S.R. Greene

Pre-Conceptual Design of a Fluoride-Salt-Cooled Small Modular Advanced High Temperature Reactor (SmAHTR)

This document presents the results of a study conducted at Oak Ridge National Laboratory during 2010 to explore the feasibility of small modular fluoride salt-cooled high temperature reactors (FHRs). A preliminary reactor system concept, SmATHR (for Small modular Advanced High Temperature Reactor) is described, along with an integrated high-temperature thermal energy storage or salt vault system. The SmAHTR is a 125 MWt, integral primary, liquid salt cooled, coated particle-graphite fueled, low-pressure system operating at 700 C. The system employs passive decay heat removal and two-out-of-three , 50% capacity, subsystem redundancy for critical functions. The reactor vessel is sufficiently small to be transportable on standard commercial tractor-trailer transport vehicles. Initial transient analyses indicated the transition from normal reactor operations to passive decay heat removal is accomplished in a manner that preserves robust safety margins at all times during the transient. Numerous trade studies and trade-space considerations are discussed, along with the resultant initial system concept. The current concept is not optimized. Work remains to more completely define the overall system with particular emphasis on refining the final fuel/core configuration, salt vault configuration, and integrated system dynamics and safety behavior.

Consumer Interruption Costing for Reliability Cost/Benefit Evaluation

A procedure for determining customer interruption costs for use in a power system reliability cost/benefit evaluation is presented. The procedure uses the results of a calculation of the frequency and duration of reserve margin states together with emergency operating procedures, customer curtailment strategies, and interruption cost coefficients to predict the total expected customer interruption costs for a given power system configuration. The customer interruption costing procedure is described, an example is given, and the results of the application of the procedure in a generation system reliability cost/benefit evaluation are discussed.

Integration of Biorefineries and Nuclear Cogeneration Power Plants - A Preliminary Analysis

Biomass-based ethanol and nuclear power are two viable elements in the path to U.S. energy independence. Numerous studies suggest nuclear power could provide a practical carbon-free heat source alternative for the production of biomass-based ethanol. In order for this coupling to occur, it is necessary to examine the interfacial requirements of both nuclear power plants and bioethanol refineries. This report describes the proposed characteristics of a small cogeneration nuclear power plant, a biochemical process-based cellulosic bioethanol refinery, and a thermochemical process-based cellulosic biorefinery. Systemic and interfacial issues relating to the co-location of either type of bioethanol facility with a nuclear power plant are presented and discussed. Results indicate future co-location efforts will require a new optimized energy strategy focused on overcoming the interfacial challenges identified in the report.

Potential effects of gallium on cladding materials

This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

The role of BWR secondary containments in severe accident mitigation: Issues and insights from recent analyses

Abstract All commercial boiling water reactor (BWR) plants in the US employ primary containments of the pressure suppression design. These primary containments are surrounded and enclosed by secondary containments. While not designed for severe accident mitigation, these secondary containments might also reduce the radiological consequences of severe accidents. This issue is receiving increasing attention due to concerns that BWR MK I primary containment integrity would be lost should a significant mass of molten debris escape the reactor vessel during a severe accident. The fission product retention capability of an intact secondary containment will depend on several factors. Recent analyses indicate that the major factors influencing secondary containment effectiveness include: the mode and location of the primary containment failure, the internal architectural design of the secondary containment, the design of the standby gas treatment system, and the ability of fire protection system sprays to remove suspended aerosols from the the secondary containment atmosphere. Each of these factors interact in a very complex manner to determine secondary containment severe accident mitigation performance. This paper presents a brief overview of US BWR secondary containment designs and highlights plant-specific features that could influence secondary containment severe accident survivability and accident mitigation effectiveness. Current issues surrounding secondary containment performance are discussed, and insights gained from recent secondary containment studies of Browns Ferry, Peach Bottom, and Shoreham are presented. Areas of significant uncertainty are identified and recommendations for future research are presented.

