L-MT-08-017, Response to Request for Additional Information Regarding 10 CFR 50.55a Request No. 15 (RR-15): Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year Inservice Inspection In
| ML080810233 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 03/21/2008 |
| From: | O'Connor T Nuclear Management Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-MT-08-017, TAC MD6854 | |
| Download: ML080810233 (9) | |
Text
Monticello Nuclear Generatina Plant Operated by Nuclear Management Company, LLG March 21,2008 L-MT-08-017 10 CFR 50.55a U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License License No. DPR-22 Response to Request for Additional Information Regarding 10 CFR 50.55a Request No. 15 (RR-15): Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(n)(5)(iii) for the Fourth Ten-Year lnservice lnspection Interval ITAC MD6854)
References:
- 1) Letter from TJ O'Connor (NMC) to Document Control Desk (NRC),
"10 CFR 50.55a Request No. 15: Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year lnservice lnspection Interval," dated September 26, 2007 (ML072710119)
- 2) Electronic mail from Peter Tam (NRC) to NMC, "Monticello - Draft RAI for Relief Request No. 15 (TAC MD6854)," dated December 3, 2007 (ML073381315)
- 3) Electronic mail from Peter Tam (NRC) to NMC, "Monticello - Revised Questions for Relief Request No. 15 (TAC MD6854)," dated December 13, 2007 (ML073480419)
By letter dated September 26, 2007 (Reference I ) , and pursuant to 10 CFR 50.55a(g)(5)(iii), Nuclear Management Company, LLC, (NMC) requested Nuclear Regulatory Commission (NRC) review and approval of 10 CFR 50.55a Request No. 15 (RR-15). Request RR-15 requests relief for the Monticello Nuclear Generating Plant (MNGP) from certain examination coverage requirements imposed by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, "Rules for lnservice lnspection of Nuclear Power Plant Components."
Request RR-15 is for weld examinations performed during the 2007 refueling outage where the required coverage of "essentially 100 percent" could not be obtained when examined to the extent practical. The basis for the 10 CFR 50.55a request is that compliance with the specified requirements is impractical due to plant design.
Document Control Desk Page 2 On December 3, 2007, the NRC staff notified NMC by electronic mail (Reference 2) that additional information was necessary for the staff to complete the review. A conference call between NMC and NRC staff was held on December 13, 2007, to clarify the requests for additional information (RAI). Following the conference call, the NRC staff sent revised RAls to NMC by electronic mail on December 13, 2007 (Reference 3). The NMC responses to the NRC RAls are included in Enclosure 1. As requested in NRC RAI 6.0, NMC is including a worksheet used to determine code coverage for one of the subject welds. The worksheet is included in Enclosure 2.
NMC submitted 10 CFR 50.55a Request RR-15 for the Fourth Ten-Year Inservice Inspection Interval scheduled to end on May 31, 2012. If you have questions regarding this request, please contact Lynne Gunderson at 715-377-3430.
ew commitments and does not revise any existing ticello Nuclear Generating Plant Enclosures (2) cc: Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC Minnesota Department of Commerce
ENCLOSURE I Responses to Requests for Additional Information Regarding 10 CFR 50.55a Request No. 15 (RR-15)
By letter dated September 26, 2007, and pursuant to 10 CFR 50.55a(g)(5)(iii), Nuclear Management Company, LLC, (NMC) requested Nuclear Regulatory Commission (NRC) review and approval of 10 CFR 50.55a Request RR-15 (Reference 1). Request RR-15 requests relief for the Monticello Nuclear Generating Plant (MNGP) from certain examination coverage requirements imposed by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components." On December 3, 2007, the NRC staff notified NMC by electronic mail (Reference 2) that additional information was necessary for the staff to complete the review. A conference call between NMC and NRC staff was held on December 13, 2007, to clarify the requests for additional information (RAI). Following the conference call, the NRC staff sent revised RAls to NMC by electronic mail on December 13, 2007 (Reference 3). NRC RAls are repeated below with the NMC response following each RAI:
I.O Discuss the applicable edition or addenda of the ASME Code,Section XI, Appendix VIII, for the ultrasonic examination of the subject welds during the 2007 refueling outage and for the remaining fourth 10-year inservice inspection (ISI) interval.
NMC Response:
As stated in Section 2 of RR-15 (Reference I ) , Attachment I , the applicable Code Edition and Addenda for the Fourth Ten-Year lnservice lnspection (ISI)
Interval is the 1995 Edition with the 1996 Addenda. ASME BPV Code,Section XI, Appendix Vlll requirements are implemented as required by, and as modified by, 10CFR50.55a. Procedures and personnel are qualified to the Performance Demonstration Initiative (PDI). The PDI Program document meets the requirements of 10CFR50.55a up through the 2001 Edition of Section XI.
2.0 [Deleted following a conference call with licensee, which clarified information submitted.]
