ML17279A045
| ML17279A045 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 10/26/2017 |
| From: | Markley M Plant Licensing Branch II |
| To: | Hutto J Southern Nuclear Operating Co |
| MOrenak, NRR/DORL/LPL2-1, 415-3229 | |
| References | |
| CAC MF9022, CAC MF9023, CAC MF9026, CAC MF9028, CAC MF9029, CAC MF9032, CAC MF9033, CAC MF9037, EPID-L-2016-LLR-0012, EPID-L-2016-LLR-0013, EPID-L-2016-LLR-0014, EPID-L-2016-LLR-0016, EPID-L-2016-LLR-0017, EPID-L-2106-LLR-0015 | |
| Download: ML17279A045 (19) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 26, 2017 Mr J. J. Hutto Regulatory Affairs Director Southern Nuclear Operating Co., Inc.
40 Inverness Center Parkway Bin 038 Birmingham, AL 35201-1295
SUBJECT:
EDWIN I. HATCH NUCLEAR PLANT, UNIT NOS. 1AND2 - RELIEF REQUESTS ISl-RR-13, ISl-RR-14, ISl-RR-18, ISl-RR-19, ISl-RR-23, AND ISl-RR-24 FOR RELIEF FROM INSERVICE INSPECTION REQUIREMENTS (CAC NOS. MF9022, MF9023, MF9026, MF9028, MF9029, MF9032, MF9033, AND MF9037; EPIDS L-2016-LLR-0012, L-2016-LLR-0013, L-2016-LLR-0014, L-2016-LLR-0015, L-2016-LLR -0016, and L-2016-LLR -0017)
Dear Mr. Hutto:
By letter dated December 27, 2016, as supplemented by letter dated July 10, 2017, Southern Nuclear Operating Company (SNC, the licensee), submitted Relief Requests 181-RR-13, ISl-RR-14, ISl-RR-15, ISl-RR-16, ISl-RR-17, ISl-RR-18, ISl-RR-19, ISl-RR-21, ISl-RR-22, lSl-RR-23, and ISl-RR-24 requesting relief from certain inservice inspection (ISi) requirements of Section XI of the 2001 Edition through the 2003 Addenda of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code for the Edwin l. Hatch Nuclear Plant (HNP}, Unit Nos. 1 and 2.
For six of the eleven requests, ISl-RR-13, ISl-RR-14, ISl-RR-18, ISl-RR-19, ISl-RR-23, and ISl-RR-24, the licensee requested relief from specified BPV Code requirements pursuant to Title 10 of the Code of Federal Regulations (1 O CFR} paragraph 50. 55a(g}( 5}(iii}, on the basis that the code requirements are impractical. Specifically, the licensee requested relief from the required ISi of certain welds specified in the ASME BPV Code, Section XI, Table IWB-2500-1, Figure IWB-2500-8(c}, and Table IWC-2500-1.
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject requests, and concludes, as set forth in the enclosed safety evaluation, that SNC has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5}(ii} and that the ASME BPV Code requirements are impractical for the subject welds. Therefore, the NRC staff grants relief for requests, ISl-RR-13, ISl-RR-14, ISl-RR-18, ISl-RR-19, ISl-RR-23, and ISl-RR-24 in accordance with 10 CFR 50.55a(g)(6)(i) for the fourth 10-year ISi program interval, which began on January 1, 2006, and ended on December 31, 2015.
The NRG staff granted Relief Request ISl-RR-15 by letter dated March 29, 2017, and Relief Requests ISl-RR-16, ISl-RR-17, ISl-RR-21, and ISl-RR-22 by letter dated October 20, 2017.
J. Hutto All other ASME BPV Code, Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including third-party review by the Authorized Nuclear lnservice Inspector.
If you have any questions, please contact the Project Manager, Randy Hall, at 301-415-4032 or by e-mail at Randy.Hall@nrc.gov.
Sincerely, Michael T. Markley, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366
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 RELIEF REQUESTS ISl-RR-13 ISl-RR-14 ISl-RR-18 ISl-RR-19 ISl-RR-23 AND ISl-RR-24 REGARDING INSERVICE INSPECTION OF REACTOR PRESSURE VESSEL AND RESIDUAL HEAT REMOVER HEAT EXCHANGER WELDS EDWIN I. HATCH NUCLEAR PLANT UNIT NOS. 1 AND 2 SOUTHERN NUCLEAR OPERATING COMPANY DOCKET NOS. 50-321 AND 50-366
1.0 INTRODUCTION
By letter dated December 27, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16362A273), as supplemented by letter dated July 10, 2017 (ADAMS Accession No. ML171918036), Southern Nuclear Operating Company (SNC, the licensee) submitted Relief Requests ISl-RR-13, ISl-RR-14, ISl-RR-15, ISl-RR-16, ISl-RR-17, ISl-RR-18, ISl-RR-19, ISl-RR-21, ISl-RR-22, ISl-RR-23, and ISl-RR-24 requesting relief from certain inservice inspection (ISi) requirements of Section XI of the 2001 Edition through the 2003 Addenda of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code for the Edwin I Hatch Nuclear Plant (HNP), Unit Nos. 1 and 2.
