ML090790588
| ML090790588 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 04/08/2009 |
| From: | Markley M Plant Licensing Branch IV |
| To: | Parrish J Energy Northwest |
| Lyon C Fred, NRR/DORL/LPL4, 301-415-2296 | |
| References | |
| 3ISI-09, TAC MD9850 | |
| Download: ML090790588 (10) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 8, 2009 Mr. J. V. Parrish Chief Executive Officer Energy Northwest P.O. Box 968 (Mail Drop 1023)
Richland, WA 99352-0968 SUB~IECT:
COLUMBIA GENERATING STATION - REQUEST FOR RELIEF NO. 31SI-09 FOR THE THIRD 10-YEAR INSERVICE INSPECTION PROGRAM INTERVAL (TAC NO. MD9850)
Dear Mr. Parrish:
By letter dated October 9, 2008, as supplemented by letter dated December 17, 2008, Energy Northwest (the licensee) submitted request for relief No. 31SI-09 to the U.S. Nuclear Regulatory Commission (NRC). The licensee requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASIVIE Code), for the third 1O-year inservice inspection (lSI) program interval at Columbia Generating Station (CGS).
Specifically, the licensee requested approval to use an alternative to certain ASME Code Section XI inspection requirements regarding examination of reactor pressure vessel nozzle-to vessel welds and nozzle inner radii. The licensee proposed to use an alternative in accordance with ASME Code Case N-702, "Alternative Requirements for Boiling Water Reactor (BWR)
Nozzle Inner Radius and Nozzle-to-Shell Welds." The ASME Code for the third 1O-year lSI program interval at CGS is the 2001 Edition with 2003 Addenda. The third 10-year lSI program interval at CGS began on December 13,2005, and ends on December 12, 2015.
Based on the information provided by the licensee in request for relief No. 3ISI-09, the NRC staff has determined that the proposed alternative provides an acceptable level of quality and safety; therefore, the proposed alternative is authorized pursuant to Title 10 of the Code of Federal Regulations Section 50.55a(a)(3)(i) for the third 1O-year lSI inspection interval at CGS.
All other ASME Code,Section XI, requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
J. V. Parrish
- 2 The detailed results of the NRC staff review are provided in the enclosed safety evaluation. If you have any questions concerning this matter, please call Mr. F. Lyon of my staff at (301) 415-2296 or by electronic mail at fred./yon@nrc.gov.
Sincerely, b <" \\w c,,,J t s ¥
~\\ "v' Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket 1\\10. 50-397
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y.0 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION THIRD 10-YEAR INSERVICE INSPECTION PROGRAM INTERVAL REQUEST FOR RELIEF NO. 31SI-09 ENERGY NORTHWEST COLUMBIA GENERATING STATION DOCKET NO. 50-397
1.0 INTRODUCTION
Bya letter dated October 9,2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082950482), supplemented by letter dated December 17,2008 (ADAMS Accession No. ML090070034), Energy Northwest (the licensee) submitted request for relief (RR) No. 3ISI-09. The licensee requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," regarding examination of reactor pressure vessel (RPV) nozzle-to-vessel welds and nozzle inner radii at Columbia Generating Station (CGS). Instead, the licensee proposed to use an alternative in accordance with ASME Code Case N-702, "Alternative Requirements for Boiling Water Reactor (BWR)
Nozzle Inner Radius and Nozzle-to-Shell Welds." The technical basis for ASME Code Case N-702 was documented in an Electric Power Research Institute (EPRI) report by the Boiling Water Reactor Vessel and Internals Project (BWRVIP), "BWRVIP-108: BWR Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radii," which was approved by the U.S. Nuclear Regulatory Commission (NRC) staff in a safety evaluation (SE) dated December 19, 2007 (ADAMS Accession No. ML073600374).