3.0 On page 4 of Request No. 15, the licensee discussed the UT inspection of the subject welds during the 2007 outage without providing the previous history of the ultrasonic examinations. Discuss the history of volumetric examinations of the subject welds, including specific year and during which IS1 interval, inspection results, and examination coverage. Discuss whether relief was requested for the examination coverage of the subject welds in the previous 10-year IS1 intervals.
NMC Response:
Per 10 CFR 50.55a(g)(l) and (4), each of the subject welds were examined to the extent practical during the First, Second and Third Ten-Year IS1 Intervals.
Prior to 1997, the MNGP did not perform examination coverage determinations Page 1 of 5
ENCLOSURE I Responses to Requests for Additional Information Regarding 10 CFR 50.55a Request No. 15 (RR-15) or submit relief requests pursuant to 10 CFR 50.55a(g)(5) for limited examinations. This was due to MNGP's misinterpretation of 10 CFR 50.55a(g)(4):
10 CFR 50.55a(g)(4) Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, components (including supporfs) which are classified as ASME Code Class I, Class 2 and Class 3 must meet the requirements, except design and access provisions and preservice examination requirements, set forth in Section XI.. .to the extent practical within the limitations of design, geometry and materials of construction of the components."
The MNGP interpreted this section to mean that interferences inherent in the design constituted impracticality, and were therefore exempted. When the misinterpretation was identified (during the Third-Ten Year IS1 Interval), the MNGP reported the lack of limited examination relief requests to the NRC in Licensee Event Report (LER)97-004, "Failure to Submit Relief Requests for Limited lnservice Inspection Examinations." This was reported pursuant to 10 CFR Part 50, Section 50.73(a)(2)(i)(B) since, at that time, MNGP Technical Specification 3.15.A.1 contained the IS1 program. In 1997, the failure to submit relief requests for examinations with inspection limitations constituted a non-compliance with Technical Specification 3.15.A. 1.
Corrective actions from the LER included a review of all Third Ten-Year IS1 lnterval examinations to determine limitations. Corrective actions indicate that limited examinations discovered during this review would be submitted to the NRC in a subsequent relief request. Although a review was completed, only the limited examinations going forward from 1998 were submitted in a relief request to the NRC. The Third Ten-Year IS1 lnterval ended May 31, 2003. Pursuant to 10 CFR 50.55a(g)(5)(iv), relief requests for limited examinations from the third ten-year interval should have been submitted and approved by May 31, 2004.
Therefore, there is no means of regaining compliance with the Third Ten-Year IS1 lnterval and retroactive 10 CFR 50.55a requests for the Third Ten-Year IS1 lnterval examination will no longer be submitted to the NRC. This issue has been entered into the NMC corrective action program.
The MNGP has taken corrective action to prevent recurrence of the issues described in LER 97-004. Actions taken include creation of procedures to determine code coverage for limited exams and to submit relief requests for impractical Code requirements pursuant to 10 CFR 50.55a(g)(5)(iv) when examination coverage is limited and Code examination requirements cannot be met.
Based on the above discussion, MNGP provides Table 1 on the following page for history of the subject welds.
Page 2 of 5
ENCLOSURE I Responses to Requests for Additional lnformation Regarding 10 CFR 50.55a Request No. 15 (RR-15)
Table I Historical Examination lnformation interval I Exam Relief Weld Results for Limited Exam NRC Approval Year Request N-2B lst 1 1978 * , no flaw indications **
2"' I 1993 * , no flaw indications **
3rd 1 2001 62% coverage, no flaw 3", IS1 RR-16 TAC No. MB5487, indications May 19,2003 N-2G lst I 1975 * , no flaw indications **
2"' I 1989 * , no flaw indications **
3" I 1998 51% coverage, no flaw 3", IS1 RR-10 TAC No. MA3397, indications August 4, 1999 N-4A / 1' 1 1974 * , no flaw indications II **
1 2nd 1 1986 1 * , no flaw indications **
3" I 1996 *, no flaw indications **
1 I 1973 * , no flaw indications **
N-6A 1 2"'11987 1 * , no flaw indications I **
3" 1 1996 * , no flaw indications lst1 1974 * , no flaw indications **
N-9 1 2"' 1 1984 I * , no flaw indications I **
3rd I 1996 *, no flaw indications **
- Code Coverage was not determined for limited exams prior to 1997
- Relief was not requested for limited exams prior to 1997 4.0 On page 5 of Request No.15, the licensee stated that the materials for subject components are A508 Class II nozzle forgings welded to A533, Class Ivessel shell plate. However, the material specifications of the welds and associated piping were not provided. Discuss material specifications for the following components: welds, pipes, safe ends, and butter (if applicable).
NMC Response:
The weld filler material for the subject joint was E8018NM. Inner diameter cladding materials are E309-15 for the base layer, and ER308L or E308L-15 for Page 3 of 5
ENCLOSURE I Responses to Requests for Additional Information Regarding 10 CFR 50.55a Request No. 15 (RR-15) subsequent layers. There are no pipe, safe end, or butter materials applicable to the nozzle-to-vessel shell welds.