For six of the eleven requests, ISl-RR-13, ISl-RR-14, ISl-RR-18, ISl-RR-19, ISl-RR-23, and ISl-RR-24, the licensee requested relief from specified BPV Code requirements pursuant to Title 10 of the Code of Federal Regulations ( 10 CFR) paragraph 50. 55a(g)(5)(iii), "ISi program update: Notification of impractical ISi Code requirements," on the basis that the code requirements are impractical. Specifically, the licensee requested relief from the required ISi of certain welds specified in the ASME BPV Code, Section XI, Table IWB-2500-1, Figure IWB-2500-8(c), and Table IWC-2500-1
2.0 REGULATORY EVALUATION
The licensee requested relief from the ASME BPV Code, Section XI, in accordance with 10 CFR 50.55a(g)(5)(iii). ASME BPV Code Class 1, 2, and 3 components must meet the requirements of Section XI of the ASME BPV Code as required by 10 CFR 50.55a(g){4),
"lnservice inspection standards requirement for operating plants," which states, in part, that:
Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, components, {including supports) that are classified as ASME Code Class 1, Class 2, and Class 3 must meet the requirements, except design and access provisions and preservice examination requirements, set forth in Section Xl of editions and addenda of the ASME BPV Code ..
Enclosure
The licensee may request relief from portions of the ASME BPV Code as provided in 10 CFR 50.55a(g)(5)(iii), which states, in part, that:
If the licensee has determined that conformance with a Code requirement 1s impractical for its facility the licensee must notify the NRC and submit, as specified in § 50.4, information to support the determinations. Determinations of impracticality in accordance with this section must be based on the demonstrated limitations experienced when attempting to comply with the Code requirements during the inservice inspection interval for which the request is being submitted.
The NRC staff may grant relief from ASME BPV Code requirements as provided in 10 CFR 50.55a(g)(6)(i), "Impractical ISi requirements: Granting of relief," which states that The Commission will evaluate determinations under paragraph (g)(S) of this section that code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are otheiwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Given that 10 CFR 50.55a(g)(4) requires the use of the ASME BPV Code, Section XI; that 10 CFR 50 55a(g)(5)(iii) permits the licensee to request relief; and that 10 CFR 50.55a(g)(6)(i) permits the NRC staff to grant relief for requests submitted under 10 CFR 50.55a(g)(S), the NRC staff finds that subject to the following technical evaluation, the licensee may request relief from the ASME BPV Code, Section XI, and the NRC staff has the regulatory authority to grant the requested relief.
Additionally, requests for relief made in accordance with 10 CFR 50.55a(g)(5)(iii) must be submitted to the NRC no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought. The licensee submitted Relief Requests ISl-RR-13, ISl-RR-14, ISl-RR-18, ISl-RR-19, ISl-RR-23, and ISl-RR-24 on December 27, 2016, for the fourth 10-year ISi interval, which is not later than 12 months after the end of the interval on December 31, 2015.
3.0 TECHNICAL EVALUATION
The NRC staff's evaluation of the licensee's requests for relief reviewed: (1) whether the ASME BPV Code requirement is impractical; (2) whether the imposition of the ASME BPV Code required inspections would result in a burden to the licensee; and (3) whether the licensee's examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds. The NRC staff finds that if these three criteria are met, the requirements of 10 CFR 50.55a(g)(6)(i) are met ASME Code of Record The Code of record for the fourth 10-year ISi interval at HNP, Units 1 and 2, is the ASME BPV Code, Section XI, 2001 Edition with 2003 Addenda. The fourth 10-year ISi interval began on January 1, 2006, and ended on December 31, 2015.
3.1 ISl-RR-13 (HNP, Units 1and2)
ASME Code Component Identification ASME Code Class: ASME Code Class 1 Examination Category: B-J Item Number: 89.11 Component: Austenitic Steel Circumferential Pipe-to-Valve Butt Weld with Overlay (308L) Installed in 1990 due to lntergranular Stress Corrosion Cracking (IGSCC) Indication.
