NUREG-0098, Forwards Safety Evaluation Supporting Util Upgraded Seismic Margin Program.Concurs W/Plans for Future Plant Changes to Assure Existing Structures,Sys & Components Not Structurally Degraded by Change

Forwards Safety Evaluation Supporting Util Upgraded Seismic Margin Program.Concurs W/Plans for Future Plant Changes to Assure Existing Structures,Sys & Components Not Structurally Degraded by Change

ML20205M610
Person / Time
Site:	Maine Yankee
Issue date:	03/26/1987
From:	Sears P Office of Nuclear Reactor Regulation
To:	Randazza J Maine Yankee
Shared Package
ML20205M614	List: ML20205M639 NUREG-0098, Forwards Safety Evaluation Supporting Util Upgraded Seismic Margin Program.Concurs W/Plans for Future Plant Changes to Assure Existing Structures,Sys & Components Not Structurally Degraded by Change
References
RTR-NUREG-0098, RTR-NUREG-98, RTR-NUREG-CR-0098, RTR-NUREG-CR-98 NUDOCS 8704020440
Download: ML20205M610 (4)

Text

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March 26,198/-

Docket No. 50-309 DISTRIBUTION

.NI FJMiraglia NRC & L PDRs ACThadani PWR #8 Rdg FCongel Mr. J. B. Randazza OELD Executive Vice President PMKreutzer Maine Yankee Atomic Power Company .PSears 83 Edison Drive OELD Augusta, Maine 04336 ACRS 10 BGrimes

Dear Mr. Randazza:

EJordan

SUBJECT:

MAINE YANKEE ATOMIC POWER STATION (MYAPS)

SEISMIC DESIGN MARGINS PROGRAM On April 17, 1979, an earthquake of approximately magnitude 4 occurred about 10 kilometers west of the plant site. This was followed by least 30 aftershocks.

On January 9, 1982, an earthquake of approximate magnitude 5-3/4 occurred in central New Brunswick, Canada. Appendix A to 10 CFR Part 100.(Seismic and Geologic Siting Criteria for Nuclear Power Plants) requires that in determining Safe Shutdown Earthquake in current licensing actions, the largest reported earthquake in a tectonic province which cannot reasonably be related to tectonic structure should be assumed to occur near the site.

As a result of the above factors, the staff held a meeting with you on May 7, 1982. At this meeting the staff expressed its concerns about the seismic hazard and seismic design adequacy of MYAPS. As a result of this-meeting, you undertook geological / seismological studies and also instituted a series of voluntary reviews and walkdowns to find any potential weak areas and identify the inherent conservatism in the plant seismic design (Ref. 3).

Several cost-beneficial upgrades, associated with equipment anchorage, were

.dentified and implemented. Based on these upgrades and the inherent design capacity of the plant, in your March 14, 1986 letter you concluded that struc-tures, systems and components at the MYAPS had sufficient strength to withstand' a seismic event of at least 0.2g with a Regulatory Guide 1.60 spectrum.

In the interim, based on the review of the your studies, results of the staff

. sponsored studies, and the staff practice in reviewing the design basis for older operating nuclear power plants under the Systematic Evaluation Program (SEP), the staff assessed that a spectrum obtained using the 50th percentile amplification factors in NUREG/CR-0098 (Ref. 5) and a peak acceleration of 0.18g represent an acceptable level to account for the April 17, 1979 and January 19, 1982 earthquakes.

By letter dated March 4, 1986, you indicated an interest in participating in an NRC-sponsored Seismic Design Margins Program (SDMP). During the past  ;

year, your staff has been working closely with the NRC staff and.'its con- j sultants on the SDMP.

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Mr. J. B. Randazza Experience data along with certain analyses were used to determine a high confidence of low probability of failure (HCLPF) capacity for components, systems, accident sequences and the plaat. The HCLPF is a conservative representatioa of capacity and in simple terms corresponds to the earth-quake level at which your plant would survive. Systems analysis was used to determine those plant systems and ccmponents (ircluding structures) that are important contributors to plant seismic safety. This allowed focusing of effort on components requiring a ma" gin review. By studying previous seismic probabilistic risk assessments (PRAs) made on pressurized water reactors, it was found that only syste.as and components needed to assure reactor subcriticality and early emergency core-coolant injection need to be considered. Further discussion of the detailed methods used in the SDMP is included in enclosure, the safety cyaluation.

