ML20248A055
| ML20248A055 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 05/15/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20248A053 | List: |
| References | |
| NUDOCS 9805290280 | |
| Download: ML20248A055 (4) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.182 TO FACILITY OPERATING LICENSE NO. DPR-20 CONSUMERS ENERGY COMPANY PALISADES PLANT DOCKET NO. 50-255
1.0 INTRODUCTION
By letter dated January 18,1996, as supplemented by letters dated October 1,1997, and January 29, and April 27,1998, Consumers Energy Company (the licensee) requested an amendment to the Technical Specifications (TS) appended to Facility Operating License No.
DPR-20 for the Palisades Plant. The proposed amendment would revise the TS regarding inspection requirements for the reactor coolant pump (RCP) flywheels and allow the application of Surdllance Requirement 4.0.2, which permits extension of surveillance intervals by up to 25%, to the flywheel inspection program. The submittal is related to the ABB Combustion Engineering report SIR-94-080, " Relaxation of Reactor Coolant Pump Flywheel inspection Requirements," which was approved by the staff, with certain conditions, on May 21,1997. The licensee proposed to change the RCP flywheels' inspection intervals in accordance with the conclusion of the safety evaluation (SE) related to SIR-94-080.
The January 29 and April 27,1998, letters provided additional clarifying information that was within the scope of the original FederalRegister notice and did not change the staff's initial proposed no significant hazards considerations determination.
2.0 EVALUATION The function of the RCP in the reactor coolant system (RCS) of a pressurized-water reactor (PWR) plant is to maintain an adequate cooling flow rate by circulating a large volume of primary coolant water at high temperature and pressure through the RCS. A concem regarding overspeed of the RCP and its potential for failure led to the issuance of Regulatory Guide (RG) 1.14 in 1971. Since then, most licensees for PWR plants, with very few exceptions, have adopted the guidelines of RG 1.14 to conduct their RCP flywheel examinations. These requirements are normally specified in the individual plant's TS as is the case for Palisades.
In the May 21,1997, SE related to ABB Combustion Engineering report SIR-94-080, the staff concluded, "(1) all flywheels meet the proposed nonductile fracture criteria, and will have adequate fracture toughness during their service periods, and (2) all flywheels except those for Waterford 3 satisfy the excessive deformation criterion of RG 1.14.* This conclusion was based on the fracture toughness (KJ values reported in S!R-94-080 for all participating plants, Mcluding Palisades. In the SE related to SIR-94-080, the staff required applicants wishing to 9805290280 980515 PDR ADOCK 05000255 P
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2-reference the report to support flywheel ins'pection interval extensions to verify tne reference temperature, RT, and to justify the use of the K versus (T-RT ) curve in Appendix A of Section XI of the American Society of Mechanical Engineers (ASME) Code for flywheels made of materials other than SA 533 8 and SA 508.
2.1' Licensee's Evaluation Tne licensee indicated in the submittal that Palisades RCP flywheels were made from ASTM A-108 (SAE 1017) low carbon steel, and the nil ductility transition (NDT) temperature for this material is 40 *F with an average Charpy % notch (CVN) energy of 100 ft-lb at 70 *F.
Using the ASME Code, the licensee concluded that the RT, for its flywheel material may be conservatively considered as 40 *F. the same as the NDT.
The licensee does not have plant-specific test data to establish the appropriate K value for its flywheel material. Nor does it have flywheels made from either SA 533 B or SA 508 material so that it can use the K., versus. (T-RT ) curve in Appendix A directly. To overcome this, the licensee used the Appendix A curve for K,, determination, but introduced a factor of 0.75 to -
cover any uncertainty on the fracture toughness. Using an operating temperature, T, of 100 *F, an RT of 40 *F, and an uncertainty factor of 0.75, the license determined the K,, value to be 85.5 ksi(in)". This fracture toughness is employed in the subsequent fracture mechanics f
analysis. The allowable flaw size is then determined by intersecting this fracture toughness 4
with the applied stress curve plotted as a function of flaw depth. The applied stress represents the combined shrink-fit and centrifugal stresses multiplied by a safety factor of 2.5, as approved in the SE related to SIR-94-080. The critical flaw size calculated by the licensee is 1.52 inches, which provides a large margin when compared to the postulated crack size of 0.343 inch from the SE related to SIR-94-080 based on an initial flaw size of 0.33 inch and a crack growth of 0.013 inch after 10 years of operation of the flywheel. Consequently, the licensee concluded that the inspection interval for Palisades' flywheels can be extended to 10 years.
