ML121070686
| ML121070686 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/11/2012 |
| From: | Michael Mahoney Plant Licensing Branch III |
| To: | Allen B FirstEnergy Nuclear Operating Co |
| mahoney, m NRR/DORL/LPLIII-2 415-3867 | |
| References | |
| TAC ME7581 | |
| Download: ML121070686 (9) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 11, 2012 Mr. Barry S. Allen Site Vice President FirstEnergy Nuclear Operating Company Davis-Besse Nuclear Power Station Mail Stop A-DB-3080 5501 North State Route 2 Oak Harbor, OH 43449-9760
SUBJECT:
DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO.1 - SAFETY EVALUATION REGARDING THE REACTOR COOLANT SYSTEM PRESSURE AND TEMPERATURE LIMITS REPORT, REVISION 1 (TAC NO. ME7581)
Dear Mr. Allen:
By letter to the U.S. Nuclear Regulatory Commission (NRC) dated October 27,2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML11304A188) as supplemented by letter dated February 21, 2012 (ADAMS Accession No. ML12048044), First Energy Nuclear Operating Company, the licensee for Davis-Besse Nuclear Power Station, Unit No.1 (DBNPS), submitted a revised pressure and temperature limits report in accordance with DBNPS Technical Specification (TS) 5.6.4, "Reactor Coolant System Pressure and Temperature Limits Report [PTLR]." Revision 1 of the PTLR takes into consideration the new reactor pressure vessel head.
Based on the NRC staffs review of the information provided in the licensee's submittal dated October 27,2011, as supplemented by letter dated February 21, 2012, the NRC staff concludes the licensee has properly incorporated the methodologies approved in license amendment number 282 dated January 28,2011 (ADAMS Accession No. ML103610148), into the PTLR, the content of the PTLR is consistent with the recommendations of NRC Generic Letter 96-03, and the P-T limits are at least as conservative as would be calculated using the methods of the America Society of Mechanical Engineers Code,Section XI, Appendix G.
The NRC staff concludes that the P-T limits of the PTLR, Revision 1, are valid until DBNPS accumulates 32 Effective Full Power Years offast neutron fluence or April 22, 2017, whichever comes first.
The NRC staffs safety evaluation is enclosed.
B.Allen
- 2 Please contact me at (301) 415-3867 if you have any questions on this action.
Siru Michael Mahoney, Proje Manager Plant Licensing Branch 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-346
Enclosure:
Safety Evaluation cc w/encl: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PRESSURE AND TEMPERATURE LIMITS REPORT FIRSTENERGY NUCLEAR OPERATING COMPANY FIRST ENERGY GENERATION CORP.
DAVIS-BESSE NUCLEAR POWER STATION. UNIT NO.1 DOCKET NO. 50-346
1.0 INTRODUCTION
By letter to the U.S. Nuclear Regulatory Commission (NRC) dated October 27, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML11304A188), as supplemented by letter dated February 17, 2012 (ADAMS Accession No. ML120481044), FirstEnergy Nuclear Operating Company (FENOC), the licensee for the Davis-Besse Nuclear Power Station, Unit No.1 (DBNPS), submitted a revised pressure and temperature (P-T) limits report in accordance with DBNPS Technical Specification (TS) 5.6.4, "Reactor Coolant System (RCS) Pressure and Temperature Limits Report (PTLR)."
Therefore, this SE addresses only Revision 1 of the PTLR. The NRC staff notes that Revision 0 and Revision 1 to the PTLR use the same methodology. The only technical difference between the two revisions is a change in the Title 10 of the Code of Federal Regulations (CFR),
Section 50, Appendix G minimum temperature requirements reflecting the replacement of the DBNPS reactor vessel closure head (RVCH).
2.0 REGULATORY EVALUATION
The NRC has established requirements in 10 CFR 50 to protect the integrity of the reactor coolant pressure boundary in nuclear power plants. The NRC staff evaluates the acceptability of a facility's proposed PTLR based on the following NRC regulations and guidance:
- Appendix G, "Fracture Toughness Requirements" to 10 CFR Part 50;
- Appendix H, "Reactor Vessel Material Surveillance Program Requirements" to 10 CFR Part 50; Regulatory Guide (RG) 1.99, Revision 2, "Radiation Embrittlement of Reactor Vessel Materials;"
- Generic Letter (GL) 92-01, Revision 1, "Reactor Vessel Structural Integrity;"
GL 92-01, Revision 1, Supplement 1, "Reactor Vessel Structural Integrity;"
- Standard Review Plan (SRP) Section 5.3.2; and Enclosure
-2
- GL 96-03, "Relocation of the Pressure Temperature Limit Curves and Low Temperature Overpressure Protection System Limits."
