ML20084D339

Submits Results of GE Review of 831222 Analysis of Scram Discharge Vol Vent & Drain Valve Closure Times in Excess of 30 S.Ge Does Not Concur W/Analysis.Closure Times Should Be Accepted as Is.Continued Plant Operation Justified

ML20084D339
Person / Time
Site:	Hatch
Issue date:	04/23/1984
From:	Gucwa L GEORGIA POWER CO.
To:	Stolz J Office of Nuclear Reactor Regulation
References
NED-84-204, TAC-53327, TAC-53328, NUDOCS 8405010302
Download: ML20084D339 (2)

Text

1 o Gw>rg a Power Corrpy

' 333 Petnant Avenue Attanta Georgia 30308 Teletrone 404 526 6526 M i+1tng Adfrew Post O!!ce Box 4M5 Attanta. Georqa 39302 Georgia Power L T. Gucwa ru urm mguc wwm Manager Nuc&ar Er7neet ng are en-t Nuciear E ve.,, NED-84-204 April 23,1984 Director of Nuclear Reactor Regulation Attention: Mr. John F. Stolz, Chief Operating Reactors Branch No. 4 Division of Licensing U. S. Nuclear Regulatory Commission Wa shi ng ton, D. C. 20555 NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 EIMIN I. HATCH NUCLEAR PLANT UNITS 1, 2 SCRAM DIS 01ARGE VOLUME VEKr AND DRAIN CLOSURE TIMES Gentlemen:

By letter of December 22, 1983, Georgia Power Company provided to NRC an analysis concerning operation with scram discharge volume (SDV) vent and drain valve closure times in excess of 30 seconds (the current GE specification). At NRC request, this analysis was provided to General Electric for myiew. Additionally, GE was asked to provide bases for the 30 second closure time specification. This letter provides the results of the GE review and our plans to resolve the closure time issue.

GE provided no quantitative basis for the 30 second closure times, and it appears that none exists. However, qualitative bases addressing three areas were provided: 1) Hydrodynamic Loads; 2) CRD Leakage Flow; and 3)

High Temperatures.

1. Hydrodynamic loads are caused when the SDV vent and drain valves close. The nature and extent of these loads is very dependent on i

pipire configuration. GE provided no correlation between hydrodynamic l loads and valve closure times.

2. CRD leakage flow could fill the SDV, resulting in water flow through

! the vent lines if the vent valve has not closed. This could result in l additional pipe loadings and possible radiological concerns.

3. High temperatures exceeding the piping and equipment design temperature of 280 F are more likely to occur if the 30 second closure time limit is exceeded. The design versus actual operating temperature of the scram discharge system has been the subject of considerable discussion among GE, industry, and NRC. GE has since specified the 30 second limit, which was not one of the of the original Hatch design criteria, to help limit temperatures of the system following a scram.

8405010302 840423 '

PDR P ADOCK 05000321 PDR

\

GeorgiaPower d U. S. Nuclear Regulatory Commission Division of Licensing April 23,1984 Page 2 As a result of their assessment of items to be considered, which was qualitative in nature, and their industry-wide posture regarding the 30 second closure times, GE was unable to concur with our analysis as provided in the December 22, 1983, letter. Since extensive analyses would be required to justify longer closure times, we are now investigating minor hartlware modifications to bring the closure times closer to the 30 second limit. A test has been scheduled for Unit 2 during the current outage to determine minimum closure times obtainable with these minor system modifications. If the results of this test indicate that minor modifications alone will not bring the closure times to within the 30 second limit, we have instructed our architect / engineer to expedite procurement and design of modifications necessary to achieve 30 second closure times.

Following completion of this test, we will provide you with a schedule for completion of necessary modifications.

We would like to reiterate that Hatch Unit I was designed, and has operated for nine years, with vent and drain valve closure times well in excess of the current GE specification. In this time, the only damage to the SDV, SDV piping, or supports that has been found has been one bent hanger, attributed to an installation error. Hatch Unit 2 did experience hydrodynamically caused damage to the floats in the SDV instrument w,Jumes.

This problem was attributed to instrument line routing and was corrected.

At the time this damage occurred, closure times for Unit 2 were measured and found to be under 30 seconds, indicatire that valve closure times were not a factor. We therefore believe that continued operation with the longer closure times represents no risk to the health and safety of the public.

Please contact this office if you desire further information. -

Very truly yours, f 7~ g e =

L. T. Gucwa REB /

xc: H. C. Nix, Jr.

J. P. O'Reilly (NRC-RII)

Senior Resident Inspector, Plant Hatch 1

f