decision makers. This paper identifies a reference set of decision makers and other users who could be informed by the results of PR assessments. Whether the INPRO, GIF, or another methodology is used, the need for useful information about the PR of their systems must be met. The paper examines the information needs of different classes of decision makers and presents ideas on how the results of the various PR studies can be interpreted and presented to them in a more usable, understandable fashion.