ML102590213
| ML102590213 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 10/01/2010 |
| From: | Nancy Salgado Plant Licensing Branch 1 |
| To: | Entergy Nuclear Operations |
| Boska J, NRR, 301-415-2901 | |
| References | |
| TAC ME3017, RR-04 | |
| Download: ML102590213 (10) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 1,2010 Vice President, Operations Entergy Nuclear Operations, Inc.
Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 Buchanan, NY 10511-0249
SUBJECT:
INDIAN POINT NUCLEAR GENERATING UNIT NO.3 - RELIEF FROM THE EXAMINATION AREA FOR REACTOR VESSEL HEAD PENETRATION NOZZLES (TAC NO. ME3017)
Dear Sir or Madam:
By letter dated December 23, 2009, as supplemented by letter dated May 13, 2010, Entergy Nuclear Operations, Inc. (the licensee) submitted a request to the Nuclear Regulatory Commission (NRC) for relief from the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(g)(6)(ii)(D)(3). The relief request pertains to volumetric and surface examinations of reactor vessel (RV) upper head penetration nozzles at Indian Point Nuclear Generating Unit NO.3 (IP3). The relief is requested for the remainder of the fourth 10 year inservice inspection (lSI) interval, which began on July 21, 2009, and is scheduled to end on July 20, 2019.
Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee requested to use the proposed alternative on the basis that the alternative provides an acceptable level of quality and safety. The proposed alternative is an examination of the J-groove weld area with a reduction in the minimum volumetric inspection distance in the non-pressure boundary section of each nozzle due to a threaded section at the end of each nozzle.
Although the licensee requested relief pursuant to 10 CFR 50.55a(a)(3)(i), the NRC authorizes this alternative pursuant to 10 CFR 50.55a(a)(3)(ii), for the remainder of the fourth 10-year lSI interval. The NRC staff reviewed the request and concludes, as set forth in the enclosed safety evaluation, that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety and that the proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components.
- 2 If you have any questions, please contact the Indian Point project manager, John Boska, at (301) 415-2901.
Sincerely, tl~f ;;( ~r~
Nancy L. Salgado, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-286
Enclosure:
As stated 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 RELIEF REQUEST NO. RR-04 ENTERGY NUCLEAR OPERATIONS, INC.
INDIAN POINT NUCLEAR GENERATING UNIT NO.3 DOCKET NO. 50-286
1.0 INTRODUCTION
By letter dated December 23, 2009, (Reference 1), as supplemented by letter dated May 13, 2010 (Reference 4), Entergy Nuclear Operations, Inc. (the licensee) submitted Relief Request (RR)-04 for Nuclear Regulatory Commission (NRC) review and approval. The licensee requested to implement an alternative to the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(g)(6)(ii)(D)(3). The request pertains to the volumetric and/or surface examinations of reactor vessel (RV) upper head nozzles, most of which are used to house control rod drive mechanisms (CRDMs), of the pressurized-water reactor (PWR) at Indian Point Nuclear Generating Unit No.3 (IP3). The duration of RR-04 is for the remainder of the fourth 1O-year inservice inspection (lSI) interval which began on July 21, 2009, and is scheduled to end on July 20, 2019. The request for authorization of the alternative was made pursuant to the provisions of 10 CFR 50.55a(a)(3)(i).
Previously, the licensee submitted a similar relief request by letter dated January 22, 2009, requesting to use this same alternative examination for the RV upper head nozzles. The NRC authorized the relief by letter dated July 8,2009, for the third 10-year lSI interval at IP3. As IP3 has moved to the fourth 1O-year lSI interval, the previous relief has expired and has been resubmitted.
2.0 REGULATORY REQUIREMENTS The lSI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) Class 1,2 and 3 components is to be performed in accordance with 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission.
10 CFR 50.55a(a)(3) permits a licensee to propose alternatives to the requirements of 10 CFR 50.55a(g). Proposed alternatives must provide an acceptable level of quality and safety as described in 10 CFR 50.55a(a)(3)(i), or resolve an issue in which compliance with the specified requirements would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety as described in 10 CFR 50.55a(a)(3)(ii). 10 CFR 50.55a(a)(3)(i) is interpreted to mean that a proposed alternative must provide an equivalent level of quality and Enclosure
- 2 safety when compared to the stated requirement. 10 CFR 50.55a(a)(3)(ii) is interpreted to mean that, in the case of a hardship, an alternative may be authorized if the improvements in safety and quality achieved by conducting the required inspections as compared to those proposed in the alternative are not commensurate with the increased difficulty.
In the present case, the licensee has requested relief from 10 CFR 50.55a(g)(6)(ii)(D)(3) under the provisions of 10 CFR 50.55a(a)(3)(i) by proposing an alternative examination area for reactor vessel penetration nozzles. This proposal is represented by the applicant as being in accordance with ASME Code Case N-729-1. This proposal utilizes Appendix I of the code case.
