ML18038B866
| ML18038B866 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 04/25/1997 |
| From: | Abney T TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-96-003, IEB-96-3, TAC-M96137, NUDOCS 9705010181 | |
| Download: ML18038B866 (12) | |
Text
CATEGORY 1 REGUIAT INFORMATION DISTRIBUTION STEM (RIDS)
ACCESSION, NhR:9705010181 DOC.DATE: 97/04/25 NOTARIZED:
NO FACIAL:5~0-296 Browns Ferry Nuclear Powe. Station, Unit 3, Tennessee AUTH.NAME AUTHOR AFFILIATION ABNEY,T.E.
Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
SUBJECT:
Provides response to NRC Bulletin 96-003, "Potential Plugging of Emergency Core Cooling Water Suction Strainers By Debris in Boiling-Water Reactors."
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TITLE: NRC Bulletin 96-03, "Potential Plugging of ECCS Strainers by NOTES:
DOCKET I 05000296 C
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E, NOTE TO ALL "RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE-WASTE.
TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD)
ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED:
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Tennessee Valley Authority, Post Office Box 2000, Decatur, Ahbarre 35609-2000
'April 25, 1997
. U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of Tennessee Valley Authority Docket No. 50-296 BROWNS FERRY NUCLEAR PLANT (BFN)
NRC BULLETIN 96 03 r POTENTIAL PLUGGING OF EMERGENCY CORE COOLING WATER SUCTION STRAINERS BY DEBRIS IN BOILING-WATER REACTORS (TAC NO. M96137)
This letter summarizes TVA's compensatory actions which were requested by NRC in letters dated January 29,
- 1997, and February 19, 1997.
Specifically, NRC granted TVA's petition to defer the actions required to resolve NRC Bulletin 96-03 for BFN during the Unit 3 Cycle 7 refueling outage if certain compensatory actions were completed.
These.included:
desludge the suppression pool; perform inspections of the drywell insulation; and perform a drywell and suppression pool inspection.
During Unit 3 Cycle 7 Outage which concluded on March 13,
- 1997, TVA completed the requested compensatory actions.
Detailed descriptions of activities taken to fulfillNRC requests are provided in the enclosure.
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U.
S. Nuclear Regulatory Commission Page 2
April 25, 1997 There are no new commitments made in this letter. If you.
have any questions please contact me"at (205) 729-2636.
S'ncerely, ney Manager of Lic sing and Industry ffairs Enclosure cc:
(Enclosure)
Mr. Mark S. Lesser, Branch Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900
- Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road
- Athens, Alabama 35611 Mr. J.
F. Williams, Project Manager U. S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Roc kville, Maryland 20852
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ENCLOSURE TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNIT 3 NRC BULLETIN 96-03, POTENTIAL PLUGGING OF EMERGENCY CORE COOLING SUCTION (ECCS)
STRAINERS BY DEBRIS IN BOILING-WATER REACTORS The purpose of this enclosure is to provide the details of the compensatory actions taken by TVA to assure the operabili;ty of the Unit 3 ECCS suction strainers during Unit 3 Cycle 8 operation.
By letter dated May 6,
- 1996, NRC provided Bulletin 96-03, which requested that TVA implement the appropriate measures to minimize the potential clogging of the Emergency Core Cooling Systems (ECCS) suppression pool strainers by debris generated during a loss of coolant accident (LOCA).
The subject bulletin concerns the potential for loss of ECCS following a LOCA due to inadequate net positive suction head (NPSH), resulting from accumulated debris on the ECCS suction strainers during the recirculation phase of a LOCA.
In the bulletin, NRC requested that corrective actions be implemented by end the first refueling outage starting after January 1,
1997.
This corresponded to the Unit 3 Cycle 7
refueling outage, which was completed in March 1997.
In a letter dated November 4,
- 1996, TVA petitioned the NRC for a delay in the implementation for Unit 3 until the Fall of 1998.
This delay is necessary to allow the completion of technical criteria development, which is critical to the successful resolution of the issue.
Based on the time table for formation and implementation of the Boiling Water Reactor Owners Group (BWROG) Suction Strainer Committee Utility Resolution Guidelines (URG) the earliest opportunity to evaluate and implement any needed modifications for BFN was Unit 2 Cycle 9 refueling outage in the fall of 1997.
By letters dated January 29, 1997 and February 19,
- 1997, NRC granted TVA's petition to defer the actions required to resolve NRC Bulletin 96-03 during Unit 3 Cycle 7 refueling outage.
- However, as a condition for the deferral, the staff requested that compensatory actions be taken.
These compensatory actions and description of TVA's implementation of these actions are provided below.
P
NRC Request 1
To minimize any accumulation of sludge in the pool prior to startup from refueling outages and to minimize the potential burden on the existing strainers, desludge the suppression pool.
TVA Action From February 25,
- 1997, through March 3,
- 1997, TVA used divers to desludge the suppression pool including the ECCS ring header suction strainers.
NRC Request 2
Perform an inspection in the drywell to verify that the insulation is not damaged and is properl'y installed.
TVA Action TVA performed a walkdown of the drywell insulation to visually inspect and verify the reflective metal insulation (RMI.) and fibrous insulation inside the drywell penetrations was not damaged and properly installed.
The walkdown resulted in only minor maintenance activities.
These activities included the repair or replacement of damaged or missing buckles, and to the extent possible, the repair of dents.
In some instances convection bands were installed to cover minor joint gaps.
A subsequent re-inspection was performed to verify the minor maintenance activities were completed.
NRC Request 3
Perform a
including
- material, materials thorough drywell and suppression pool inspection,
- vents, and downcomers, to verify that all foreign such as maintenance
- tools, equipment, construction and miscellaneous
- debris, has been removed.
TVA Action The required suppression pool inspection was performed concurrent with the suppression pool -desludging effort.
The inspection verified that the ring header strainers were clean and that there was no debris floating in the downcomer legs.
As part of the Unit 3 Suppression Pool inspection the as
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Cound condition of the pool (including the ECCS'trainers) was video taped.
The results of. the inspection indicated that the Suppression Pool and ECCS strainers were in good condition and relatively free from debris.
A small amount of fibrous material was found on the ECCS ring header strainers.
TVA estimates that an area of approximately one square foot of the strainers was covered by the fibrous material.
The material appeared to be similar to the vacuum bag identified during the Unit 3 restart effort, as described in a letter to NRC dated November 15, 1995.
The fibrous material along with any other materials adhered to the strainers was removed.
Other items found in the pool such as tools, a plastic tie
- wrap, and scaffolding wire were also removed.
During the suppression pool inspection an approximately 18 inch by 36 inch cloth was removed from a torus drain.
The cloth was found lodged in one of the torus drain lines.
Because of the location of the cloth and how it was lodged in the drain, it would have remained lodged in the drain and therefore, could not impact ECCS operation.
As part of the drywell closeout, TVA performed a visual inspection of all elevations of the Unit 3 drywell utilizing guidance provided by General Operating Instruction (GOI) 3-GOI-200-2, Drywell Closeout.
The GOI requires in part, that personnel perform a walkdown of the drywell elevations to visually verify that construction material has been removed.
A final Suppression Pool foreign material exclusion underwater inspection was performed on March 4,
- 1997, and identified foreign material was removed.
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