Weld Number: 1B31-1RC-28B-13 ASME Code Requirement ASME BPV Code Section XI, Table IWB-2500-1, Item 89.11 requires surface and volumetric examinations of essentially 100 percent of the weld length for circumferential butt welds each ISi interval.
Licensee's Relief Request For the subject weld, the licensee achieved less than 100 percent coverage of the required examination volume for weld 1831-1 RC-288-13 due to the configuration of the weld overlay_
The licensee is requesting relief from the ASME BPV Code requirements described above.
Impracticality of Compliance The licensee stated that this full structural weld overlay was designed to the requirements of NUREG-0313, "Technical Report on Material Selection and Processing Guidelines for BWR
[Boiling Water Reactor} Coolant Pressure Boundary Piping," Revision 2 (ADAMS Accession No. ML031470422), and that this design was issued several years prior to ASME Code Case N-504, "Alternative Rules for Repair of Classes 1, 2, and 3 Austenitic Stainless Steel Piping Section Xl, Division 1," being included in Regulatory Guide (RG) 1 147, Revision 11, "lnservice Inspection Code Case Acceptability -ASME Section XI, Division 1" (ADAMS Accession No. ML003739955) in October 1994. The licensee also stated that the cast austenitic stainless steel (CASS) valve and the 308L butt weld are known to be IGSCC-resistant and confirmed that no incidences of IGSCC in weld metal or castings in BWRs have been reported.
Figure RR-13-3 of the submittal shows the required examination volume associated with this weld overlay and the limitations imposed by the configuration. The licensee composite ultrasonic examination coverage was calculated as 60 percent by examination personnel.
The most susceptible portion of the examination volume was examined with automated phased-array ultrasonic techniques. The remainder of the examination volume is located above cast material, which as discussed earlier, has no history of IGSCC.
Examinations from the upstream and downstream sides included 25, 45, 60, and 70 degree refracted longitudinal waves plus a 0 degree longitudinal wave. Only non-relevant indications and acoustic interface were recorded.
Examinations looking for axial flaws included 45, 60, and 70 degree refracted longitudinal waves. Only non-relevant indications and acoustic interface were recorded.
Licensee's Basis for Relief The licensee stated that a significant volume of the examination coverage was obtained, VT-2 examinations associated with the Class 1 leakage tests are performed each refueling outage, and operational leakage can be determined by the leakage detection system (LOS) located in the drywell.
NRG Staff Evaluation The design and configuration of the weld overlay, pipe, and valve were the predominant limitations that prevented the licensee's ultrasonic testing (UT) from achieving essentially 100 percent coverage of the ASME BPV Code-required volume_ Additionally, the examination volume had to be modified because of the atypical configuration of the weld overlay, which does not extend past the weld on the valve side, and the weld's particular design configuration prevented the licensee from scanning the weld on both sides. Based on the above, the NRC staff finds that achieving essentially 100 percent coverage is impractical The licensee stated that increasing the examination coverage of the weld overlay would require a modification of the weld overlay. The licensee also stated that, in addition to personnel radiation exposure, the cost of a new weld overlay would be 2 million dollars. The licensee listed another option that would require replacing the section of piping with IGSCC-resistant material, which would require more radiation exposure and higher costs than a new weld overlay. Therefore, the only means to appreciably increase examination coverage would place a burden on the licensee.
The NRC staff considered whether the licensee's proposed alternatives provided reasonable assurance of structural integrity and leak tightness of the subject weld based on: (1) the examination coverage achieved and (2) safety significance of unexamined volumes (e.g., the presence or absence of known active degradation mechanisms and essentially 100 percent coverage achieved for similar welds in slmilar environments subject to similar degradation mechanisms).
The licensee stated that approximately 60 percent coverage was obtained for these examinations. In evaluating the licensee's proposed alternative, the NRC staff assessed whether the licensee obtained the maximum coverage achievable. The NRC staff reviewed the submittal and Figures RR-13-1 to RR-13-3, and found that:
- The weld was examined using the appropriate equipment, ultrasonic modes of propagation, probe angles, frequencies, and scanning directions to obtain maximum coverage;
- The UT procedures used were qualified as required by regulation;
- The coverage was limited by physical access (i.e., the configuration of one side of the weld did not permit access for scanning); and
- No unacceptable indications were identified
Therefore, the NRC staff finds that the licensee made every effort to obtain as much coverage as reasonably possible with the ASME BPV Code-required UT.