Appendix G to 10 CFR SO requires that facility P-T limits for the reactor vessel (RV) be at least as conservative as those obtained by applying the linear elastic fracture mechanics methodology of Appendix G to Section XI of the ASME Code.
Appendix H to 10 CFR Part SO establishes requirements related to facility RV material surveillance programs.
RG 1.99, Revision 2 contains methodologies for determining the increase in transition temperature and the decrease in upper-shelf energy resulting from neutron irradiation.
GL 92-01, Revision 1 requested that licensees submit the RV data for their plants to the NRC staff for review, and GL 92-01, Revision 1, Supplement 1, requested that licensees provide and assess data from other licensees that could affect their RV integrity evaluations.
SRP, Section S.3.2 provides an acceptable method for determining the P-T limits for ferritic materials in the beltline of the RV based on the ASME Code,Section XI, Appendix G methodology.
The most recent version of Appendix G to Section XI of the ASME Code which has been endorsed in 10 CFR SO.SSa, and therefore by reference in 10 CFR SO, Appendix G, is the 2004 Edition of the ASME Code. This edition of Appendix G to Section XI of the ASME Code incorporates the provisions of ASME Code Case N-S88 and N-640. Additionally, Appendix G to 10 CFR SO imposes minimum RV closure flange temperatures when system pressure is at or above 20% of the preservice hydrostatic test (PSHT) pressure.
GL 96-03 establishes the information which must be included in an acceptable PTLR methodology and in an acceptable PTLR.
Technical Specification Task Force (TSTF) Standard Technical Specification Change Traveler TSTF-419, "Revise PTLR Definition and References in ISTS S.6.6, RCS PTLR," dated September 16,2001 (ADAMS Accession No. ML012690234) was approved by the NRC staff by letter dated March 21, 2002 (ADAMS Accession No. ML020800488). TSTF-419 made changes to the standard technical specifications contained in NUREG-1430, "Standard Technical Specifications -
Babcock and Wilcox Plants," NUREG-1431, "Standard Technical Specifications - Westinghouse Plants," and NUREG-1433, "Standard Technical Specifications General Electric Plants (BWRl4)." The first change was to revise the definition of PTLR to delete the reference to the TSs containing the limits specified in the PTLR. The second change was to revise the requirement in Improved Technical Specification (ITS) S.6.6, "Reactor Coolant System (RCS) PTLR," to identify the NRC staff approval document by date to allow the TRs to be identified by number and title, and to add a requirement to the reviewer's note to specify the complete citation in the PTLR for each TR including the report number, title, revision, date, and any supplements.
The justification for the first change is that references to the particular specifications that address RCS pressure and temperature limits are addressed in both the definition and
-3 ITS 5.6.6a, so the change eliminated duplication. The justification for the second change was that allowing TRs to be identified by number and title (without the revision number) allowed licensees to use current TRs to support limits in the PTLR without having to submit an amendment to the facility operating license every time a TR was revised.
The PTLR would provide specific information identifying the particular approved TRs used to determine the P-T limits or low temperature overpressure protection (L TOP) system limits. This still provided assurance that only the approved versions of the referenced TRs would be used for the determination of the P-T limits or L TOP system limits since the complete citation would be provided in the PTLR. However, by letter dated August 4,2011 (ADAMS Accession No. ML110660285), the NRC staff communicated a revised position on TSTF-419 to the industry. The revised position allows licensees to implement TSTF-419 with the modification that references to TRs in the TS must include the full TR citation including the date and revision number of the TR.
3.0 TECHNICAL EVALUATION
3.1 Licensee's Evaluation In its October 27, 2011 letter, the licensee provided a revised final PTLR incorporating the use of ASME Code Cases N-588 and N-640, and SAW-2308, Revisions 1-A and 2-A. The PTLR contains P-T limit curves for heatup and cooldown during normal operation for two different pressure measurement locations, and another P-T limit curve for hydrostatic and leak test. The introduction section of the PTLR indicates that the PTLR also includes the information recommended in Attachment 1 to GL 96-03 is included in the report. Section 3.1 of the PTLR indicates that the P-T limits are valid until the RV has accumulated 32 effective full power years (EFPY) offast neutron fluence or April 22, 2017, whichever comes first. However, the NRC staff notes that the neutron fluence values in Table 1 of the PTLR are for 52 EFPY.