It is noted that a significant amount of work in the SDMP consisted of collecting data during walkdowns. During each of the walkdowns and during most of the meetings between parties concerned with the SDMP, cognizant NRC l personnel were present and participating. The Lawrence Livermore National Laboratory (LLNL) was the primary cor. tractor to the NRC for SDMP. The results of the SDMP are documented in a three volume report by LLNL (NUREG/CR-4826, UCID-20948). The staff has reviewed this report and concurs with the tech-nical findings as they relate to the haine Yankee Nuclear Power Station.

The SDMP identified certain areas where the seismic ruggedness of the plant could be effectively enhanced. By letter dated February 26, 1987, you indica- l ted that you would make those upgrades and listed the completion dates indicated in the Table below of the enclosure. Those changes will be reviewed as part of the ongoing inspection of 10 CFR 50.59 changes. You should insure that the up-grades are not negated by any systems interactions aspects (for example, new f batteries might be installed in a different location, or with inadequate slack '

in cables, etc.) which adversely affect the assumptions made in the study.

Descripton Schedule Completion Change Date I

l o Diesel fuel day tank anchorage upgrade done 1 l o Control Room cooler anchorage upgrade done o Welding cart / gas bottle tiedown done o Security lighting tiedown done o Main control board alarm tiedown done o Strengthen blockwall VE 21-1 1987 Outage o Upgrade anchors for fans 44A & B 1987 Outage o Install internal anchors for transformers 507 & 608 1987 Outage o Replace safety class batteries 1 & 3 1987 Outage o Replace safety class batteries 2 & 4 1988 Outage o Refueling water storage tank anchorage 1988 Outage upgrade

I so wl l Mr. J. B. Randazza Based on our evaluation and your commitment to upgrade the items identified in the above Table 3 we conclude that the upgraded MYAPS will have the HCLPF capacity in the range of 0.27g. This capacity is significantly higher than the earthquake event defined by 50% spectrum of the NUREG/CR-0098 (Ref. 5) anchored to a peak acceleration of 0.18g. Therefore, all the issues associated with the design basis for MYAPS and hence the seismic design adequacy of the plant are considered resolved.

In your March 24, 1986 letter, you stated "In performing future changes to the plant, Maine Yankee will ensure that the seismic ruggedness of existing struc-tures, systems and components is maintained. New systems, and their associated structures and components will be designed to 0.18g NUREG-0098 50th percentile with SEP allowables (i.e., for piping, damping = 3% or PVRC, allowable stress =

2.4Sg no OBE) up to any interface with existing structures, systems and compo-nentV." Thus, for future plant changes, you would assure the existing structures, systems and components are not structurally degraded by the change. We agree with your plans.

Sincerely,

/s/

Patrick M. Sears, Project Manager PWR Project Directorate #8 Division of PWR Licensing-B

Enclosure:

As stated cc w/ enclosure:

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Mr. J. B. Randazza Maine Yankee Atomic Power Company Maine Yankee Atomic Power Station cc:

Charles E. Monty, President Mr. P. L. Anderson, Project Manager Maine Yankee Atomic Power Company Yankee Atomic Electric Company 83 Edison Drive 1671 Worchester Road Augusta, Maine 04336 Framingham, Massachusetts 07101 Mr. Charles B. Brinkman Mr. G. D. Whittier Manager - Washington Nuclear Licensing Section Head Operations Maine Yankee Atomic Power Company Combustion Engineering, Inc. 83 Edison Drive 7910 Woodmont Avenue Augusta, Maine 04336 Bethesda, Maryland 20814 John A. Ritsher, Esquire Ropes & Gray f

225 Franklin Street Boston, Massachusetts 02110 State Planning Officer Executive Department 189 State Street Augusta, Maine 04330 Mr. John H. Garrity, Plant Manager Maine Yankee Atomic Power Company P. O. Box 408 Wiscasset, Maine 04578 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 First Selectman of Wiscasset Municipal Building U.S. Route 1 Wiscasset, Maine 04578 Mr. Cornelius F. Holden Resident Inspector c/o U.S. Nuclear Regulatory Commission P. O. Box E Wiscasset, Maine 04578