2CAN110905, Request to Extend the Inservice Inspection Interval for the Visual Examination of Accessible Interior to Reactor Vessel Attachment Weld
| ML093090314 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 11/04/2009 |
| From: | David Bice Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2CAN110905 | |
| Download: ML093090314 (7) | |
Text
Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802 Tel 479-858-4710 David B. Bice Acting Manager, Licensing Arkansas Nuclear One 2CAN110905 November 4, 2009 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
Request to Extend the Inservice Inspection Interval for the Visual Examination of Accessible Interior to Reactor Vessel Attachment Weld Arkansas Nuclear One, Unit 2 Docket No. 50-368 License No. NPF-6
REFERENCES:
- 1. Entergy letter to the NRC, dated October 29, 2009, Request for Alternative ANO2-ISI-004 Proposed Alternative to Extend Third 10-year Inservice Inspection Interval for Reactor Vessel Weld Examinations (2CAN100902)
Dear Sir or Madam:
Pursuant to 10 CFR 50.55a(a)(3)(ii), Entergy Operations, Inc. (Entergy) requests permission to extend the Inservice Inspection (ISI) interval that is required by Examination Categories B-N-2 and B-N-3 of Table IWB-2500-1 of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code, 2001 Edition, 2003 Addenda for the fourth 10-year interval for Arkansas Nuclear One, Unit 2 (ANO-2). Table IWB-2500-1, examination categories B-N-2 and B-N-3 requires a visual examination of the accessible interior attachment welds within and beyond the beltline region and a visual examination of the accessible core support structure surfaces of the reactor pressure vessel once each ten-year interval.
Reference 1 is the Entergy request to extend the ANO-2 Inservice Inspection interval for the reactor vessel weld examination from once every 10 years to once every 20 years. This request is currently being reviewed by the NRC. In light of that request, this proposed relief is requested because compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The hardship or unusual difficulty that would result from compliance consists of significant personnel radiation exposure, increased outage duration, and an additional removal of the reactor vessel internals with the potential of damage to the vessel. The details of the request are attached.
This submittal contains no new commitments.
2CAN110905 Page 2 of 2 Entergy requests approval of the proposed request for alternative by January 15, 2011, in order to support the spring 2011 refueling outage for ANO-2. Although this request is neither exigent nor emergency, your prompt review is requested.
If you have any questions or require additional information, please contact me.
Sincerely, DBB/rwc
Attachment:
Request for Relief ANO2-ISI-005 cc: Mr. Elmo E. Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 NRC Senior Resident Inspector Arkansas Nuclear One P. O. Box 310 London, AR 72847 U. S. Nuclear Regulatory Commission Attn: Mr. Kaly Kalyanam MS O-8 B1 One White Flint North 11555 Rockville Pike Rockville, MD 20852
Attachment to 2CAN110905 Request for Relief ANO2-ISI-005
Attachment to 2CAN110905 Page 1 of 4 REQUEST FOR RELIEF ANO2-ISI-005 American Society of Mechanical Engineers (ASME) Code Components Affected The affected component is the Arkansas Nuclear One, Unit 2 (ANO-2) reactor pressure vessel (RPV), specifically the following ASME Boiler and Pressure Vessel (BPV) Code,Section XI (Reference 1), examination categories and item numbers covering examinations of the RPV.
These examination categories and item numbers are from IWB-2500 and Table IWB-2500-1 of the ASME BPV Code,Section XI.
Examination Category Item No. Description B-N-2 B13.50 Interior Attachments Within Beltline Region B-N-2 B13.60 Interior Attachments Beyond Beltline Region B-N-3 B13.70 Core Support Structure Throughout this request, the above examination categories are referred to as the subject examinations and the ASME BPV Code,Section XI, is referred to as the Code.
Applicable Code Edition and Addenda
ASME Code Section XI, Rules and Inservice Inspection of Nuclear Power Plant Components, 2001 Edition through 2003 Addenda.
Applicable Code Requirement
Table IWB-2500-1, examination categories B-N-2 and B-N-3, item numbers B13.50, B13.60, and B13.70 requires a visual examination of the accessible interior attachment welds within and beyond the beltline region and a visual examination of the accessible core support structure surfaces of the RPV once each ten-year interval. The ANO-2 third 10-Year Inservice Inspection (ISI) interval is schedule to end on March 25, 2011. In accordance with IWA-2430(2)(d)(1),
Entergy extended the ANO-2 ISI interval one year.
Reason for Request
In Westinghouse Topical Report WCAP-16168-NP-A, Revision 2 (Reference 3), the Pressurized Water Reactor Owners Group provided the technical and regulatory basis for decreasing the frequency of inspections by extending the ASME Code Section XI ISI interval from the current 10 years to 20 years for ASME Code Section XI examination categories B-A and B-D RPV welds. The Nuclear Regulatory Commission (NRC) approved the topical report by letter dated May 8, 2008 (Reference 4). To implement the change presented in Reference 3, Entergy submitted a relief request (Reference 5) in accordance with the Safety Evaluation (Reference 4)
Attachment to 2CAN110905 Page 2 of 4 to request an alternative from the Code requirements pursuant to 10 CFR 50.55a(a)(3)(i) on the basis that the alternative inspection interval (20 years) provides an acceptable level of quality and safety. In Reference 5, 2018 is identified as the year in which future inspections of the examination categories B-A and B-D RPV welds will be performed. The intent of this relief request is to allow deferral of the subject examinations to the same time (2018 refueling outage) as the examination categories B-A and B-D RPV welds described in Reference 5.
