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Title: Scoping Study Investigating PWR Instrumentation during a Severe Accident Scenario

The accidents at the Three Mile Island Unit 2 (TMI-2) and Fukushima Daiichi Units 1, 2, and 3 nuclear power plants demonstrate the critical importance of accurate, relevant, and timely information on the status of reactor systems during a severe accident. These events also highlight the critical importance of understanding and focusing on the key elements of system status information in an environment where operators may be overwhelmed with superfluous and sometimes conflicting data. While progress in these areas has been made since TMI-2, the events at Fukushima suggests that there may still be a potential need to ensure that critical plant information is available to plant operators. Recognizing the significant technical and economic challenges associated with plant modifications, it is important to focus on instrumentation that can address these information critical needs. As part of a program initiated by the Department of Energy, Office of Nuclear Energy (DOE-NE), a scoping effort was initiated to assess critical information needs identified for severe accident management and mitigation in commercial Light Water Reactors (LWRs), to quantify the environment instruments monitoring this data would have to survive, and to identify gaps where predicted environments exceed instrumentation qualification envelop (QE) limits. Results from themore » Pressurized Water Reactor (PWR) scoping evaluations are documented in this report. The PWR evaluations were limited in this scoping evaluation to quantifying the environmental conditions for an unmitigated Short-Term Station BlackOut (STSBO) sequence in one unit at the Surry nuclear power station. Results were obtained using the MELCOR models developed for the US Nuclear Regulatory Commission (NRC)-sponsored State of the Art Consequence Assessment (SOARCA) program project. Results from this scoping evaluation indicate that some instrumentation identified to provide critical information would be exposed to conditions that significantly exceeded QE limits for extended time periods for the low frequency STSBO sequence evaluated in this study. It is recognized that the core damage frequency (CDF) of the sequence evaluated in this scoping effort would be considerably lower if evaluations considered new FLEX equipment being installed by industry. Nevertheless, because of uncertainties in instrumentation response when exposed to conditions beyond QE limits and alternate challenges associated with different sequences that may impact sensor performance, it is recommended that additional evaluations of instrumentation performance be completed to provide confidence that operators have access to accurate, relevant, and timely information on the status of reactor systems for a broad range of challenges associated with risk important severe accident sequences.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Rempe and Associates, LLC, Idaho Falls, ID (United States)
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  3. Lutz Nuclear Safety Consultant, LLC, Asheville, NC (United States)
Publication Date:
OSTI Identifier:
1236807
Report Number(s):
INL/EXT--15-35940
TRN: US1600279
DOE Contract Number:
AC07-05ID14517
Resource Type:
Technical Report
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; NUCLEAR POWER PLANTS; INFORMATION NEEDS; THREE MILE ISLAND-2 REACTOR; EVALUATION; REACTOR ACCIDENTS; FUKUSHIMA DAIICHI NUCLEAR POWER STATION; ACCIDENT MANAGEMENT; PERFORMANCE; DAMAGE; HAZARDS; MITIGATION; MONITORING; OUTAGES; SENSORS; REACTOR INSTRUMENTATION; PWR TYPE REACTORS; SURRY-1 REACTOR; DISPLAY DEVICES Accident Tolerant Instrumentation; PWR Instrumentation