ML20044H503
| ML20044H503 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 06/01/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20044H501 | List: |
| References | |
| NUDOCS 9306090115 | |
| Download: ML20044H503 (3) | |
Text
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W,j NUCLEAR REGULATORY COMMISSION
'E WASHINGTON, D.C. 20506 0001 s
%,.....a SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.173TO FACILITY OPERATING LICENSE NO. DPR-66 AMENDMENT NO. 52 TO FACILITY OPERATING LICENSE NO. NPF-73 DUQUESNE LIGHT COMPANY OHIO EDISON COMPANY PENNSYLVANIA POWER COMPANY THE CLEVELAND ELECTRIC ILLUMINATING COMPANY THE TOLED0 EDISON COMPANY BEAVER VALLEY POWER STATION UNIT N05. 1 AND 2 DOCKET NOS. 50-334 AND 50-412
1.0 INTRODUCTION
In a letter of December 30, 1992, as supplemented March 12, 1993, Duquesne Light Company (the licensee) submitted an amendment request to the licenses for Beaver Valley Power Station, Units 1 and 2, proposing steam generator (SG) tube sleeving in accordance with the Westinghouse and the Babcock and Wilcox processes.
The March 12, 1993, supplement provided additional and clarifying information in support of the original request and did not change the NRC's proposed finding of no significant hazards consideration determination.
The Westinghouse process consists of a laser welding technique to secure a sleeve inside a steam generator tube to serve as the primary barrier within a degraded tube.
The technical justification supporting the Westinghouse process is given in WCAP-13483, Rev. 1, " Beaver Valley Units 1 and 2 Westinghouse Series 51 Steam Generator Sleeving Report," which is still under review.
Therefore, this safety evaluation applies only to the Babcock and Wilcox process described below.
The Babcock and Wilcox (B&W) process uses a kinetic welding technique to secure the sleeves inside SG tubes.
The technical justification supporting the B&W process is given in BAW-2094PA, Rev. 1, " Recirculating Steam Generators Kinetic Sleeve Qualification for 7/8 Inch OD Tubes," a topical report that was previously found acceptable for referencing by the NRC.
2.0 BACKGROUND
Tubes in an operating pressurized water reactor (PWR) SG can be degraded by such corrosion phenomena as wastage, pitting, intergranular attack, stress corrosion cracking, crevice corrosion, as well as by such other phenomena as denting and vibration wear.
Tubes that become excessively degraded reduce the integrity of the primary-to-secondary pressure boundary and must be removed from service or repaired. Historically, SG tubes that have degraded below a 9306090115 930601 PDR ADOCK 05000334 p
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calculated minimum wall thickness value, termed the " plugging limit," were-plugged at both the inlet and outlet ends of the tube.
Installing plugs in SG tubes decreases the heat transfer surface area available for reactor core cooling.
)
Recently, SG tubes experiencing localized degradation have been fitted with sleeves over the degraded area to reestablish the integrity of the primary-to-secondary pressure boundary.
The sleeves are expanded and sealed inside the tubes to provide an acceptable leak resistance, load-carrying path.
Installing sleeves inside the SG tubes slightly reduces the heat transfer capability and slightly restricts the primary flow through the sleeved tubes.
The licensee has performed eddy current testing (ECT) to measure the degradation of the SG tube and developed similar testing for sleeves. When ECT measurements exceed the plugging limit in a tube, the tube can be either I
sleeved or plugged; and when the measurements exceed the plugging limit in a sleeve, the tube is plugged. The plugging limit conservatively accounts for the uncertainties in ECT measurements and contains an additional margin for expected or postulated degradation during service. The amendment identifies the plugging limit for the B&W process as 40 percent of the sleeve wall.
Since 1983, B&W has installed kinetically welded sleeves in recirculating SG tubes located in Europe and the United States. The sleeves are of three basic designs:
(1) kinetic welds in both tube-to-sleeve joints (joints) completely -
within the tube sheet, (2) kinetic or rolled joints within the tube sheet and a freespan kinetic weld above the tube sheet, and (3) freespan kinetic welds on each side of a tube support plate.
The kinetic welds are given a postweld heat treatment (PWHT) for stress relief.
3.
DESCRIPTION AND EVALUATION OF BAW-2094PA. Rev. 1 The proposed amendment would modify a portion of the Technical Specifications that specifies that degraded tubes must be removed from service by plugging the tubes. The modification would allow the option of sleeving to repair degraded tubes.
The sleeving process consists of cleaning the tube and sleeve j
surfaces at the contact areas, expanding the sleeves against the tubes, attaching the sleeves to the tubes by welding or hard rolling, inspecting the assembly to confirm weld acceptability and to establish an inspection baseline. The design, installation, and inspection of the sleeves will be done in accordance with American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section III (Code).
By adherence to industry standards, the pressure boundary integrity is preserved.
The structural analysis has been performed for SG pressure, temperature, and to determine minimum primary pressure-boundary wall thickness.
The structural integrity has been demonstrated by means of fatigue testing, tensile testing, thermal cycling, and leak testing.
Corrosion resistance of the sleeves has been demonstrated by means of corrosion testing.
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s The-technical justification supporting the B&W process is given in BAW-2094PA, Rev.1, a topical report that was previously found acceptable for referencing -
in licensing applications by the NRC; therefore, the staff did not conduct a detailed review. The staff concluded that the licensee's use of the B&W sleeves will be bounded by the parameters stated in BAW-2094PA, Rev. 1, which does not address bowed sleeves.
The licensee has committed to PWHT of the welded joints.
r Based on the preceding analysis, the NRC staff concludes that the operation of Beaver Valley Power Station, Units 1 and 2, in accordance with the proposed amendments to include the repair of SG tubes using kinetic welded sleeves that are installed with the B&W process is acceptable.
lhe staff also finds that the use of the eddy current equipment and techniques as described in BAW-2094PA, Rev. 1, or their equivalent, to be currently.
dCCeptable.
The licensee has committed to utilize advanced state-of-the-art eddy current inspection techniques as they are developed and verified, after a 10 CFR 50.59 review.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR l
Part 20.
The NRC staff has determined that the amendments involve no i
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 amendments involve no significant hazards consideration, and there has been no public comment on such finding (58 FR 17912).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR Sl.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, j
that:
(1) there is reasonable assurance that the health and safety of the i
public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, l
and (3) the issuance of the amendments will not be inimical to the common j
defense and security or to the health and safety of the public.
Principal Contributor: D. Naujock Date:
June 1, 1993
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