ML20210J256
| ML20210J256 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 03/27/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20210J243 | List: |
| References | |
| NUDOCS 8604030400 | |
| Download: ML20210J256 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION g
.E WASHINGTON, D. C. 20555
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i SAFETY EVA'.UATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 42 TO FACILITY OPERATING LICENSE NO. DPR-22 NORTHERN STATES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT DOCKET N0. 50-263
1.0 INTRODUCTION
By letter dated September 24, 1982 (Reference 1), Northern States Power Company (NSP/the licensee) proposed revised Technical Specifications (TS) 3.6.G and 4.6.G and the associated bases to include the recomended jet pump monitoring procedures in General Electric Service Information Letter i
(SIL) 330. The licensee stated that the proposed modification would provide additional assurance that jet pump degradation would be detected prior to jet pump failure.
In its letters of September 29, 1983 and November 15, 1985 (References 2 and 5), the licensee revised the earlier submittal by adding to the bases a brief reference to the data base used to determine the normal operating range of two jet pump parameters involved in the surveillance procedures.
In addition, changes were made to the surveillance procedure involving recirculation pump operation at speeds below 60%.
2.0 EVALUATION During 1980 and 1981, hold-down beam bars for jet pumps at six BWR/3 plants and one BWR/4 plant were found to have stress corrosion cracking. At two BWR/3 plants, the ~ cracking was severe enough to cause failure of a beam bar with a resultant displacement of the jet pump mixer section. The mixer displacement causes degradation of jet pump performance during normal operation. Of greater concern is the effect of the mixer displacement on core conditions following a pastulated LOCA. The elevation of the jet pump inlets corresponds approximately to the two-thirds height of the active fuel region and helps assure maintenance of a relatively high water level in the core region following a postulated break in a recirculation line.
However, displacement of the mixer section opens a lower level leakage path for injected water and might reduce the margin of safety during postulated accidents.
Staff and industry concerns with respect to this issue are presented in References 3 and 4.
IE Bulletin No. 80-07, "BWR Jet Pump Assembly Failure" l
(Reference 3) provided staff requirements for justification of continued operation. A surveillance program specified in the bulletin was to be followed until either (a) the plant TS were changed or (b) the cause of beam failure was identified and corrected.
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0604030400 860327 DR ADOCK O 2
General Electric SIL 330, " Jet "::mp Beam Cracks," (Ref. 4) provides a discussion of jet pump performance monitoring to detect potential beam failure and gives recommendations for modifications to the TS to improve detection of impending failure.
In addition, General Electric has de.veloped improved hold-down beam bars. Although no cracking of beam bars was detected at Monticello Nuclear Generating Plant, all 20 beam bars were replaced in 1982 with improved beam bars which are BWR/4 type bars with a new heat treatment. Complete replacement of beam bars has been done at four other operating BWR plants.
The revision prescribes a program to monitor various parameters, such as core flow, core plate differential pressure, recirculation pump flow and speed, so the acceptability of jet pump performance can be clearly deter-mined. The proposed limiting condition for operation contains the minimum acceptable standards 'for jet pump operability and when they are not met, the reactor would be shut down within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
In addition, the surveillance requirements will include evaluation of the jet pump deviation every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> whenever the recirculation pump speed is below 60%. The revised surveillance program would provide additional assurance that jet pump degradation will be detected before actual jet pump failure.
The staff has reviewed the proposed changes and concludes that the revised TS 3.6.G and 4.6.G and the associated bases will reflect the recommended procedures in General. Electric SIL 330.
In addition, with the replacement of the beam bars and the changes in the TS, Monticello has satisfied the Short-term and Long-term Actions Criteria on page D-3 of NUREG/CR-3052, "Closecut of IE Bulletion 80-07: BWR Jet Pump Assembly Failure," November 1984. The staff, therefore, finds.the proposed changes acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
S This amendment involves a change to the requirements 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 in surveillance requirements.
The staff has determined that the amendment involve's no significant increase l
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 Connission has previously issued a proposed finding that this amendment involves no I
significant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the eligibility criteria l
for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 l
CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
4.0 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 be conducted in compliance with the Commission's regulations l
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and the issuance of the amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
C. Graves Dated: March 27,1986 4
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r REFERENCES 1.
Letter from D. Musolf.of Northern States Power Company to Director of NRR, " Licensee Amendment Request dated September 24, 1982, Miscellaneous Technical Specifications Changes."
2.
Letter from D. Musolf of Norther.n States Power Company to Director of NRR, " Revision No. I to Licensee Amendment Request dated September 24, 1982", September 29, 1983.
3.
US NRC, IE Bulletin No. 80-07, "BWR Jet Pump Assembly Failure", April 4, 1980.
4.
General Electric Service Information Letter (SIL) 330, " Jet Pump Beam Cracks", June 9, 1980.
5.
Letter from D. Musolf of Northern States Power Company to Dresden to NRR, " Revision No. 2 to License Amendment Request Dated September 24, 1982", November 15, 1985.
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