HL-5652, Forwards,For Clarity,Original Question 2 & Complete Revised Answer to 980630 Response to 980414 NRC Ltr Re GL 96-06, Waterhammer in Containment Coolers

Forwards,For Clarity,Original Question 2 & Complete Revised Answer to 980630 Response to 980414 NRC Ltr Re GL 96-06, Waterhammer in Containment Coolers

ML20236M981
Person / Time
Site:	Hatch
Issue date:	07/08/1998
From:	Sumner J SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-96-06, GL-96-6, HL-5652, TAC-M96819, TAC-M96820, NUDOCS 9807140348
Download: ML20236M981 (3)

Text

_ __ . _ _ . _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

. Lewis Sumner Southern Nuclear

. VerPresident Operating Company. Inc.

Hatch Project Support - 40 lovemess Parkway Post Office Box 1295 Birmingham. Alabama 35201 Tel 205992.7279 Fax 205.992.0341 SOUTHERN h COMPANY Energy toServe YourWorld

July 8, 1998 Docket Nos. 50-321 HL-5652 50-366 Tac Nos. M96819 M96820 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Edwin I. Hatch Nuclear Plant Response to Request for AdditionalInformation:

Generic Letter 96 Waterhammer in Containment Coolers RevisedResponse to Ouestion 2 Gentlemen:

On June 30,1998, Southern Nuclear Operating Company (SNC), submitted the Plant Hatch response to a Request for Additional Information (RAI) concerning post-accident waterhammer and two-phased flow in containment coolers per Generic Letter (GL) 96-06 per NRC letter dated April 14,1998.

Subsequent to the response, SNC has realized that the answer to question 2 (Enclosure page E-4 of the June 30 letter) of the RAI requires clarification. The clarification does not impact the conclusions reached by SNC regarding the susceptibility for waterhammer and two-phased flow. Specifically, the last paragraph of the SNC response to question 2 reads:

"The system does not have a safety related function, and thus no power is available to the  ;

system during a LOOP. However, if offsite power is restored during the accident, then  !

l, the operator.. "

The paragraph should be clarified to read:

4 "The system does not have a safety related function, and thus power from the emergency diesel generators (EDGs) is not automatically available to the system during a LOOP.

However, if power from the EDGs is manually restored (or if ofTsite power becomes available) to the RBCCW system during the accident, then the operator.. " s

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9007140348 980708 PDR P

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, U.S. Nuclear Regulatory Commission Page 2 July 8, 1998 i

For clarity, the original question and the complete revised answer is provided in the l

enclosure to this letter.

We apologize for any inconvenience this may have caused. Should you have any

. questions in this regard, please contact this office.

Sincerely, H. L. Sumner, Jr.

JAW /eb

Enclosure:

Response to Request for Additional Information:

Generic Letter 96 Waterhammer in Containment Coolers Revised Response to Question 2 cc: Southern Nuclear Operatine Company L Mr. P. H. Wells, Nuclear Plant General Manager SNC Document Management (R-Type A02.001)

U.S. Nuclear Reeutatory Commission. Washington. D.C.

Mr. L. N. Olshan, Project Manager - Hatch U.S. Nuclear Regulatorv Commission. Region H Mr. L. A. Reyes, Regional Administrator Mr, J. T. Munday, Senior Resident Inspector - Hatch l

i HL-5652

d h

Enclosure Edwin I. Hatch Nuclear Plant Response to Request for AdditionalInformation:

Generic Letter 96 Waterhammer in Containment Coolers Revised Response to Question 2 NRC OUESTION 2 The licensee's response indicates that because EOPs do not provide for use of the RBCCW system and the containment equipment coolers, this system is not a concern for.

waterhammer. However, during an accident, operators may consider the RBCCW system to still be available as an option for accident mitigation. Discuss measures that exist to assure that operators will not use the RBCCW system as an option during periods when waterhammer and two-phase flow could compromise system integrity.

SNC RESPONSE On both Units 1 and 2, the Reactor Building Closed Cooling Water (RBCCW) systems provide cooling to reactor building equipment, including the recirculating pumps and sump coolers in the primary containment. The system has a surge tank at its high point, which will maintain system pressure if the system is not operating.

The RBCCW system is a closed loop in containment, and thus its primary containment isolation valves do not automatically close following a LOCA or a LOCA/ LOOP. Some boiling could occur only at accident peak temperatures, following a system trip due to the LOOP.

The system does not have a safety related function, and thus power from the emergency diesel generators (EDGs) is not automatically available to the system during a LOOP.

However, if power from the EDGs is manually restored (or if offsite power becomes available) to the RBCCW system during the accident, then the operator could restart the system if needed for functions other than drywell equipment cooling. In this case, it is not anticipated that the system would be restarted until well into the event, thus boiling would not be' expected. In the unlikely event that the operator were to restart the system during peak temperature conditions, procedural controls are in place to prevent the possibility of significant water hammer conditions. The system operating procedure requires closing the associated RBCCW pump discharge valve prior to starting each pump. After starting the l pump, its manual discharge valve is slowly opened by the operator. These procedure steps

[ will prevent the possibility of rapid void collapse which could lead to a waterhammer event.

i HL-5652 E-1