ML20083K344
| ML20083K344 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 04/10/1984 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8404160139 | |
| Download: ML20083K344 (4) | |
Text
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE 374o1 400 Chestnut Street Tower II
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April 10, 1984 l
Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation
_U.S. Nuclear Regulatory Commission
. Washington, D.C. 20555
Dear W. Denton:
s In the Matter of the
)
Docket Nos. 50-259 Tennessee Valley Authority
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We are enclosing some additional information regarding the February 14, 1984 loss of normal shutdown cooling event on Browns Ferry unit 1.
The information was requested by R. Bernero of NRC. Please let us know if N
you have additional questions.
Very truly yours, TENNESSEE VALLEY AUTHORITY L.
. Mills,lianager Nuclear Licensing s
Subscribe (a sworn to efor me th a ' /l) day o 1984.
aM
. #B1 Notary Public d~ g 9
L My. Commission Expires "/ "<=:/ 'O Enclosure cc (Enclosure):
U.S. Nuclear Regulatcry Commission Region II ATTN: James P. O'Reilly, Regional Administrator 101 Marietta Screet, NW,~ Suite 2900 Atlanta,- Georgia 30303 Mr. R. J. Clark Browns Ferry Project Manager U.S. Nuclear Regulatory Commission 7929 Norfolk Avenue
!Bethesda, Maryland 20814 I.
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- .81 8404160139 840410
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ENCLOSURE
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Rece'it news sources have quoted Representative Edward Markey as having concerns regarding the February 14, 1984 incident at Browns Ferry Nue?, ear Plant (BFN). We also have a copy of the letter that Representative Markey
.sent to.your Chairman Pallidino detailing these concerns. The incident of Febr6ai y 14, 1984, occurred when one of the normal decc.y heat removal process systems became temporarily inoperable due to an electrical failure r
I of a valve. Another normal system was used for removal of decay heat, and the. plant was brought to a cold shutdown. The inoperable system was x
subsequently repaired. For details, see the attached sequence of events.
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As 'we understand.it, Representative Markey's particular concern is the relationship of this incident to the conclusions in the BFN
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Interim Reliability Evaluation Program (IREP) Report NUREG-CR/2802.
That report stated. that accident-sequences involving failures in the
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, Residual Heat Removal (RHR) System represent a significant contributor
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to core melt frequency at.BFN.
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TVA has numerous technical disagreements (with the IREP Report, which
_ e believe, 'if resolved,' would have a substantial efrect on the w
j' conclusions. However, it -is-important to note that the'evant which
-occurred at< BFN should not be categorized as-an accident sequence t
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evaluated by.IREP. The incident at' BM was the temporary loss-of the
. normal shutdown cooling capability of the RHR-system, which is one of
. two'. modes of. RHR ' system operation capable of removing l decay heat from-the core. : Another' normal means of removing decay heat,- the main condenser, was ' operating throughout the event? so that cold shutdown conditions were achieved and maintained. ' The safety arade portions of
'the1RHR system were also available and would have been used had the ~
W need arisen. The accident 'mquences identified by theIREP study l considered that normal methods for remeving decay heat, such as the normal shutdown cooling function of the RRR system' and the main' condenser,- plus all-safety-grade methods are not available'. The
' event 1on February 14, 1984,:clearlyfdid.not approach:suchJ
- condition..-
a deg'*aded1
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- In summary, the event on. February.14,L1984, clearlydid.not' approach-the
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conditions causing 1 concern in the IREP~ Report and did.not represent an-
" accident waiting to happen.'" We,believe!that BFN is~being operated ~
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isafely, and;we believeiNRC agrees with this; conclusion..
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AfTACmiENT
-BROWNS FERRY (BFN) ALERT ON FEBRUARY 14, 1984 SEQUENCE OF MAJOR EVENTS Time (CST)
Description 0107 BFN unit 2 was shut down in response to a potential design nonconformance on the air-release valves on the RHRSW/EECW pumps. Unit 3 was in a refueling outage.
0245 Unit 1 was shut down for the same reason.
0800 Units 1 snd 2 were approaching cold shutdown using the condensate and CRD systems for vessel makeup with the condenser being used for heat rejection and pressure control.
In addition, RWCU was being used with letdown to the condenser to aid in level control.
Unit 1 was at 10 psig and 2300F indtcated when the cperators attempted to place the EHt system in the shutdown cooling mode.
Hcwever. in attempting to realign in this mode, the common RHR shutdown (S/D) cooling suction line inboard isolation valve (FCV-74-48) failed to open.
This' valve failure rendered the RHR S/D cooling mode inoperable and an alert was declared as required by the BFN Radiological Emergency Plan.
All TVA Bnergency Centers were staffed and NRC and the State of Alabama were notified. All required safa*y modes of the RHR systems were still operable and. unaffected by the valve' failure.
0845 Obtained unit -1 drywell-(DW) atmosphere sample to allow purging to de-inert the drywell. This would allow operators to enter the DW and manually open FCV-74-48.
0907' Electricians confirmed by meggar ' testing that the valve operator motor was shorted out.
4 0943--
- Unit 1 DW purging was begun.
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A;opare valve operator motor was confirmed to be onsite for. replacement. -
- 1008 Unit 1 achieved' cold shutdown using the condenser
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foriheat rejection.
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- Unit-- 2-was being placed in S/D. cooling when the '2A -
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- RHR pump failed _'to start because of a faulty breaker test switch.
Of. the other three available
. RHR pumps, 2C was started: and unit' 2 was placed 'in S/D. cooling..
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Unit 2 achieved cold S/D using the RHR system in 1122 the S/D cooling modo.
1202 Unit 2,2A RriR pump breaker was repaired and made operable.
1334 Initially entered unit 1 DW for air sampling.
1442 DW air samples were acceptable and DW entry for valve repair was started.
1510 FCL74-48 was confirmed visually to be closed.
1520 Lost auxiliary boilers being used to maintain steam seals and operate steam jet air ejectors on the condensers. Began losing some vacuus on unit 1.
Mechanical vacuum pumps were available as a backup to steam jets.
1534 one auxiliary boiler 1:as returned to service.
1538 Second auxiliary boiler was returned to servica.
1540 FCV-74-48 was manually opened and maintenance personnel began removal of the faulty valve operator motor.
1655 Surveillance was completed on the RHR system to allow placing reactor in S/D cooling.
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'1657 FCV-74-48 motor was removed from valve.
1715
1725' "he alert waa cancelled upon reatoration of the RHR' 3/D cooling mode.
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