ML20134M652

Requests Myap Response to Listed Questions Re Rept of Independent Safety Assessment of Licensee Conducted During Summer of 1996

ML20134M652
Person / Time
Site:	Maine Yankee
Issue date:	11/21/1996
From:	Dan Dorman NRC (Affiliation Not Assigned)
To:	Frizzle C Maine Yankee
References
TAC-M96589, NUDOCS 9611250218
Download: ML20134M652 (5)

Text

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U NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30006 4001

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k...../ Mr. Charles D. Frizzle, President November 21, 1996 Maine Yankee Atomic Power Company i 329 Bath Road

Brunswick, ME 04011 L

SUBJECT:

. ADEQUACY OF THE OFFSITE POWER SY9 TEM AT MAINE YANKEE ATOMIC POWER STATION.(TAC NO. M96589)

J

Dear Mr. Frizzle:

i l By letter dated October 7,1996, the NRC issued the report of the Independent Safety Assessment (ISA) of Maine Yankee Atomic Power Company (MYAPCo)

! conducted by the NRC staff during the summer of 1996. The ISA examined the offsite power system and identified concerns regarding the adequacy of Section j

69 of the 115 kV offsite power system (referred to as the Suroweic line.)

Specifically, as a result of a voltage study of the grid conducted by Central

! Maine Power, MYAPCo identified that its electrical system analyses failed to I consider the effect of.a motor-driven feedwater pump (MDFWP) automatic start

[ following fast transfer of plant loads to the reserve 115 kV offsite power j- system.

o MYAPCo informed the ISA that a back-feed from the main trar.sformer through the normal station service transformers would serve as an alternate source of

, reserve power. The ISA did not consider the back-feed an acceptable basis _for compliance with the plant Final Safety Analysis Report (FSAR) and Maine Yankee.

Design Criterion 39. However, the ISA team considered this situation to be of

! low safety significance considering the historical stability of the grid, the

! existence of two independent reserve power transformers, and the limited

!: conditions under which the Suroweic line would be unavailable.

i On November 9, 1396, with the Suroweic line unavailable due to breaker

! maintenance, a faalt in the grid end of Section 207 of the 115 kV system (the i Mason line) caused a failure of a lightning arrestor at the Maine Yankee site

and loss of all 115 kV offsite power to the site. The Suroweic line was

! restored approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> into the event. The event was terminated when

the Mason line was restored 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 23 minutes into the event. The plant

, operated throughout the event, providing power to plant loads from the main j generator through the normal station service transformers.

By letter dated February 29, 1980 (WMY 80-32), MYAPCo submitted a voltage i study, " Auxiliary Power System Voltage Study for Maine Yankee Atomic Power i Station," that was conducted to determine "if the offsite power system and onsite electric distribution system is of sufficient capacity with capability i to automatically start and operate all safety loads if all onsite power i j- sources are not available." In that letter, MYAPCo stated that, "We have also F reviewed the electric power systems at Maine Yankee and found total compliance h

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with [ General Design Criterion (GDC)] 17." O 1

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I 9611250218 961121 PDR ADOCK 05000309 P. PDR h

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, Mr. Charles D. Frizzle ,

i On November 15, 1996, the NRC staff conducted a telephone conference call with j members of your staff regarding the event of November 9 and the adequacy of 2

the offsite power system at Maine Yankee. The NRC staff understands that

Suroweic is no longer capable of sustaining required voltage while receiving a 3' fast transfer of plant loads as the second (delayed) offsite power source. It appears that MYAPCo has changed the licensing basis from GDC 17 to Criterion 39 and has now chosen the 345 kV back-feed as the delayed offsite power i source. During the conference call, the NRC staff tried to convey the

! following understanding:

1) Based on the 1980 adequacy study, MYAPCo took a position of total compliance with GDC 17 for the offsite power system. It has been the NRC staff's understanding during subsequent l discussions regarding the offsite power system that MYAPCo was i working toward satisfying that requirement. The NRC staff was

not aware of MYAPCo's new position.

s l 2) Criterion 39 requires that the onsite and offsite power systems be independent and each system be single failure

' proof. Therefore, Criterion 39 is more stringent than GDC 17.

. Because a single failure proof offsite power system is not l attainable, GDC 17 does not require the offsite power system j design to be single failure proof.