In addition to the coverage analysis described above, the NRG staff evaluated the safety significance of the unexamined volumes of the weld. The NRC staff reviewed the submittal and the July 10, 2017, supplement, and found that:
- The letter dated June 29, 1990 (ADAMS Legacy Accession No. 9007060312),
referenced in the submittal, states that the weld overlay was designed to have an as-deposited ferrite content greater than 7.5 ferrite number and the weld overlay material was designed as Type 308L or equivalent. The weld overlay was installed to cover the susceptible piping material. Also, the pipe is wrought stainless steel, the weld metal is Type 308L, and the valve is CASS
- The licensee's examinations obtained 60 percent of the ASME BPV Code-required coverage. Scans for circumferential and axial flaws found only non-relevant indications and acoustic interface.
- The licensee stated that the volume that was not inspected is contained within the CASS valve and that the ferrite content in the valve material is 14.6 percent.
- The weld overlay covers the wrought stainless steel pipe, heat affected zone, and adjacent weld.
- As documented in NUREG-0313, austenitic materials considered by the NRC staff to be adequately resistant to sensitization by welding include low carbon weld metal of Type 30BL and similar grades with a minimum of 7.5 percent ferrite as deposited.
Additionally, the licensee stated in the submittal that VT-2 examinations associated with the Class 1 leakage test will be performed each refueling outage and that operational leakage can be determined by the LDS located in the drywell. These additional examinations, the coverage obtained with no relevant indications identified, and the resistance of the materials to sensitization and IGSCC provide reasonable assurance of structural integrity and leak tightness of the subject weld.
Based on the above, the NRC staff concludes that the ASME BPV Code requirement is impractical, the imposition of the ASME BPV Code required inspections would result in a burden to the licensee, and the licensee's examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds.
3.2 ISl-RR-14 (HNP, Unit 1)
ASME Code Component Identification ASME Code Class: ASME Code Class 1 Examination Category: B-F Item Number: 85.20 Component Nozzle-to-Safe-End Butt Welds Weld Numbers: N16A, N16B
ASME Code Requirements The examination requirement for nozzle-to-safe-end butt welds that are less than nominal pipe size (NPS) 4 is 100 percent surface examination as described in Table IWB-2500-1 and Figure IWB-2500-B(b)
Licensee's Relief Request For the subject welds, the licensee was unable to perform the surface examination of the nozzle-to-safe-end butt welds N16A and N16B because the reactor pressure vessel insulation, concrete shield wall, and shield blocks prevent access. The licensee is requesting relief from ASME BPV Code, Section XI, Table IWB-2500-1, Item 85.20, which requires 100 percent surface examinations for dissimilar metal nozzle-to-safe-end butt welds less than NPS 4.
Burden Caused by Compliance The licensee stated that a redesign of the 1N16 nozzles would be required to allow access to perform these examinations_
Licensee's Basis for Relief The licensee stated that VT-2 examinations in conjunction with the Class 1 system leakage/hydrostatic test each refueling outage, are performed such that any flaw(s} that might have propagated through the subject welds are identified and repaired prior to returning the plant to power operation. Furthermore, the licensee stated that during operation, leakage can be determined by the LOS located in the drywell {as described in the HNP, Unit 1, Final Safety Analysis Report (FSAR) Section 4 10).
NRG Staff Evaluation The NRG staff reviewed the descriptions and pictures of the welds. The design and configuration of the reactor pressure vessel insulation, the concrete shield wall, and the shield blocks prevented the licensee from performing the ASME BPV Code-required examinations.
In addition, access to the welds via the 5 square-inch access port is limited. The welds' particular design configuration prevented the licensee from performing the required examinations. Therefore, the NRG staff finds that achieving 100 percent coverage is impractical.
The licensee stated that the 1N16 nozzles would have to be redesigned to allow access to perform the required examinations. The NRG staff finds that the only means to allow examinations would be to redesign or replace the subject components, which would place a burden on the licensee.
The NRG staff evaluated the safety significance of the unexamined surfaces of the welds. For each of the welds, the nozzle, nozzle butter, and nozzle-to-safe-end weld are made of lnconel, and the safe-end is made of austenitic stainless steel. Therefore, the welds are the most susceptible to forms of degradation that originate from the inside of the weld, such as IGSCG.
The purpose of the surface examinations is to identify any cracks that have penetrated through the thickness of the weld. Through-wall flaws can be identified through leakage detection_ To provide additiona! assurance that flaws that propagate through the subject welds are identified and repaired prior to returning to power operation, the licensee proposed VT-2 examinations in
conjunction with Class 1 leakage/hydrostatic tests each refueling outage. During operation, leakage will be detected by the LDS located in the drywell. The staff finds that the proposed inspections and leakage testing provide reasonable assurance of structural integrity, such that service*induced degradation will be identified and repaired prior to returning the plant to operation.
