ML14080A242
| ML14080A242 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/2014 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| Download: ML14080A242 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, DC 20555 - 0001 March 31, 2014 The Honorable Allison M. Macfarlane Chairman U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001
SUBJECT:
SUMMARY
REPORT - 612th MEETING OF THE ADVISORY COMMITTEE ON REACTOR SAFEGUARDS, MARCH 6 - 8, 2014
Dear Chairman Macfarlane:
During its 612th meeting, March 6 - 8, 2014, the Advisory Committee on Reactor Safeguards (ACRS) discussed several matters and completed the following letters:
LETTERS Letters to Mark A. Satorius, Executive Director for Operations, NRC, from John W. Stetkar, Chairman, ACRS:
Chapters 3 (Partial) and 14 of the Safety Evaluation Report with Open Items for Certification of the US-APWR Design, dated March 13, 2014.
Chapters 3 (Partial), 9, and 14 of the Safety Evaluation Report with Open Items for the Comanche Peak Nuclear Power Plant, Units 3 and 4, US-APWR Reference Combined License Application, dated March 14, 2014.
HIGHLIGHTS OF KEY ISSUES
- 1.
Selected Chapters of the Safety Evaluation Report (SER) with Open Items Associated with the US Advanced Pressurized Water Reactor (US-APWR) Design Certification and the Comanche Peak Combined License Application (COLA)
The Committee met with representatives of Mitsubishi Heavy Industries, LTD. (MHI), Luminant Generation Company (Luminant), and the NRC staff to discuss the United States - Advanced Pressurized Water Reactor (US-APWR) design control document (DCD), Comanche Peak Units 3 and 4, Reference Combined License Application (RCOLA), and the staffs safety evaluation report associated with these topics. MHI presented US-APWR DCD Chapter 3, "Design of Structures, Systems, Components and Equipment," and Chapter 14, "Verification Programs."
Luminant described Chapter 9, Auxiliary Systems, in addition to Chapters 3 and 14 of the Comanche Peak, Units 3 and 4, RCOLA. The NRC staff made presentations on all these items.
The main issue discussed for the US-APWR design certification and Comanche Peak RCOLA was Chapter 3 which summarizes evaluations of hazards such as high winds, tornadoes, hurricanes, flooding that originates inside plant structures, flooding from external sources, ruptures of high energy piping, turbine missiles, wind-generated missiles, and aircraft crashes.
These hazards have the potential to affect multiple structures and systems.
Committee Action The Committee issued two letters on these matters:
(1) In the letter to the Executive Director for Operations, dated March 13, 2014, on Chapters 3 and 14 of the SER with Open Items for certification of the US-APWR design, the Committee did not identify any issues that would preclude certification of the design and will review the staffs resolution of open items during future meetings.
The Committee noted that hazards evaluated in Chapter 3 have the potential to affect multiple structures and systems and will comment on potential safety implications from these hazards in future letter reports.
(2) In the letter to the Executive Director for Operations, dated March 14, 2014, on Chapters 3, 9, and 14 of the SER with Open Items for the Comanche Peak Nuclear Power Plant, Units 3 and 4, US-APWR RCOLA, the Committee did not identify any issues that would preclude issuance of the combined license and will review the staffs resolution of open items during future meetings. The Committee noted that hazards evaluated in Chapter 3 have the potential to affect multiple structures and systems and will comment on potential safety implications from these hazards in future letter reports.
- 2.