In its December 19, 2007, SE for the BWRVIP-1 08 report, the NRC staff stated that Licensees who plan to request relief from the ASME Code,Section XI requirements for RPV nozzle-to-vessel shell welds and nozzle inner radius sections may reference the BWRVIP-1 08 report as the technical basis for the use of ASME Code Case N-702 as an alternative. However, each licensee should demonstrate the plant-specific applicability of the BWRVIP-108 report to their units in the relief request by showing that...general and nozzle-specific criteria are satisfied.
The licensee's submittal addressed the plant-specific requirements for the relevant CGS RPV nozzle-to-vessel welds and nozzle inner radii, as evaluated below.
Enclosure
- 2
2.0 REGULATORY EVALUATION
Inservice inspection (lSI) of the ASME Code Class 1, 2, and 3 components is performed in accordance with Section XI of the ASME Code and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Parqgraph 50.55a(g), except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Section 50.55a(a)(3) of the 10 CFR states that alternatives to the requirements of paragraph (g) may be used, when authorized by the staff, if: (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Section 50.55a(g)(4) of 10 CFR states further that ASME Code Class 1,2, and 3 components (including supports) must meet the requirements, except for design and access provisions and preservice examination requirements, set forth in the ASME Code,Section XI, to the extent practical within the limitations of the design, geometry, and materials of construction of the components. The regulations require that lSI examination of components and system pressure tests conducted during the first 1O-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable lSI Code of record for the third 10-year lSI interval of the CGS plant is the 2001 Edition of ASME Code,Section XI, 2003 Addenda. The third 1O-year lSI program interval at CGS began on December 13, 2005, and ends on December 12, 2015.
For RPV nozzle-to-vessel shell welds and nozzle inner radii, ASME Code,Section XI requires 100 percent inspection during each 10-year lSI interval. However, ASME Code Case N-702 proposes an alternative which reduces the inspection of RPV nozzle-to-vessel shell welds and nozzle inner radius areas from 100 percent to 25 percent of the nozzles for each nozzle type during each 1O-year interval. The NRC staff has approved BWRVIP-108, the underlying technical basis document for ASME Code Case N-702. The December 19, 2007, SE regarding BWRVIP-108 specified the following plant-specific requirements to be satisfied by the licensees using ASME Code Case N-702:
Each licensee should demonstrate the plant-specific applicability of the BWRVIP-108 report to its plant in a relief request by showing that all the following criteria are met:
(1) maximum RPV heatup/cooldown rate is limited to less than 115 of/hour -- criterion 1 (2) recirculation inlet and outlet nozzles (a) recirculation inlet nozzles (N2):
RPV pressure stress factor -- criterion 2 (pr/t)/CRPV < 1.15 p = RPV normal operating pressure, r = RPV inner radius, t = RPV wall thickness, and
- 3 CRPV =19332 [Le., 1000 psi x 110 inch/5.69 inch. based on the BWRVIP-108 recirculation inlet nozzle/RPV finite element model (FEM)];
recirculation inlet nozzle stress factor -- criterion 3 p = RPV normal operating pressure, ro = nozzle outer radius, rj = nozzle inner radius, and CNOZZLE =1637 [Le., 1000 psi x (13.9882 + 6.8752) / (13.9882 - 6.8752)], based on the BWRVIP-1 08 recirculation inlet nozzle/RPV FEM model];
(b) recirculation outlet nozzles (N1):
RPV pressure stress factor -- criterion 4 (pr/t)/CRPV < 1.15 P = RPV normal operating pressure, r = RPV inner radius, t = RPV wall thickness, and CRPV =16171 (Le., 1000 psi x 113.2 inch/7.0 inch, based on the BWRVIP-108 recirculation outlet nozzle/RPV FEM model); and recirculation outer nozzle stress factor -- criterion 5 p = RPV normal operating pressure, ro = nozzle outer radius, rj =nozzle inner radius, and CNOZZLE =1977 [Le., '1000 psi x (22.31 2 + 12.782) / (22.31 2 -12.782)], based on the BWRVIP-108 recirculation outlet nozzle/RPV FEM model].
