ML20153B147

Summary of Instrumentation & Control Sys Subcommittee 880324 Meeting in Washington,Dc to Review NRC Analysis & Study to Limit Scope of USI A-47, Safety Implications of Control Sys, & to Examine Validity of Limiting Process

ML20153B147
Person / Time
Issue date:	03/31/1988
From:	Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
TASK-A-47, TASK-OR ACRS-2565, NUDOCS 8807120723
Download: ML20153B147 (8)

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gggs-M66 G f pf '?/ilf f Puf 7 7iQ DATE ISSUED: 3/31/88

'l I'll8f MEETING MINUTES /

SUMMARY

OF THE INSTRUMENTATION AND CONTROL SYSTEMS SUBCOMMITTEE MEETING MARCH 24, 1988 WASHINGTON. D.C.

PURPOSE The purpose of the meeting was to review the NRC Staff's analysis and study to limit the scope of USI A-47, "Safety Implications of Control Systems," and to examir.c the validity of that limiting process.

ATTENDEES ACRS NRC Staff J. Ebersole, Chairman N. Anderson, RES H. Lewis, Member R. Baer, RES C. Michelson, Member A. Szukiewicz, RES C. Wylie, Member D. Thatcher, RES P. Davis, Consultant M. El-Zeftawy, Staff G. Brown, Fellow Others S. Ball, ORNL D. Fitzgerald, GA0 X. Arn, Serch Licensing l R. Borsum, B&W l

f MEETING HIGHLIGHTS, AGREEMENTS, AND REQUESTS

1. Mr. Ebersole, Subcomittee Chairman, stated the purpose of the Subcomittee meeting and introduced the other present ACRS members l

and consultants. Mr. Ebersole commented that he is bothered by the limited vision and understanding with which the NRC Staff is E M NATE3 ORIGINAI, 88071%h pgg

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Instrumentation & Control Systems Meeting Minutes March 24, 1988 handling USI A-47. (He cited an example of a man looking for his lost jewel under a light on the street just because it is the only place where there is some light to see). He advised the Staff to look at processes quite distant from the ultimate effect on the core and anticipates to uncover some critical cascades.

2. Mr. R. Baer, NRC/RES, presented an overview of the Staff's method-ology to handle USI A-47, "Safety Implications of Control Systems."

He indicated that some of the confusion had resulted from two factors. One factor is that the Staff usually discusses with the ACRS the resolution of one USI at a time, and there is no existing format to treat the interrelationship and overlap between different USIs. The other factor is that the Staff tends to emphasize those areas where new requirements can be justified via a cost / benefit process. The NRC Staff usually tends not to emphasize areas where a low residual risk and consequently additional requirements could n9t be justified.

Mr. Baer connented that as far as the resolution of USI A-47, the Staff did follow the agreed-upon scope and did not just focus on one or two events.

3. Mr. N. Anderson, NRC/RES, presented a general discussion regarding the scope of generic issues. He indicated that the first step is

! identification of a safety concern. The issue may come from any sources (e.g., individual safety concerns, concerns of ACRS, AEOD reports, operating reactor events, etc.). Generally, the initial scope is defined by the initiator. The scope is further defined during prioritization which is subjected to management review. If prioritization warrants, issue is assigned to a task manager to develop a task action plan (TAP). The scope could be changed as necessary, but only with management review and approval.

Instrumentation & Control Systems Meetie.9 Minutes March 24, 1988

4. Mr. A. Szukiewicz, NRC/RES, Task Manager of USI A-47 described the issue as a program to evaluate the effects of non-safety grade control system failures on plant safety. Mr. Szukiewicz presented the efforts in the TAP as follows:

• Identify control systems whose failure can lead to significant primary system transients.

• Develop and conduct computer simulation studies on 4 plant designs.

• Identify failure modes of significant control systems.

Evaluate effects of loss of power supply to control systems.

• Determine the need for control for protection systems.

Provide criteria for evaluation of control systems (if neces-sary).

Identify control systems that could lead to overfill or overcooling transients.

• Evalutte the potential for waterhamer in the steam lines as a result of a steam generator or reactor vessel overfill.

• Perform risk analysis and cost / benefit analysis on significant control systems.

The basic assumptions are as follows:

• Potential effects of comon cause events (such as earthquakes, flood, fire, sabotage, or operator errors of omission or

Instrumentation & Control Systems Meeting Minutes March 24, 1988 l

I conmission), were evaluated in a limited manner by evaluating selected multiple failures.

Transients during LC0 and ATWS events were excluded from scope.

• Plant-specific designs were appropriately modified to comply with IE Bulletin 79027 ("Loss of Non-Class IE Instrumentation and Control Power System Bus DurinC Operation") and NUREG-0737 (TMI Action Plan) USI A-47.