Diablo Canyon Power Plant, Units 1 and 2, Digital Replacement of the Process Protection System (RPS) and Portions of the Reactor Trip System (RTS) and Engineering Safety Features Actuation System (ESFAS)
The Committee met with representatives of the NRC staff to discuss the status of their review of the license amendment request for replacement of the digital process protection system (PPS) at Diablo Canyon Power Plant (DCPP), Units 1 and 2. The review was conducted using ISG 6 and ISG 2. The proposed upgrade will replace the current Eagle 21 digital safety system with a combination of a triply modular redundant (TMR) Tricon Programmable Logic Controller (PLC) and a diverse Advanced Logic System (ALS) Field Programmable Gate Array-based safety system which internally has diverse and redundant safety logic. The replacement system employs two layers of functional redundancy and two layers of diversity within a division where formerly there was only a single processor. The Tricon PLC will monitor neutron flux, reactor coolant system temperatures, pressurizer level, reactor coolant flow, pressurizer pressure, and steam generator level. The ALS will monitor pressurizer pressure, steam generator level, containment pressure, and steam line pressure. The presentation covered key aspects of the new PPS architecture, diversity and defense in depth, the Secure Development and Operating Environment, and response times.
Committee Action The Committee plans to review the staffs final safety evaluation associated with this license amendment request during a future meeting.
- 3.
Pellet Cladding Interaction Fuel Failures during Anticipated Operational Occurrences The Committee met with representatives of the NRC staff to discuss the assessment of the vulnerability of PWR fuel to pellet cladding interaction stress corrosion cracking (PCI/SCC) failures during certain anticipated operational occurrences (AOOs). The staff described screening criteria for identifying potentially limiting transients for PCI/SCC failures. The staff also performed two analyses of power ramps for fuel rods operated at different power histories using the FRAPCON 3-4 code. The staff concluded that the existing safety reactor trip functions are adequate to provide reasonable assurance against PCI/SCC cladding failure. However, the staff expressed concern that core follow trends of PWR operation may increase vulnerability to PCI/SCC fuel failures.
The NRC staff also discussed the Studsvik Cladding Integrity Program (SCIP) which investigates the dominant failure mechanisms for light water reactor fuel cladding during normal operation or anticipated transients. The SCIP program covers multiple failure mechanisms including pellet cladding mechanical interaction; PCI/SCC; hydrogen embrittlement; and delayed hydride cracking. From the review of the SCIP power ramp data and their FRAPCON analyses, the staff noted that the hoop stress threshold for PCI/SCC failure ranged from 200 MPa to 250 MPa. The staff concluded that a new or revised regulatory acceptance criterion is not warranted to preclude PCI/SCC fuel failures for PWRs since the current fuel design system acceptance criteria provides adequate protection.
Committee Action The Committee has been concerned with the lack of any empirical or analytical capability to quantitatively assess the risk of PCI fuel failures during certain AOOs. The Committee will provide its recommendation for developing such capabilities in the 2014 ACRS biennial review of the NRC research program.
- 4.
Biennial Review of the NRC Safety Research Program The Committee continued discussion of its biennial review of the NRC safety research program.
Committee Action The Committee will finalize its report on the biennial review of the NRC safety research program during its April 10-11, 2014 Meeting.
- 5.
Meeting with the Commission On March 7, 2014, the Committee met with the Commission to discuss the following topics of mutual interest:
Overview o Accomplishments o Ongoing/Future Activities Fukushima Near-Term Task Force Recommendation 1 Expedited Transfer of Spent Fuel Guidance on the Hardened Vents Order Proposed Revisions to 10 CFR Part 61
- 6.
Significant Operating Experience The Chairman of the Plant Operations and Fire Protection Subcommittee provided the Committee a summary of FY 2012 and FY 2013 significant operating experience. The Subcommittee Chairman discussed significant Reactor Oversight Process findings, loss of offsite power events, significant Near-Term Task Force flooding findings, human performance events, Industry Trends Program results, and highlights from the FY 2012 Report to Congress on Abnormal Occurrences.
Committee Action This was an information briefing. No Committee action was necessary.
