ML20235N313
| ML20235N313 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 02/21/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20235N305 | List: |
| References | |
| NUDOCS 8903010152 | |
| Download: ML20235N313 (4) | |
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NUCLEAR REGULATORY COMMISSION
.E WASHINGTON, D. C. 20555 k..... o SAFETY EVALUATION BY THE 0FFICE 0F NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT.N0.128 TO FACILITY OPERATING LICENSE _NO. DPR-46 NEBRASKA PUBLIC POWER. DISTRICT COOPER NUCLEAR STATION DOCKET N0. 50-298
1.0 INTRODUCTION
By letter dated February 9,1989 and a supplement thereto dated February 10, 1989, the Nebraska Public Power District (the licensee) requested an amendment to Facility Operating License No. DPR-46 for the Cooper Nuclear Station. The proposed amendment will change the implementation date for a portion of previously issued Amendment No. 115 from February 11, 1989 to "before fuel loading during the 1989 refueling outage" presently scheduled to begin in April 1989. The portion of the amendment to which this change applies requires addition of the negative voltage sensing relays to trip the Source Range and Intermediate Range Monitoring channels.
The licensee originally proposed that the modifications to these instruments should be installed with the plant at power by bypassing one redundant channel
,.at a time.. The instrument channels are required to be in operation when the plant is shutdown for refueling and when operating at startup mode with the reactor operating at power.
In the run mode, the Source Range and Intermediate Range Channels protective functions are taken over by the average Power Range Monitors and the SRM and IRM channels may be bypassed.
2.0 EVALUATION SRM and IRM Requirements: On June 16, 1986, while in the refueling mode of operation, a BWR/3 f acility experienced multiple failures of IRM 3/4 Ampere fuses connected to the 24 VDC bus. The event was caused by a surge in the 24 VDC system resulting from a transient while switching on the 480 VAC power supply. Af ter replacing only the blown fuses for the 24 VDC bus all inoperative IRM channels appeared to be operating normally. The loss of signal processing, which requires -24 VDC, was not detected until later surveillance tests were conducted prior to startup. During the period of loss of -24 VDC power, certain signal processing functions of the SRM and IRM systems were lost rendering the systems inoperable. Subsequently, the NSSS vendor recommended a plant modification to provide negative voltage sensing relays to trip SRM/IRM channels to IN0PERABLE status upon loss of -24 VDC power (General Electric Co. Service Information Letter 445). Such instrumentation was provided originally for the +24 VDC power supplies only.
By letter dated December 1,1987, the licensee requested an amendment to the facility Technical Specifications to revise the Source Range Monitor (SRM) and Intermediate Range Monitor (IRM) operability requirements to clarify that negative power supply voltage is required for operability. Amendment No. 115 to the Cooper Nuclear Station License was issued on February II,1988 and established an effective date of February 11, 1989.
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. i In December 1988, subsequent to the issuance of Amendment No. 115, NPPD had completed plans for the 1989 refueling outage that includes the complete unloading of the reactor core.
Because there will be no requirement for the operability of the IRM or SRM channels in the defueled condition the licensee has reappraised its previous position regarding conducting the modification at power and has requested an extension of the implementation date until the core is unloaded during the outage.
The protective functions provided by the SRM and IRM system are not required for protection against.the analyzed transient-and accidents applicable to Cooper. For the Rod Withdrawal Event and Control Rod Drop Event, the 120 percent APRM trip function, which is not affected by loss of negative voltage, is credited for protection. The modification is, however, desirable for the purpose of providing backup protection during plant operation and core monitoring during subcritical operations.
Based upon the above discussion the NRC staff has concluded that the deferral of the implementation of this modification for approximately 3 months will not adversely affect the safety of operation of the plant since no credit is taken in the safety analysis for plant operation for the protective functions of the SRM and IRM.
The staff finds it acceptable to defer the installation of the negative voltage sensing relays required to implement Amendment No.115 until the reactor core is defueled during the 1989 refueling outage.
3.0 EMERGENCY CIRCUMSTANCES The licensee. originally had intended to implement the IRM/SRM loss of negative power supply voltage modification while operating at power during the current operating cycle before February 11, 1989.
In December 1988 the licensee decided that the entire core would be off-loaded during the 1989 refueling outage. With no fuel in the reactor core the IRM/SRM power supplies could be completely deenergized thereby eliminating any electrical hazards for technicians working on the modification and preventing unscheduled shutdowns of the reactor that might be caused by the modifications.
Based upon these considerations the licensee decided during January 1989 to defer the modification until the reactor would be defueled in May 1989. At the time that NPPD management decided to defer the modification, they fai'ed to realize that the previous date for implementing the modification had been incorporated into their license by Amendment No. 115. When the NPPD management did recognize that the implementation date was a license condition, it was too late to provide the NRC staff with sufficient time to provide the customary advance notice of the proposed implementation date change.
The NRC staff has reviewed the licensee's reasons for failing to file their application sufficiently in advance of their need to modify their license and
i t concludes that although NPPD has failed to apply for this amendment in a timely fashion, the failure was not an attempt to abuse the emergency provision but was rather caused by their failure to recognize that their commitment date was part of their license.
Accordingly, the staff concludes that an emergency situation exists, in that failure to act would result in shutdown of the nuclear power plant.
4.0 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 consideration if the operation of the facility in accordance with the amendment would nct:
(1)
Involve a significant increase in the probability or consequences of an accident previously evaluated; or j
(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 proposed change to the plant involves the installation of an additional SRt1 and IRM inoperative trip caused by the loss of negative supply voltage.
This protective function is not required for protection against the analyzed transients and accidents applicable to Cooper. The modification is, huwever, desirable for the purpose of providing backup protection during plant operation and core monitoring during subcritical operations. Based upon the above, the staff has concluded that deferring the installation of the loss of negative supply voltage inoperable trip will not create a possibility of a new or different accident, and does not affect any margins of safety.
Based on the above evaluation the staff concludes that operation of the facility in the proposed manner would not involve a significant increase in the probability or consequences of an accident previously evaluated, would not create the possibility of a new or different kind of accident from any accident previously evaluated, and would not involve a significant reduction in a margin of safety.
Accordingly, we conclude the amendment involves no significant hazards consideration.
5.0 STATE CONSULTATION
In accordance with the Commission's regulation, consultation was held with the state of Nebraska by telephone. The State expressed no concern either from the standpoint of safety or no significant hazards consideration determination.
6.0 ENVIRONMENTAL CONSIDERATION
S This amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR j
< Part 20, and changes surveillance requirements. The staff has determined that the amendrent involves 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 Commission has made a final nc significant hazards consideration finding with respect to this amendment. Accordingly, this amendment meets the eli categorical exclusion set forth in 10 CFR 51.22(c)(9)gibility criteria for Pursuant to 10 CFR 51.22(b) no environmental impact statenant or environmental assessment need be prepared in connection with the issuance of this amendment.
7.0 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 the an;endment will not be inimical to the common defense and security or te the health and safety of the public.
Date: Februa ry 21, 1989 Principal Contributor:
Paul W. O'Connce
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