The NRC staff finds that, in this case, there is a regulatory basis for the licensee to request relief from 10 CFR 50.55a(g)(6)(ii)(D)(3) under either 10 CFR 50.55a(a)(3)(i) or 10 CFR 50.55a(a)(3)(ii). The NRC staff also finds that the applicant's use of Code Case N-729-1 in this relief request is appropriate since the use of this code case is mandated by 10 CFR 50.55a(g)(6)(ii)(D)(1). However, as stated in 10 CFR 50.55a(g)(6)(ii)(D)(6), use of Appendix I of the code case requires NRC approval.
While the NRC staff finds that there is a regulatory basis for the licensee to request relief in this case, the NRC staff's ability to authorize such relief depends on the technical merits of the licensee's request as well as the staff's determination of the existence of an equivalent level of safety between the stated requirement and the proposed alternative or the existence of a hardship. These issues will be considered in Section 4, Staff Evaluation.
3.0 TECHNICAL PROPOSAL 3.1
Applicable Code Edition and Addenda
The Code of Record for the fourth 1O-year lSI interval for IP3 is the 2001 edition through the 2003 addenda. For the component under consideration, lSI is governed by 10 CFR 50.55a(g)(6)(ii)(D), which mandates the use of Code Case N-729-1 (with conditions).
3.2 Components for Which Relief is Requested Component:
RV Upper Head CRDM Nozzles Having Pressure Retaining Partial Penetration Welds Code Class:
Class 1 Examination Category:
PWR RV Upper Head in Table 1 of ASME Code Case N-729-1 Code Item No.:
B4.20 in Table 1 of ASME Code Case N-729-1 In its original request, the applicant failed to state for which of the 78 penetrations relief was being sought. By letter dated May 13, 2010, the licensee responded to an NRC request for additional information (RAI) by stating that relief was being requested for reactor head penetration nozzles 1 through 37 (they fail to meet the 1.5" acceptance criterion for incident angles less than or equal to 30°),38,41 through 44, 47, 48, 52, 55, 56, 61,62,65,67,68,70 through 78 (they fail to meet the 1" acceptance criterion for incident angles greater than 30°).
The licensee also preemptively requested relief for penetration nozzles 40, 49, 50, 53, 54, 57, 58, 60, 64, and 66. The licensee stated that when previously measured these penetration nozzles were within 0.08" of the acceptance criteria. The NRC staff finds this preemptive
- 3 request acceptable because slight variations in the manner in which the nozzles are measured could cause these nozzles to fail to meet the acceptance criteria which would necessitate an exigent relief request. The preemptive request for relief for these components on the part of the licensee ensures their orderly inspection without a loss of safety.
3.3 Inspection Requirements for the Component Under Consideration 10 CFR 50.55a(g)(6)(ii)(D)(3) requires, in part, that the licensee perform a volumetric and/or surface examination of essentially 100 percent of the required volume or equivalent surfaces of the nozzle tube, as identified by Figure 2 of ASME Code Case N-729-1. Figure 2 identifies the required volume of tube to be inspected, a distance "a" above the highest point of the root of the J-groove weld to a distance "a" below the lowest point of the toe of the J-groove weld. Distance "a" is equal to 1.5 inches for incidence angle less than or equal to 30° to the horizontal plane, or 1.0 inch for incidence angle greater than 30° to the horizontal plane.
3.4
Reason for Request
The licensee stated that the design of its RV head penetration nozzles includes a threaded section which is approximately % inches in length and is located at the bottom of the nozzles.
The licensee also stated that due to the presence of this threaded region, the inspectable distance below the toe of the J-groove weld was less than required by Figure 2 of the code case for some nozzles.
3.5 Proposed Alternative The licensee proposes to perform a volumetric inspection of each penetration nozzle from a distance "a" above the J-groove weld and the minimum required ultrasonic test (UT) coverage below the J-groove weld as defined in Table 1.
Table 1. Minimum Inspection Coveraqe Requirement (Table 1 of Reference 1)
Nozzle Penetration No.
Nozzle Angle of Incidence (degrees)
I'l Minimum Required UT Coverage Below J-groove Weld with >2 EFPY by Crack Growth Evaluation (inches)
Time, Effective Full Power Years (EFPY),
to Reach the Lowest Point of the Toe of the J-groove Weld (year) 1 throuqh 29 oto 24.8 0.4 3.0 30 through 37 26.2 0.4 2.7 38 through 69 30.2 to 38.6 0.4 2.7 70 throuqh 73 44.3 0.3 3.0 74 through 78 48.7 0.3 4.2 (1) length below the lowest point at the toe of the J-groove weld (downhill side) that has an operating stress level of 20 ksi: 0.86 inches at nozzles 1 through 29; 0.50 inches at nozzles 30 through 69; 0.35 inches at nozzles 70 through 73 and 0.35 inches at nozzles 74 throuqh 78.
