ML18025C002
| ML18025C002 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/28/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18025C001 | List: |
| References | |
| NUDOCS 8310110551 | |
| Download: ML18025C002 (6) | |
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UNITED STATES NUCLEAR REGULATORY COMMISS ION WASHINGTON, D. C. 20555 SAFETY EVA'ATION BY. THE OFFICE OF NUCLEAR REACTOR REGULATION SU?PORTING AM=NDMENT NO.
90 TO FACILITY OPERATING LICENSE NO.
86 TO FACILITY OPERATING LICENSE NO.
59 TO FACILITY OPERATING LICENSE NO.
DPR-68 TENNESSEE VALLEY AUTHORITY BRC'nNS FERRY NUCLEAR PLANT UNIT NOS.
1 2
AND 3 DOCKET NOS. 50-259, 50-260 AND 50-296 1.0 Introduction By: etter dated June 13, 1983 (TVA BFNP TS 189) the Tennessee Valley Aut:".ority (the licensee or TVA) "requested emergency amendment to licenses DPR-33, DPR-52 and DPR-68 to change'the technical specifications of Bro;:ns Ferry Nuclear Plant, Unit Nos. 1, 2 and 3."
The proposed amend-ments would change Section 4.7.B.G.a of the Technical Specifications (TS) to modify the required surveillance interval for testing the standby gas treatment system t,SGTS) from once per year to once per operating cyc Ie to be consistent with the requirements in the BWR Standard Technical Speci ications (NUREG-0123).
TVA "requested an emergency amendment" to the licenses because of a revised interpretation of how the surveillance tes should be conducted.
The licensee stated that the revised interpre-tation would require Browns Ferry Unit 3 to shutdown by July 3, 1983 to tes the initiating relays.
2.0
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d In the event of an accident, the standby gas treatment system provides a
means for minimizing the release of radioactive material from the contain-men-to the environs by filtering and exhausting the air from any or all zones of the reactor building and maintaining the building at a negative pressure (such that air leakage is into, not out of, the building) during con ainment isolation conditions.
Elevated release is assured by exhausting to he plant stack.
At Browns Ferry, the SGTS consists of three filter trains and associated
- blowers, arranged in parallel.
The trains are located in 'two SGTS buildings.
- However, the three filter trains serve all three Browns Ferry units.
Upon an accident signal in any unit, all three SGTS units will start.
Sin"e any two trains will maintain the design negative pressure in a unit, the operator ray shutdown one of the trains.
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2-The secondary containment isolation is initiated from any of three signals:
low reactor water level; high drywell pressure or high activity in a ventilation exhaust duct; or by manual alignment and operation from the main control room.
Each signal simultaneously isolates the secondary containment'one or zones, shuts down'normal ventilation equipment, opens dampers to and from the standby gas treatment system and starts the standby gas treatmentsystem blower.
The isolation condition is removed and the standby gas treatment system shut down only by manual reset.
The SGTS, which is common to all three units, can be and is - tested while the units are operating
-'o check filter performance, air flow, etc.
However, operation of the SGTS cannot be automatically initiated using any of the acci dent isolation logic ci rcuits (i.e., hi gh drywell pressure, low reactor water level or high radiation) in an operating unit, because it would trip the unit.
As noted above, when the SGTS is activated using these logic circuits, the signal also shuts down the normal ventilation system to preclude possible release of acti vity 'to the environment.
This includes shutting off the normal airflow in the main steam tunnel.
There are 16 temperature sensors in the main steam tunnel to detect a possible steam line break.
If the sensors indicate a temperature of 200oF or more, the reactor is tripped.
Without the normal air flow in the steam tunnel, the temperature rapidly exceeds 200oF.
Thus, it is not possible to initiate operation of the SGTS using the isolation logic in one of the operating units without causing a trip of the unit and closure of the main steam isolation valves.
Table 4;2.A of the present technical specifications requi res a functional test of the Group 2, 3, 6 and 8 logic components each operating cycle.
- Thus, when each of the units are down for refueling, there is a surveillance test of secondary containment isolation which automatically starts the SGTS.
Since the Browns Ferry'units are on a
nominal 18-month fuel cycle, the common SGTS has general'ly been tested twice a year because of this requirement.
In addition to the logic test discussed
- above, Section 4.7.B.3.a of the TSs requires that "at least once per year, automatic initiation of each branch of the standby gas treatment system shall be demonstrated from each units'ontrols".
Initially, the Browns Ferry units were on an annual refueling cycle and performance of the logic test required by Table 4.2.A also satisfied requirement 4.7.B.3.a.
When the units went on an 18-month fuel cycle, the requirement of Section 4.7.B.3.a was satisfied by plugging a signal in downstream of the units'rimary containment isolation logic. It was - and is - TVA's interpretation that Section 4.7.B.3.a does not require a logic functional test from the primary sensor (e.g.,
high drywell pressure) to SGTS actuation (since the word "logic" is not mentioned in the requirement)'nd is satisfied by actuating the SGTS from an appropriate relay (16A-K-23) in each units'rimary containment isolation system logic on a once per year interval.
3.0 Evaluation The BWR Standard Technical Specification~equi.re-a-logic<unctional and system performance test of the SGTS once per operating cycle (nominally, every 18 months) on the basis that this frequency is adequate to detect possible equipment degradation prior to development of significant defects.
The Standard Technical Specifications are recognized by the staff as an acceptable means of implementing our requirements concerning this issue.
The change proposed by TVA would conform the frequency of testing the SGTS at Browns Ferry to the frequency required in the BWR Standard Technical Specifications and is therefore acceptable.
There would be no benefit in shutting down a unit part way through a fuel cycle to test the SGTS with respect to either equipment reliability or the effect on public.health and safety.
In fact, the transients and cool-down/heatup associated with a unit shutdown are likely to adversely affect plant equipment.
In summary, a complete test of the SGTS more than once per operating cycle is not necessary to detect equipment deterioration and requiring shutdown of a unit solely to perform such a test is not warranted.
4.0 Environmental Considerations We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental
- impact, and pursuant to 10 CFR
$51.5(d)(4), that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
5.0 Conclusion We have concluded, based on the considerations 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.
Dated:
September 28, 1983 Principal Reviewers:
R. Clark J. Boegli
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