ML20210C648

Forwards Safety Evaluation Re Adequacy of Offsite Power Sys for Facility,Per Util 861107 Request.Use of Surowiec Line Unacceptable Substitute for Mason Line to Startup Unit

ML20210C648
Person / Time
Site:	Maine Yankee
Issue date:	04/23/1987
From:	Sears P NRC
To:	Randazza J Maine Yankee
Shared Package
ML20210C653	List: ML20210C648 ML20210C663
References
NUDOCS 8705060259
Download: ML20210C648 (3)

Text

P o O APR 2 31987 Docket No.: 50-309 Distribution:[Dockebile NRC & L PDRs PKreutzer PSears PWR #8 Files OELD ACRS 10 EJordan JPartlow BGrimes FNiraglia AThadani Mr. J. B. Randazza Executive Vice President Maine Yankee Atomic Power Company 83 Edison Drive Augusta, Maine 04336

Subject:

Safety Evaluation Concerning the Adequacy of the Offsite Power System for the Maine Yankee Atomic Power Station By letter dated November 7,1986, you requested a safety evaluation concerning the adequacy of your offsite power system for the Maine Yankee Atomic Power Station (MYAPS). In December 1982, a low voltage condition occurred while the plant was starting up and was being supplied only by the 115 kv Surowiec offsite power line. Another offsite power line, the 115 v Mason line was out of service at the time. A similar low voltage event occurred in July 1986.

The emergency buses at MYAPS are supplied from the main generator during normal plant operation via two separate auxiliary transformers. During plant startup, or upon the loss of the main generator the emergency buses are supplied from the 115 kv switchyard which utilizes a ring bus arrangement.

Two of the four outgoing 345 kv lines supply power to the Mason station and Surowiec substation. Voltage from this station and substation is stepped down to 115 kv and then supplied to the 115 kv switchyard at the Maine Yankee plant. In the event that both 115 kv lines are lost, the emergency buses can be supplied by disconnecting the main generator from the main transformers and energizing the auxiliary transformers. Furthermore, the plant technical specifications require only one 115 kv line to be operable whenever the reactor coolant system temperature and pressure exceeds 210 F and 400 psig.

The existing offsite power system at MYAPS satisfies the requirements set forth in Ceneral Design Criterion 17 when the 115 kv Mason line is one of the lines in service. When the Surowiec line is the only 115 kv in service, there are two situations where the capacity of the line has not been demonstrated to be adequate. One is following a unit trip concurrent with or without an accident. Under this condition, you have not shown that there is sufficient capacity in the line to supply all conncected non-safety loads in addition to the emergency loads required to mitigate the consequences of the accident or to shutdown the reactor. The other situation concerns the capacity of the g f o g h h5 g P

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Mr. Randazza Surewiec line to startup the unit which was demonstrated to be insufficient during the low offsite power voltage event in December 1982. If the capacity of the Surowiec line is demonstrated to be adequate during accident or reactor.

shutdown conditions, then this line can be used as an acceptable substitute for the Mason line during normal power operations, however, the sole use of the Surowiec line for plant startup would not he' permitted until the question of adequate line capacity is resolved during this mode of operation.

Based on the information available to the staff, we cannot reach a favorable conclusion about the acceptability of the Surowiec. Therefore, we consider this line to be an unacceptable substitute for the Mason line.

Our Safety Evaluation is enclosed.

Sincerely, Patrick M. Sears, Project Manager PWR Project Directorate No. 8 Division of PWR Licensing-B

Enclosure:

As stated h

DRP DI-3 LA/D -3 PP -3 PSears MRus b+ook efses 04/1/87 3 04/ 87 04/13/87

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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 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 i Wiscasset, Maine 04578 1

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