This plant-specific information was required by the NRC staff to ensure that the probabilistic fracture mechanics (PFM) analysis documented in BWRVIP-108 applied to the RPV of the licensee's plant.
3.0 TECHNICAL EVALUATION
- 3. '1 Licensee Evaluation ASME Code Requirement for which Relief is Requested The licensee requested relief from the following requirements of ASME Code,Section XI, 2001 Edition, 2003 Addenda:
Table IWB-2500-1 "Examination Category B-O, Full Penetration Welded Nozzle in Vessels - Inspection Program B"
-4 Class 1 nozzle-to-vessel weld and nozzle inner radii examination requirements are given in Item Numbers B3.90 "Nozzle-to-Vessel Welds" and B3.1 00 "Nozzle Inside Radius Section." The method of examination is volumetric. All nozzles with full penetration welds to the vessel shell (or head) and integrally cast nozzles are examined each interval. All of the nozzle assemblies identified in Attachment 1 of the October 9,2008, submittal are full penetration welds.
Component(s) for which Relief is Requested Code Class:
1 Component Numbers:
N3, N5, N6, N7, N8, N9, N16 and N18 Nozzles (see Attachment 1 of the October 9,2008, submittal for specific nozzle identifications)
Examination Category:
B-D Item Number:
B3.90 and B3.1 00 Licensee's Proposed Alternative to the ASME Code Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee requested relief from performing the required examinations on 100 percent of the identified nozzle assemblies (see Attachment 1 of the October 9, 2008, submittal). As an alternative for all welds and nozzle inner radii, except for the recirculation inlet and outlet nozzle welds, CGS proposes to volumetrically examine a minimum of 25 percent of the nozzle-to-vessel welds and inner radius sections, including at least one nozzle from each system with the exception of recirculation system in accordance with ASME Code Case N-702. The licensee proposes to inspect at least one nozzle/inner radius section from each of the groups identified in Table 2 of Attachment 1 of the October 9,2008, submittal.
Licensee's Bases for Alternative The licensee stated that the BWRVIP-1 08 report is used as the basis for ASME Code Case 1'J-702. The evaluation found that failure probabilities at the nozzle blend radius region and nozzle-to-vessel shell weld due to a Low Temperature Overpressure event are very low (Le.,
<1 x 10-6 for 40 years) with or without lSI. The report concludes that inspection of 25 percent of each nozzle type is technically justified. Section 5.0, "Plant-Specific Applicability," of the NRC staff's SE for the BWRVIP-108 report indicates that each licensee who plans to request relief from the ASME Code,Section XI requirements for RPV nozzle-to-vessel shell welds and nozzle inner radius sections may reference the BWRVIP-108 report as the technical basis for the use of ASME Code Case N-702 as an alternative. However, the staffs SE states that each licensee should demonstrate the plant-specific applicability for the BWRVIP-108 report to its plant in a relief request by showing that all the general and nozzle-specific criteria addressed below are satisfied:
(1)
The maximum RPV heatup/cooldown rate is limited to less than 115 of per hour.
The CGS Technical Specification Surveillance Requirement (SR) for monitoring reactor vessel heatup/cooldown (SR 3.4.11.1) limits the rate to less than or equal to 100 of in any 1-hour period.
- 5 (2)
For the recirculation inlet nozzles, the following criteria must be met:
(a)
(pr/t)/CRPV <1.15.
The calculation for the CGS N2 Nozzles results in 0.70, which is less than 1.15 and meets criterion 2 in Section 5.0 of the staff's SE for the BWRVIP-1 08 report dated December 19,2007.
(b)
[p(ro2+ri2)/(ro2-ri2)]/C NOZZLE <1.15.
The calculation for the CGS N2 Nozzles results in 1.32, which is greater than 1.15 and hence does not meet criterion 3 in Section 5.0 of the staff's SE for the BWRVIP-108 report dated December 19, 2007.
(3)
For the recirculation outlet nozzles, the following criterion must be met:
(a)
(pr/t)/CRPV <1.15.
