ML17329A137

Concludes That analog-to-digital Instrumentation Replacement Has Potential Safety & Regulatory Significance.Nrc Encourages Use of Microprocessor Based Hardware

ML17329A137
Person / Time
Site:	Cook
Issue date:	08/22/1991
From:	Boger B Office of Nuclear Reactor Regulation
To:	Fitzpatrick G AMERICAN ELECTRIC POWER SERVICE CORP., INDIANA MICHIGAN POWER CO.
References
TAC-80119, TAC-80120, NUDOCS 9108290050
Download: ML17329A137 (6)

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Docket Nos

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50-315 and 50-316 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 August 22, 1991 Mr. Gene Fitzpatrick, Vice President+~g Indiana Michigan Power Company c/o Ameri can Electri c Power pgpS Service Corporation 1 Riv erside Plaza

Columbia, Ohio 43216

SUBJECT:

ANALOG-TO-DIGITALINSTRUMENTATION REPLACEMENT UNDER 10 CFR 50.59-DONALD C.

COOK NUCLEAR PLANT UNITS 1 AND 2 (TAC NOS.

80119 AND 80120)

The staff met with representatives of your staff and representatives from Asea Brown Boveri-Combustion Engineering (ABB-CE) on April 29, 1991.

The purpose of the meeting was to discuss your proposed replacement for the D AC.

Cook Nuclear Plant of portions of the existing reactor protection and control process instrumentation, as manufactured by Foxboro, with similar instrumentation as manufactured by ABB-CE Taylor under a 10 CFR 50.59 review.

The results of the meeting are contained in the staff's May 13, 1991 meeting summary.

As stated during the meeting, the staff had intended to audit your 10 CFR 50.59 review of this modification.

A copy of your 10 CFR 50.59 Safety Evaluation was requested by the staff.

In order to facilitate staff's audit, a visit to the vendor's (ABB-CE) facility was accomplished during the week of July 8-12, 1991.

Following a review of your Safety Evaluation, and based on reviews'f similar instrumentation replacements for other utilities, the staff has concluded that analog-to-digital instrumentation replacement is an issue of potential safety and regulatory significance.

Overall, the staff has been encouraging the use of microprocessor based hardware in the nuclear industry due to the reduced drift, enhanced reliability, and flexibilityof its operation.

However, to obtain these positive attributes, certain design and installation considerations must be addressed "up-front" prior to the actual installation of the equipment.'he need for these "up-front" considerations has been evidenced by microprocessor failures experienced internationally and nationally in nuclear and non-nuclear applications.

The most notable areas of concern are in the correct application of software and characteristics of the new digital electronics which could result in new failure modes and system malfunctions that were either not considered as part of initial plant design or may not have been evaluated in sufficient detail to support the qualifications of new digital systems.

In the case of software, a

comprehensive mechanism must be in place from the early design stages and into the implementation stages, to ensure that the final software package can fully and correctly perform its intended function.

Such a mechanism (verification 9108290050 9l0822 PDR ADDCI( 05000315 P

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Mr.

Gene Fitzpatrick Indiana Michigan Power Company Donald C.

Cook Nuclear Plant CC:

Regi ona1 Admini strator, Regi on III U.S.

Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Attorney General Department of Attorney General 525 West Ottawa Street

Lansing, Michigan 48913 Township Supervisor Lake Township Hall Post Office Box 818 Br idgman, Michigan 49106 Al Blind, Plant Manager Donald C.

Cook Nuclear Plant Post Office Box 458 Bridgman, Michigan 49106 U.S.

Nuclear Regulatory Commission Resident Inspectors Office 7700 Red Arrow Highway Stevens vi 1 1 e, Michigan 49127 Gerald Charnoff, Esquire

Shaw, Pittman, Potts and Trowbridge 2300 N Street, N.W.

Washington, DC 20037 Mayor, City of Bridgman Post Office Box 366

Bridgman, Michigan 49106 Special Assistant to the Governor Room 1 - State Capitol Lansing, Michigan 48909 Nuclear Facilities and Environmental Monitoring Section Office Division of Radiological Health Department of Public Health 3500 N.

Logan Street Post Office Box 30035 Lansing, Michigan 48909 Mr.

S.

Brewer American Electric Power Service Corporation 1 Riverside Plaza

Columbus, Ohio 43216

DISTRIBUTION

/Docket Ftle>

NRC & LPDRs B.

Boger J. Zwolinski L. Marsh T. Colburn C. Carpenter P. Shuttleworth OGC (For inform. Only) 15-B-18 E. Jordan MNBB-3701 ACRS (10)

P-315 PDIII-1 r/f D.

C.

Cook File S.

Newberry ll/D/23 E.

Greenman RIII

and validation) establishes a benchmark for the evaluation of safety system performance and reliability.

Additionally, digital (versus analog) system sensitivity to plant environments such as EMI, temperature, power quality and grounding raises questions regarding plant conditions.

To date, we do not believe your analysis has fully resolved all of these concerns.

1 Further, it is the staff s belief that this modification does create the possibility for an accident or malfunction of' different type than any evaluated previously in the safety, analysis report (excluding plants licensed with microprocessor based systems) and is, therefore, an unreviewed safety question.

To support the conclusion, the staff examined the history of 10 CFR 50.59 and compared it to the issue at hand.

It is clear that a technology change, i.e.,

analog to digital, will have new potential failure mechanisms (software,

EMI, etc.).

It is equally clear, that plant safety analyses that were performed prior to the use of microprocessors do not specifically address such failure mechanisms.

It is the staff's belief that these potential new failure mechanisms create the possibility of system malf'unctions not previously reviewed in the safety analysis.

With respect to your facility, we have determined that a formal staff review will be necessary to address the above concerns and any related concerns which may arise.

It is expected that with timely responses to staff requests for additional information from either your organization or the vendor, the staff shall be able to expedite the review process and allow the staff to complete the review prior to your scheduled installation.

If you have any questions, please contact T. Colburn at (301) 492-1341.

Sincerely, Original signed by Bruce A. Boger, Director Division of Reactor Projects - III/IV/V Office of Nuclear Reactor Regulation cc:

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