ML20214L152

Submits Addl Info Re Loss of Offsite Power for Both Units W/One Diesel Generator Available & Reactor Coolant Seal Integrity Following Loss of Offsite Power.Seal Cooling Water Supply Not Required to Assure Seal Integrity

ML20214L152
Person / Time
Site:	Calvert Cliffs
Issue date:	09/05/1986
From:	Salyards L BALTIMORE GAS & ELECTRIC CO.
To:	Thadani A Office of Nuclear Reactor Regulation
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.25, TASK-TM NUDOCS 8609090442
Download: ML20214L152 (3)

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BALTIMORE GAS AND ELECTRIC CHARLES CENTER . P.O. BOX 1475 + BALTIMORE, MARYLAND 21203 NUCLEAR ENGINEERING SERVICES DEPARTMENT CALVERT CUFFS NUCLEAR POWER PLANT LUS8Y. MARYLAND 20657 September 5,1986 U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C. 20555 ATTENTION: Mr. Ashok C. Thadani, Director PWR Project Directorate #8 Division of PWR Licensing-B

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Exigent Request for Amendment

REFERENCES:

(a) Letter from Mr. 3. A. Tiernan (BG&E), to Mr. A. C. Thadani (NRC),

dated August 25,1986, same subject (b) Letter from Mr. 3. A. Tiernan (BG&E), to Mr. A. C. Thadani (NRC),

dated August 1,1986, same subject (c) Letter from Mr. E. 3. Butcher (NRC), to Mr. A. E. Lundvall, Jr.,

(BG&E), dated October 7,1985, NUREG-0737 Item II.K.3.25 (d) Letter from Mr. A. E. Lundvall, Jr. (BG&E), to Mr. 3. R. Miller (NRC), dated November 30, 1984, Reactor Coolant Pump Seal Integrity Following Loss of offsite Power Gentlemen:

In response to requests from Mr. S. A. McNeil of your office, we are providing the following information to clarify certain sections of Reference (a). We hope this information will aid you in processing Reference (b).

Deterministic Analysis in Reference (a), we provided an analysis based on a scenario postulated by your office.

We were to assume a loss of offsite power for both units with only one diesel generator available and a Reactor Coolant Pump Sealleak of 40 gpm on the unit other than the one to which the diesel generator is aligned. Our analysis of this hypothetical event showed that the decay heat load can be removed by natural circulation and that the Reactor

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Mr. Ashok C. Thadani September 5,1986 Page 2 Coolant System (RCS) pressure will not exceed the Pressurizer safety valve setpoint as long as Steam Generator inventory is maintained. The initial RCS inventcry, excluding the Pressurizer, was conservatively assumed to shrink to a volume consistent with a temperature of 212 F and a pressure of 2500 psia. Calculations show there is adequate fluid volume without makeup flow to keep the core covered for at least 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />. in the postulated scenario, we had only to assume that AC power would be unavailable for four hours, after which the power would be restored.

The four-hour restoration time assumed in Reference (a) is supported by several NRC and

. Industry sources. In NUREG-1109," Regulatory Analysis for the Resolution of Unresolved Safety Issue A-44, Station Blackout," the median restoration time for offsite power was given as about one-half hour, with 90% of the losses being restored in three hours or less. NUREG-1032, " Evaluation of Station Blackout Accidents at Nuclear Power Plants,"

includes graphs that display the probability of restoring offsite power following plant-centered and grid-related losses. Figures A.2a, A.2b, and A.4 in NUREG-1032 show that greater than 90% of the losses can be restored within four hours. These data are consistent with the conclusions of NSAC-103, EPRI's study of loss of offsite power events.

In addition, our grid system studies show that at least one of our 500 kv power lines will be restored within four hours following a loss of offsite power. The system restoration study for PEPCO's electrical system was reviewed. In this study, SMECO is identified as a portion of PEPCO's load that would be restored early, within two hours if possible, during their system restoration. Therefore, we feel a four-hour restoration time for offsite power is both realistic and reasonable.

Reactor Coolant Pump Seal Leakage Regarding NUREG-0737 Item II.K.3.25, " Reactor Coolant Pump Seal (RCP) Integrity Following Loss of Offsite Power," the industry's position has been that seal cooling water flow is not required to maintain RCP seal integrity. This position was reiterated in Reference (d). In fact, Reference (c) found BG&E in compliance with this NUREG-0737 Item.

Based on industry data, a two-hour loss of seal cooling could damage seal non-metallics that may initiate RCP seal leakage on the order of 0-10 gpm. However, there is no apparent reason to believe that a loss of RCP seal cooling to an idle pump can directly violate the reactor coolant pressure boundary integrity. Therefore, the seal cooling water supply is not required to assure seal integrity following a loss of offsite power. We do not believe that a complete loss of seal function will occur as the result of a loss of offsite power.

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Mr. Ashok C. Thadani September 5,1986 Page 3 Should you have further questions regarding this subject, we would be pleased to discuss

< them with you.

Very truly yours, q

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% W L. E. Salyards Principal Engineer - Licensing Unit LES/SRC/ dim cc: D. A. Brune, Esquire

3. E. Silberg, Esquire S. A. McNeil, NRC T. Foley, NRC T. Magette, DNR I

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