The Summary of the proposed resolution to USI A-47 is as follows:

• Limited number of requirements.

• Provide overfill protection (all plants).

• Provide periodic verification of overfill protection (tech specs).

• Provide diverse automatic initiation of EFW (0conee only).

Improve emergency procedures for SBLOCA (CE plants with low head pumps).

5. Mr. D. Thatcher, NRC/RES, presented an overview for USI A-17, "Systems Interactions." The A-17 proposed resolution is as fol-lows:

• Generic 1.etter:

- Provide information to all licensees.

- Request verification of flooding evaluations.

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Instrumentation & Control Systems Meeting Minutes March 24, 1988

• Acknowledge relation with A-46, "Pressurized Thennal shock."

• Provide Power supply information TI GI-128.

• Provide system interaction information for PRAs.

• Develop other concerns for separate treatment - multiple system responses.

6. Mr. Baer presented a new program called "Multiple Systems Response Program." This program is designed to nandle the residual issues or overlap between A-47 and A-17. The program plan is as follows:

Identify concern from sources (e.g., ACRS letters and meet-ings).

Classify concern (one of tnree options):

- Covered under another program or issue.

- Develop a basis for why concern is not a safety issue.

- Develop concern into issue for prioritization.

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• Publish results into a report.

• Prioritize issues.

7. As a result of the Subcommittee's discussion, the Subcommittee members raised some concerns regarding the following:

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• Mr. Ebersole expressed some concern in regard to the focal point in the Staff's study which is mainly on protection systems and not the control systems as a whole. The Staff responded that the NRC does not have too many requirements on control systems, but it has many requirements on protection 1

Instrumentation & Control Systems Meeting Minutes March 24, 1988 4

systems, and consequently due to that fact, the Staff is constrained in dealing with USI A-47.

• Mr. Michelson expressed some concern in regard to the process of resolving an issue, and commented that the Staff must continue to monitor experience to verify that the experience was bounded by the resolution of this issue. The Staff responded that the current morning report process should cover this concern. Mr. Michelson disagreed and mentioned that there is a whole set of events that deal with design defi-ciencies which usually escape the morning report process and he cited for example (Peach Bottom, Limerick, Sequoyah, and Kewauneeevents).

' Mr. Michelson questioned the process for identifying a generic problem and commented that NRR not necessarily study the short-range view problems as generic problems.

Mr. Wylle expressed some concern regarding the prioritization process and how the NRC Staff decides on dropping certain issues. The Staff responded that it is usually done on a cost / benefit analysis, and then it is subjected to the Staff peer review.

• Mr. Michelson questioned the prioritization process and the Staff's peer review which are perfomed based on office letters and memos, and not through a manual chapter proco.ss.

' Mr. Ebersole stated the scope of USI A-47 has been vastly truncated and the title of this USI should be modified to reflect this limitation.

Instrumentation & Control Systems Meeting Minutes March 24, 1988

• Mr. Ebersole mentioned that the Staff in its study excluded important and fundamental events, e.g., excessive voltage or frequency and hydrogen explosion.

• Mr. Michelson comented that the Staff also excluded events like the air system failures especially in the excessive direction of more air supply. Mr. Michelson also cited the Kewauneeevent(LER#87-012-Rev.01)whichindicatesa potential for control valve failure in the non-safe mode due to overpressurized solenoid valves.

• Mr. Michelson expressed some concern regarding a condition of a non-safety grade control system interfacing with a safety-grade control system. He cited the Peach Bottom event (LER

1. 87-028) which involves four relays with mercury tube switches in the diesel generator room carbon dioxide fire suppression system control circuits that are classified as safety-related or seismic, could initiate diesel generator trip signals during a loss of offsite power event if actuated by seismic conditions. Mr. Michelson also cited another event (Limerick, LER#87-055). Mr. Ebersole shared the same concern.

• Mr. Michelson expressed some concern regarding the Multiple Systems Response Program and comented that this program should include an item to handle the high energy line pipe break. The Staff agreed.

FUTURE ACTION The Subcomittee Chaiman or his delegates may wish to brief the full Comittee during April 7-9, 1988, regarding the Subcomittee rHvities on this issue. The full Cumittee may then decide to write kiter on this subject.

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Instrumentation & Control Systems Meeting Minutes March 24, 1988 NOTE: Additional meeting details can be obtained from a transcript of this meeting available in the NRC Public Document Room, 1717 H Street, N.W., Washington, D.C., or can be purchased from Heritage Reporting Corporation, 1220 L Street, N.W.,

Washington, D.C. 20555,(202)628-4888.