NUREG-0606, Discusses 336th Meeting of ACRS on 880407-09 Re Proposed Resolution of USI A-47, Safety Implications of Control Sys. Disagrees That NRC Recommendations Constitute Resolution of USI A-47 as Originally Defined

Discusses 336th Meeting of ACRS on 880407-09 Re Proposed Resolution of USI A-47, Safety Implications of Control Sys. Disagrees That NRC Recommendations Constitute Resolution of USI A-47 as Originally Defined

ML20151L958
Person / Time
Issue date:	04/12/1988
From:	Kerr W Advisory Committee on Reactor Safeguards
To:	Zech L NRC COMMISSION (OCM)
References
REF-GTECI-A-47, REF-GTECI-SY, RTR-NUREG-0606, RTR-NUREG-606, TASK-A-47, TASK-OR ACRS-R-1295, NUDOCS 8804220204
Download: ML20151L958 (3)

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%'og UNITED STATES fhY NUCLEAR REGULATORY COMMISSION

$  ; ,E ADVISORY COMMITTEE ON REACTOR SAFEGUARDS O WASHINGTON, D. C. 20655 April 12, 1988 The Honorable Lando W. Zech, Jr.

Chairman U.S. Nuclear Regulatory Comission Washington, D.C. 20555

SUBJECT:

PROPOSED RESOLUTION OF USI A-47, "SAFETY IMPLICATIONS OF CONTROL SYSTEMS" - ACRS COMMENTS During the 336th meeting of the Advisory Comittee on Reactor Safe-guards, April 7-9, 1988, we discussed the NRC Staff's proposed resolu-tion of USI A-47, "Safety Implications of Control Systems." We prev-icusly met -with members of the NRC Staff and reviewed the proposed resolution during cur 331st meeting on November 5-7, 1987. Our Sub-comittee on Instrumentation and Control Systems met on October 29, 1987 and March 24, 1988 to consider this matter. We also had the benefit of the documents referenced.

The proposed resolution of USI A-47 requires certain design modifica-tions or upgrades for many plants, technical specification modifications for all plants, and issuance of an information letter to all applicants and licensees. These matters are currently scheduled to be published for public coment in April 1988, and the final resolution is scheduled to be issued in April 1989.

Although we agree with the proposed resolution of USI A-47 as it relates to steam generator and reactor vessel overfill, we believe that the scope of the issue has been unduly truncated. The problem description of USI A-47 in the last revision of the Aqua Book (NUREG-0606, "Unre-solved Safety Issues Sumary," now discontinued) gave a much broader l issue for evaluation, with steam generator / reactor vessel overfill and l overcooling transients identified only as a subtask. Other tasks  !

included evaluation of all control system failures that have safety implications and evaluation of the effects of loss of power on control systems. It is not clear that these tasks were performed. We believe that they should be. l l

When reconsidering the scope, we recomend including an evaluation of 1 the safety implications of failures in nonsafety-grade control systems that result from comon-cause external events such as earthquakes, fires, and other potentially far-reaching events such as high or mod-erate energy pipe breaks. Such events were not evaluated in USI A-47, and we do not believe that they are adequately treated elsewhere in the context of this USI.

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r The Honorable Lando W. Zech, Jr. April 12, 1988 We recommend also that other events be included, such as the degradation or loss of control power or control air and the improper functioning of heating, ventilating, and air conditioning systems 1particularly when temperature-sensitive devices are in the effected environment). Our questions to the Staff concerning these events met with less than satis-factory assurances that they have been considered in the program.

In conjunction with these efforts, the Staff should develop its position on how similar events will be included when resolving USI A-17, "Systems Interactions in Nuclear Power Plants," which considers safety-grade protection systems and protective actions. Since such events are likely to affect more than one system or component, whether safety grade or not safety grade, it is necessary to show how the evaluations performed for A-U end A-47 collectively cover the situation.

We cannot agree that the Staff's recomendations constitute resolution of USI A-47 as originally defined. We re:omend that the proposed resolution be issued as the resolution of an appropriately redefined generir. issue and that the remaining concerns, as identified above, be included in c new generic issue, which need not necessarily be accorded 051 stetus.

Sincerely,

. b W. Kerr Chainnan Re ferencas:

T.' U.S. Nuclear Regulatory Comission, Draf t NUREG-1217, "Evaluation of Safety Implications of Control Systems in LWR Nuclear Power Plants," Technical Findings Related to Unresolved Safety Issue A-47, April 1987.

2. U.S. Nuclear Regulatory Comission, Draft NUREG-1218, "Regulatory Analysis for Proposed Resolution of USI A-47, Safety Implications of Control Systems," April 1987.

3. U.S. Nuclear Regulatory Comission, NUREG/CR-4265, "An Assessment of the Safety Implications of Control at the Calvert Cliffs 1 Nuclear Power Plant," Volumes 1 and 2. April 1986 and July 1986, respectively. j

4. U.S. Nuclear Regulatory Ccmmission, NUREG/CR-3958, "Effects of  !

Control System Failures on Transients Accidents and Core-Melt l Frequencies at a Combustion Engineering Pressurized Water Reactor,"

March 1986.

i The Honorable Lando W. Zech, Jr. April 12, 1988

5. U.S. Nuclear Regulatory Comission, NUREG/CR-4047, "An Assessment of the Safety Implications of Control at the Oconee 1 Nuclear Plant," March 1986.

6. U.S. Nuclear Regulatory Comission, NUREG/CR-4386, "Effects of Control System Failures on Transients, Accidents, and Core-Melt Frequencies at a Babcock and Wilcox Pressurized Water Reactor,"

Dece.ober 1985.

7. U.S. Nuclear Regulatory Comission, NUREG/CR-4387, "Effects of Centrol System Failures on Transients, Accidents, and Core-Melt Frequencies at a General Electric Boiling Water Reactor," December 1985.

8. U.S. Nuclear Regulatory Comission, NUREG/CR-4385, "Effects of Control System Failures on Transients, Accidents, and Core-Melt Frequencies at a Westinghouse PWR," November 1985.

9. U.S. Nuclear Regulatory Comission, NUREG/CR-4326, "Effects of Control System Failures on Transients and Accidents at a 3-Loop, Westinghouse Pressurized Water Reactor," Volumes 1 and 2. August 1985 and October 1985, respectively.

10. U.S. Nuclear Regulatory Comission, NUREG/CR-4262, "Effects of Control System Failures on Transients and Accidents at a General Electric Poiling Water Reactor," Volumes 1 and 2, May 1985.

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