ML16224A792
| ML16224A792 | |
| Person / Time | |
|---|---|
| Issue date: | 03/11/1992 |
| From: | Ward D Advisory Committee on Reactor Safeguards |
| To: | Taylor J NRC/EDO |
| References | |
| Download: ML16224A792 (16) | |
Text
D920311 MEMORANDUM FOR: James M. Taylor Executive Director for Operations FROM: David A. Ward Chairman
SUBJECT:
PROPOSED PRIORITY RANKINGS OF GENERIC ISSUES: SEVENTH GROUP During the 383rd meeting of the Advisory Committee on Reactor Safeguards, March 5-7, 1992, we reviewed the priority rankings proposed by the staff for the group of generic issues identified in Table A, attached. During this meeting, we had the benefit of discussions with representatives of the NRC staff.
We have deferred action on Generic Issue 138, "Deinerting of BWRs with Mark I and II Containments During Power Operations Upon Discovery of Reactor Cooling System Leakage or a Train of a Safety System Inoperable," because the staff's evaluation is poorly written and the concerns to be addressed are inadequately de-scribed. We request that the staff revise its evaluation of this issue and submit it to us for consideration.
Generic Issue A-19, "Digital Computer Protection System," is categorized as a "Licensing Issue." We believe that the staff should revise its evaluation of this issue to properly describe the current situation with respect to the use of reactor protection systems using digital technology. We are particularly concerned by the statement that the use of digital technology will not result in a change in the safety of current nuclear power plants. This is an improper basis for the "Licensing Issue" classification, given the extraordinary energy being expended by the staff, the ACRS, and the industry to understand the novel safety implications (positive and negative) of this technology.
Our comments on various generic issues considered during this meeting are contained in the following attachments:
Attachment 1 lists those generic issues for which we agree with the proposed priority rankings.
Attachment 2 includes those issues for which we agree with the proposed priority rankings, but have comments.
Attachment 3 identifies those issues for which we disagree with the proposed priority ranking.
We request that the NRC staff provide written responses to our comments. We will continue our review of the proposed priority rankings for additional generic issues when they become available.
Attachments:
As noted above TABLE A GENERIC ISSUES REVIEWED BY THE ACRS DURING THE 383RD, MARCH 5-7, 1992, MEETING
© Generic Priority Ranking Issue Proposed by Reference Number Title the NRC Staff Document
ýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýý
ýµ 24 Automatic Emergency Core MEDIUM Memorandum from Cooling System Switch-E. S. Beckjord for over to Recirculation W. Minners, July 23, 1991 38 Potential Recirculation DROP Memorandum from System Failure as a (The safety concerns E. S. Beckjord for Consequence of Ingestion of this Issue were W. Minners, August of Containment Paint addressed in the 16, 1991 Flakes or Other Fine resolution of USI Debris A-43, "Containment Emergency Sump Performance")
72 Control Rod Drive Guide DROP Memorandum from Tube Support Pin Failures(Control rod drive E. S. Beckjord for guide tube support B. M. Morris, pins susceptible to October 9, 1990 stress corrosion cracking have been
replaced with guide pins of improved design at operating Westinghouse reac-tors. Thus the safety concerns of this Issue have been addressed) 73 Detached Thermal Sleeves Nearly Resolved Memorandum from E. S. Beckjord for W. Minners, August 20, 1991 100 Once-Through Steam DROP Memorandum from Generator Level E. S. Beckjord for W. Minners, September 24, 1991
TABLE A (Cont'd)
© Generic Priority Ranking Issue Proposed by Reference Number Title the NRC Staff Document
ýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýý
ýµ 116 Accident Management HIGH Memorandum from
