ML17285B097
| ML17285B097 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 03/07/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17285B096 | List: |
| References | |
| NUDOCS 9003190079 | |
| Download: ML17285B097 (9) | |
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t UNITEDSTATES t NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AIIENDNENT NO. 78 TO FACILITY OPERATING LICENSE NO. NPF-21 WASHINGTON PUBLIC POWER SUPPLY SYSTEM NUCLEAR PROJECT NO.
2 DOCKET NO. 50-397 1.0
2.0 INTRODUCTION
By letter dated March 2, 1990 (G02-90-032)
Washinqton Public Power Supply System proposed certain chanqes to the Technical Specifications for Nuclear Project No. 2.
Specifically the Supply System requested that notes be added to Specification 3.4.2, "Safety Relief Valves",
and to Tables 3.3.7.5-1, "Accident Honitorinq Instrumentation",
and 4.3.7.5-1, "Accident Honitorinq Instrumentation Surveillance Requirements",
to allow the acoustic monitors, on the SRVs to be inoperable until the plant shuts down for its next scheduled refueling outage.
The note on Table 4.3.7.5-1 specifies com-pensatory survei llances of the tailpipe temperatures of the valves.
Action c for Specification 3.4.2, "Safety Relief Valves",
and action 80.a for Technical Specification Table 3.3.7.5-1, "Accident Honitorinq Instrumen-tation", require that the plant be shutdown if an inoperable safety/relief valve indicator channel is not restored to operable status within seven (7) days.
On February 27 the licensee received a report of a recent environ-mental qualification failure of a replacement connector/cable assembly for the acoustic monitors.
The licensee's assessment of the qualification test report led them to the conclusion that the monitor cables have the potential for failure when subjected to a
LOCA followinq radiological and thermal aqinq.
Accordingly, the Supply System entered the seven day LCO at 5:00 p.m.
PST on February 28, 1990.
It has been determined that the plant will be required to be shutdown and cooled down in order to replace the cablinq for the acoustic monitors, unless an amendment is ~anted to allow the Supply System to continue to operate until the next scheduled outage.
The licensee is scheduled to shutdown for a refuelinq outaqe on or about April 13, 1990.
EVALUATION Relief requests for inoperable relief valve acoustic monitors were made by the licensee on October 13, 1987, on July 25, 1988 and on February 14, 1990.
The Supply System has made modifications to the acoustic monitors and changed procedures to increase the reliability of the monitors.
The environmental qualification testinq which identified the cablinq inadequacy was being done in conjunction with a desiqn change that would allow accessi-bility, without plant shutdown.
9003190079 900307 PDR ADOCK 05000397 P
The requirement for operability of the accident monitoring instrumentation is based on the need to ensure that sufficient information is available on selected plant parameters (e.q.,
SRV position indication) to monitor and assess important variables followinq an accident.
THI Action Plant Item II.D.3 "Direct Indication of Relief and Safety-Valve Position" requires that "reactor coolant system relief and safety valves shall be provided with a positive indication in the control room derived from a reliable valve-position detection device or a reliable indi-cation of flow in the discharqe pipe".
The technical specifications for MNP-2 reouire two instrumentation channels for providing this in-formation on valve position.
One channel utilizes an acoustic monitor.
The second channel utilizes thermocouples to detect a temperature in-crease indicative of flow past the valve.
The redundancy contributes to reduction in accident risk.
The loss of either channel on one or more SRVs does not prevent accurate determination of the position of the associated SBV(s).
Total loss of position indica-tion would allow an SRV to be stucl: in the open position without this beinq known immediately to the operator.
As discussed in the safety analysis of this event (llNP-2 FSAR 15.1.4),
the operator response to this event is triqqered by a suppression pool temperature alarm not by an "open" alarm from the SRV position indication instruments.
The mitiqatinq actions for the stuck open valve are to locate and attempt to close the open SRV and to establish suppression pool coolinq within 20 minutes.
As discussed in the FSAR analysis, even if the valve fails to close (worst case) the consequences of the event are mild.
Hence the failure of an acoustic monitor causinq an operator to review other instru-mentation (as listed below) to determine which valve is open does not increase the severity of the transient.
The loss of position indication of a Safety/Relief Valves does not reduce the capahi lity of the SRV to perform its intended function, nor does it prevent accurate determination of the position of the associated SRV.
During normal operation or durinq a small break LOCA, the followinq miti-gating and compensatory factors provide assurance that the valve position is reliably known:
1.
Tail pipe temperature is monitored and recorded.
An increase in temperature would indicate that the valve is open, and steam was entering the suppression pool via the tail pipe.
This indication has remained capable of indicating valve actuation since the failed monitor was identified.
Channel checks of the temperature recorder are currently performed monthly per LCO 3/4.3.7.5.
Until the acous-tic monitors for HSRV-RV-2C and 2D are declared
- operable, the tail pipe'emperature surveillance will be performed daily instead of monthly.
A control room annunciator alarms on hiqh tail pipe temper-ature (greater than 250'F).
An annunciator response procedure addressinq the tailpipe temperature alarm will be revised to uniquely identify appropriate actions for the relief valves.
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2.
Suppression Pool temperature indication is available, and is set to alarm at 85'F.
An increase in suppression pool temperature would indicate an open SRV.