In view of MYAPCo's position, the staff requests MYPACo to respond to the j following questions within seven days of the date of this letter.

j 1) Provide the assumptions and results of any analyses (i.e.,

f systems and voltages) that demonstrate the ability to maintain j safe shutdown (i.e., not exceeding fuel design limits,

maintaining reactor coolant pressure boundary, etc.) of the

! plant during the period required (i.e., 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />) to establish 1 the back-feed.

i 2) Identify MYAPCo's intention regarding the licensing basis I (i.e., GDC 17 or Criterion 39) for the offsite power system

! and state any plans to amend the plant technical j specifications to reflect the licensing basis. In addition, l submit a copy of your safety evaluation that provided the i~ bases for your determination that the change in the design criterion for the offsite power system did not involve an unreviewed safety question.

l 3) Provide MYAPCo's plans and schedule to restore the adequacy of i the Suroweic line and/or to reduce the required time to l establish the back-feed.

Mr. Charles D. Frizzle November 21, 1996 If you have any questions regarding this matter, please call me at (301)415-1429.

Sinc.erely.

Original s,igned by:

Daniel H. Dorman, Project Manager Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket No. 50-309 cc: See next page DISTRIBUTION:

Docket File. > EPeyton PUBLIC DDorman PD1-3 Reading OGC

SVarga ACRS JZwolinski RConte, RI

. JCalvo i- DOCUMENT NAME: G:\D0RMAN\M96589.LTR To receive a copy of this document,indcate in the ben: *C* = Copy without ettechment/ enclosure "E* = Copy with attachment / enclosure "N" = No copy 0FFICE DRPE:PM l PD4-2:LA l NRR:DE p ,l , DRPE:D V f'l l j NAME DDorman:dt# W EPeyton m FU JCalvo v^" JZwolin(kT j DATE 11/21/96 11/91/96 11 8.//96 11/M/96 11/ /96 i 0FFICIAL RECORD COPY k

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l. Mr. Charles D. Frizzle .

l If you have any questions regarding this matter, please call me at (301)415-1429.

. Sincerely, 4 d, _o- -

Daniel H. Dorman, Project Manager Division of Reactor Projects - I/II

Office of Nuclear Reactor Regulation l Docket No. 50-309 cc

See next page

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Maine Yankee Atomic Power Station Maine Yankee Atomic Power Company cc:

Mr. Robert W. Blackmore Mr. Charles B. Brinkman Plant Manager Manager - Washington Nuclear Maine Yankee Atomic Power Station Operations P.O. Box 408 ABB Combustion Engineering Wiscasset, ME 04578 12300 Twinbrook Parkway, Suite 330 Rockville, MD 20852 Mr. G. D. Whittier, Vice President Licensing and Engineering l Thomas G. Dignan, Jr., Esquire Maine Yankee Atomic Power Company l Ropes & Gray 329 Bath Road  !

One International Place Brunswick, ME 04011 l Boston, MA 02110-2624 l Mr. Patrick J. Dostie Mr. Uldis Vanags State of Maine Nuclear Safety State Nuclear Safety Advisor Inspector l State Planning Office Maine Yankee Atomic Power Station State House Station #38 P.O. Box 408 Augusta, ME 04333 Wiscasset, ME 04578 Mr. P. L. Anderson, Project Manager Mr. Graham M. Leitch l Yankee Atomic Electric Company Vice President, Operations 580 Main Street Maine Yankee Atomic Power Station Bolton, MA 01740-1398 P.O. Box 408 Wiscasset, ME 04578 '

Regional Administrator, Region I U.S. Nuclear Regulatory Commission Mary Ann Lynch, Esquire 475 Allendale Road Maine Yankee Atomic Power Company King of Prussia, PA 19406 329 Bath Road Brunswick, ME 04578 First Selectman of Wiscasset Municipal Building Mr. Jonathan M. Block U.S. Route 1 Attorney at Law Wiscasset, ME ~04578 P.O. Box 566 Putney, VT 05346-0566 Mr. J. T. Yerokun Senior Resident Inspector Maine Yankee Atomic Power Station U.S. Nuclear Regulatory Commission P.O. Box E Wiscasset, ME 04578 Mr. James R. Hebert, Manager Nuclear Engineering and Licensing Maine Yt.nkee Atomic Power Company 329 Bath Road Brunswick, ME 04011 Friends of the Coast P.O. Box 98 Edgecomb, ME 04556