3.2
NRC Staff Evaluation
FENOC had previously relocated the P-T limits from the TSs to a PTLR. The new PTLR includes a change in methodology to incorporate the use of American Society of Mechanical Engineers (ASME) Code Cases N-588, "Attenuation to Reference Flaw Orientation of Appendix G for Circumferential Welds in Reactor Vessels,Section XI, Division 1" and N-640, "Alternative Reference Fracture Toughness for Development of P-T Limit Curves,Section XI, Division 1," and Sabcock and Wilcox Topical Report (TR) SAW-2308, Revisions 1-A and 2-A, "Initial RT NDT of Linde 80 Weld Materials."
NRC staff approved the proposed new methodologies by license amendment number 282 dated January 28,2011 (ADAMS Accession No. ML103610148). Approval of the new methodologies also required the NRC staff to issue a plant-specific exemption to use SAW-2308, Revisions 1-A and 2-A, dated December 14,2010 (ADAMS Accession No. ML103060213). During the review of the new methodologies, the NRC staff reviewed an unapproved version of the revised PTLR (ADAMS Accession No. ML110100755).
The NRC staff previously reviewed a draft of the PTLR to ensure that the recommended information of GL 96-03 was included and that the P-T limits generated were reasonable. In the license amendment number 282, the NRC staff concluded that the licensee's proposed
-4 alternative methodology for generating the P-T curves was acceptable. The NRC staff also concluded in license amendment number 282 that the licensee had properly incorporated the proposed new methodologies into the unapproved revised PTLR, the content of the unapproved PTLR is consistent with the recommendations of GL 96-03, and the P-T limits are at least as conservative as would be calculated using the methods of the ASME Code,Section XI, Appendix G.
The NRC staff's review of the PTLR, Revision 1 determined that it uses the same methodology as the unapproved PTLR previously submitted, including the description of the methodology.
There are minor changes to the actual P-T limits. Other changes include the addition of a reference to the NRC staff's SE for license amendment number 282 approving the change in methodology, and a change in one pressurized thermal shock (PTS) reference temperature (RTPTS) value in Table 1, "Davis-Besse Nuclear Power Station Reactor Vessel Beltline Region Data."
Since the RT PTS and adjusted reference temperature (ART) values in Table 1 were generally not verified in license amendment number 2821, the NRC staff performed a confirmatory calculation of the ART and RT PTS values. The NRC staff's calculation was done in accordance with RG 1.99, Revision 2, for the ART values, and 10 CFR 50.61, "Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events," for the RT PTS values.
The table provides the wetted surface f1uence at 52 EFPY, the ART at the one-quarter thickness (1I4T) and three-quarter thickness (3/4T) locations at 52 EFPY, and the RT PTS, for all the DBNPS RV beltline materials. Since Table 1 did not provide the copper or nickel values, the chemistry factors, or the initial RT NOT values, the NRC staff obtained these values from the DBNPS License Renewal Application (ADAMS Accession No. ML102450563). The NRC staff also verified that the initial RT NOT values that the licensee indicated were determined using the method of BAW-2308, Revision 1-A and 2-A, were consistent with those approved in December 14, 2010 exemption. The NRC staff's calculation confirmed the ART and RTpTs values in Table 1 of the final SE, including the RT PTS value that changed from the draft to the final PTLR, for "Nozzle Belt to Upper Shell Weld (inner diameter (ID) 9%)," material identification WF-232. The ART values for those materials for which the initial RT NOT values were derived from BAW-2308, Revision 1-A and 2-A, were also confirmed to be consistent with those reported in license amendment number 282.
The NRC staff performed a comparative calculation to determine if the P-T limits were equally or more conservative to those required by 10 CFR 50, Appendix G. The NRC staff's calculation accounted for the pressure differential between the RV and the two measurement locations, of 60 pounds-per-square inch (psi) for Hot Leg "1 (B)" and 85 psi for Hot Leg "2(A)", which were provided by the licensee's February 17, 2012 letter. For the inservice leak and hydrostatic test, the NRC staff used the larger of the pressure differentials of 85 psi.
