ML19332G037

Summarizes Util Plans to Recaulk & Seal Plant Refueling Floor Precast Concrete Panel Walls,Per 891129 Telcon. Special Purpose Procedure Developed to Ensure That Containment Integrity Maintained During Recaulking

ML19332G037
Person / Time
Site:	Hatch
Issue date:	12/13/1989
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
HL-864, NUDOCS 8912200060
Download: ML19332G037 (4)

Text

5

/M Georg a Power Company '

/

by!W 333 Piectmont Amnue M. . Atlanta. Goorgia 30300 Qj[D , Tolephone 404 5?G3195- ,.. ,

l Maihng Address f 40 inverness Conter Parkway ,

R Post Off ce Box 1295 /

[ Birmingham. Alabama 35?01 bephone 20s 868 $581

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5 ftv wunvm c!wint micm o W. o. Hairston, ill -

l Senior Vr.e President  ;

Nuclear bporations HL-864 0458V December 13, 1989 3

U.S. Nuclear Regulatory Commission

. ATTN: Document Control Desk >

Hashington, D.C. 20555 PLANT HATCH - UNITS 1, 2 i NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 REQUEST FOR INFORMATION ON SECONDARY CONTAINMENT PRECAST PANEL SEALING Gentlemen: .

1 As requested in a telephone call between Georgia Power Company (GPC) and Nuclear Regulatory Commission (NRR) personnel on November 29, 1989, this letter provides information on GPC's plans to recaulk and seal the l

Plant Hatch Unit 1 and Unit. 2 refueling floor precast concrete panel'

. walls._ Specifically, the staff verbally requested details on the ,

. requirements and precautions which will:be taken during the recaulking to

i. ensure that secondary containment integrity can be maintained. The k enclosure provides a brief description of the precast panels and the i impact .on secondary containment integrity during recaulking, as well as

-the requirements and precautions being implemented to control the work.

c 'He believe : the administrative . Wntrols and additional testing which

! will be in place during the performance of this task provide adequate assurance that -' secondary containment will be - available, and that no unreviewed safety question exists. ~If you have any questions please contact this office.

9 Sincerely, l

l.

gl. k . / k ! S H. G. Hairston, III GKM/eb

Enclosure:

Request for Information Secondary, Containment Precast Panel Sealing c: (See next page.) [()P /

'8912200060 891213 ip PDR ADOCK 05000321 PDC l[l

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'/df ~ Georgia Power d -

e-U.S. Nuclear Regulatory Commission December 13, 1989 Page Two c: Georaia Power ComDanV Mr. H. C. Nix, General Manager - Nuclear Plant Mr. J. D. Heidt, Manager Engineering and Licensing - Hatch GO-NORMS l

U.S. Nuclear Regulatory Commission. Washinaton. D.C.

Mr. L. P. Crocker, Licensing Project Manager - Hatch U.S. Nuclear Regulatory Commission. Region II Mr. S. D. Ebneter, Regional Administrator Mr. J. E. Menning, Senior Resident Inspector - Hatch p.

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0458V l

i.

ENCLOSURE  !

! 1 PLANT HATCH - UNITS 1, 2 NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 RE0 VEST FOR INFORMATION ON SECONDARY CONTAINMENT PRECAST PANEL SEALING

Background

The secondary containment _ is: a structure which encloses the primary  ;

containment and those components which may contain primary system fluid.  !

. The structure forms a control volume which serves to dilute fission products which may escape from primary containment following an accident. To minimize ground level exfiltration of post-accident fission products, while allowing the secondary containment to be designed as a conventional structure, the secondary containment requires support i systems to maintain the control volume pressure less than external ambient pressure. The standby gas treatment system (SGTS) is designed to take suction from the control volume and exhaust it though appropriate

' treatment equipment, while maintaining a 1/4 inch (water) vacuum.

The-Plant Hatch refueling floor is part of secondary containment and is shared by both units. Integrity of secondary containment is required at all times when either unit is operating. The secondary containment boundary at the refueling floor is formed by precast concrete panels.

The design gap between a pair of precast panels is 1/4 inch and reduces

.to 1/8 -inch at the panel -tongue and groove mating point. This gap, or

-joint, is filled with backing and caulking. The backing alone is capable of providing leakage path sealing for maintaining the secondary containment boundary, however when the old caulking is removed, the backing will potentially also be pulled out and need to be replaced.

Design calculations of the drawdown capabilities of the SGTS assume a total inleakage area.of 0.13 square feet. If the backing is removed with

- the caulking, and no other leakage path is assumed, this corresponds to about 12 linear feet of panel-to-panel joint. Administrative controls will restrict the length of the joint that can be exposed at any time for cases where backing is or is not installed. Periodic testing of the SGTS drawdown capability will be performed to verify the secondary containment is being resealed properly.

0458V HL-864 E-1

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, l ENCLOSURE (Continued)  !

REQUEST FOR INFORMATION ON SECONDARY CONTAINMENT PRECAST PANEL SEALING

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Controls. Reauirements and Precautions l A special purpose procedure has been developed to provide adequate as'surance that secondary containment integrity is maintained during the -

recaulking of the Unit 1/ Unit 2 refueling floor precast panel walls. The procedure will allow no more than 12 linear feet of joint to be stripped  :

without immediately replacing the backing materials, and no more than 52 ,

linear feet of joint may be in an unsealed /uncaulked state at any time '

even with the backing material installed. Under no circumstances will ,

any length of joint be left unattended without the backing material in j place. Approximately 8300 linear feet of joints in the Hatch reactor >

building are to be resealed. Each small strip will have existing loose ;

.or deteriorated sealing and waterproofing material removed, the surfaces i cleaned, and new sealant (caulking) and any necessary backing applied.  !

Secondary containment integrity will be verified after a few sections are j resealed (i.e., early in the process), after the job is complete, and at hold points. corresponding to approximately one third and two thirds  !

complete.

The 12 linear feet of exposed joint is equivalent to the 0.13 square feet inleakage area assumed in design, and represents a reasonable length of joint to work with in order to accomplish the job in a timely manner. ,

The exposed joint may not be the only secondary containment leakage '

path. Therefore, in addition to the limitations described above, jcints

, will not be exposed unless an appropriate length of backing is on band l for the worker. Also, the workers will maintain radio communications with the control room at all times. When work is biing performed using

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scaffolding, backing material and radio equipment will be on the i scaffold. Workers will be prepared to immediately close any open joint with backing material if directed to do so by control room personnel.

Considering the stringent controls limiting the gap size, the low probability of an accident which would cause significant fission products to be deposited in secondary containment, realistic accident progression time (i.e., time to core damage), and the short amount of tims required for reinstalling the backing material, the administrative controls and precautions are reasonable and appropriate. Based on the above information, we can take credit for secondary containment being maintained throughout the caulking replacement activity.

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l 0458V i HL-864 E-2 1