ML19291C209

Forwards Addl Response to NRC 791023 Ltr Re Containment Purge.Commits on Interim Basis to Block 18-inch mini-purge Valves to Open No Greater than 50 Degrees,Until NRC Review Is Complete

ML19291C209
Person / Time
Site:	Farley
Issue date:	01/15/1980
From:	Clayton F ALABAMA POWER CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
NUDOCS 8001230139
Download: ML19291C209 (5)

Text

Alabama Power Company 600 North 18th Street Post Office Box 2641 Birmingham Alabama 35291 Telephone 2C5 323-5341 nk Lko%7e4%i"in, AlabamaPower im sourne m extrc s, stem January 15, 1980 Docket No. 50-348 Director, Office of Nuclear Reactor Pegalation U. S. Nuclear Regulatory Ccmnission Washington, D. C. 20555 Attention: Mr. A. Schen r

Dear Mr. Schencer:

J. M. FARLEY NUCLEAR PIANT E NIAINMENT PURGE My letter of Decezrber 10, 1979 on this subject was intended tc respond to your letter of October 23, 1979.

Discussions betseen your staff and Alabatra Pcser Company in-dicate that additional response is required under oath per 10GR 50.54 (f) . The enclosure to this letter provides additional response as required. Please note the additional a:ranitment to block the 18-inch mini-purge valves to open no greater than 50 degrees on an interim basis until the NBC review of this subject is mmplete.

I certify that the infor: ration contained herein is true and wrrect to the best of my knowledge, infor: ration and belief.

Yours very truly, bL.Clayton,Y. J FICjr/TNE/nTrb Enclosure SVOICI TO AND SUBSCRIBED BEFOFE SE THIS n DAY OF JANCARY, 1980.

d_.

. .gs.

8 03S' 179j I N N PCBU C

}4}

%.~. ,. - l/

_/ ~~ ; w 0 l3g

1

. Ibcket FO. 50-348 Director, Office of Nuclear Peactor Ibgulation U. S. '.tclear Pegulatory Cn M ssion Washi.cton, D. C. 20555 Attention: Mr. A. Schwe.ncer

~

cc: 35. R. A. Thras

>T. G. F. Trcwbridge I

1791 344

ENCIDSURE NPC Interim Position:

1. Whenever the containnent integrity is required, emphasis should be placed on operating the mntainment in a passive mode as much as possible and on limiting all purging and venting times to as low as achievable. To justify venting or purging, there must be an established need to improve working conditions to perform a safety related surveillance or safety related maintenance pro-cedure. (Examples of improved working conditions would include deinerting, reducing temperature *, humid ty*, and airborne activity sufficiently to permit efficient performance or to significantly reduce occupational radiation exposures).

APCD RESPONSE:

The ENP purge system is u.a.w sed of 48-inch main purge valves and 18-inch mini-purge bypass valves around the 48-inch valves.

Alabama Power Orpany previously conmitted to maintain the 48-inch valves closed in nodes 1,2,3 and 4 until their operability can be denenstrated. This will be accomplished either by analysis which will be subnitted for NFC review, or by blocking the valves to allow opening to 50 degree open, or less. The valve vendor stated that 650 cpen was acceptable. After the above is accceplished on the 48-inch valves, use of those valves during nodes 1,2,3 and 4 will be only for purging to improve working conditions to perform safety related surveillance or safety related maintenance activities.

The mini-purge system is used at the Farley Plant for purging to improve working conditions and to prevent a pressure build-up in the containment. During reactor operation containment pressure builds at a rate of about 1 psig per every 24-48 hours. Farley Nuclear Plant tedinical specifications require that containment internal pressure be maintained between -1.5 and 3.0 psig. Farley Nuclear Plant does not ham a separate containment vent system acceptable for use during re-actor operation. The 4-inch post accident hydrogen vent system uses manual valves that are not capable of autcmatic closure upon contain-ment isolation signals and are, therefore, maintained closed during reactor operation.

The mini-purge system is not designed to be placed in service with a positive back pressure in containment. If pressure is allowd to build in the containnent and the purge system is then placed in operation, damage can occur to the purge system duct wrk outside con-tainment beyond the outboard isolation valve. It is, therefore, necessary to continuously purge through the 18-inch mini-purge valves which were designed for this purpose, to meet the Farley Nuclear Plant technical specifications. The 18-inch valves have been demonstrated operable per Alabama Pcwr Company's letter of December 10, 1979 under the nest severe design basis accident flow condition loading and can close within the time limit stated in the Farley Nuclear Plant technical specifications. i 1791 345

NPC Interim Position:

2. Raintain the contairant purge and vent isolation valves closed when-ever the reactor is not in the cold shutdown or refueling rode until such time as you can show that:

a. All isolation valves greater than 3" nonunal diameter used for containment purge and venting operations are operable under the most severe design basis accident flow condition loading and can close within the time limit stated in your Technical Specifications, design criteria or operating pro dures. 'Ihe cperability of butterfly valves ray, on an interim bisis, be demonstrated by limiting the valve to be no more than 300 to 500 open (900 being full open). The raximum opening shall be determined in con-sultation with tne valve supplier. 'Ihe valve opening must be such that the critical valve parts will not be damaged by DBA-IlXA loads and that the valve will tend to close when the fluid dynamic forces are introduced.

APCO RESPCMSE:

As stated above and in Alabara Pc7mr Ccmpany's letters dated August 7, 1979 and Decenter 10, 1979 on this subject, the 48-inch main purge valves at Farley Nuclear Plant will be raintained closed in nedes 1,2,3 ard 4 until the requirements of Item 2.a above are met.

As described in Alabara Pcwer Company's letter of Decerber 10, 1979, a detailed analysis was performed which derenstrated that the 18-inch Henry Pratt Ct:mpany valves with Bettis valve operators are operable under the rest severe desien basis accident flow condition loading and can close within the time limit stated in the Farley Nuclear Plant Technical Specifications.

As an additional measure of conservatism; hc%ever, Alabara Power Ccnrany hereby comits to install nemssary equipment to block on an interim basis, the 18-inch mini-purge valves such that they cannot be nere than 500 open.

'Ihe equipmnt necessary for this modification is being procure d on an expedited basis. It is planned to install these blocking devices curing an outage scheduled for January 31, 1980, subject to parts availability. If parts are not available during this outage, installation will be accxrplished during the earliest subsequent outage.

NPC Interim Position:

2b: dbdifications, as necassary, have been rade to secregate the contain-nunt ventilation isolation signals to ensure that, as a rtinimum, at least ene of the autoratic safety injection actuation signals is unirhibited and operable to initiate valve closure when any other isolation signal may be blocked, reset, or overridden. .

1791 346

APCO RESPCNSE:

A detailed review of the safety actuation signal circuits for the Farley Nuclear Plant contamment purge system (including mini-purge) was conducted by Bechtel Power (brporation, the Farley Nuclear Plant Architect Engineering firm. It was determirad that overriding the safety actuation signals for the purge system (including mini-purge) containment isolation valves is not possible.

'Ihis subject was reviewed and determined to be acceptable by NFC staff merrbers in a meeting with Bechtel and SCSI engineers and Alabama Power persennel in Bethesda, Maryland on July 31, 1979.

1791 i47'.