Based on the above, the NRC staff concludes that the ASME BPV Code requirement is impractical, the imposition of the ASME BPV Code required inspections would result in a burden to the licensee, and the licensee's proposed inspections and leakage testing provide reasonable assurance of structural integrity and leak tightness of the subject welds, such that service-induced degradation will be identified and repaired prior to returning the plant to operation.
3.3 ISl-RR-18 (HNP, Unit 2)
ASME Code Component Identification ASME Code Class: ASME Code Class 1 Examination Category: B-J Item Number: 89.11 Component: lnconel Buttered 316 NG Stainless Steel Pipe to Carbon Stee!
Elbow Welds Welded Using lnconel 82 Weld Numbers: 2E11-1 RHRM-24A-10, 2E11-1RHRM-24B-10 ASME Code Requirements The examination requirement for circumferential welds (NPS 4 or larger) is surtace and volumetric examinations of essentially 100 percent of the weld length as described in Table IWB-2500-1, Item 89.11 and Figure IWB-2500-S(c)
ASME Code Case N-460, "Alternative Examination Coverage for Class 1 and Class 2 Welds, Section XI, Division 1," which was approved for use by the NRC in RG 1.147, Revision 17, "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1" (ADAMS Accession No. ML13339A689), states that a reduction in examination coverage due to interterence by another component or part geometry for any ASME Class 1 or Class 2 weld is acceptable provided that the reduction is less than 10 percent (i.e., greater than 90 percent examination coverage is obtained). In addition, RG 1.147, Revision 17, also approved Code Case N-663, "Alternative Requirements for Classes 1 and 2 Surtace Examinations, Section XI, Division 1," which states, in part, that:
. in lieu of the surtace examination requirements for piping welds of Examination Category ... B-J (NPS 4 and larger) ... surtace examinations may be limited to areas identified by the Owner as susceptible to outside surtace attack.
Susceptibility to outside surtace attack is determined using Table 1 in ASME Code Case N-663.
Licensee's Relief Request For the subject welds, the licensee achieved a composite Code coverage of 87 percent.
The licensee is requesting relief from Table IWB-2500-1 and ASME Code Case N-460.
Burden Caused by Compliance The licensee stated that compliance would require the replacement of the elbows with new components fabricated with a special design to allow examination.
Licensee's Basis for Relief The licensee stated that examination coverage was limited due to taper created by the difference in the outside diameter of the elbow versus the outside diameter of the pipe.
Although the ultrasonic examination was limited for axially-oriented flaws, the circumferential flaw coverage of the weld joint was scanned from both sides with both the 45 degree refracted longitudinal (RL) wave transducer and the 60 degree RL transducer for 100 percent coverage.
Furthermore, the licensee stated that a VT-2 visual examination of these welds is performed each refueling outage as part of the Class 1 leakage test and, during operation, HNP, Unit 2, leakage can be determined by the LDS located in the drywell (as described in the HNP, Unit 2, FSAR Section 5.2.7).
NRC Staff Evaluation
The licensee stated that the tapers on welds limited the examinations of the welds. Based on the fact that the tapers prevent a complete directional scan, the NRC staff finds that it would be impractical for the licensee to perform the ASME BPV Code-required examinations.
For the licensee to achieve 100 percent volumetric coverage, the elbows would have to be replaced with new components fabricated with a special design, which would result in a very substantial capital cost and extended outage time for the licensee. Therefore, compliance with the ASME BPV Code requirements to perform the required examinations would place a burden on the licensee.
The NRC staff considered whether the licensee's proposed alternatives provided reasonable assurance of structural integrity and leak tightness of the subject weld based on: (1) the examination coverage achieved and (2) safety significance of unexamined volumes (e.g., the presence or absence of known active degradation mechanisms and essentially 100 percent coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
The licensee performed an evaluation using Table 1 from Code Case N-663 and determined that neither HNP unit had locations that were susceptible to outside surface attack. Therefore, surface examinations of the subject welds were not required and the licensee performed only volumetric examinations. The licensee's volumetric examinations achieved a composite coverage of 87 percent. In evaluating the licensee's proposed alternative, the NRC staff assessed whether it appeared that the licensee obtained the maximum coverage achievable.
The NRC staff reviewed the submittal and Figures RR-18-1 to RR-18-3 and found that:
- The weld was examined using the appropriate equipment. ultrasonic modes of propagation, probe angles, frequencies, and scanning directions to obtain maximum coverage:
- The UT procedures used were qualified as required by regulation; and
- The coverage was limited by physical access (i.e., the tapers of the welds limited the scan volume).
Additionally, the licensee stated that no recordable indications were identified. Therefore, the NRC staff finds that the licensee made every effort to obtain as much coverage as reasonably possible with the ASME BPV Code-required UT.