(Since the safety E. S. Beckjord for concerns of this W. Minners and Issue are being ad-B. Sheron, Septem-dressed in the Acci-ber 6, 1990 dent Management element of the NRC plan for the closure of severe accident issues, as described in SECY-88-147 and Generic Letter 88-20, Supplement 2, this Issue will not be pursued separately) 118 Tendon Anchor Head RESOLVED Memorandum from Failure E. S. Beckjord for W. Minners, January 17, 1992 120 On-Line Testability MEDIUM Memorandum from of Protection Systems E. S. Beckjord for W. Minners, Novem-ber 23, 1990 123 Deficiencies in the Regu-DROP Memorandum from lations Governing DBA (The safety concerns E. S. Beckjord and Failure Criterion of this Issue have for W. Minners,
Suggested by the Davis-been or will be December 9, 1991 Besse Incident of June 9,addressed in the 1985 resolution of USIs A-17, A-44, A-45, and A-47, and the IPE program) 138 Deinerting of BWRs LOW Memorandum from with Mark I and II E. S. Beckjord Containments During for W. Minners, Power Operations Upon October 17, 1991 Discovery of Reactor Cooling System Leakage or a Train of a Safety System Inoperable
TABLE A (Cont'd)
© Generic Priority Ranking Issue Proposed by Reference Number Title the NRC Staff Document
ýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýý
ýµ 142 Leakage Through Electri-MEDIUM Memorandum from cal Isolators in Instru-E. S. Beckjord for mentation Circuits W. Minners, June 20, 1990 143 Availability of Chilled HIGH Memorandum from Water Systems and Room E. S. Beckjord for
Cooling W. Minners, March 29, 1991 150 Overpressurization of DROP Memorandum from Containment Penetrations E. S. Beckjord for W. Minners, August 23, 1991 151 Reliability of Anticipa-MEDIUM Memorandum from ted Transient Without E. S. Beckjord for Scram Recirculation Pump W. Minners, August Trip in BWRs 27, 1991 153 Loss of Essential Service HIGH Memorandum from Water in LWRs E. S. Beckjord for W. Minners, March 29, 1991 154 Adequacy of Emergency LOW Memorandum from and Essential Lighting E. S. Beckjord for W. Minners, January 24, 1992 156.1.2 Dam Integrity and Site DROP Memorandum from Flooding (The safety concerns E. S. Beckjord of this Issue will for W. Minners, be addressed in the January 27, 1992 implementation of the
IPEEE and Dam Safety Programs) 156.1.3 Site Hydrology and DROP Memorandum from Ability to Withstand (The safety concerns E. S. Beckjord Floods of this Issue will for W. Minners, be addressed in the January 27, 1992 implementation of the IPE, IPEEE, and Dam Safety Programs)
TABLE A (Cont'd)
© Generic Priority Ranking Issue Proposed by Reference Number Title the NRC Staff Document
ýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýý
ýµ 156.1.5 Tornado Missiles DROP Memorandum from (The safety concerns E. S. Beckjord of this Issue will for W. Minners, be addressed in the January 27, 1992 implementation of the IPEEE Program) 156.1.6 Turbine Missiles DROP Memorandum from (The safety concerns E. S. Beckjord of this Issue were for W. Minners, addressed in the October 23, 1991 evaluation of Generic
Issue A-37, "Turbine Missiles")
156.2.1 Severe Weather Effects DROP Memorandum from on Structures (The safety concerns E. S. Beckjord of this Issue will for W. Minners, be addressed in the January 29, 1992 implementation of the IPEEE Program) 156.3.4 Isolation of High and DROP Memorandum from Low Pressure Systems (The safety concerns E. S. Beckjord for of this Issue are W. Minners, being addressed in December 11, 1991 the resolution of Generic Issue 105, "Interfacing Systems LOCA in LWRs")
156.3.5 Automatic Emergency Core DROP Memorandum from Cooling System Switchover(The safety concerns E. S. Beckjord for of this Issue will beW. Minners, addressed in the November 7, 1991 resolution of Generic Issue 24, "Automatic Emergency Core Cool-ing System Switchover to Recirculation")
TABLE A (Cont'd)
© Generic Priority Ranking Issue Proposed by Reference Number Title the NRC Staff Document
ýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýýý
ýµ 156.4.1 Reactor Protection DROP Memorandum from System and Engineered (The safety concerns E. S. Beckjord for Safety Features Systems of this Issue will W. Minners, Isolation be addressed in the November 6, 1991 resolution of Generic Issue 142, "Leakage Through Electrical Isolators in Instru-mentation Circuits" A-19 Digital Computer Protec-Licensing Issue Memorandum from tion System (Staff efforts are E. S. Beckjord for under way in pursuit B. Sheron, of this Issue) November 15, 1990 B-22 LWR Fuel DROP Memorandum from E. S. Beckjord for
W. Minners, June 3, 1991 B-29 Effectiveness of UltimateLicensing Issue Memorandum from Heat Sinks (Resolved) E. S. Beckjord for B. M. Morris, August 16, 1990 B-32 Ice Effects on Safety-DROP Memorandum from Related Water Supplies (The safety concerns E. S. Beckjord for of this Issue will beB. M. Morris, addressed in the August 27, 1990 evaluation of Generic Issue 153, "Loss of Essential Service Water in LWRs")
ATTACHMENT 1 LIST OF GENERIC ISSUES FOR WHICH THE ACRS AGREES WITH THE PRIORITY RANKINGS PROPOSED BY THE NRC STAFF Generic Issue No. Title 24 Automatic Emergency Core Cooling System Switchover to Recirculation 38 Potential Recirculation System Failure as a Conse-quence of Ingestion of Containment Paint Flakes or Other Fine Debris 72 Control Rod Drive Guide Tube Support Pin Failures 73 Detached Thermal Sleeves 100 Once-Through Steam Generator Level 116 Accident Management 118 Tendon Anchor Head Failure 143 Availability of Chilled Water Systems and Room Cooling 150 Overpressurization of Containment Penetrations 154 Adequacy of Emergency and Essential Lighting 156.1.2 Dam Integrity and Site Flooding 156.1.3 Site Hydrology and Ability to Withstand Floods 156.1.5 Tornado Missiles 156.2.1 Severe Weather Effects on Structures 156.3.4 Isolation of High and Low Pressure Systems 156.3.5 Automatic Emergency Core Cooling System Switchover 156.4.1 Reactor Protection System and Engineered Safety Features Systems Isolation B-22 LWR Fuel B-32 Ice Effects on Safety-Related Water Supplies
ATTACHMENT 2 LIST OF GENERIC ISSUES FOR WHICH THE ACRS AGREES WITH THE PROPOSED PRIORITY RANKINGS BUT WITH COMMENTS Generic Issue No.: 120
Title:
On-Line Testability of Protection Systems Proposed Priority Ranking: MEDIUM ACRS Comment: We are concerned about the logic used to reach the value of the estimated decrease in risk produced by an estimated increase in the frequency of testing. Experience indicates that a significant number of unplanned trips are produced by the testing of safety systems at power. This must produce an increased risk, but no account is taken of this increase in the analysis. We recommend that the analy-sis be extended to include the estimated effects of errors in testing while at power.
Generic Issue No.: 142
Title:
Leakage Through Electrical Isolators in In-strumentation Circuits Proposed Priority Ranking: MEDIUM ACRS Comment: We note that the analysis of this issue is a good example of a situation in which so many unsupported assumptions were necessary to reach a conclusion that the final numerical result has little credibility. Further, we observe that no attention is given to the possibility of eliminating voltage or current surges, many of which probably result from inadequate plant grounding systems.
Generic Issue No.: 151
Title:
Reliability of Anticipated Transient Without Scram Recirculation Pump Trip in BWRs Proposed Priority Ranking: MEDIUM ACRS Comment: We are puzzled that no consideration appears to have been given to replacing the faulty circuit breakers with breakers having higher reliability.
Generic Issue No.: 153
Title:
Loss of Essential Service Water in LWRs Proposed Priority Ranking: HIGH ACRS Comment: In our August 13, 1991 letter to Mr. James M.
Taylor, EDO, regarding "Proposed Resolution of Generic Issue 130, 'Essential Service Water System Failures at Multi-Unit Sites' and Task Action Plan for Generic Issue 153, 'Loss of Essential Service Water in LWRs,'" we provided the following comments:
"... we note that RES has recently developed a Task Action Plan (TAP) for Generic Issue 153,
'Loss of Essential Service Water in LWRs.'
