ML20217B770

Submits Corrected Info to NRC 980528 RAI Re Util Response to GL 96-06, Assurance of Equipment Operability & Containment Integrity During Design-Basis Accident Conditions

ML20217B770
Person / Time
Site:	Peach Bottom
Issue date:	10/06/1999
From:	Hutton J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-96-06, NUDOCS 9910130061
Download: ML20217B770 (4)

Text

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' E-- A NRC GL 96-06 g v lPECOLNUCLEAR i

esco ere c-965 Chesterbrook Boulevard A Unit of PECO Energy wayne, PA 19087-569 f October 6,1999 Docket Nos. 50-277 50 278 Lbense Nos. DPR-44 DPR-56

. U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

' Peach Bottom Atomic Power Station, Units 2 and 3 Correction to NPC Request for Additional Information (RAI)

Regarding Generic Letter 96-06

Dear Sir /Medam:

By letter dated May 28,1998, the NRC requested additional information (RAl) related to PECO Energy Company's (PECO) response to Generic Letter (GL) 96-06 " Assurance i

'of Equipment Operability and Containment Integrity During Design-Basis Accident

Conditions," for Peach Bottom Atomic Power Station (PBAPS), Units 2 and G. PECO provided a response to the NRC RAI by letter dated September 11,1998.

A subsequent discussion with the NRC staff reviewer regarding the September 11, 1998, GL RAI response lead to the discovery of an error contained in the RAI response.

Specifically, the maximum expected temperature of the reactor building closed cooling water (RBCCW) within the unit cooler cooling coils at the time of RBCCW pump restart

was indicated to be 124*F. - While reviewing the unit cooler vendor data a misinterpretation of the data with regard to the amount of coolant contained within the unit cooler cooling coils was discovered. Our original essessment used a water weight of 712 pounds per cooling coil, whereas the true water weight is approximately 62

. pounds. This . misinterpretation led to a non-conservative assessment of the water temperature. During this same review, PECO also discovered the analysis did not consider a potential loss of a nitrogen support system which could impact the unit cooler inlet valves. L Considering such a scenario would also increase the water temperature within the cooling coil to be as high as 145'F prior to the postulated

. LOCA/ LOOP rather than the 65'F originally assumed in our September 11,1998, RAI response.

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October 6,1999 Page 2 PECO has performed a comphte review of both our original response to the GL and our response to the RAl. The misinterpretation of the vendor data and the new worst-case scenario are the only instances of non-conservative data and assumptions made in our evaluation. The affected values of the water mass within the cooling coil and the

- initial temperature of the water within the cooling coil at the initiation of the postulated

- loss of coolant accident (LOCA) concurrent with a loss of offsite power (LOOP) was only used in assessing the response to question number 1 of the RAI (i.e., immediate response waterhammer potential). Therefore, PECO's response to all other NRC RAI questions are unchanged from our September 11,1998 letter. The revised worst case highest water temperature following a LOCA/ LOOP using the same methodology contained in our September 11,1990, response and considering the above corrections has been iecalculated to be 202'F. PECO has placed this error issue in its corrective action program for further investigation.

However, PECO has reconsidered our original response methodology contained in our letter dated September 11,1998, and submits the following responso that supersedes our original response to RAI question number 1 with regard to the immediate response watertiammer.

QUESTION:

Discuss specific system parameter requirements that must be maintained to assure that waterhammer will not occur (e.g., RBCCW head tank and DCWS expansion tank level, temperature, pressure), and state the minimum margin to boiling that exists, including l consideration of measurement and analytical uncertainties. Describe andJustify a reliance on any non-safety relatedinstrumentation and controls for assuring that l waterhemmer will not occur, and explain why it would not be appropriate to establish  !

Technical Specification requirements for maintaining these parameters. ]

RESPONSE

The worst-case event for the immediate response waterhammer concem is the LOCA /  !

LOOP. The electrical load sequence for this event is contained in the PBAPS Updated l Final Safety Analysis Report (UFSAR) Table 8.5.1. The containment temperature i response for this event is provided in the PBAPS UFSAR Figure 14.6.11 A. During this event a peak drywell temperature of 295*F is reached approximately (9) seconds

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t following the event initiation. The drywell temperatore then drops to 276'F j approximately 15 seconds following initiation of the evont.

l The bottom of the RBCCW tank is at elevation 281' 9" and the highest unit cooler is at

. elevation 152' 0".' With an assumed water temperature of 135*F in the RBCCW tank l and lines (this temperature is chosen to bound the maximum normal reactor building )

temperature of 104'F), the RBCCW system head (i.e., from the bottom of the tank to j the unit cooler) provides a line pressure vathin the unit cooler of at least 55 psig. The j saturation temperature at this pressure is 302*F. ,

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With a conservatively low pressure in the unit cooler cooling coils of 55 psig (saturation temperature of 302*F) and a peak containment temperature for the large-break LOCA of 295'F, water in the cooling coils is not expected to void. The minimum margin to boiling, 302*F - 295'F = 7'F, is conservative since it assumes instantaneous and perfect heat transfer to the water within the cooling coils.

Considering the system head pressure and resulting r turation temperature, the peak drywell temperature for the large-break LOCA will not cause the water in the RBCCW system to void. This assumes that the system is filled and operating prior to the postulated scenario, if normal system parameters are not present the RBCCW system would not be operating and the reactor will be shut down to protect plant equipment.

No non-safety related instrumentation or controis are relied upon for this assessment

. and there are no system parameter requirements that must be maintained to assure waterhammer will not occur, with the exception of the assumption of water level at the

' bottom of the RBCCW hee.d tank, as stated earlier.

The system instruments (i.e., system temperature and tank level) are non-safety I related, however, they provide positive measures which are considered acceptable to l support normal and EOP-directed actions. Although these instruments perform support i functions for equipment already contained in PBAPS Technical Specifications (i.e., I containment), they themselves do not meet the criteria for laclusion into Technical Specifications. instruments monitoring diverse parameters also provide assurances that changes within the drywell cooling system are detected and appropriate actions are taken, in conclusion, the PBAPS design and operation assures that waterhammer in the containment unit cooler cooling coils will not occur during the immediate (automatic) system response. ,

I If you have any questions regarding this submittal, please contact us. i Very truly yours,

. A. Hutton Director- Licensing

- Attachments cc: H. J. Miller, Administrator, Region I, USNRC A. C. McMurtray, USNRC Senior Resident inspector, PBAPS

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' COMMONWEAL.TH OF PENNSYLVANIA . : I

ss COUNTY CF CHESTER  :

J. J. Hagan, being first duly sworn, deposes and says: that he is Senior Vice President of PECO Energy Company, the Applicant herein; that he has read the enclosed corrected response to NRC RAI regarding Generic Letter 96-06 " Assurance of Equipment Operability and Containment integrity During Design-Basis Accident Conditions," for Peach Bottom

, Atomic Power Station, Units 2 a.id 3, Facility Operating License Nos. DPR-44 and DPR-56, and knows the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information, and belief, ce esident Subscribed and swom to l before me this/d day of 9999.

I N/tary Public

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Carol A.Wunon  %;c q^ w'M% @b c

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