The NRC staff's calculation showed that DBNPS' proposed P-T limits for the heatup and cooldown curves and the inservice leak and hydrostatic tests are more conservative than the I The NRC staff performed a confirmatory calculation, documented in license amendment number 282, of the ART values for the Nozzle Belt-to-Upper Shell weld (outer diameter (OD) 91%), materials identification WF-233, and the Upper Shell-to-Lower Shell Weld, material identification WF-182-1, since these were the materials that the licensee requested an exemption to use the BAW-2308.
-5 corresponding limits determined using the methods of the ASME Code,Section XI, Appendix G, and are therefore acceptable. In addition, since Revision 1 of the PTLR reflects changes to the maximum RT NOT of the RV closure flange region, the NRC staff verified that the P-T limits are in compliance with the minimum temperature requirements of 10 CFR 50, Appendix G, which are based on the maximum RTNOT of the closure flange region. For example, for normal operation, with the core not critical, the pressure may exceed 20% of the PSHT pressure only when the temperature exceeds the maximum RT NOT of the "material in the closure flange region that is highly stressed by the bolt preload", by 120°F or greater. However, since the licensee did not provide the highest RT NOT of the RV closure flange region accounting for the replacement of the RVCH, in request for additional information (RAI) number 1, the NRC staff requested this information. In response to RAI 1, the licensee's February 17, 2012 letter stated the RT NOT of the material in the reactor vessel closure flange region, taking into account the replacement of the reactor vessel head, is (-)50 degrees Fahrenheit CF). Based on a maximum closure flange area RT NOT of (-)50 of, for normal operation with the core not critical, the pressure could exceed 20% of the PSHT pressure at ((-)50 of + 120 of = 70 OF). Based on Figures 1 and 2 of the PTLR, 20% of the PSHT pressure (when the correction term for the pressure differential between the RV and the measurement location is applied) is exceeded above 80 of, which is acceptable since it exceeds the maximum RT NOT of the closure flange region by more than 120 of. The NRC staff also verified that the DBNPS P-T limits meet all the other minimum temperature requirements of 10 CFR 50, Appendix G. Finally, since the licensee provided the information requested in RAls 1 and 2, the NRC staff finds the RAls are resolved.
The NRC staff also checked the changes to the DBNPS TS against the recommendations of TSTF-419, as modified by the NRC staff's August 4, 2011 letter. In the revised DBPNS TS 5.6.4, included in the attachment to license amendment number 282, (the equivalent of Standard TS 5.6.6), the licensee referenced two TRs, BAW-10046A, Revision 2, "Methods of Compliance with Fracture Toughness and Operational Requirements of 10 CFR 50 Appendix G," and BAW-2308, Revisions 1-A and 2-A. The ASME Code Section XI, Appendix G, 1995 Edition with Addenda*through 1996, as modified by the alternative procedures provided in ASME Code Case N-640 and ASME Code Case N-588, is also referenced in TS 5.6.4. The TR references include the date and revision number; therefore meeting recommendations of TSTF-419 as modified by the March 7, 2011 letter. The dates and revisions of the TRs are provided in the PTLR, which also meets the recommendation of TSTF-419. In accordance with the modified version of TSTF-419, the licensee will have to submit a license amendment request if it wishes to revise the TS to reference a different revision of any of the TRs that describe the methodology used to generate the DBNPS P-T curves.
The NRC staff finds that Revision 1 of the DBNPS PTLR properly incorporates the new methodologies approved in license amendment number 282, the content of the PTLR is consistent with the recommendations of GL 96-03, and the P-T limits are at least as conservative as would be calculated using the methods of the ASME Code,Section XI, Appendix G. In addition, the NRC staff found the PTLR meets the recommendations of TSTF-419 as modified by the August 4, 2011 letter. Therefore, the NRC staff finds Revision 1 of the PTLR as acceptable.
-6 the licensee has properly incorporated the methodologies approved in license amendment number 282 into the PTLR, the content of the PTLR is consistent with the recommendations of GL 96-03, and the P-T limits are at least as conservative as would be calculated using the methods of the ASME Code,Section XI, Appendix G.
The NRC staff concludes that the P-T limits of Revision 1 of the PTLR are acceptable and valid until the DBNPS RV accumulates 32 EFPY of fast neutron fluence or April 22, 2017, whichever comes first.
Principle Contributor: JPoehler, NRR Date: May 11, 2012
ML121070686 OFFICE NAME
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