During the 10-year ISI of the ANO-2 RPV shell, lower head, and nozzle welds in 1999, Entergy also performed visual examinations of the RPV interior attachment and the core support structure. Since the core support structure (called a core barrel on Combustion Engineering designed plants) requires removal to facilitate examination of the RPV shell, lower head, and nozzle welds, the visual examinations of ASME examination categories B-N-2 and B-N-3 have historically been performed during the same outage at the end of the ISI interval.
Performing all core-barrel-removed related examinations during the same refueling outage will result in significant savings in dose and outage duration since the same equipment and personnel used for visual and volumetric examination of the RPV shell welds and nozzle welds from the RPV interior can be used to implement the required reactor vessel inspection (RVI) examinations. Additionally, removing the RPV internals only once to accommodate all the examinations discussed in this relief request would result in significant savings in radiation exposure.
Proposed Alternative and Basis for Use The fourth 10-year ISI interval for ANO-2 begins on March 26, 2010. ANO-2 proposes to perform the subject examinations for the fourth ten-year ISI interval on or before March 25, 2020. The subject examinations are currently scheduled to be performed during the 2R26 refueling outage. The proposed alternative inspection would enable the subject examinations to be performed during the 2018 refueling outage with the risk-informed extension of the reactor vessel (RV) ISI. In accordance with 10 CFR 50.55a(a)(3)(ii), this interval extension is requested on the basis that performing the examination of the RPV interior attachments and core support structure in an outage different from the RPV shell, head, and nozzle welds inspections would result in hardship or unusual difficulty without a compensating increase in quality or safety.
The full scope examination required by ASME examination categories B-N-2 and B-N-3 requires the removal of all the fuel and the core barrel from the RPV. An unnecessary risk is created by removal of the core barrel to perform a visual examination without a compensating increase in quality or safety. Further, the radiation exposure to establish the conditions for and perform the ASME examination categories B-N-2 and B-N-3 examinations would essentially double if the subject examinations were performed in an outage different from the RPV shell, lower head, and nozzle weld examinations.
The visual examinations of the RPV interior attachments and the core support structure have been performed several times at ANO-2 with no relevant indications noted during the examinations. The examinations were last performed during the 1999 refueling outage with acceptable results. Additionally, review of industry surveys indicate that these examinations
Attachment to 2CAN110905 Page 3 of 4 have been performed many times by the industry without any significant findings relevant to the ANO-2 reactor vessel design.
As stated in Reference 3 it must be recognized that all reactor coolant pressure boundary failures occurring to date have been identified as a result of leakage, and were discovered by visual examination. The proposed RV ISI interval extension does not alter the visual examination interval. The reactor vessel would undergo, as a minimum, the Section XI Examination Category B-P pressure tests and visual examination conducted at the end of each refueling before plant start-up, as well as leak tests with visual examinations that precede each start-up following maintenance or repair activities.
The minimum visual examinations discussed in Reference 3 are not the subject examinations (i.e., B-N-2 and B-N-3) of this relief request. During the 2R22 refueling outage, ANO-2 will be performing the ASME examination category B-N-1 visual examination. This examination will include the space that is made accessible for examination by the removal of components during normal refueling outages. This examination is required once each period and will provide reasonable assurance of structural integrity. As discussed further in Reference 3, defenses against human errors are preserved with the increase in inspection interval. Specifically, the increase in the inspection interval reduces the frequency for which the RV lower internals need to be removed thereby reducing the possibility for human error and damage to the core internals.
Therefore, in accordance with 10 CFR50.55a(a)(3)(ii), this interval change from 10 to 20 years for the subject examinations is requested on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Duration of Proposed Alternative This proposed alternative is applicable to the third 10-year ISI for the examination categories B-N-2 and B-N-3, Items B13.50, B13.60 and B13.70 visual examinations.
Precedent Calvert Cliffs Nuclear Power Plant, Docket No 50-318, Safety Evaluation for Relief Requests ISI-020 and 021 Reactor Vessel Weld Examination Extension - Calvert Cliffs Nuclear Power Plant, Unit NO. 2 (TAC NOS MD9773 AND MD9774)
Donald C. Cook Nuclear Plant, Docket 50-316, Donald C. Cook Nuclear Plant, Unit 2 (CNP-2)
- Evaluation of Relief Request (ISIR-30) to Extend the Third 10-Year Inservice Inspection (ISI)
Interval for Visual Examination of the Reactor Pressure Vessel Interior Attachment Beyond the Beltline Region and Core Support Structure (TAC NO. ME0770)
Attachment to 2CAN110905 Page 4 of 4 References
- 1. ASME Boiler and Pressure Vessel Code,Section XI, 2001 Edition through 2003 Addenda
- 2. Entergy letter to the NRC, dated June 8, 2009, Request for Alternative to Use 2001 Edition Through 2003 Addenda in Lieu of the 2004 Edition (2CAN060902)
- 3. WCAP-16168-NP-A, Revision 2, Risk Informed Extension of Reactor Vessel In-Service Inspection Interval, June 2008
- 4. Final Safety Evaluation for Pressurized Water Reactor Owners Group (PWROG) Topical Report (TR) WCAP-16168-NP, Revision 2, Risk-Informed Extension of the Reactor Vessel In-service Inspection Interval (TAC No. MC9768), dated may 8, 2008
- 5. Entergy letter to the NRC, dated October 29, 2009, Request for Alternative ANO2-ISI-004 Proposed Alternative to Extend Third 10-year Inservice Inspection Interval for Reactor Vessel Weld Examinations, (2CAN100902)