The calculation for the CGS N1 Nozzles results in 0.84, which is less than 1.15, and meets criterion 4 in Section 5.0 of the staff's SE for the BWRVIP-1 08 report dated December 19, 2007.
(b)
[p(ro2+ri2)/(ro2-ri2)]/CN_1NOZZLE <1.15.
The calculation for the CGS N1 Nozzles results in 1.61, which is greater than 1.15 and hence does not meet criterion 5 in Section 5.0 of the staff's SE for the BWRVIP-108 report dated December 19,2007.
Based upon the above information, the licensee concluded that all RPV nozzle-to-vessel shell welds and nozzle inner radii sections identified in Table 1 of Attachment 1 of the October 9, 2008, submittal meet the criteria specified in Section 5.0 of the staff's SE for the BWRVIP-108 report dated December 19, 2007. Therefore, ASME Code Case N-702 is applicable to these items. ASME Code Case N-702 would not be applied to the recirculation inlet and outlet nozzles, since they do not comply with the criteria specified in Section 5.0 of the staff's SE for the BWRVIP-108 report dated December 19,2007.
In conclusion, the licensee stated that use of ASME Code Case N-702 provides an acceptable level of quality and safety pursuant to 10 CFR 50.55a(a)(3)(i) for all RPV nozzle-to-vessel shell welds and nozzle inner radii sections identified in Table 1 of Attachment 1 of the October 9, 2008, submittal. Code Case N-702 would not be applied to Recirculation Inlet (N2) and Outlet (N1) nozzles.
3.2 Staff Evaluation The NRC staff's SE dated December 19, 2007, for the BWRVIP-108 report specified five plant specific criteria that licensees shall comply with to demonstrate that the BWRVIP-1 08 report results apply to their plants. The five criteria are related to the driving force of the PFM analyses for the recirculation inlet and outlet nozzles. The staff stated in the December 19, 2007, SE that the nozzle material fracture toughness related RTNDT values used in the PFM analyses were
- 6 based on data from the entire fleet of BWR RPVs. Therefore, the BWRVIP-108 PFM analyses are bounding with respect to fracture resistance. It was also stated in the December 19, 2007, SE that, except for the RPV heatup/cooldown rate, the plant-specific criteria are applicable to the recirculation inlet and outlet nozzles only because the probabilities of failure, P(FIE)s, for other nozzles are an order of magnitude lower.
The licensee provided in the October 9,2008, submittal, its evaluation of the criteria established in the NRC staff's SE dated December 19, 2007. The licensee's evaluation indicated that the third criterion related to recirculation inlet nozzle was not satisfied. Regarding the recirculation outlet nozzles, the fifth criterion specified in the staff's December 19, 2007, SE was not satisfied.
The staff verified the licensee's evaluation by using the guidelines of the BWRVIP-108 report, and finds the licensee's evaluation acceptable. As a result, the reduced inspection requirements in accordance with ASME Code Case N-702 do not apply to CGS RPV recirculation inlet and outlet nozzles. The staff agrees with the licensee's decision to exclude the CGS RPV recirculation inlet and outlet nozzles from the scope of this request based upon its evaluation.
The staff notes that RPV feedwater nozzles and control rod drive return line nozzles are outside the scope of ASME Code Case N-702 and are, accordingly, outside the scope of this application.
To ensure that there is no active aging degradation in the nozzle welds that are listed in the licensee's October 9, 2008, submittal, the staff requested by letter dated November 14, 2008, that the licensee confirm that the previous ultrasonic test results of the aforementioned nozzle welds did not show any service-induced defects. By letter 9ated December 17, 2008, the licensee stated that the previous ultrasonic results indicated no defects in these welds. Absence of any defects in the subject welds indicates that there is no active aging degradation in these welds, and is, therefore, acceptable.
