ML20127P685

Responds to NRC 850404 Request for Addl Info Re Small Break LOCA Drywell Temp Profiles Used for Environ Qualification of Electrical Equipment.Curves & Rept Describing Methodology Used in Generating Curves,Transmitted w/

ML20127P685
Person / Time
Site:	Hatch
Issue date:	05/10/1985
From:	Gucwa L GEORGIA POWER CO.
To:	Stolz J Office of Nuclear Reactor Regulation
References
0606Y, 606Y, NED-85-356, TAC-42505, TAC-42506, NUDOCS 8505240053
Download: ML20127P685 (3)

Text

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Georgia Power Company 333 Piedmont Avenue e

Atlanta, Georga 30308 Telephone 404 5266526 Ma: ling Address:

. Post Offce Box 4545

- Attanta. Georgia 30302 Georgia Power L T. Gucwa the southern eiwitc system Manager Nuclear Engineenng and Chief Nuclear Engneer NED-85-356 0606y May 10, 1985 Director of N.1 clear Reactor Regulation

-Attention: Mr. John F. Stolz, Chief Operating Reactors Branch No. 4 Division of Licensing l

U. S.' M2 clear Regulatory Conmission Washington, D. C.

20555 I

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NRC DOCKE7IS 50-321, 50-366

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OPERATING LICENSES DPR-57, NPF-5 EDWIN I. HA'101 NUCLFIR PLANT UNITS 1, 2 RESPONSE 'IO RtJJurBf' EUR ADDITIO4AL INEORMATION ON DRYWELL TEMPERA'IURE EQUIPMENT QUALIEUATION PROFILES Gentlemen:

. By ' letter dated April 4, 1985, the NRC regaested that Georgia Power Conpany (GPC) sulnit additional information regarding the Small Break Loss

' of ' Coolant Accident (SBIOCA) drywell temperature profiles used for environmental catalification of electrical ecalignent under 10 CFR 50.49 at Plant Hatch. - These curves, along with' a report describing the methodology used in their generation, were originally transmitted to the NRC as an enclosure to letter NED-84-079 (dated February 24, 1984).

The referenced NRC letter req 2ested that GPC:

1)

Demonstrate for all types and sizes of primary system breaks, that -

the operator can remove a low -presa2re injection system for its reactor vessel core cooling function after 20 minutes following onset of the accident and still meet the vessel core cooling and coverage regairements.

Standard licensing assunptions should be used in this analysis, including loss of offsite power and the most limiting single failure in the safety systems needed to mitigate the accident.

hyg PDR IQ

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l GeorgiaPower

, Director of M1 clear Reactor Regulation

. Attention:. Mr. John F.:Stolz, Chief' Operating Reactors Branch No. 4 May 10, 1985 Page Two 2):

Demonstrate that the control room instrumentation and emergency-operating procedires available.to the control room operators are L alfficiently clear and single to follow so as -to allow for operator-

- action to initiate the drywell sprays & ring the 10 minute interval

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.'after the ' low presaire system can' safely be transferred to the

' drywell~ spray function. '!he time split between the system transfer

- c and. operator action, 20 minutes and ' 10 minutes, - respectively, is based on the staff's understanding of the physical realities 'of the situation. Different time splits can be utilized by the licensees,

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- if justified, so long as the total-time-is ecalal to or less than 30 minutes, if the enclosed curves are to-be used for emipment qualification purposes.

iWith ~ regard to item 1 above, GPC has addressed this isale for small breaks :in J the report (NSED-52-0583)' which was enclosed with our February 24,

-1984 attaittal (Section 5.0; Asainptions. 3,11, and 16).

The Resi&al Heat Removal :(RHR)' System which provides low presaire coolant injection to the

-reactor vessel as well as the primary containment spray capability for each

. Hatch unit is dedicated ~ to.the spray functions d1 ring a SBWCA and is

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asalmed to provide no make-up to the reactor vessel d1 ring these events. In

' addition, one of' the two trains of RHR is -asalmed to be inoperable, since this represents-the most limiting single. failure for the small line breaks.

'For in-containment line breaks larger than those addressed in -NSED-52-0583, T

the tenperature profiles which are expected are mich less severe than those

. predicted for the - small break events even without' use.of the containment-

. sprays (see Unit 1 FSAR Section 14.4, Unit 2 FSAR Section 6.2)..Therefore,

. containment; spray operation is not necessary to enaire' catalified ecalipment alrvival: for line breaks greater than 0.5 ftZ.

With~ regard.to Litem 2 above, GPC is in the process of form 11ating new Emergency Operating Procedires (EOPs) for Plant Hatch.

These procedtres will. contain provisions which would effectively recatire operator action to zinitiate drywell sprays within 30 mimtes following certain in-containment

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ihigh energy.line ~ breaks.

Any line break which could otherwise pro & Ice' an

in-containnent environment harsher than that ~ for which drywell 10 CFR 50.49 master-list" equipnent has been catalified, will be ' covered by these procedures.

The criteria for : initiation of the' spray system will te based

- on drywell' pressires and' tenperatures which analyses show would occur d1 ring t

the ' accidents of concern.

These accident scenarios have been acted out using 'the Plant Hatch main control room similator, utilizing these new EOPs as operator ' instructions daring the _ accident sequences.

In each case, the drywell. sprays ' were initiated' by operator action as directed by these

. procedtres within 30 mimtes of commencement of the sinulated line break.

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' Director of Nuclear Reactor' Regulation Attention: -Mr. John F. Stolz, Chief Operating Reactors Branch No. 4 May 10,-.1985 Page Three The' emergency procedires carrently in 'use at Plant Hatch which deal with

' operator = action to initiate drywell sprays (procedures HNP-1-1111, 1902; ItiP-2-1111, 1902) will be revised to realire < operator action to initiate

-contairunent~ spray upon occurence of - the same parameters used for marmal spray initiation in' the new EDPs. These revisions will be coupleted by July 31,1985. : Confirmation that these revised procedures consistently result in operator - initiation'of the sprays within 30 mirutes after any of the pipe breaks of. concern will be obtained using the control room similator.

- The above referenced accident ' sin 11ations have or will demonstrate that T the control room _ instrumentation now in. use, the current plant emergency procedures with the above proposed revisions, and : the proposed new EOPs which, will.soon be - available to the control room operator are alfficiently-clear so as to allow for operator action to initiate drywell sprays when

necessary. for : protection. of qualified in-contairunent equipment.from

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excessive; tenperatures.'

As also - realested by your April 4, 1985 ' letter GPC has evaluated the appropriate drywell equipment against the 00mDIPT code profile generated by.-

the' NRC ' staff for' Plant Hatch.

Environmental test data and ' analyses currently.on file _ demonstrate that. each piece of. this eslipment will contirne to 2 perform its intended safety function for the req 11 red time

interval diring and after exposure to that-tenperature profile.

-Should 1you have any further calestions regarding this issue _ please i

contact this office.

Very truly yours,

/ f 4G' e+

L. T. G1 cwa l

CBS

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- xc:1 H. C. Nix, Jr.

NRC Regional Administrator Senior Resident Inspector 170077S '