ML20239A413
| ML20239A413 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/09/1987 |
| From: | Gordon A, Jacqwan Walker TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| LER-LER-870909, NUDOCS 8709170322 | |
| Download: ML20239A413 (4) | |
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BERO-50-259/773 R1 3a, Identification of Occurrence l
I,1 quid release from RHR service water heat exchanger 1A.
Conditions Prior to Occurrence j
i At 0645, 1/4/77, torun-to-drywell. vacuum breaker FCVs64-28E remained in an open i
position following a routine surveillance test. Technical specifications governing thin condition required the unit to be placed in a cold shutdown condition within
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24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Following a load reduction, unit 1 was scrammed from 420 MWe at 1328, and the unit was placed in the shutdown cooling mode of operation at 1940 hours0.0225 days <br />0.539 hours <br />0.00321 weeks <br />7.3817e-4 months <br /> using the 1A Rl(R heat exchanger.
Description of Occurrence At approximately 2050, the radiation monitor on the RHR service water discharge line from 1A heat exchanger showed an increase in radiation levels. A sample of the heat exchanger service water effluent was taken at 2130 for analysis. This analysis, which was completed just prior to 0200, 1/5/77, showed that 11guid waste effluent limits were exceeded. 1A RHR heat exchanger was removed from service at 0200 1/5/77; and 1C heat exchanger was placed in service for shutdown cooling. However, because of a communication misunderstanding, the shift engineer did not realize _that allowabic release limits had been exceeded. Apparently, the chemical laboratory analyst had given the operator both the plant warning value as well as the concentration actually released; and the shift engineer understood and logged in his journal that the rele'ase was at the plant warning value well within allowable release limits.
(The license release limit for gross activity is 1E-7pC1/m1, but the plant has always observed a warning limit of 7E-8pCi/ml.) It was not until approximately 1000, 1/5/77, that plant management received indication that a release exceeding the license limit had occurred. The assistant plant superintendent, acting as the plant emergency director in the absence of the plant superintendent, initiated applicable portions of the plant radiological emergency plan. This resulted in notification of NRC.and State of Alabama officials as well as appropriate TVA emergency personnel. Water sampling war initiated in the river at several locations below the plant.
Designation of Appare'nt Cause of Occurrence The release occurred because of a leaking inner head gasket in the 1A heat exchanger.
The release was not detected earlier because the operator did not notice the increased activity displayed on the recorder chart in the control room and because he did not acknowledge the annunciation received when the radiation monitor reached the alarm level. Had he recognized the alarm, procedures required him to stop the discharge of the ifquid effluent stream. The four hours required for a sample analysis, while not exccasive for a routine gross activity analysis, could have been improved had the analyst been aware of the urgency and given it his full attention.
Analysis of the Occurrence Although the plant release exceeded license limits, the quantity released was so small that no adverse effect on the safety of the public was involved. Subsequent sampling analyset, and computations revealed that the total amount of activity released s
was less than 0.289 curie. This is based on the assumptian that the release was continuous between 1940 and 0200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> while recorded information indicates the release did not commence until approximately 2100. The actual isotopes which exceed the' limits contained in 10 CFR 20 are I-131 and I-133. Following the h
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TENNESSEE VALLEY AUTHORITY Browns Ferry Nuclear Plant P.O. Box 2000 Decatur, Alabama 35602 September 9, 1987 U.S. Nuclear Regulatory Commisuton Document Control Desk i
Washington, D.C.
20555
Dear cir:
TENNESSEE VALLEY AUT{iORITY - BR0VNS FERRY NUCLEAR PLANT UNIT 1 - DOCKET NO. 50-259 - FACILITY OPERATING LICENSE DPR REPORTABLE OCCURRENCE REPORT BFR0-50-259/773 R1 The enclosed report provides information regarding a liquid release from a residual heat removal service water heat exchanger which occurred on January 4, 1977 This report was originally submitted in accordance with technical specification reporting requirements.
Very truly yones, TENNESSEE VALLE AUTHORITY G. Walker lant Manager Browns Ferry Nuclear Plant Enclosures cc (Enclosures):
Regional Administration INPO Records Center U.S. Nuclear Rogulatory Commission Suite 1500 Office of Inspection and Enforcement 1100 Circle 75 Parkway Region II Atlanta, Georgia 30339 101 Marietta Street, Suite 2900 Atlanta, Georgia 30303 NRC Resident Inspector, Browns Ferry Nuclear Plant
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I release, 72 river samples were taken between the plant and a-point 11 miles downstream, and none showed activity present above normal background. The most significant adverse aspect of this event is the combination of circumstances which permitted the release to continue over an extended period of time.
1 Records indicate that the 1A RHR heat exchanger was satisfactorily leak tested J
on April 6, 1976, and had not beon inservice since. This, together with documentation of previous sampilng whenever the heat exchanger had been in service, confirms that the leatage was not an existing condition and probably started after the heat exchanger had been in service for one hour on 1/4/77.
Corrective Action Inspection revealed that the heat exchanger gasket leak occurred because stud bolts had becomo loose in service.
In repairing the leak and replacing the gasket, locknuts were installed on each stud bolt to help prevent future loosening in service. This modification was made to all plant RHR heat exchangers when they were opened for maintenance or inspection.
The operator failed to notice increasing recorded values of activity and the accompanying alarm.
Plant effluent monitors had a history of indicating false values due to high background activity, and this may have contributed to this oversight.
In addition, because the unit was in a shutdown condition, a number of abnormal annunciations were displayed because the plant annunciation system is designed to accommodate a unit in power operation.
The color of all process radiation monitoring annunciator windows has been changed to distinguish them from other annunciators. This event was reviewed by licensed operators to impress upon them the necessity for prompt action on the first indication of an abncemal condition. Chemical laboratory sampling procedures have been revised to i
require that an isotopic analysis be conducted on initial effluent samples along with the gross activity analyses. This will reduce the' time required to obtain meanir.gful results since an isotopic analysis can be made under normal conditions in approximately one hour.
To' preclude the possibility of misunderstanding, the results of the liquid offluent analyses whlch exceed i
limits will be given to the shift engineer in a written as well as verbal form.
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