ML20246A860
| ML20246A860 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 04/28/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246A801 | List: |
| References | |
| NUDOCS 8905080347 | |
| Download: ML20246A860 (4) | |
Text
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'o UNITED STATES Fg
!" M NUCLEAR REGULATORY COMMISSION n
- i WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 158 TO FACILITY OPERATING LICENSE NO. DPR-49 IOWA ELECTRIC LIGHT AND POWER COMPANY CENTRAL IOWA POWER COOPERATIVE CORN BELT POWER COOPERATIVE DUANE ARNOLD ENERGY CENTER DOCKET NO. 50-331
1.0 INTRODUCTION
By letter dated September 15, 1986 (Reference 1), the Iowa Electric Light and Power Company (IELP) proposed revised Technical Specifications (TS) for the Duane Arnold Energy Center (DAEC).
The proposed changes would revise TS's 3.6.E. and 4.6.E. and their associated bases to improve monitoring of jet pump performance to detect any impending failures of jet pumps or their holddown beams.
The proposed changes incorporate the guidance provided in NRC IE Bulletin 80-07, "BWR Jet Pump Assembly Failere," dated April 4, 1980 (Reference 2), and General Electric Service Information Letter (SIL) No. 330, " Jet Pump Beam Cracks," dated June 9, 1980 (Reference 3).
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 postulated 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.
In response to this concern, the NRC staff issued Reference 2, which specified a surveillance program to be followed until either the plant TS were changed or the cause of beam failure was identified and corrected.
The DAEC implemented the improved jet pump surveillance specified in Reference 2 and has continued to perform them pending revision of the applicable TS's.
In Reference 3, General Electric issued recommendations for modifications to the TS to improve l
r 8905080347 890428 ADOCK0500g1 PDR P
, jet pump performance monitoring and detection of impending failure-of hold down beams.
The proposed TS for the DAEC incorporate these recommendations.
In addition, General Electric has developed improved hold-down beam bars which are subjected to a new heat treatment.
Although no cracking of beam bars was observed at the DAEC, all 16 beam bars were replaced during the 1988 refueling outage with those of improved design.'
'The specific changes proposed consist of the following:
(1) Revise the' Limiting Condition for Operation for jet pump operability (Section 3.6.E) to specify the actions to be taken if the surveillance requirements cannot.be met.
Different actions are indicated depending upon the value of recirculation pump speed.
For speeds less than 60%
of rated, additional daily surveillance are required until.'the specified evaluations are performed at higher pump speeds.
If the speed is greater than or equal to 60% of rated and the requirements are not met, i.e., the jet pumps are verified to be. inoperable, the reactor must be in a cold shutdown condition ~within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
(2) Revise the Surveillance Requirements for jet pump operability (Section 4.6.E) to incorporate the improvements in monitoring performance of jet pumps, outlined in GE SIL No. 330, as:follows:
(a) Delete the " simultaneous" requirement of the present Technical Specifications, as it is no longer needed to ensure that anomalous readings are discounted.
(b) Replace the present performance parameters (flow imbalance and independent core flow measurements) with better indicators of jet pump performance, i.e., ratios of recirculation pump flow to speed and jet pump loop flow to recirculation pump speed.
(c) Revise the acceptance requirement for deviation of individual jet pump differential pressure (AP) from average loop AP from the present 10% to 20%.
(d) Clarify the present requirements to specify that, during single loop operation (SLO), the surveillance requirements of 4.6.E.1 and.2 apply only to the active loop.
(e) Add a requirement to update the baseline data base after each refueling to ensure that any changes due to the new core loading are incorporated into the data base.
l (3) Update the Bases Section for 3.6.E/4.6.E to reflect the above l
changes.
1 e l These proposed changes require monitoring various parameters, including core flow, core plate differential pressure, recirculation pump flow and speed, and jet pump loop flow and differential pressure.
Monitoring these parameters will result in a more accurate evaluation of jet pump performance.
The proposed Limiting Conditions for Operation (LCO) contain the minimum acceptable standards for jet pump operability, requiring shut down within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if a jet pump is determined to be inoperable.
For recirculation pump speeds below 60% of rated, jet pump flow and differential pressure signals are inherently noisy and thus do not provide reliable indication of jet pump performance.
Therefore, when the parameters of proposed Surveillance Requirement 4.6.E.1 are exceeded, proposed LC0 3.6.E.1.a and Surveillance Requirement 4.6.E.2 require daily evaluations of individual jet pump deviations from average loop differential i
pressure, until an accurate evaluation of jet pump operability can be performed at recirculation pump speeds above 60%.
These specifications will preclude unnecessary plant shutdowns due to anomalous data while providing for enhanced i
monitoring of suspect jet pumps during operation at low recirculation pump l
speeds.
This additional surveillance provides added assurance that any jet pump degradation will be detected prior to jet pump failure.
The staff has reviewed the proposed changes and concludes that revised TS 3.6.E and 4.6.E and the associated bases incorporate the recommended procedures of Reference 3 for improved monitoring of jet pump performance.
These procedures were approved by the staff in NUREG/CR-3052, " Closeout of IE Bulletin 80-07:
BWR Jet Pump Assembly Failure," Appendix D, November 1984 (Reference 4).
In addition, the replacement of the original jet pump hold down beams with improved l
beams during the 1988 refueling outage provides added assurance that jet pump l
failures will not occur.
Therefore, the staff finds the proposed changes acceptable.
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3.0 ENVIRONMENTAL CONSIDERATION
S This amendment changes a requirement with 12spect to installation or use of a i
facility component located within the restricted area as defined in 10 CFR Part 20 or changes a surveillance requirement.
The staff has determined that the 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.
The Commission'has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding.
Accordingly, the 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 the 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, and the issuance of the amendment will not be inimical to the common defense and security or to I
'the health and safety of the public.
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5.0 REFERENCES
1.
Letter from R. McGaughy, IElP,.to H. Denton, NRC,~" Technical Specification-,
Change (RTS-206) Jet Pump Operability," September 15, 1986, NG-86-3011.
I 2.
USNRC IE Bulletin No. 80-07, "BWR Jet Pump Assembly. Failure,". April'4, 1980.
3 3.
General Electric Company Service Information Letter (SIL) 330, " Jet Pump Beam Cracks," June 9, 1980.
4.
USNRC NUREG/CR-3052, " Closeout of IE Bulletin 80-07: BWR Jet Pumps Assembly Failure," November, 1984.
Principal Contributor:
J. R. Hall Dated: April 28, 1989
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