Carbon/low alloy steel welds are not subject to stress-corrosion cracking (SCC), whereas nickel base alloy welds (specifically welds fabricated with shielded metal arc welding process using 182 weld material, designated as UNS W86182, F-No. 43) are subject to SCC in a BWR environment.
Some BWR plants have nozzles welded with 182 weld metals; hence the staff determined that it should not grant relief from the inspection criteria specified in Table IWB-2500-1 of the ASME Code,Section XI for 182 welds. For 182 welds, the reduction in inspection requirements as permitted per ASME Code Case N-702 is disallowed. The staff requires that 182 welds be examined per Table IWB-2500-1 of the ASME Code,Section XI criteria. By letter dated November 14, 2008, the staff requested that the licensee confirm that the subject nozzle welds described in this relief request were fabricated with carbon/low alloy steel weld metal. By a letter dated December 17, 2008, the licensee stated that the subject nozzle welds were fabricated with carbon/low alloy steel weld metal. Since there is no active aging degradation in carbon/low alloy steel welds, the welds are acceptable.
The staff reviewed the licensee's justification for using the guidelines addressed in the BWRVIP-108 report as technical bases for adopting ASME Code Case N-702 for the RPV nozzle-to-vessel shell welds and nozzle inner radii sections described in Attachment 1 of the October 9, 2008, submittal, and finds it acceptable based on the following:
(1) the licensee successfully demonstrated that the RPV nozzle-to-vessel shell welds and nozzle inner radii sections of the subject nozzles described in Attachment 1 of the October 9, 2008, submittal meet the requirements of the BWRVIP-1 08
- 7 report and the plant-specific criteria specified in the staff's December 19, 2007, SE for the BWRVIP-108 report, (2) previous ultrasonic results of the subject welds indicated no defects, hence it can be concluded that there is no active aging degradation in these welds, (3) the subject welds addressed in the Relief Request are fabricated with carbon/low alloy weld metals which are not subject to SCC. Therefore, reduction in inspection requirements per ASME Code Case N-702 for these welds is acceptable, (4) a similar request by the licensee for the Duane Arnold Energy Center was approved by the staff (ADAMS Accession No. ML082040046), and, (5)
BWRVIP-108 PFM analyses are bounding with respect to fracture resistance of nozzles described in Attachment 1 of the October 9, 2008, submittal.
Based on the above, the NRC staff determined that the licensee's proposed alternative for the RPV nozzle-to-vessel shell welds and nozzle inner radii sections of the nozzles described in request for relief No. 31SI-09 provides an acceptable level of quality and safety.
4.0 CONCLUSION
The NRC staff has reviewed the submittal and finds that the CGS RPV nozzle-to-vessel shell welds and nozzle inner radii sections meet the criteria specified in the staffs December 19, 2007, SE for the BWRVIP-108 report, which provides technical bases for use of ASME Code Case N-702. Since the plant-specific criteria applicable to recirculation inlet and outlet nozzles were not met, the licensee excluded them from the scope of this request. Consequently, pursuant to 10 CFR 50,55a(a)(3)(i), relief is authorized through the end of the third 1O-year lSI interval from the requirements of Table IWB-2500-1 (Inspection Program B) of ASME Code,Section XI, pertaining to inspection of the RPV nozzle-to-vessel shell welds and nozzle inner radii described in Attachment 1 of the licensee's submittal dated October 9, 2008. The licensee's proposed alternative of using ASME Code Case N-702 is authorized because an acceptable level of quality and safety can be maintained. This determination has considered the licensee's intention to perform volumetric examinations for all the affected nozzle inner radii.
All other requirements of the ASIVIE Code,Section XI, for which relief has not been specifically requested and approved, remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor:
G. Cheruvenki Date:
Apr; 1 8, 2009
ML.D90790588
- memo dated OFFICE LPL4/PM LPL4/LA DCI/CVIB/BC OGC LPL4/BC NAME FLyon JBurkhardt MMitchell*
MMaxin MMarkley BSingal for DATE 3/24/09 3/24/09 3/18/09 3/27/09 4/8/09