In addition to the coverage analysis described above, the NRC staff evaluated the safety significance of the unexamined volumes of weld. Although ultrasonic examination was limited for axial flaws, the licensee was able to obtain 100 percent coverage of the weld joint for circumferential flaws. As shown in the submittal, approximately 65.5 percent of the ASME BPV Code-required examination coverage for axial flaws was obtained because of the inability to scan on the weld. Furthermore, the licensee stated that 81.0 percent of the wetted surface was examined for the presence of axial flaws. Based on the licensee's figures, the 0.59 square inches that was examined out of the ASME-required 0.90 square inches (0.59/0.90 -
65.5 percent) covered nearly 100 percent of the volume outside the weld metal, with no recordable indications identified by the licensee. Considering the coverage obtained, the NRC staff finds that evidence of significant service-induced degradation would have been detected, if present. In addition, the 0.31 square inches not examined (i.e., the weld material) is made of lnconel 82, which is resistant to IGSCC.
Additionally, the subject welds undergo a VT-2 visual examination each refueling outage as part of the leakage test, and leakage can be determined by the LOS located in the drywell during operation. The coverage obtained in the examinations performed, the resistance of the weld material to IGSCC, and the leakage tests performed during refueling outages and operation provide reasonable assurance of structural integrity and leak tightness of the subject welds.
Based on the above, the NRC staff concludes that the ASME BPV Code requirement is impractical, the imposition of the ASME BPV Code required inspections would result in a burden to the licensee, and the licensee's examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds.
3.4 ISl-RR-19 (HNP, Units 1 and 2)
ASME Code Component Identification ASME Code Class: ASME Code Class 1 Examination Category: B-J Item Number: B9.11 Component: 8 Austenitic Piping Welds 1 Ferritic Piping Weld
Table RR-19-1 Weld Number Components Materials Covera( e 1831-1 RC-4A-1 QA Cap A240 Gr 304 or equivalent 50°/o Weld A240 Gr 304 or equivalent Branch Connection A182 Gr 304 1831-1 RC-128R-E-1 Pipe A240 Gr A304 50°/o Weld ER308 '
Branch Connection A182Gr304 *- -
1E21-1 CS-108-20A Safe-End A182Gr316 75°/o Weld ER308L or E308L Safe-End Extension A182 Gr 316 1 G31-1 RWCUM-6-0-5 Valve A351 Gr CF-BM .. - 50°/o Weld ER308 Elbow A403 Gr WP304 1G31-1 RWCUM-6-D-16 Penetration SA182 Gr F304 50°/o I Wel_d -
ER308 Pipe A376 Gr TP304 2831-1 RCM-22A-1 Cross Low Carbon GE Type 316 NG 65°/o Weld E308L ~
Manifold Low Carbon GE Type 316 NG 2831-1 RCM-28AD-5 *Low Carbon GE Type 316 NG I Soo/o
- Pine - *-
Weld E30BL Cross Low Carbon GE Type 316 NG 2831-1 RCM-2880-5 Pioe Low Carbon GE Type 316 NG 50°/o E308L
- Weld - ---
~ Cross Low Carbon GE Type 316 NG Ferritic steel 65°/o 1E21-1CS-10A-7 (ferritic weld)
I Valve Weld -* j Ferritic steel Elbow Ferritic steel ASME Code Requirements The examination requirement for circumferential welds (NPS 4 or larger) is surface and volumetric examinations of essentially 100 percent of the weld length as described in Table IWB-2500-1, Item 69.11 and Figure IWB-2500-B(c).
ASME Code Case N-460, which was approved for use by the NRG in RG 1.147, Revision 17, states that a reduction in examination coverage due to interference by another component or part geometry for any ASME Class 1 or Class 2 weld is acceptable provided that the reduction is less than 10 percent (i.e., greater than 90 percent examination coverage is obtained). In addition, RG 1.147, Revision 17, also approved Code Case N-663, which states, in part that:
... in lieu of the surface examination requirements for piping welds of Examination Category . B-J (NPS 4 and larger) .. surface examinations may be limited to areas identified by the Owner as susceptible to outside surface attack.
Susceptibility to outside surface attack is determined using Tab!e 1 in ASME Code Case N-663.
Licensee's Relief Request For the subject welds, the licensee achieved composite Code coverages as shown in Table RR-19-1 and is requesting relief from ASME BPV Code, Section XI, Table IWB-2500-1, Item 89.11, which requires surface and volumetric examinations for 100 percent of the weld length for pressure retaining circumferential welds NPS 4 or larger.
Burden Caused by Compliance The licensee stated that compliance would require the replacement of the existing components with new components fabricated with a special design to allow examination.
