ML20246A003
| ML20246A003 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/11/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246A001 | List: |
| References | |
| NUDOCS 8908220333 | |
| Download: ML20246A003 (5) | |
Text
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,,,0p UNITED STATES
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4; NUCLEAR REGULATORY COMMISSION
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ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 124 TO FACILITY OPERATING LICENSE NO. DPR-77 AND AMENDMENT NO. 113 TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY-
.SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 1
DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
requested a waiver of compliance with Surveillance Requirement (SR) 4.5.1.14 of the Sequoyah Nuclear Plant, Units 1 and 2, Technical Specification (TS).
This' SR applies to the water level and-pressure instrumentation channels forf the cold leg injection accumulators and requires that all these channels must be operable.
TVA requested the waiver of compliance until_ the staff could act on an emergency TS change concerning the number of.the water level and pressure channels for each accumulator that would be allowed to be inoperable.
' These proposed amendments to the TS would temporarily add two ' additional Action statements:for-the Limiting Condition for Operation (LCO) 3.5.1.1, Cold Leg
' Injection Accumulatt
, of the Sequoyah Nuclear Plant, Units 1 and 2, Technical Specifications (TS).
The two Action statements would state that (1) with one water level or presso e channel inoperdble per accumulator, return the inoper-able channel to operable status within 30-days or shut down the unit and (2)
-with more than one channel, water level or pressure, inoperable per accumula-tor. innediately declare the affected accumulators inoperable and enter Action statement "a" to retten the inoperable channels to operable status within one
. hour or shut down the. unit.
These changes to the TS are. temporary. They are only effective for both units'from the date of this evaluation until the restart of Unit 2 from the Unit 2 Cycle 4 refueling outage.
This is presently scheduled for late 1990.
On August 7 '1989, there was a water level channel on an accumulator for each unit which was inoperable.
In its request TVA stated that the TS do not
.specifically address the loss of only one instrumentation channel out of the two redundant channels on each accumulator.
Each accumulator has two redundant
- pressure channels and two redundant water level channels. The Action statement for LCO 3.5.1.1 assumes the accumulator is inoperable and requires if the accumulator cannot be made operable within an hour the licensee shall shut down the:affected unit. TVA concluded that the inoperable water level channel for the two respective accumulators did not warrant shutting down the two units because the affected accumulator for each unit was still meeting the LCO with
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the other water level channel which is operable. The water level channels could not be repaired in an hour.
Therefore, TVA requested emergency relief from the TS to prevent shutting down the units.
As discussed below, the Comission (1) granted TVA a Waiver of Compliance at 1:30 p.m. on August 7, 1989 for Sequoyah to not have to comply with Surveil-lance Requirement 4.5.1.1.2 until the staff could act on this application but no later than September 6, 1989 and (2) determined pursuant to 10 CFR 50.91 that emergency conditions existed and these amendments should be implemented as soon as possible to prevent shutdown of Units 1 and 2.
We concluded that TVA acted in good faith to promptly address the inoperability of the level channel for each unit but could not avoid the need for an emergency TS change.
By telephone call on August 11, 1989 TVA explained the status of the repairs to the inoperable water level channels.
The inoperable channel for Unit 2 was returned to service on August 9, 1989. After returning this channel to service, it was determined that the redundant water level channel was inoperable. The rtdundant channel was reading slightly different from the channel which was returned to service -- the readings were within 5 percent --
and the cause for this was with the redundant channel. The inoperable channel for Unit I was returned to service on August 11, 1989. Therefore, emergency.
conditions still exist.
2.0 EVALUATION The cold leg injection accumulators are four pressure vessels filled with borated water and pressurized with nitrogen gas.
There is one accumulator for each cold leg of the reactor coolant system (RCS).
During normal operation, each accumulator is isolated from the RCS by check valves.
Should the RCS pressure fall below the accumulator pressure, as during an accident, the borated water in the accumulators is forced into each cold leg of the RCS. The accumulators are designed for the large break loss-of-coolant accident (LOCA).
The proposed changes are to add requirements to the TS to specifically addre s the loss of instrumentation channels for the accumulators.
Each accumulator has four instrumentation channels:
two redundant pressure channels and two redundant water level channels.
These four channels are required in the NRC Standard Technical Specifications for Westinghouse pressurized water reactors (STSWPWR) to determine operability of the accumulators and are recommended in Regulatory Guide (RG) 1.97, " Instrumentation for Light-Water-Cooled Nuclear Power Plants to Assess Plant and Environs Conditions During and Following An Accident." The STSWPWR and RG 1.97 apply to Sequoyah.
TVA has proposed that with the loss of one channel per accumulator, the unit may continue operating while the channel is being repaired.
With only one channel being inoperable per accumulator, there is one parameter, pressure or water level,' with redundant operable channels available and the other parameter with a single operable channel.
Therefore, both the pressure and the water level of the accumulators can still be measured and TVA can still determine if the accumulator is operable.
