ML20043C034
| ML20043C034 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 05/25/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20043C032 | List: |
| References | |
| NUDOCS 9006010224 | |
| Download: ML20043C034 (4) | |
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION t.
WASHINGTON, 0. C. 20666 g...*f l
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATFD TO AMENDMENT NO.160 TO FACILITY OPERATING LICENSE NO. NPF-1 P0,RTLAND GENERAL ELECTRIC COMPANY THE CITY OF EUGENE. OREGON PACIFIC POWER AND LIGHT' COMPANY TROJAN NUCLEAR PLANT DOCKET NO. 50-344
1.0 INTRODUCTION
By letters dated November 30, 1989, January 25,)1990 and April 16, 1990, Portland General Electric Company (the licensee, submitted a proposed amendment for the Trojan Nuclear Plant. The proposed amendment would change the Technical Specification (TS) to allow sleeving of steam generator tubes.
The TS now requires that all defective steam generator tubes be plugged.
Plugging tubes reduces reactor coolant flow and is less desirable in some i
cases than a repair technique that does not remove the tubes.from service.
l The changes in the TS will allow sleeving of steam generator tubes as a-I corrective or preventive maintenance action.
Primary water stress corrosion cracking (PWSCC) resulted in the plugging of a significant number of steam generator tubes during Trojan's 1989 Refueling Outage. A number of corrective actions are being taken to arrest the further development of PWSCC; however, according to.the licensee, there exists a real possibility that the number of tubes required to be plugged during the 1990 Refueling Outage could exceed the presently analyzed limit of 11-1/2 percent uniform tube plugging. Therefore, to address this contingency, the licensee requested the amendment to permit sleeving.
Two vendors have been selected by the licensee for use at Trojan.
Reports which describe their use are as follows:
1.
BAW-2094P, " Recirculating Steam Generators Kinetic Sleeve I
Qualification for 7/8-inch OD Tubes," October 1989.
2.
a.
BKAT-01-P, Tubes-by Sleeving," Revision 1, April 1989.
" Topical Report:
Repair of Defective Steam Generator 9006010224 900525 i
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i b.
EDR-TRJ-01-P, " Design Report:
Repair of Defective Steam i
Generator Tubes by Sleeving for Trojan Nuclear Power Plant "
October 1989.
2.0 BACKGROUND
1 Operatingpressurizedwaterreactor(PWR)steamgeneratorsexperience difficulties associated with tube degradation related to corrosion phenomena such as wastage, pitting, intergranular attack, stress corrosion cracking, and crevice corrosion, and other phenomena such as denting and l
vibration wear. Tubes that experience excessive degradation reduce the integrity of the primary-to-secondary pressure boundary. These tubes are considered defective and must be removed from service. Historically, the corrective action taken where degradation of the steam generator tube wall has been severe has been to install plugs at the-inlet and outlet 4
of the steam generator tube when the reduction in wall thickness reached a calculated value referred to as the " plugging limit." Eddy current i
testing (ECT) has been used to measure the degradation of the steam generator tube, and the tube plugging limit accounts for the uncertainties in ECT measurements and an additional margin in wall thickness for postu-lated degradation during service.
3.0 EVALUATION BKAT-01-P, Revision 1, " Topical Report: Repair of Defective Steam Generator Tubes by Sleeving," was acce applications by the staff on February gted for referencing in licensing i
l 1990.
In accordance with NUREG-0390andstaffpositions,thestaffdidnotrepeatitsreviewof the matters described and found acceptable in the report. The staff did review EDR-TRJ-01-P, Revision 0, " Design Report:
Repair of Defective Steam Generator Tubes by Sleeving for Trojan Nuclear Power Plant," which described the characteristics of the Trojan sleeves that are different from the sleeves described in the Topical Report. The differences in design, installation procedure and testing were reviewed and found not to affect the conclasions stated 'in the staff's topical report review.
It i
is stated that a fatigue analysis was performed specifically for Trogan that demonstrates that the new sleeve designs meet the: criteria described in the Topical Report.
The Trojan design report states that a fracture mechanics analysis was made with respect to the heat affected zone in the tube sheet from the sleeve-to-tube weld within the tube sheet region, and the results were l
found to meet ASME Section XI criteria, and are therefore acceptable to l
the staff. The licensee has committed to providing confirmatory l
information regarding the fracture mechanics analysis result.
Based on the staff's previous review and approval of the Topical Report and the-current review of the desi process to be acceptable. gn report for Trojan, we find the above sleeving
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BAW-2094P, Revision 1, " Recirculating Steam Generators Kinetic Sleeve Qualification for 7/8 Inch OD Tubes," was reviewed and found to be an extension of the sleeving technology described in BAW-2045P, ' Recirculating Steam Generator Kinetic Sleeve Qualification for 3/4 Inch OD Tubes."
This Topical Report was accepted for referencing in licensing applications oh January 4.-1990.
BAW-2094P, Revision 1, additionally describes a newly i
developed tube support plate kinetic sleeve. The staff has reviewed these differences and finds they do not affect the conclusions stated in the safety evaluation accepting the topical report.
Based on the staff's previous review and approval of the B&W topical report and our review of the above documents, we find the new sleeving process to be acceptable.
Based on Regulatory Guide 1.121 guidelines for tube degradation limits, an appropriate plugging limit has been established.
Eddy current techni-
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ques are available to perform necessary sleeve and tube inspections for defect detection and to verify proper installation of the sleeve.
Available techniques are capable of providing adequate defect sensitivity in the required areas of the tube and sleeve pressure boundary. A pro-prietary method is described in the reports with supporting validation i
data that demonstrates the inspectability of the sleeve and underlying tube. The licensee has provided a commitment to validate the adequacy of any system that is used for periodic inservice inspections. The licensee has also committed to evaluate and to implement testing methods as better methods are developed and validated for commercial use.
j 4.0 CONTACT WITH STATE OFFICIAL The NRC staff has notified the Oregon Department of Energy of the proposed.
issuance of this amendment along with the proposed determination of no significant hazards consideration.
No comments were received.
5.0 ENVIRONMENTAL CONSIDERATION
t This amendment involves a change in a requirement with respect to the 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 increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there it, no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously published 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 eli categorical exclusion set forth in 10 CFR 51.22(c)gibility criteria for (9). Pursuant to 10 CFR51.22(b),noenvironmentalimpactstatementorenvironmentalassessment need be prepared in connection with the issuance of the amendment.
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6.0 CONCLUSION
We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, (2) public such activities will be conducted in compliance with the Commission's regu.
lations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
PRINCIPAL CONTRIBUTORS:
H. Conrad Roby Bevan i
Dated:
May 25, 1990 i
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