ML20140B637

Responds to NRC 860117 Request for Addl Info Concerning Response to Generic Ltr 83-08 Re Mod of Vacuum Breakers on Mark I Containments

ML20140B637
Person / Time
Site:	Hatch
Issue date:	03/13/1986
From:	Gucwa L GEORGIA POWER CO.
To:	Muller D Office of Nuclear Reactor Regulation
References
0397C, 397C, GL-83-08, GL-83-8, SL-441, TAC-57156, TAC-57157, NUDOCS 8603240254
Download: ML20140B637 (7)

Text

. Georgia Power Company 333 Piccmont Averue Atlanta, Georgia 30308 Telephone 404 5264526 Maang Address:

Post Office Box 4545 Atlanta. Georgia 30302 h Georgia Power L T. Gucws tre scattem Mrtnc system Manager Nuclear Safety and Licensing SL-441 0397C March 13, 1986 Director of Nuclear Reactor Regulation Attention: Mr. D. Muller, Project Director BWR Project Directorate No. 2 Division of Boiling Water Reactor Licensing

! U. S. Nuclear Regulatory Commission Washington, D. C. 20555 HRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 EDWIN I. HATCH NUCLEAR PLANT UNITS 1, 2 MODIFICATION OF VACUUM BREAKERS ON MARK 1 CONTAINMENTS (GENERIC LLIIER 83-08)

Gentlemen:

By letter dated January 17, 1986, the NRC requested additional information related to the GPC response to Generic Letter 83-08 dated June 9,1983. In response to this request GPC submits the following:

Question 1.

Is the chugging source rate used in the Hatch evaluation the same as the one developed in CDI Report (#84-3)? If not the same provide the chugging source rate with the supporting justification (please note CDI Report corrected from #83-3 to #84-3).

Response

The original Hatch evaluation has been modified to reflect the methodology followed in CDI Report No. 84-3. Revised pages to the GPC evaluation are attached.

Question 2.

Did the Hatch calculation apply the 1.07 load factor to account for the uncertainty in calculating the underpressure (Section IV of the staff's generic evaluation).

8603240254 e60313 PDR P

ADOCK 05000321 PDR _

Georgia Powerkh Director of Nuclear Reactor Regulation Attention: Mr. D. Huller, Project Director BWR Project Directorate No. 2 March 13,1986 Page 2

Response

The load factor used to assure conservative prediction of

, the underpressure and detailed in response to question 2 of

" Response to NRC Request for Additional Information on Mark I Containment Program Wetwell to Drywell vacuum Breaker Load Methodology, Revision 0," Continuum Dynamics, Inc.

Technical Note No. 84-11, October 1984, was applied to the Hatch evaluation. The load factor used in the plant unique evaluation was 1.06 and yields a conservative prediction of the underpressure.

Question 3.

Have the Hatch calculations used the drywell model which results in the most conservative prediction (Section V of the generic evaluation)?

Response

Drywell modeling was examined in Continuum Dynamics, Inc.

Technical Note No. 84-11, October 1984 'For the Hatch evaluation the acoustic volume model . results in a more conservative forcing function, and was therefore used.

Should you have any questions regarding this subject, please contact this office.

Very truly yours,

. T. Gucwa JDH/lc attachment c: J. P. O'Reilly J. T. Beckham, Jr.

H. . C. Nix, Jr.

Dr. J. N. Grace (NRC-Region II)

Senior Resident Inspector V00775

e ATTACHMENT TO LETTER SL-441 8

I

1. Develop a dynamic model of the vent system, steam water interface and pool slosh with the condensation rate of the interface unknown.

2. Use measured drywell pressure to determine the condensation rate.

3. With the condensation rate determined, predic c ansteady pressures at other vent locations to validate the model.

4. Use the condensation source at the vent exit to drive dynamic models to determine plant unique vacuum breaker forcing functions.

The details of the Vacuum Breaker Model development were originally presented in Continuum Dynamics, Inc. (CDI) Technical Note 82-31 " Mark 1 Vacuum' Breaker Improved Valve Dynamic Model", September 1982. This document was later supplmented by CDI Report No. 84-3 " Mark 1 Wetwell to Drywell Vacuum Breaker Load Methodology", February 1984. These reports have.been reviewed and accepted by the NRC subject to the restrictions imposed by Sections IV and V of Generic Letter 83-08 dated January 17, 1986. The Generic Letter also Rev. 1 includes a " Request for Additional Informa tion Related to the Modification of Vacuum Breakers on Mark I Containment Edwin I. Hatch Nuclear Plant, Units 1 and 2". .

The vacuum breaker model was applied to the wetwell/drywell vacuum breakers to derive a pallet impact velocity. Plant unique parameters were revised to reflect a two cylinder configuration for the drywell in order to treat each W **&

, ,.-+.r--,w y w. , - - - - ,--s = -

TABLE 3 Plant Characteristics /Rev 1 for Hatch 1 Value Used Parameter In Computation Vent / pool area ratio 0.045 Drywell volume / main vent 596.10 /Rev 1 area ratio (ft)

Main vent area /downcomer area 0.99 Main vant length (ft) 37.32 Header area /downcomer area 1.47 Header length (ft) ~15.0 ft Downcomer area (ft)2 3.01 ft 2 Downcomer length (ft) 10.8 ft Submergence head (f t) 3.77 ft water * /Rev 1 Lower drywell volume length 50.21 ft /Rev 1 2

Lower drywell volume area 2081.3 ft /Rev 1 i Upper drywell volume length 51.9 ft /Rev 1 Upper drywell volume area 512.9 ft 2 /Rev 1

• Submergence head with AP removed is 4.0 ft water. The value used leads to additional conservatism. /Rev 1 t

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, TABLE 4 Plant Characteristics /Rev 1 for Hatch 2 Value Used Parameter In Computation Vent / pool area ratio 0.045 Drywell volume / main vent

• 534.24 /Rev 1 area ratio (ft)

Main vent area /downcomer area 0.99 Main vent length (ft) 37.32 Header area /downcomer area 1.47 Header length (ft) 15.0 Downcomer area (ft2 ) 3.01 Downcomer length (ft) 10.8 Submergence head (ft water) 4.0* /Rev 1 Lower drywell volume length 50.21 ft /Rev 1 Lower drywell volume area 2081.3.fc2 '/Rev 1 Upper drywell volume length 51.9 ft /Rev 1 2

4 Upper drywell volume area 512.9 ft /Rev i

• Submergence head with A P removed is 4.33 f t. The value used leads to additional conservatism. /Rev 1 4

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TABLE 6 Vacuum Breaker Valve Response for Edwin I. Hatch Nuclear Plant Units 1 & 2 Unit 1: .

Maximum closing impact velocity 4.19 rad /see Maximum opening angle 0.038 rad Rev. 1 Number of closing impactsabove 1 rad /sec 6 Unit 2:

Maximum closing impact velocity 4.11 rad /sec Maximum opening angle - 0.032 ' rad Rev. 1 Number of closing impacts above 1 rad /sec 6 9

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