ML17278A378
| ML17278A378 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 07/19/1985 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML17278A377 | List: |
| References | |
| TAC-59235, NUDOCS 8509110433 | |
| Download: ML17278A378 (10) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION
'AMENDMENT NO.
16 TO NPF-21 WPPSS NUCLEAR PROJECT N0.2 DOCKET NO. 50-397 INTRODUCTION By Reference 1, Washington Public Power Supply System (WPPSS) proposed Technical Specification changes for WNP-2.
The amendment would add a new Technical Specification Section 3/4.3.10, entitled Neutron Flux Monitoring Instrumentation and supporting licensing bases and would modify Technical Specification Section 3/4.4.1 (Recirculation Loops) to permit operation at a higher power level than is currently authorized under Single Loop Operation (SLO).
EVALUATION The WNP-2 submittal provides an improved means for maintaining thermal-hydraulic stability by restricting power level to values that depend on flow rate instead of a constant upper limit.
In addition, it requires operators to monitor LPRM flux signals as well as APRM signals in order to avoid or control abnormal neutron flux oscillations.
The staff has reviewed the changes proposed by WPPSS and finds them acceptable for the following reasons:
1.
They meet the recommendations made by General Electric in SIL 380 (Ref. 2) which have been found by the staff (Refs. 3, 4) to be an acceptable method for meeting General Design Criteria 10 and 12 with regard to Thermal-Hydraulic Stability.
2.
The proposed Technical Specification changes are very similar to those which were previously proposed by Iowa Electric for Duane Arnold.
The Duane Arnold Tech Specs have been reviewed and approved by the staff in Reference 5.
EVALUATION OF WASHINGTON STATE COMMENTS The State of Washington's Energy Facility Site Evaluation Council in Olympia was contacted by telephone on July 17, 1985.
Discussions were held with Mr. William Fitch, Executive Secretary and Mr. Ilichael Mills, Engineer for the Council.
A concern regarding the safety implications of operation with a single feedwater pump in conjunction with single recirculation loop operation was raised.
The two issues are entirely separate and are governed by two separate Technical Specifications.
The issue of the flow-power instability that is a concern when the power level is high and the recirculation flow rate is low is not affected by the source of the feedwater-one pump or two.
The feedwater flow rate must match the power level and as long as that relationship is maintained the flow-power instability is unaffected.
For a given recirculation flow rate, the 8509110433 850905 PDR ADOCK 05000397' PDR
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maximum acceptable power level is governed by the onset of the flow-power instability which i's indicated by a significant increase in the noise levels of both the core plate pressure drop and the neutron flux.
On July i8, 1985 the Chairman of the Council, t1r. Curtis Eschols, called to say that he and many on his committee have not 'had sufficient time for a
meaningful review of the amendment change requested by the Supply System.
Therefore, as a representative of. the State of Washington, he declined to take a position relative to safety.
FINAL NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION A proposed amendment to an operating l.icense for a facility involves no significant hazards consideration if operation of the facility in accordance with the proposed amendment would not (I) involve a significant increase in the probability or consequences of an accident previously evaluated; (2) create the possibility of a new or different kind of accident from an accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
We have evaluated the licensee's request for the proposed Technical Specifications for compliance with the above cited standards:
1.
Consideration of Probabilit and Conse uences of Accidents Our evaluation of the proposed changes indicates that the principal accident associated with a single recirculation loop operating would be an inadvertent startup of the idle recirculation loop pulp causing a transient.
However; such a transient was evaluated in the WNP-2 Final Safety Analysis Report (FSAR) and found to satisfy the Comnission's regulations.
In addition, the licensee has proposed more restrictive Technical Specification changes related to NCPR limits, flow-biased scram and rod block setpoints, and reduced YAPLHGR operating limits, to ensure that the probabilities and the consequences of accidents with single recirculation loop operation will not be significantly increased.
We have also evaluated the implication of thermal-hydraulic stability for both single and dual loop operations after the licensee's proposed Technical Specifi-cation changes based on the GE recommendations in SIL 380, Revision 1 are incorporated.
Our evaluation shows that the proposed changes would alleviate the concerns related to the thermal-hydraulic instability by adding surveillance requirements for detecting thermal-hydraulic instabilities and specifying the remedial operator actions for responding to them.
Such operator actions will also assure that there will be no significant increase in the probability or consequences of an accident.
Based on the above discussion, we find that the proposed changes are not expected to significantly increase the probability or consequences of previously evaluated accidents.
2.