- 4 3.6 Licensee's Technical Basis The licensee provided a basis for the adequacy of the proposed alternative based on three components: a finite element stress analysis of the nozzles near the J-groove weld; a postulation of an initial flaw size and crack growth rate based on the stress analysis; and a proposal for an alternate inspection area such that the postulated crack is not expected to grow sufficiently to reach the toe of the J-groove weld prior to the next inspection (2 years for the present case).
The licensee stated that, in all cases, the inspection requirements of Figure 2 of the code case for inspection above the J-groove could be met.
Based on the stress analysis and crack growth rate predictions, the licensee proposed minimum UT inspection coverage requirements. These values are contained in Table 1 of the relief request and are reproduced here for the convenience of the reader.
By letter dated May 13, 2010, the licensee, in response to an NRC RAI, confirmed that the proposed inspection area was at least as large as the required inspection area as listed in Table
- 1.
4.0 Staff Evaluation The NRC staff reviewed the applicable inspection requirements for the components under consideration as contained in licensee's relief request and as stated in 10 CFR 50.55a(g)(6)(ii)(D)(3). The staff agrees with the licensee that these are the appropriate inspection requirements for these components.
The NRC staff reviewed the licensee's reason for requesting relief from the inspection requirements for these components. The staff agrees with the licensee that satisfactory UT inspection of the threaded regions at the lower ends of the penetration nozzles is unlikely. The staff also agrees that the distance between the toe of the J-groove welds and the top of the threaded region of the nozzle is, in some cases, less than the inspection distance required by Figure 2 of Code Case N-729-1. The staff notes that, although surface examination of the components is an acceptable option, the length of time required to perform the inspection in combination with the projected dose rate (3 to 5 Rem/hr) would result in a significant radiation exposure to the inspector.
The NRC staff reviewed the basis upon which the licensee's proposed alternative inspection area is based. This basis relies upon stress analyses and crack growth projections to predict that a crack, which lies outside the proposed inspection area in one inspection, cannot grow sufficiently to reach the toe of the J-groove weld prior to the next inspection. Cracks which do not affect the J-groove weld are not part of the pressure boundary of the reactor vessel and do not constitute a safety hazard. Cracks which affect the J-groove weld could lead to a breach of the pressure boundary. The staff agrees with the licensee that this approach will prevent a crack from reaching the J-groove weld and will, therefore, provide an adequate level of safety to allow the staff to grant relief under 10 CFR 50.55a(a)(3)(ii).
- 5 The NRC staff reviewed the method used by the licensee to demonstrate that its proposed inspection area was sufficient to preclude cracks from reaching the toe of the J-groove weld between any two inspections. The staff considered the method used to produce the stress analysis; the method used to predict crack growth; the method used to postulate the initial crack length; the minimum inspection coverage requirement; and the proposed inspection coverage.
The NRC staff reviewed the licensee's methods for predicting stresses and crack growth rates.
The staff found that the licensee employed commonly used techniques. The staff finds the techniques employed and the predictions derived from these methods and techniques to be acceptable.
The NRC staff reviewed the method used by the licensee to postulate the length of the initial crack. The staff noted the use of two significant assumptions. These assumptions include: 1) the lower tip of the postulated crack is located at the point where circumferential stresses on either the inside surface or the outside surface of the nozzle become compressive, indicating that a through wall crack below this point is unlikely; 2) the postulated crack length is such that the stress intensity factor is equal to the stress intensity factor required for crack growth (threshold stress intensity factor) (8.19 ksi/in"). The staff finds these assumptions reasonable because they specify the minimum crack length required for growth, or alternatively, cracks which do not meet these criteria cannot grow.
The NRC staff reviewed the minimum inspection coverage. The staff noted that the end of the required inspection area lies at the postulated location of the upper crack tip. Based on the values reported in Table 1 (above), this point is either 0.3 or 0.4 inches below the toe of the J-groove weld. Through the use of this approach, the licensee has defined both the postulated crack geometry, which defines the potential crack growth rate and the maximum allowable growth between inspections as 0.3 or 0.4 inches depending on the penetration. Through the use of the crack growth prediction methodology discussed above, the licensee predicted the length of time required for the postulated crack to grow from the uninspected area to the toe of the J-groove weld. These projections are also reported in Table 1 above as the Time, Effective FUll-Power Years (EFPY), to Reach Toe of J-groove Weld. The staff agrees with the applicant that an inspection area of 0.3 or 0.4 inches, respectively, is adequate because, in all instances, the time required for the postulated crack to grow the necessary distance to reach the toe of the J-groove weld exceeds the time interval between inspections.
