ML18026B189
| ML18026B189 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/15/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18026B188 | List: |
| References | |
| NUDOCS 8408290292 | |
| Download: ML18026B189 (8) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.
109. TO FACILITY OPERATING LICENSE NO.
DPR-33 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-259 1.0 Introduction By letter dated July 31, 1984, the Tennessee Valley Authority proposed certain changes to the Technical Specifications for the Browns Ferry Nuclear Plant, Unit 1.
Valve FCV-84-8B (CAD supply.to the.torus; System A, see attached figure) was declared inoperable on July 17, 1984.
Upon investigation, it was found that the valve could not be repaired without 'breaking primary containment.
This would require the unit to be brought to a cold shutdown before repair s could be made.
In light'f this valve failure and pursuant to Specification 3.7.G.3, Browns Ferry Unit 1 has been in a Limiting Condition'or Operation (LCO) since July 18, 1984 which would require plant shutdown on Aug 16, 1984.
2.0 Evaluation By its letter dated July 31, 1984, the licensee requested a temporary suspension of Specification 3.7;G.3 s'o that it may, continue operating the plant with valve FCV-84-8B in an inoperable status until either 180 days from July 20, 1984, or until the next cold shutdown of Unit 1, whichever occurs first.
To support the continuing operation for Unit 1, the licensee stated that the Containment Atmosphere Dilution (CAD) system has two trains, with each train having valves to admit nitrogen to both the torus (wetwell) and the drywell.
The nitrogen is added to keep the post-LOCA hydrogen concentration below four percent and oxygen concentration below five percent.
The system also has vent valves to vent the drywell and torus atmospheres through the standby gas treatment system (SGTS).
Inoperability of valve FCV-84-8B leaves only one path through train B to introduce nitrogen directly into the torus.
However, should train B fail, an alternate path via the drywell and downcomers provides a backup for dilution of the torus atmosphere.
The licensee contends that if nitrogen is only added to the drywell, a
mixing flow toward the torus will be established through the downcomers.
This flow will be further enhanced if venting is done through the torus vent path or by intermittent operation of the drywell spray.
The licensee SaOsaSO292 S40SlS
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stated that current operating instructions provide for adding nitrogen and venting and intermittent use of spray as necessary to control the hydrogen concentration in both the drywell and torus.
Therefore, train A can still meet its design objective (i.e., maintain an inerted containment) with valve FCV-84-8B declared inoperable.
The licensee further stated that surveillance tests on valves in the redundant B train will be increased from once per month to once per week to reduce the potential for an undetected failure as indicated in the proposed TS changes.
The staff has completed its review of the licensee's submittal and concludes that the proposed Technical Specification changes are acceptable.
The bases which were used to arrive at this conclusion are provided below.
1.
The failure of valve FCV-84-8B, by itself,. does not prevent train A from meeting its design objective. (maintaining an inerted containment post-LOCA).
An additional single failure is necessary to disable the system.
2.
Train A, with the failure, has only one inlet to the containment which is to the drywell.
The normal wetwell inlet has been isolated due to the valve failure.
However, communication between the drywell and wetwell still exists via the downcomer-vent system.
This pathway will allo'w nitrogen addition to both containment volumes.
As a.result, flexibilityof operation is reduced but not the ability to meet the design objective.
3.
.The licensee has also'taken.steps to assure that no further degradation of train B will occur for this interim period until valve repairs can be made.
The authorization for such interim operating would expire at the first cold shutdown of unit 1 after July 20, 1984, or on January 17, 1985, whichever occurs first.
The surveillance interval will be weekly rather than monthly.
Emer enc Circumstances
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The valve was declared inoperable on July 17, 1984 and determined to require cold shutdown for repair on July 19, 1984.
From July 20, 1984 to July 31, 1984 the licensee prepared an analysis indicating that the CAO system could perform its function consistent with SRP 6.2.5 criteria, with the valve in an inoperable condition.
On July 31, 1984 the licensee submitted an emergency amendment request to avoid shutdown.
The request was received without sufficient time to permit prior notice and opportunity for public comment..
No Si nificant Hazards Consideration Determination
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The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant>'"'azards considerations if operation of the facility in accordance with the amendment would not:
(I)
Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2)
Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3)
Involve a significant reduction in a margin of,safety.
The information in this SE provides the basis for evaluating. this license amendment against these criteria.
Since the requested operational
- mode, plant operating conditions, the physical status of the plant, and dose consequences of potential accidents are the same as without the requested
- change, the staff concludes that:
(I)
Operation of the facility in accordance with the amendment would not significantly increase the probability or conse'quences of an accident previously evaluated.
(2)
Operation of the facility in accordance with the amendment would not create the possibility of a new or differe'nt kind of accident from any accident previously eval.uated.
(3)
Operation of the facility in accordance with the amendment would not involve a significant reduction in a margin of safety.
Accordingly, we conclude that the amendment to Facility Operating License No.
DPR-33 permitting CAD train A to be'onsidered operable with valve 84-8B inoperable involves no significant hazards considerations.
State Consultation In accordance with the Commission's regulations, consultation was held with the State of Alabama by telephone.
The State expressed no concern either from the standpoint of safety or of no significant hazards consideration determination, in view of the interim nature of the amendment and the compensatory measures.
3.0 Environmental Considerations The amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and a change on a surveillance requirement.
The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has made a final no significant hazards consideration finding with respect to this amendment.
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
4.0 Conclusion We have concluded, based on the consideration's discussed above, that.(1) there is reasonable assurance that the health and safety of the public-will not be endangered by operation in the proposed
- manner, and (2) such
'activities will be conducted in compliance with the Commission's-regulations, and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
F.'ltawi la Dated:
August lS, 1984
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