Initiating Event Analysis of a Lithium Fluoride Thorium Reactor

The primary purpose of this study is to perform an Initiating Event Analysis for a Lithium Fluoride Thorium Reactor (LFTR) as the first step of a Probabilistic Safety Assessment (PSA). The major objective of the research is to compile a list of key initiating events capable of resulting in failure of safety systems and release of radioactive material from the LFTR. Due to the complex interactions between engineering design, component reliability and human reliability, probabilistic safety assessments are most useful when the scope is limited to a single reactor plant. Thus, this thesis will study the LFTR design proposed by Flibe Energy. An October 2015 Electric Power Research Institute report on the Flibe Energy LFTR asked “what-if?” questions of subject matter experts and compiled a list of key hazards with the most significant consequences to the safety or integrity of the LFTR. The potential exists for unforeseen hazards to pose additional risk for the LFTR, but the scope of this thesis is limited to evaluation of those key hazards already identified by Flibe Energy. These key hazards are the starting point for the Initiating Event Analysis performed in this thesis. Engineering evaluation and technical study of the plant using a literature review and comparison to reference technology revealed four hazards with high potential to cause reactor core damage. To determine the initiating events resulting in realization of these four hazards, reference was made to previous PSAs and existing NRC and EPRI initiating event lists. Finally, fault tree and event tree analyses were conducted, completing the logical classification of initiating events. Results are qualitative as opposed to quantitative due to the early stages of system design descriptions and lack of operating experience or data for the LFTR. In summary, this thesis analyzes initiating events using previous research and inductive and deductive reasoning through traditional risk management techniques to arrive at a list of key initiating events that can be used to address vulnerabilities during the design phases of LFTR development

Model-Based Cyber-Security Framework for Nuclear Power Plant

A model-based cyber-security framework has been developed to address the new challenges of cyber threats due to the increasing implementation of digital components in the instrumentation and control (I&C) system of modern nuclear power plants. The framework is developed to detect intrusions to pressurized water reactor (PWR) systems that could result in unnecessary reactor shutdown events due to out-of-range water levels of steam generators. The generation of potential attack scenarios demonstrated a process for identifying the most susceptible attack pathways and components in the I&C system. It starts with identifying two key I&C divisions of the modern AP1000 design related to the reactor trip functions, protection and safety monitoring system, and plant control system. The attack tree analysis is performed on the steam generator (SG) water level control system using the SAPHIRE 8.0.9 code. To quantify the system susceptibility to cyber-attack events, causing reactor trips, we propose sensitivity metrics to identify the low-order sets of components that may be compromised and the degree of perturbations needed for each component. The multi-path event tree (MPET) structures are developed to efficiently and intuitively display a large number of dominant or risk-significant attack scenarios instead of the traditional event trees representing minimal cut sets. A reduced order model (ROM) has been developed to efficiently represent the SG dynamics and facilitate the detection of potential cyber-attacks. The dynamic ROM is built on the energy balance equation for a single vertical boiling channel approximating a U-tube steam generator. The ROM provides an essential relationship connecting the reactor power, water level, and feedwater flow rate. An application programming interface (API) for the I&C systems serving as the interface between the RELAP5 system code and the ROM has been developed. A Kalman filtering based detection method has been proposed, providing optimal tracking of SG water level combining the uncertain simulation results with the observation data subject to statistical fluctuations. An observed plant state with significant deviation from the optimal system projection could then indicate potential intrusions into the system. Finally, a mitigation strategy considering the controller feedback is proposed to avoid the reactor trip due to attack on SG water level sensors. The worst-case attack within this issue space is defined, and the maximum delay time allowed for the mitigation is obtained.PHDNuclear Engineering & Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/162955/1/gjunjie_1.pd

Publications of the Jet Propulsion Laboratory, July 1961 through June 1962

Jpl bibliography on space science, 1961-196

Activities in nuclear engineering at M.I.T.

"List of theses"--Pages 130-133Progress report; December 198

Activities in nuclear engineering at M.I.T.

"List of theses"--Pages 120-123Progress report; January 198

Activities in nuclear engineering at M.I.T.

"List of theses (February 1986-June 1987)"--Pages [133]-[138]Progress report; August 198

Publications of the Jet Propulsion Laboratory, July 1966 - June 1967 - A bibliography

Bibliography with abstracts of official reports in sciences and engineering as released by Jet Propulsion Laboratory, July 1966 - June 196

Activities in nuclear engineering at M.I.T.

"List of theses"--Pages 120-123Progress report; September 198