RECONCILIATION OF ACRS COMMENTS AND RECOMMENDATIONS The Committee considered the EDOs response of January 31, 2014, to the conclusion and recommendation included in the December 12, 2013, ACRS letter on Chapters 2, 3, 9, 13, and 14 of the Safety Evaluation Report with Open Items associated with the Calvert Cliffs Nuclear Power Plant, Unit 3, reference combined license application for the Evolutionary Power Reactor. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of January 16, 2014, to the conclusions included in the December 18, 2013, ACRS letter on Chapters 2, 6, and 7 of the Safety Evaluation Report with Open Items associated with the Comanche Peak Nuclear Power Plant, Units 3 and 4, reference combined license application for the United States - Advanced Pressurized Water Reactor. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of February 11, 2014, to the conclusions in the January 6, 2014, ACRS letter regarding the Safety Evaluation Report for Topical Report MUAP-07001, Revision 5, The Advanced Accumulator, associated with the United States - Advanced Pressurized Water Reactor design. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of January, 31 2014, to the conclusions in the December 18, 2013, ACRS letter on the staff evaluation and recommendation for the Japan Lessons Learned Tier 3 issue on expedited transfer of spent fuel. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of January 9, 2014, to the conclusions in the November 26, 2013, ACRS letter regarding the interim review of the Watts Bar Nuclear Plant, Unit 2 operating license application. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of February 24, 2014, to the conclusions and recommendations in the December 24, 2013, ACRS letter regarding Chapters 6 and 7 of the Safety Evaluation Report with Open Items associated with the US-APWR design and related long-term core cooling issues. The Committee wasnt satisfied with the response and will consider a letter back to the EDO during its April 10-11, 2014 meeting.
SCHEDULED TOPICS FOR THE 613th ACRS MEETING The following topics are scheduled for the 613th ACRS meeting, to be held on April 10-11, 2014:
Thermal Conductivity Degradation Overview of the B&W mPower Small Modular Reactor Design NRC Staff Activities Regarding Small Modular Reactors Overview of NRC Operating Experience Program Economic Simplified Boiling Water Reactor Supplemental Final Safety Evaluation Report Biennial Review of the NRC Safety Research Program Sincerely,
/RA/
John W. Stetkar Chairman The Committee considered the EDOs response of January 16, 2014, to the conclusions included in the December 18, 2013, ACRS letter on Chapters 2, 6, and 7 of the Safety Evaluation Report with Open Items associated with the Comanche Peak Nuclear Power Plant, Units 3 and 4, reference combined license application for the United States - Advanced Pressurized Water Reactor. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of February 11, 2014, to the conclusions in the January 6, 2014, ACRS letter regarding the Safety Evaluation Report for Topical Report MUAP-07001, Revision 5, The Advanced Accumulator, associated with the United States - Advanced Pressurized Water Reactor design. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of January, 31 2014, to the conclusions in the December 18, 2013, ACRS letter on the staff evaluation and recommendation for the Japan Lessons Learned Tier 3 issue on expedited transfer of spent fuel. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of January 9, 2014, to the conclusions in the November 26, 2013, ACRS letter regarding the interim review of the Watts Bar Nuclear Plant, Unit 2 operating license application. The Committee was satisfied with the EDOs response.
The Committee considered the EDOs response of February 24, 2014, to the conclusions and recommendations in the December 24, 2013, ACRS letter regarding Chapters 6 and 7 of the Safety Evaluation Report with Open Items associated with the US-APWR design and related long-term core cooling issues. The Committee wasnt satisfied with the response and will consider a letter back to the EDO during its April 10-11, 2014 meeting.
SCHEDULED TOPICS FOR THE 613th ACRS MEETING The following topics are scheduled for the 613th ACRS meeting, to be held on April 10-11, 2014:
Thermal Conductivity Degradation Overview of the B&W mPower Small Modular Reactor Design NRC Staff Activities Regarding Small Modular Reactors Overview of NRC Operating Experience Program Economic Simplified Boiling Water Reactor Supplemental Final Safety Evaluation Report Biennial Review of the NRC Safety Research Program Sincerely,
/RA/
John W. Stetkar Chairman Accession No:
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