Licensee's Basis for Relief The licensee categorized the welds subject to Relief Request ISl-RR-19 as Category A or Category C in accordance with Generic Letter 88-01, "NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping" (ADAMS Accession No. ML031430193), and BWRVIP-75-A, "BWR Vessel and Internals Project, Technical Basis for Revisions to Generic Letter 88-01 Inspection Schedules" (ADAMS Accession No. ML053070149). Category A welds have no known cracks and have a low probability of experiencing IGSCC. The one ferritic weld, 1E21-1 CS-1 OA-7, also has a low probability of cracking. Category C welds are considered susceptible to IGSCC but have been mitigated by stress improvement after more than two cycles of operation. The licensee stated that each austenitic piping weld was stress improved using either the induction heating stress improvement (IHSl) or the mechanical stress improvement {MSIP) and that the nine piping welds were examined to the maximum extent practical with no unacceptable indications recorded.
Furthermore, the licensee stated that VT-2 visual examinations on the subject welds are performed each refueling outage and operational leakage can be determined by the LDS located in the drywell.
NRC Staff Evaluation
The design and configuration of each weld and adjacent components were the predominant limitations that prevented the licensee's UT from achieving essentially 100 percent coverage of the ASME BPV Code-required volumes. The NRC staff reviewed the limitations and obstructions in each of the descriptions and figures and finds that achieving essentially 100 percent coverage for each of the welds is impractical.
To increase the examination coverage for each of the welds, the licensee would need to replace the existing components with specially-designed components, resulting in a very substantial capital cost and extended outage time. Therefore, compliance with the ASME BPV Code requirements to perform the required examinations would place a burden on the licensee.
The NRC staff considered whether the licensee's proposed alternatives provided reasonable assurance of structural integrity and leak tightness of the subject weld based on: (1) the examination coverage achieved and (2) safety significance of unexamined volumes (e.g., the presence or absence of known active degradation mechanisms and essentially 100 percent coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
The licensee stated that approximately 50 to 75 percent coverage was obtained for each of the welds. In evaluating the licensee's proposed alternative, the NRC staff assessed whether the licensee obtained the maximum coverage achievable The NRC staff reviewed the submittal and found that
- The weld was examined using the appropriate equipment, ultrasonic modes of propagation, probe angles, frequencies, and scanning directions to obtain maximum coverage;
- The UT procedures used were qualified as required by regulation; and
- The coverage was limited by physical access.
Therefore, the NRC staff found that the licensee made every effort to obtain maximum coverage with the ASME BPV Code-required UT.
In addition to the coverage analysis, the NRC staff evaluated the safety significance of the unexamined volumes of weld. From a review of the submittal, the NRC staff found that:
- Eight of the subject welds are austenitic and one weld is ferritic.
- Each of the eight austenitic welds was stress improved by either IHSI or MSIP to mitigate their susceptibility to IGSCC.
- Consistent with NUREG-0313, ferritic welds are considered to be resistant to sensitization and IGSCC.
Additionally, the subject welds undergo a VT-2 visual examination each refueling outage as part of the leakage test, and during operation, leakage can be determined by the LDS located in the dryweU. These additional examinations, the coverage obtained with no relevant indications identified, the stress improvements performed on each of the austenitic welds, and the resistance of the materials to IGSCC provide reasonable assurance of structural integrity and leak tightness of the subject welds.
Based on the above, the NRC staff concludes that the ASME BPV Code requirement is impractical, the imposition of the ASME BPV Code required inspections would result in a burden to the licensee, and the licensee's examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds.
3.5 ISl-RR-23 (HNP, Units 1 and 2)
ASME Code Component Identification ASME Code Class ASME Code Class 2 Examination Category: C-F-2 Item Number: C5.51 Component: Circumferential Pressure Retaining Welds in Carbon or Low Alloy Steel Piping We!d Numbers: 1E11-2RHR-1 OB-SWDS-4; 1E21-2CS-16A-TS-2; 2E11-2RHR-6B-TSP-5; 2E41-2HPCl-16-TS-18
ASME Code Requirements The examination requirements for circumferential pressure retaining welds in carbon or low alloy steel piping are surface and volumetric examinations of 100 percent of the weld, as described in Table IWC-2500-1, Item C5.51 and Figure IWC-2500-7 Code Case N-460, which was approved for use by the NRC in RG 1 147, Revision 17, states that a reduction in examination coverage due to interference by another component or part geometry for any ASME Class 1 or 2 weld is acceptable provided that the reduction is less than 10 percent {i e., greater than 90 percent examination coverage is obtained). In addition, RG 1.147, Revision 17, also approved Code Case N-663, which states that in lieu of the surface examination requirements for piping welds of Examination Category ... B-J (NPS 4 and larger) .. surface examinations may be limited to areas identified by the Owner as susceptible to outside surface attack.