This parameter will be monitored on a daily basis.
3.
Suppression Pool level indication is available, and is set to alarm at +0.5"/-1" of Normal Level (466'3").
An increase in suppression pool level would indicate an open SRV.
This para-meter will be monitored on a daily basis.
4.
Other plant parameters are affected by an SRV actuation and are available as confirmation.
Examples are main turbine governor valve position indication chanoe, generator output change, main turbine steam flow change, steam/feedwater flow mismatch and the resultant reactor pressure perturbation.
Other indicators provide adeouate feedback for ADS (reactor pressure) and SRV operation, and Alternate Shutdown Cooling operation (reactor pressure/temperature) if they are required.
With the compensatory measures proposed by the licensee, the staff finds the safety significance to be small and the proposed temporary amendment to be acceptable.
3.0 EMERGFNCY CIRCUMSTANCES Failure of the acoustic monitors based on failure of the cabling to meet environmental qualification requirements has only recently been identified.
The licensee declared the monitors for the valve inoperable at 5:00 p.m.,
February 28, 1990.
It was not possible to anticipate this event and sub-mit this request in a more timely manner.
The licensee has determined that correction will require that the reactor he shut down and cooled down in order to permit drywell entry.
Based on the above, the licensee requested the emergency temporary change to the technical specifications to allow continued operation until the refueling outage of Absent this amendment, the Supply System would be required to unnecessarily shutdown by Harch 7, 1990.
The outage for refueling will start on or about April 13, 1990.
The staff reviewed the circumstances associated with the request and concluded that the licensee provided a sufficient basis for finding that the situation could not have been avoided by prior application.
Therefore, in accordance with 10 CFR 50.91(a)(5),.
a valid emerqency existed.
- 4. 0 ENVIRONHENTAL CONS IDERATION This amendment involves changes in requirements with respect to the use or installation of a faci lity component located within the restricted area as defined in 10 CFR Part 20 and in surveillance requirements.
The staff has determined that this amendment involves no significant increase in the
- amounts, and no significant change in the types, of any effluents that may
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Accordinqly, this amendment meets the eliqibility 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 this amendment.
5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no siqnificant hazards considerations if operation of the facility in accordance with the amendment would not:
l.
Involve a siqnificant incr ease in the probability or the consequences of any 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 marqin of safety.
The licensee has evaluated the amendment aqainst these standards.
A dis-cussion of the standards as they relate to the amendment request follows:
1.
The change does not involve a significant increase in the probabi lity or consequence of an accident previously evaluated because the SRV position indication channels are not assumed to function in the initiation of an'nalyzed accident.
The inoperability of these indication channels does not affect ADS operation of the SRYs.
The analysis for an inadvertent opening of an SRV (FSAR Section 15.1.4) assumes the function of these alarm-only instrument channels for the purpose of having the operator assess the need for commencinq suppression pool coolinq with RHR.
As discussed
- above, the operator has many diverse indications available to indicate the need for commencing suppression pool coolinq as a result of an open SRV and the SRV position indication is not the primary indication.
Loss of an SRY position indication channel will not adversely affect the operator's ability to respond to this event as assumed in the analysis.
The proposed chanqe affects only the operabi lity of the SRV position indication and does not affect automatic or manual actuation of the SRV.
Therefore, this change will not involve a siqnificant increase in the probability 'or consequences of an accident previously evaluated.
2.
The change does not create the possibility of a new or different kind of accident from any accident previously evaluated because SRV operation, including the ADS function, remains unaffected.
No new modes of operation of any equipment result due to this chanqe.
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~ Sufficient diverse indication remains available to adequately deter-mine whether an SRV is inadvertently open, therefore this change will not result in a failure to assess the need for suppression pool coolinq.
This change will not create the possibility of a new or different kind of accident from any accident previously evaluated.
3.
The change does not involve a significant reduction in a marqin of safety because, as discussed above, the operator has many diverse indications available to indicate the need for commencinq suppression pool coolinq.
Loss of an SRV position indication channel will not adversely affect the operator's ability to respond to this event as assumed in the analysis.
The additional surveillances to monitor the suppression pool temperature while operation continues with an inoperable channel will compensate for the loss of position indication channel.
Therefore, this change will not involve a significant reduction in the margin of safety.
Accordingly, the Commission has determined that this amendment involves no siqnificant hazards consideration.
6.0 CONTACT WITH STATE OFFICIAL In accordance with 10 CFR 50.91, the licensee provided the State of Washinqton with a copy of its March 2, 1990 letter.
The HRC staff advised the Washinqton Energy Facility Sitinq Council of the final determination of no significant hazards considerations by telephone on March 7, 1990.
The State of Washinqton did not have any comment on this determination.
- 7. 0 COI'lCLUSION In summary, based on the assertion that no siqnificant hazard is created bv the proposed amendment and that the proposed compensatory actions pro-vide reliable indication of SRV position, approval of the proposed amend-ment does not represent an undue risk to the health and safety of the public.
We have concluded, based on the considerations discussed above, that:
(I) there is reasonable assurance that the health and safety of the public wi 11 not be endanqered by operation in the proposed
- manner, (2) such act-ivities will be conducted in compliance with the Commission s regulations, and (3) 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:
Robert B. Samworth
~Dated:
March 7, 1990
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