Consideration of Possibilit of a New or Different Kind of Accident The WNP-2 operation with one recirculation loop is not expected to create the possibility of a new or different, kind of accident from any previously analyzed, as all abnormal operating transients which could be initiated with single loop
operation, such as an inadvertent startup of an idle recirculation pump or pump trip have already been analyzed in the FSAR, and reviewed and accepted by the staff.
For single and dual loop operation, the addition of the surveillance require-ments and remedial actions for thermal-hydraulic instability detection and response involve normal pl.ant. operating. practices and, therefore, are not expected to create a new or different kind of accident from any previously analyzed in the FSAR.
3.
Consideration of Reduction in a Mar in of Safet The licensee has proposed the revised operating limits and procedures for the proposed single loop operation.
Our evaluation of the licensee's proposal indicated that the proposed changes will ensure that the FSAR margins of safety will not be reduced during normal operation and with one recirculation pump not operating.
Our conclusions are based on our review of the evaluations by GE in support of the single loop operation presented in the GE report NED0-24011.
For single loop operation, the additional surveillance requirements and remedial actions required of the operator for detection of and response to thermal-hydraulic instability will increase the present margin of safety.
Based on the above considerations the staff concludes that the proposed amendment meets the Commission's standards in 10 CFR 50.92(c).
Therefore, the staff has made a final determination that the application involves no significant hazards consideration.
BASIS" FOR EMERGENCY SITUATION This amendment is being issued on an emergency basis.
Prior to the scheduled maintenance, M-3, outage in the spring of 1985, a reactor recirculation flow control valve hydraulic line weld failed.
The line was repaired and the subsequent failure analysis attributed the failure to excessive piping vibration.
Data collected and analyzed from vibration instruments installed on recirculation pump B indicated the cause to be excessive pump vibration.
During the M-3 outage the pump was partially disassembled and damage was found in the radial bearing and seal assembly.
The failure of the bearing was considered by the pump manufacturer's technical representative, a
GE technical representative and the Supply System's technical personnel to have caused the vibration problem.
The pump was reassembled and tested while in cold shutdown.
The vibration data collected during the test were evaluated and indicated that the problem had been solved.
During power escalation following the M-3 outage, the vibration reappeared and increased to unacceptable levels.
The vibration levels experienced are such that extended operation at rated speed is not prudent.
The Supply System could not have anticipated the reoccurrence of high vibration levels in pump B.
Pump technical representatives believed that the problem had been identified and repaired and data from a test of the pump indicated the
repairs to be successful.
Nevertheless on July 8 the vibration levels of the pump exceeded the manufacturer's recommended shutdown limits and the pump was subsequently secured.
Between July 8 and July 16 the plant operated with a single recirculation loop while engineering options for repair were considered.
On July 17 a shutdown was performed which allowed visual examination of the pump and other attempts to mitigate the effects of the vibrations.
The plant has since returned to power and the pump was tested at 60 Hz with unsatisfactory..
results; consequently, it was concluded that pump repair must be accomplished as soon as possible.
This repair will require several weeks after spare parts are obtained which may require several months.
In the meantime the plant is operating on a single recirculation loop and, under the 'present Technical Specifications, is limited to fifty percent power.
Safe operation on one recirculation loop at power levels considerably in excess of fifty percent has previously been demonstrated and approved by the staff.
(See EVALUATION
- section, above).
Thus on July 17, 1985 it became apparent that the emergency technical specification change was necessary to avoid continued derating and the request was made the same day.
ENVIRONMENTAL CONSIDERATION This amendment involves a change to the requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The staff has determined that the amendment involves no significant change in the types or significant increase in the amounts 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 determined that this amendment involves no significant hazards consideration.
Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR Section 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.
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:
July 19, 1985
l
REFERENCES 1.
- Letter, G. C. Sorensen (WPPSS) to W. R. Butler (NRC), "Nuclear Plant No.
2 Operating License NPF-21, Request for Technical Specification Amendment Under Emergency Circumstances,"
dated July 17, 1985.
2.
GE Service Information Letter (SIL), No. 380, Revision 1, dated February 10, 1984.
3.
- Letter, C. 0.
Thomas (NRC) to H. C. Pfefferlen (GE), "Acceptance for Referencing of Licensing Topical Report NEDE-24011, Rev. 6, Amendment 8, "Thermal-Hydraulic Stability Amendment to GESSAR II,""
April 24, 1985.
4.
51emo.,
H. R. Oenton to V. Stello, "Close Out Generic Issue 8B Thermal-Hydraulic Stability," Nay 21, 1985.
5.
- Letter, M. C. Thadani.(NRC), to L. Lui (Iowa Electric), dated Nay 28, 1985.
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