This work represents an expansion of GI-130 to the remaining 99 operating LWRs. The TAP states that the IPEs for the population of operating plants '... may provide information related to the ESW system' and '... may also result in an ESW risk model for each plant, which may be useful for this task.' We fail to see how a meaningful IPE can be performed without a detailed evaluation of a plant's ESWS and the accident sequences that could result from partial or complete loss of ESWS."
"We believe that GI-153 is well enough defined that it could be resolved on a plant-specific basis as part of the IPE process, and we recommend that this approach be followed. We believe also that there may be other generic issues at a similar stage of development and suggest that work on their resolution could be deferred until enough IPEs have been received and evaluated to determine if the expenditure of staff resources to deal with them as gener-ic issues is warranted."
We continue to have this position on this generic issue.
Generic Issue No.: B-29
Title:
Effectiveness of Ultimate Heat Sinks Proposed Priority Ranking: Licensing Issue (Resolved)
ACRS Comment: This issue centers on concerns associated with the validity of the mathematical models used by the NRC staff to predict the performance of the ultimate heat sink (UHS) used to cool the core following a design-basis accident. The resolution approach selected by the staff, as well as the methodology supporting the confir-mation of the NRC models, appears appropriate.
However, no mention is made of the use of natural draft cooling towers for UHS duty. We request that the staff determine if natural draft towers are used for such duty at any nuclear plants and, if so, whether the staff's models include their use.
ATTACHMENT 3 GENERIC ISSUES FOR WHICH THE ACRS DISAGREES WITH THE PROPOSED PRIORITY RANKING Generic Issue No.: 123
Title:
Deficiencies in the Regulations Governing DBA and Failure Criterion Suggested by the Davis-Besse Incident of June 9, 1985 Proposed Priority Ranking: DROP (The safety concerns of this issue have been or will be addressed in the resolution of USIs A-17, A-44, A-45, and A-47, the evalua-tion of Generic Issue 117, the IPE Program, and the Maintenance Rule)
ACRS Recommendation: HIGH Reasons: The conclusion of the staff to drop Generic Issue 123 as a new and separate issue is based on the position that all the safety concerns of this issue have been adequately addressed by the resolution of USIs A-17, A-44, A-45,
and A-47, all of which have been considered resolved.
During our review of the proposed resolution of USIs A-17 and A-47, we were told that several issues that were not addressed in the proposed resolution would be evaluated under the Multiple System Responses Program (MSRP).
The MSRP, that was completed in October 1989, identified several items for further consider-ation. These items are being evaluated by the staff to determine whether they should be pursued as generic issues. The MSRP items do not appear to have been factored into the priority evaluation of Generic Issue 123.
Consideration of the MSRP items may impact on the staff's conclusion to drop this issue.
Therefore, we believe that the staff should consider the MSRP items in the priority evalu-ation of Generic Issue 123. Until this is done, we recommend that this issue be assigned a HIGH priority.
Generic Issue No.: 156.1.6
Title:
Turbine Missiles Proposed Priority Ranking: DROP (The safety concerns of this issue were addressed in the evaluation of Generic Issue A-37, "Turbine Missiles")
ACRS Recommendation: HIGH Reasons: In our July 18, 1991 letter to Mr. James M.
Taylor, EDO, regarding "Concerns Related to the General Electric Advanced Boiling Water Reactor Design," we recommended that the staff consider the development of a set of preopera-tional and periodic operational inspection, evaluation, and acceptance requirements for new and replacement low pressure (LP) turbine rotors that utilize the new integral forging technology. We were particularly concerned about the use of unbored integral rotors. We have not yet received a response from the EDO to this recommendation.
A related concern is the need for this same kind of requirement for new and replacement Brown-Boveri LP turbine rotors that are manu-factured by welding forged disks together.
We note that catastrophic failure of a turbine rotor can occur at normal operating speed if undetected flaws grow to critical size. Thus, avoidance of overspeed does not resolve this issue.
In addition, the lessons learned from the November 9, 1991 turbine-generator overspeed event that occurred at the Salem Nuclear Plant, Unit 2, need to be evaluated with re-spect to the assumptions that have been made historically in the turbine missile risk analysis.
We believe that each of these issues need to be addressed before this generic issue can be resolved.