5.0 [Deleted following a conference call with licensee, which clarified information submitted.]
6.0 In Enclosure 2, Table A, of the September 26, 2007, submittal, the licensee calculated various percentages of examination coverage obtained for each of the five welds. The staff calculated the percentages of examination coverage of the subject welds using the diagrams in Enclosure 3 of the submittal. However, the staff was not able to verify the percentages of coverage as shown in Table A.
(a) Provide the worksheet for one of the subject welds showing how the percentage of coverage is determined.
(b) It is not clear from the diagrams in Enclosure 3 of the September 26,2007, submittal whether the unexamined volume is in the reactor vessel nozzles, the welds, butter, or safe ends. Please provide the axial dimensions for the weld, piping, and safe end. Also, identify the interface line among the weld, nozzle, safe end, and pipe.
NMC Response:
The method NMC used to determine coverage is based on field measurements applied to a two dimensional plot. This allows an informed approximation to be made of the coverage achieved. This is appropriate to the application in that the limitations are physical and the methods applied to the examination are established by the qualified techniques. Variations in the percent coverage obtained in previous examinations are the result of changes in examination technique and/or required coverage. The current coverage determinations are different from past examinations due to the use of PDI qualified techniques and a reduced volume obtained by use of Code Case N-613-1.
The coverage drawings included in Enclosure 3 of Reference 1 include a representation of the examination volume and the weld interface line in the same manner as the figure included in Code Case N-613-1. The area of coverage is identified by the shaded or cross-hatched areas on the drawings and the remaining areas with no shading or cross-hatching indicate no coverage. The coverage drawings indicate the nozzle side of the weld by the location of the blend radius. The area on the opposite side of the weld from the nozzle represents the reactor vessel shell. Though there is variation, most of the limited coverage is in the nozzle base material with a lesser amount in the weld and base material on the vessel shell side. A worksheet from weld N-2B NV is provided as Enclosure 2 of the letter.
Pipe, safe end, and butter material are not applicable to the subject welds included in this relief request.
Page 4 of 5
ENCLOSURE I Responses to Requests for Additional Information Regarding 10 CFR 50.55a Request No. 15 (RR-15)
References:
- 1. Letter from TJ O'Connor (NMC) to Document Control Desk (NRC),
"10 CFR 50.55a Request No. 15: Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year lnservice lnspection Interval," dated September 26, 2007 (ML072710119)
- 2. Electronic mail from Peter Tam (NRC) to NMC, "Monticello - Draft RAI for Relief Request No. 15 (TAC MD6854)," dated December 3,2007 (ML073381315)
- 3. Electronic mail from Peter Tam (NRC) to NMC, "Monticello - Revised Questions for Relief Request No. 15 (TAC MD6854),19dated December 13, 2007 (ML073480419)
- 4. LER 97-004, "Failure to Submit Relief Requests for Limited lnservice Inspection Examinations," dated March 24, 1997 Page 5 of 5
ENCLOSURE 2 Responses to Requests for Additional Information Regarding 10 CFR 50.55a Request No. 15 (RR-15)
Determination of Code Coverage Worksheet for Weld N-2B NV from Supplemental Examination Report Number 2007UT058 One (1) Page to Follow
Enclosure 2 to L-MT-08-017 Moarfe to RPV Coverane CalcuttBsnm Cov~ragemfcufat& fo reqdremenb af Code case N613 Note: caicufatlbns perfarmed using 2D piot oniy Area reqlifred fa be examined Axial scan dlwtlon: Ht*ighl x width
- 5.25 iinches x 3.057 Inches equais 18.0483 square inches Parallel scan direction: Height x wMth
- 825 inches x , 3,057 Inches equals i8.0493 square inches To&#a m required ta be examined -32,0985 sqwte Inches required fofcamptccta exam Aotual area examined 6O degree RL Axial scan diraflon: Hclfght x width 23 inches x 3.057 inches equafs 16.0493 square inches f &Ingulararea not examined {if applies) - base 123 lf2 x x h e f g h t equals -square inches Axial scan direction arm examined - la598 square inches
- 61) degree R t Pafalfel scan direction: Height x width
- 4.46 in~hes x r.82 Incks equals 8;_ltfr;squareinches AddlUonai inner 15% area acttietred using 60 & 4!i degree shear techniques: Height x width
- 0.7875 inches x - 3.057 inches equals 2.60739 square inches C~mblnlngaii scan directio~s: =square inches for total exam DEvide!area exami~ledby required area: &quaiscoverage acBfeved - 78.27 % coverage far tataf exam Calcufatlons perlorma by: J e r m m Level I31 MonNceflo revkw Level Enclosure 2 Page 1 of 1