ML17285B042
| ML17285B042 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 02/20/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17285B041 | List: |
| References | |
| NUDOCS 9003020041 | |
| Download: ML17285B042 (9) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 75 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 February 14, 1990 (G02-90-025)
Washington Public Power Supply System proposed certain changes 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 Monitoring Instrumentation, and 4.3.7.5-1 Accident Monitoring Instrumentation Surveillance Requirements to allow a single acoustic monitor on each of two SRVs to be inoperable until the plant shuts down for its next scheduled refueling outage or until the first forced outage of sufficient duration to effect repair, whichever occurs first.
The note on Table 4.3.7.5-1 specified additional compensatory sampling of the tailpipe temperatures of the two affected valves.
Action c for Specification 3.4.2, Safety Relief Valve and action 80.a for Technical Specification Table 3.3.7.5-1, Accident Monitoring Instrumentation, require that the plant be shutdown if an inoperable safety/relief valve indicator channel is not restored to operable status within seven (7) days.
Due to apparent failure of the Acoustic Monitor for MS-RV-2D, the Supply System entered the seven day LCO at 5:27 p.m.
PST on February 13, 1990.
It has been determined that the plant will be required to be shutdown and cooled down in order to repair/replace this acoustic monitor, unless an amendment is granted to allow the Supply System to continue to operate until either the next forced outage or the next scheduled outage.
The licensee is scheduled to shutdown for a refueling outage on or about April 13, 1990.
The acoustic monitor for MS-RV-2C is exhibiting behavior similar to that observed on the MS-RV-2D acoustic monitor prior to its failure.
From these similar observations it has been concluded that a similar failure of the acoustic monitor for MS-RV-2C is likely.
For this reason relief is re-quested for both acoustic monitors.
EVALUATION 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.g.,
SRV position indication) to monitor and assess important variables following an accident.
TMI Action Plant Ii P
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 discharge pipe."
The technical specifications for WNP-2 require 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 f'low past the valve.
The redundancy contributes to reduction in accident risk.
The loss of eithei channel on one or more SRVs does not prevent accurate determination of the position of the associated SRV(s).
Total loss of position indica-tion would allow an SRV to be stuck in the open position without this being known immediately to the operator.
As discussed in the safety analysis of this event (WNP-2 FSAR 15.1.4),
the operator response to this event is triggered by a suppression pool temperature alarm not by an "open" alarm from the SRV position indication instruments.
The mitigating actions are to locate and attempt to close the open SRV and establish suppression pool cooling 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 causing an operator to review other instrumentation (as listed below) to determine which valve is open does not increase the severity of the transient.
The loss of position indication for one or more of the eighteen (18) Safety/
Relief Valves does not reduce the capability of the SRV to perform its in-tended function, nor does it prevent accurate determination of the position of the associated SRV.
Similar relief requests for inoperable relief valve acoustic monitors were made by the licensee on October 13, 1987 and on July 25, 1988.
Subsequently the Supply System has made modifications to the acoustic monitors and changed procedures to increase the reliability of the monitors.
This effort is ongoing.
A design change is in progress that would allow accessibility, without plant shutdown, of the suspected failed component pending success-ful environmental qualification.
The signal amplifiers (suspected component) and associated cabling for these monitors with the exception of 20 have been replaced.
The monitor MSRV-2D is scheduled to be replaced at. the next out'age.
Further a Vendor representative site visit has been requested to assist in identifying additional enhancements to system reliability.
The Supply System has been and is continuously working to improve this system.
The following mitigating 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 acoustic
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moni tor s for HSRV-RV-2C and 2D are decl ar ed operable, the tail pipe temperature surveillance will be performed daily instead of monthly; A control room annunciator alarms on high tail pipe temperature (greater than 250oF).
An annunciator response pro-cedure addressing the tailpipe temperature alarm will be revised to uniquely identify appropriate actions for HS-RV-2C and 2D.
2.
Suppression Pool temperature indication is available, and is set to alarm at 85oF.
An increase in suppression pool temperature would in-dicate 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.
Cross talk due to noise pickup from acoustic monitors on adjacent SRVs will indicate flow through the SRV with the failed monitor but will not alarm.
This capability has been demonstrated to be a
reliable diagnostic tool on several occasions in the past.
5.
Other plant parameters are affected by an SRV actuation and are available as confirmation.
Examples are main turbine governor valve position indication change, generator output change, main turbine steam flow change, steam/feedwater flow mismatch and the resultant reactor pressure perturbation.
Other indicators provide adequate feedback for ADS (reactor pressure) and SRV operation, and Alternate Shutdown Cooling operation (reactor pressure/temperature) if they are required.
Additionally, HS-RV-2C and 2D are not controlled on either of the remote shutdown panels and are not ADS valves.
Mith 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 EMERGENCY CIRCUHSTANCES Failure of these acoustic monitors has only recently been identified.
The licensee declared the monitor for valve HS-RV-2D INOPERABLE AT 5:27 p.m., February 13, 1990.
It was not possible to anticipate this event and submit this request in a more timely manner.
The licensee has determined that repair will require that the reactor be 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 next outage of sufficient duration to effect the necessary repairs.
Absent this amend-ment, the Supply System would be required to unnecessarily shutdown by February 20, 1990.
The next scheduled outage for refueling will start on or about April 13, 1990.
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t The staff reviewed the circumstances associated with your request and concluded that you 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 emergency existed.
4.0 ENYIRONMENTAL CONSIDERATION This amendment involves changes in requirements with respect to the use or installation of a facility 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 be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
Accordingly, this 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 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 significant hazards considerations if operation of the facility in accordance with the amendment would not:
1.
Involve a significant increase 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 margin of safety.
The amendment has been evaluated against these standards in 10 CFR 50.92.
A discussion of these standards as they relate to the amendment request follows:
1.
The change does not involve a significant increase in the probability or consequence of an accident previously evaluated because the SRV position indication channels are not assumed to function in the initiation of an analyzed accident.
The inoperability of these indication channels does not affect ADS operation of the SRVs.
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 commencing suppression pool cooling with RHR.
As discussed
- above, the operator has many diverse indications available to indicate the need for commencing suppression pool cooling as a result of an open SRV and the SRV position indication is not the primary indications.
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 proposed change affects only the operability of the SRV position indication and does not affect automatic or manual actuation of the SRV.
MS-RY-2C and 2D are not ADS valves nor are
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they controlled from either of the remote shutdown panels (Appendix R).
Therefore, this change will not involve a significant 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 because SRV operation, including the ADS function, remains unaffected.
No new modes of operation of any equipment result due to this change.
Sufficient diverse indication remains available to adequately determine whether an SRV is inadvertently open, therefore this change will not result in a failure to assess the need for suppression pool cooling.
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 create a significant reduction in a margin of safety because, as discussed
- above, the operator has many diverse indications available to indicate the need for commencing suppression pool cooling.
Loss of an SRV position indication channel wi11 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 wi 11 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 significant hazards consideration.
6.0 CONTACT WITH STATE OFFICIAL In accordance with 10 CFR 50.91, the licensee provided the State of Washington with a copy of its February 14, 1990 letter.
The NRC staff advised the Washington Energy Facility Siting Council of the final determination of no significant hazards considerations by telephone on February 20, 1990.
The State of Washington did not have any comment on this determination.
- 7. 0 CONCLUSION In summary, based on the assertion that no significant hazard is created by 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 pub 1 ic.
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, (2) such act-ivities wi 11 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:
February 20, 1990
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