Are Current U.S. Nuclear Power Plants Grid Resilience Assets

Abstract This paper examines the concept of Grid resilience in the context of the North American electricity supply system and the role existing (Generation II) light water–cooled nuclear power plants (NPPs) play in enabling and enhancing Grid resilience. (Because of similarities in technology and plant design, it is likely that most of the discussion in the paper is also relevant to Generation III and Generation III+ light water NPP designs. The applicability of the analysis to Canadian CANDU and Russian VVER technology has not been assessed.) The paper asks and answers three compound questions: (1) what is Grid resilience, and what is a resilient Grid? (2) what is a resilient nuclear power plant (rNPP), and what are the basic functional requirements of rNPPs? and in light of the answers to these questions, (3) are today’s U.S. NPPs significant Grid resilience assets? The conclusion reached is that existing U.S. commercial NPPs are safe and efficient capacity, energy, and reliability assets and they have demonstrated some Grid resilience benefit during regional weather events. However, today’s NPPs do not deliver the Grid resilience benefits nuclear power can and should provide the nation. The author argues that nuclear power’s unique fuel security (an attribute that could allow NPPs to energize the Grid during extended periods in which fuel could not be delivered to other types of power plants) is a compelling reason to develop future rNPPs that would deliver strategic Grid resilience benefits in the face of evolving hazards and threats to the U.S. Grid.

The Canary, the Ostrich, and the Black Swan: A Historical Perspective on our Understanding of BWR Severe Accidents and Their Mitigation

Abstract Between 1980 and 1995, Oak Ridge National Laboratory (ORNL) was engaged in an intense effort to understand commercial boiling water reactor severe accident phenomenology, severe accident progression, and the potential role of the reactor operator in severe accident mitigation. This paper presents a summary of the major findings and conclusions from that period. Both detailed accident- and plant-specific results are discussed. The author, who was a member of the ORNL research team that performed the work, offers a historical perspective on lessons learned, lessons ignored, and lessons forgotten from that period. The relevancy of these findings in the post-Fukushima world is addressed. The author discusses the evolution of the current risk-informed regulatory framework, and identifies some key questions to be addressed and critical steps to be taken to inform the development of the new nuclear safety construct required in the wake of the Fukushima Daiichi accident. Finally, the author closes by sharing an ethos of nuclear reactor safety that can guide a new generation of reactor safety professionals in the post-Fukushima era.

FMDP reactor alternative summary report. Volume 1 - existing LWR alternative

Significant quantities of weapons-usable fissile materials [primarily plutonium and highly enriched uranium (HEU)] are becoming surplus to national defense needs in both the United States and Russia. These stocks of fissile materials pose significant dangers to national and international security. The dangers exist not only in the potential proliferation of nuclear weapons but also in the potential for environmental, safety, and health (ES&H) consequences if surplus fissile materials are not properly managed. This document summarizes the results of analysis concerned with existing light water reactor plutonium disposition alternatives.

Enhancing Electric Grid, Critical Infrastructure, and Societal Resilience with Resilient Nuclear Power Plants (rNPPs)

Abstract This paper, the fourth in a series, presents the results of a study conducted to explore the role current U.S. commercial nuclear power plants (NPPs) play and the role a new type of NPP—a resilient nuclear power plant (rNPP)—could play in enhancing U.S. electric Grid, Critical Infrastructure, and societal resilience. A rNPP is a NPP intentionally designed, sited, interfaced, and operated in a manner to enhance Grid resilience. Four specific rNPP applications are discussed: (1) rNPPs as “flexible operations” electricity generation assets, (2) rNPPs as anchors of nuclear hybrid energy systems, (3) rNPPs as Grid Black Start Resources, and (4) rNPPs as anchors of Resilient Critical Infrastructure Islands. These four applications, individually and collectively, could enhance U.S. Grid, Critical Infrastructure, and societal resilience during normal conditions and in the wake of major national calamities stemming from natural hazards and/or malevolent human actions. rNPPs would be both tactical and strategic resilience assets, thereby extending the value proposition of nuclear energy well beyond that associated with nuclear power’s traditional baseload electricity generation. These are important topics as society grows increasingly dependent on electricity, and the natural hazard and malevolent human threat portfolio to the Grid continues to evolve.

The Key Attributes, Functional Requirements, and Design Features of Resilient Nuclear Power Plants (rNPPs)

Abstract This paper builds on previous work that characterized the nature of the nuclear power plant (NPP)–electric Grid system, the concept of Grid resilience, and the potential of current U.S. NPPs to enhance the U.S. Grid, integrated Critical Infrastructure, and societal resilience. The concept of a resilient nuclear power plant (rNPP) is defined. Two rNPP Key Attributes and Six rNPP Functional Requirements are presented. A preliminary discussion of some rNPP design features that could enable an NPP to achieve the Six rNPP Functional Requirements is presented, along with a preliminary discussion of some rNPP regulatory, siting, and economic considerations. Taken as a package, the Six rNPP Functional Requirements define an NPP performance envelope that extends the societal value proposition of nuclear energy well beyond that of traditional baseload electricity generation. The paper lays the foundation for exploration of high-value rNPP applications and for future rNPP conceptual design studies.