There is an alarm function on each channel so that the LCO setpoints for the accumulators will not be exceeded and this function will remain for both pressure and water level for each accumulator
. altnough one channel is inoperable.
If there is more than one accumulator of the four with a water level or a pressure channel that is inoperable, TVA is expected to address the possibility of a common mode failure and additional channels may in fact be inoperable.
TVA proposed that one channel of water level or pressure per accumulator may be inopereble for up to 30-days before the affected accumulator must be declared inoperable.
This 30-day period is consistent with SR 4.5.1.1.2 for determining the operability of the channels and is consistent with the importance of the channels.
The accumulators are a passive system with no active control func-tions.
When the RCS pressure drops below the nitrogen pressure in the accumu-lator, the borated water in the accumulator is forced into the RCS cold legs.
The redundant pressure and water level channels monitor the pressure and water level in each accumulator but do not perform a control or actuation function.
They are Type D Category 2 channels in RG 1.97 in that they provide information to indicate the status of a safety system and have less stringent requirements imposed on them by the staff than on channels which have actuation functions as instrumentation channels in the reactor protection system.
The current TS on the accumulators are the same as in the STSWPWR and in the TS for many Westinghouse PWR; therefore, the proposed amendments may be considered as the solution for any PWR with such a problem as TVA is experiencing with the inoperable instrumentation channels on the accumulators at Sequoyah. The staff acts to avoid using the emergency license amendment provisions of 10 CFR 50.91 to issue such amendments.
Therefore, these amendments, will be effective until the restart of Unit 2 from its Cycle 4 refueling outage.
This will provide j
approximately 18-months for tha staff to develop a generic solution to this problem which is applicable for all Westinghouse PWR. TVA is expected to submit these proposed changes following staff resolution of the generic issue.
The staff, based on its review, concludes that TVA's proposed changes are acceptable.
3.0 FINAL N0 SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION TVA and the NRC staff have evaluated these proposed changes with regard to the determination of whether or not a significant hazards consideration is involved. The Commission has provided standards for a significant hazards j
consideration determination in 10 CFR 50.92(c).
Therefore, in accordance with 10 CFR 50.92, such a determination has been made by the staff and is given below.
The proposed amendments will not involve a significant increase in the probability or consequences of an accident previously evaluated.
The proposed changes allow one of two instrumentation channels per accumulator to be inoperable.
The remaining operable channel will provide the required indication of either pressure or water level in the accumulator to allow TVA to detennine if the accumulator is itself operable in accordance with LCO 3.5.1.1.
The accumulator is a passive system which does not rely on the instrumentation channels to perform its intended function during an accident.
The proposed amendments will not create the possibility of a new or different accident from any previously analyzed.
The instrumentation cha1nels only
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provide information on the status of the accumulators and do not provide any control function for operation of the accumulators.
These channels are not needed for the accumulators to perform their intended function during an accident..
These amendments do not. significantly reduce a margin of safety. Although one channel per accumulator is inoperable, the remaining three channels are oper-able so that both the pressure and the water level of the accumulators are still being measured.
able for only 30-days before the affected accumulator is itself declar inoperable and the unit is shut down.
the affected accumulator from performing its function during an accident.T a
On August 10 and 11, 1989, and the proposed amendments were discussed.the State of Tennessee was cont On August 11, 1989, the State of Tennessee had no comments on the determination that the amendments significant hazards. consideration and could be issued without a prior hearing.
No public coments were received by close of business August 11, 1989.
4.0 FINDINGS THAT THE EMERGENCY WARRANTED AMENDMENTS WITHOUT TVA's application for an emergency TS change pursuant to 10 CFR 50.91 has been timely.
TVA stated that the need for the proposed changes was only recently identified and it has pursued the changes on a priority basis.
The staff concludes that failure to grant the proposed changes in a timely manner would cause an unnecessary shutdown of both Sequoyah units.
We find that TVA could not reasonably have avoided the situation causing the TS to be changed, that TVA has responded in a timely manner and that TVA has not delayed its application to take advantage of the emergency license amendment provisions of 10 CFR 50.91. Accordingly, the staff concluded that TVA satisfied the requirements of 10 CFR 50.91(a)(5) and that a valid emergency existed.
5.0 _ ENVIRONMENTAL CONSIDERATION These amendments involve a change to a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements.
The staff has determined that the amendments involve 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 Comission has made a final no significant hazards consideration finding with respect to these amendments.
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuantto10CFR51.22(b),no environmental impact statement nor environmental assessment need to be prepared in connection with the issuance of these amendments.
6.0 _ CONCLUSION The staff has 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
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ibe conducted in compliance with the' Comission's ' regulations, and the' is'suarce.
of the amendments will not be inimical to the common defense and security nor..
. to.the health and safety of the. public..
Principle Contributor:
Jack Donohew 1
2
. Dated:/ August;11,1989 e
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