The NRC staff reviewed the proposed inspection coverage. The staff noted that the applicant stated that inspections would be conducted "on the inside surface of each RPV head penetration nozzle from 1 inch and 1 Y2 inch above the J-groove weld (Le., the upper boundary limit defined in Figure 2 of Code Case N-729-1) and extending down the nozzle to at least the top of the threaded region. In its response to a staff RAI, the licensee confirmed that in each case for which relief was sought, the inspectable distance from the toe of the J-groove weld exceeded the minimum required UT coverage as shown in Table 1. The staff finds the licensee's proposed inspection coverage adequate because any crack which lies outside the proposed inspection area will not be able to grow sufficiently before the next inspection to reach the toe of the J-groove weld and thereby create the possibility that the reactor pressure boundary will be breached. Therefore, the staff finds that the licensee's proposed alternative provides reasonable assurance of public health and safety, and requiring compliance with the regulations would impose a radiological hardship on the licensee.
- 6 The NRC staff reviewed the applicant's proposal to determine whether it provided a level of safety and quality which was equivalent to the specified requirement. The staff noted that the proposed alternative provides for a smaller inspected area and relies on predicted, as opposed to measured, levels of stress. The staff cannot, therefore, conclude that the proposed alternative will provide an equivalent level of safety to the specified requirement.
The NRC staff reviewed the applicant's proposal to determine whether the specified requirement created a hardship and whether the improvements in safety and quality achieved by the specified requirement were commensurate with the increased difficulty of meeting that requirement as opposed to the proposed alternative. The staff noted that meeting the specified requirement through the use of internal UT inspection is not possible for all penetrations. The staff also noted that the specified requirement could be met through the use of a manual surface exam but that the length of time required to perform the inspection in combination with the projected dose rate (3 to 5 Rem/hr) would result in a significant radiation exposure to the inspector. The staff considers this to be a hardship. The staff further notes that the analyses performed by the applicant are sufficient to indicate that the performance of surface exams will not result in an increase in safety or quality, when compared with the proposed alternative, commensurate with the resulting radiation exposure. Therefore, the staff finds sufficient basis to authorize relief under 10 CFR 50.55a(a)(3)(ii).
5.0 CONCLUSION
As set forth above, the NRC staff concludes that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety and that the proposed alternative provides reasonable assurance of structural integrity and leak tightness of the subject components. Therefore, the staff authorizes the proposed alternative at IP3 for the remainder of the fourth 1O-year lSI interval.
All other requirements for which relief was not specifically requested and approved in this relief request remain applicable, including the third party review by the Authorized Nuclear Inservice Inspector.
6.0 REFERENCES
- 1.
Entergy letter NL-09-163 to NRC dated December 23, 2009, "Relief Request IP3-ISI-RR-04 for Fourth 1O-Year Inservice Inspection Interval, Indian Point, Unit No.3,"
Agencywide Documents Access and Management System (ADAMS) Accession No. ML100050207.
- 2.
Entergy letter NL-09-130 to NRC dated September 24,2009, "Response to Request for Additional Information Regarding Relief Request 09 for Fourth 10-Year Inservice Inspection Interval (TAC No. ME1658), Indian Point, Unit Number 2," ADAMS Accession No. ML092800242 (Information herein provided addresses both Indian Point 2 and Indian Point 3).
- 3.
NRC email to Entergy dated March 16, 2010, regarding request for additional information, ADAMS Accession No. ML100750136.
- 7
- 4.
Entergy letter NL-10-050 to NRC dated May 13, 2010, "Request for Additional Information on Relief Request IP3-ISI-RR-04 for Fourth 10-Year lnservice Inspection lnterval (TAC No. ME3017)," ADAMS Accession No. ML101410295.
Principal Contributor: D. Alley Date: October 1, 2010
- 2 If you have any questions, please contact the Indian Point project manager, John Boska, at (301) 415-2901.
Sincerely, Ira!
Nancy L. Salgado, Chief Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-286
Enclosure:
As stated cc w/encl: Distribution via Listserv DISTRIBUTION:
PUBLIC RidsNrrDorlLpl1-1 RidsNrrPMlndianPoint RidsOGCRp LPL1-1 Reading File RidsNrrLASLittie RidsAcrsAcnw_MailCTR DAiley RidsNrrDorlDpr RidsRgn1 MailCenter RidsNrrDciCpnb ADAMS ACCESSION NO*.. ML102590213
- See memo dated 9/15/10 OFFICE LPL1-1/PIVI LPL1-1/LA CPNB/BC*
LPL1-1/BC NAME JBoska SLittie TLupold NSalgado DATE 9/16/10 9/16/10 9/15/10 10/1/10 OFFICIAL RECORD COpy