2.2 Staff's Evaluation According to the ASME Code, if the NDT, which can be estimated by the drop-weight test,4 40 *F, then the RTa is also 40 *F, provided that the Charpy energy at 100 *F (40 *F+60 *F) exceeds 50 ft-Ib and the lateral expansion exceeds 35 mils. Since the Palisades flywheel material has an average Charpy energy of 100 ft-Ib at 70 *F, it would have a Charpy energy far exceeding 50 ft-lb at a temperature higher than 70 *F. Because of this large margin, the material is also very likely to meet the lateral expansion threshold of 35 mils. Hence, the staff accepts the RT, of 40 *F for the Palisades flywhee; material.
The licensee applied the Appendix A curve to estimate the K,, value for its flywheels. To cover the uncertainty involved in applying a curve based on SA 533 B and SA 508 vessel material l
data to the Palisades flywheel material of SAE 1017 low carbon steel, the licensee applied a l
factor of 0.75 to reduce the K = value to 85.5 kai(in)". The rest of the licensee's approach is in accordance with the flaw evaluation procedure in Section XI of the ASME Code. The staff concludes that in addition to the uncertainty factor of 0.75, there is margin associated with the fact that the calculated flaw size after 10 years of operation (0.343 inch) is far less than the critical flaw size (1.52 inches).
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. c To further evaluate the K, value of 85.5 ksi(in)", the staff conducted a literature search.
i Page 175 of the book, Linea Elastic Fracture Mechanics. by D. Broek, indicates that the K = for the low strength carbon steelis greater than 200 ksi(in)". Page 877 of the American Society for Metals (ASM) Handbook, Fatious and Fracture. by S. Lampman, et al., indicates that the Mean-minus-2-sigma K, for 1018 steel is 215 ksi(in)". The staff did not find the K = value for the 1017 steel. However, considering that both 1017 and 1018 materials have the same carbon, sulfur, and phosphorus contents (manganese content is 0.4% for 1017 and 0.8% for l
1018), and their K,, values may not be significantly different, the staff accepts the K = value of 85.5 ksi(in)".
The staff has reviewed the licensee's requsst and has determined that the analysis in the submittal meets the intent of the ABB Combustion Engineering topical report SIR-94-080, and the combined margin is adequate to cover the uncertainty in applying the Appendix A K = curve.
Hence, the staff accepts the licensee's proposed change to implement 10-year inspection intervals for the RCP flywheels.
2.3 Related Prooosed Chances The licensee proposed to delete the footnote appended to TS 6.5.6a. regarding deferral of the flywheelinspections during the refueling outage at the end of cycle 12. This refueling outage was completed in December 1996; therefore, the footnote is no longer applicable. This change is acceptable to the staff.
The licensee proposed to add paragraph b. to TS 6.5.6, to apply the provisions of Surveillance
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Requirement 4.0.2, which permits extension of surveillance ir:tervals b) up to 25%, to the j
flywheel inspection program. However, this proposed change would allow the licensee to extend the flywheel inspection interval to as long as 12.5 years, which is not in accordance with the staffs conclusion in the SE related to SIR-94-080, and the licensee's submittal did not include sufficient information for the staff to evaluate the proposed change. Consequently, this proposed change is denied.
3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Michigan State official was notifed of the proposed issuance of the amendment. The Michigan State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
Tie amendment changes a requirement with respect to the installation or use of a facility 4
component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. 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 cumulstive j
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 auch finding (62 FR 59915). Accordingly, the amendment meets the eligibility j
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a criteria for categorical exclusion set ' orth 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.
5.0 CONCLUSION
The Commission 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, (2) such act!vities will be conducted in compliance with the Commission's regulations, 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 Contributor: S.Sheng Date: May 15, 1998 1