ML19345E124
| ML19345E124 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 12/15/1980 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8012230257 | |
| Download: ML19345E124 (3) | |
Text
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TENNESSEE VALLEY AUTHORITY n.
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I CH ATTANOOG A. TE N NESS EE 37401 g.
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a December 15, 1980 c
h Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Denton:
In the Matter of the
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 TVA provided an initial response to D. G. Eisenhut's October 1, 1980, letter to All BWR Licensees, regarding the BWR scram system, by letter dated October 27, 1980, for the Browns Ferry Nuclear Plant. We have reviewed the scram system at our Browns Ferry plant and enclosed is a brief summary of the areas of planned modifications. We believe these modifications meet the intent of the BWR Owners' Group Design Criteria. However, at this time we have not received written notification that NRC has completed their Safety Evaluation Report for the BWR Owners' Design Criteria.
Beitause we have not completed our determination of availability of lorig lead-time procurement items, TVA anticipates providing additional information regarding our implementation schedule on or before February 1, 1981.
Very truly yours, TENNESSEE VALLEY AUT,40RITY i
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L. M. Mi Is, nager Nuclear Regulation and Safety Subscribeg d sworn to bep re
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1980.
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Notary Public My Comm'ssion Expires i
Enclosure 1
An Ecual Opportunity Employer 8
1
ENCLOSURE ADDITIONAL RESPONSE TO D. G. EISENHUT'S LETTER DATED OCTOBER 1, 1o80, TO ALL BWR LICENSEES,
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BROWNS FERRY NUCLEAR PLANT
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TVA has reviewed the scram system at Browns Ferry Nuclear Plant and intends to nake several modifications. We believe these modifications meet the intent of the BWR Owners' Group design criteria. However, at this time we have not received written notification that NRC has completed their Safety Evaluation Report for the BWR Owners' Design Criteria. These modif.' cations emphasize improving the hydraulic coupling of the scram di: sharge header (SDH) with the scram discharge instrument volume (SDIV). The modifications to be made are briefiv summarized below and are divided into three general categories; pio4ng, valving, and instrumentation.
Pioine Modifications Each unit will have two SDIV's, one on each side of the reactor.
The SDH drain to the SDIV will be equal in diameter to the SDH piping (six inches). Each SDIV will have a four-inch overflow drain that comes off the SDIV above the SDIV alarm (three-five gal). The drain piping will slope continuously down to the drain point.
Piping modifications wi 1 also be made to the SDH vents.
On each side of the reactor a four-inch vertical riser will be added to an existing drain stub and will rise above the SDH.
The SDH vent will slope continuously from the riser down to the SDH.
The vents will be crosstied in a manner that will prevent loss of venting in case of a single vent valve closure.
Valvine Modifications The vent and drain lines will have two isolation valves in series.
The valves will be of a type whose internals or the orientation of the valve itself will not allow water to pool and form a loop seal in the valve.
/
-2 Instrupentation Modifications Each SDIV will have two nain control room alarnt. (one at the
'hree-five gal level and one at the CRD withdrawal inhibit level) to alert the operator of the accunulation of water in the SDIV. Each SDIV wiil have full (four channel) scram instrumentation so that the accumulation of 50 gallons of water in each SDIV will result in a scram initiation. The instrument lines will tap into the side of the SDIV.
TVA is also currently investigating the suitability of differential pressure (dP) transmitters for use as level switches on the SDIV.
Should TVA determine that dP transmitters are suitable for the application, the scram level monitoring of the SDIV will have diverse logic.
Inolementation Sc'edule We have not ccapleted our determination of availability of long lead-time items such as qualified differential pressure instrumentation.
Therefore, TVA anticipates being able to provide a long-term implementatior schedule by February 1, 1981.
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