Susceptibility to outside surface attack is determined using Table 1 in ASME Code Case N-663.
Licensee's Relief Request For the subject welds, the licensee achieved composite Code coverages between 70 percent and 85.7 percent and is requesting relief from ASME, Section XI, Table IWC-2500-1, Item C5.51, which requires 100 percent surface and volumetric examinations for circumferential pressure retaining welds in carbon or low alloy steel piping.
Burden Caused by Compliance The licensee stated that increasing the coverage would require the redesign of these welds and components to allow access Licensee's Basis for Relief The licensee stated that a volumetric examination was performed on these welds with results as noted on the attached tables in the licensee's submittal. In addition, VT-2 visual examinations associated with the Class 2 leakage test are performed each inspection period for these welds.
NRC Staff Evaluation
The design and configuration of the welded components (i.e., obstructions due to welded attachment, torus, and restraint) were the predominant limitations that prevented the licensee's UT from achieving essentially 100 percent coverage of the ASME BPV Code-required volume.
Therefore, the NRC staff finds that achieving essentially 100 percent coverage is impractical.
To increase the examination coverage of the welds, the licensee would need to redesign the welds and components to allow access, resulting in a very substantial capital cost and extended outage time. Therefore, compliance with the ASME BPV Code requirements to perform the required examinations would place a burden on the licensee.
The NRC staff considered whether the licensee's proposed alternatives provided reasonable assurance of structural integrity and leak tightness of the subject weld based on: (1) the
examination coverage achieved and (2) safety significance of unexamined volumes (e.g., the presence or absence of known active degradation mechanisms and essentially 100 percent coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
The licensee stated that composite coverages of approximately 85.7 percent. 70 percent, 78.9 percent, and 80 percent were achieved for welds 1E11-2RHR-10B-SWDS-4; 1E21-2CS-16A-TS-2; 2E11-2RHR-6B-TSP-5; and 2E41-2HPCl-16-TS-18, respectively In evaluating the licensee's proposed alternative, the NRC staff assessed whether it appeared that the licensee obtained the maximum coverage achievable. The NRG staff reviewed the submittal and found that:
- The licensee performed an N-663 evaluation using Table 1 and determined that neither HNP unit had locations that were susceptible to outside surface attack. Therefore, surface examinations of the subject welds were not required and the licensee performed only volumetric examinations.
- The weld was examined using the appropriate equipment, ultrasonic modes of propagation, probe angles, frequencies, and scanning directions to obtain maximum coverage.
- The UT procedures used were qualified as required by regulation.
- The coverage was limited by physical access (i.e., the configurations of the components did not permit access for scanning).
- No unacceptable indications were identified.
Therefore, the NRG staff finds that the licensee made every effort to obtain as much coverage as reasonably possible with the ASME BPV Code-required UT.
The NRG staff also evaluated the safety significance of the unexamined volumes of weld.
The NRG staff reviewed the submittal and found that:
- The components subject to Relief Request ISl-RR-23 are made of carbon or low alloy steel and joined with ferritic welds.
- Consistent with NUREG-0313, carbon steels, low alloy steels. and ferritic welds are considered to be resistant to sensitization and IGSCC.
Additionally, the licensee stated in the submittal that VT-2 examinations associated with the Class 1 leakage test will be performed each refueling outage and that operational leakage can be determined by the LDS located in the drywell. These additional examinations, the coverage obtained with no relevant indications identified, and the resistance of the materials to sensitization and IGSCC provide reasonable assurance of structural integrity and leak tightness of the subject weld.
Based on the above, the NRC staff concludes that the ASME BPV Code requirement is impractical, the imposition of the ASME BPV Code required inspections would result in a burden to the licensee, and the licensee's examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject welds.
3.6 ISl-RR-24 (HNP, Unit 2)
ASME Code Component Identification ASME Code Class ASME Code Class 2 Examination Category: C-G Item Number: C6.10 Component: Core Spray Circumferential Pump A Outlet Nozzle Elbow to Flange Weld Weld Number. 2E21-2CS-POP-A-2 ASME Code Requirements The examination requirements for pump casing welds is 100 percent surface examinations of welds in all components as described in Table IWC-2500-1, Item C6.10 and Figure IWC-2500-8.
In the case of multiple pumps or valves of similar design, size, function, and service in a system, required weld examinations may be limited to all the welds in one pump or one valve in the same group or distributed among any of the pumps or valves of that same group. The examination may be performed from either the inside or outside surface of the component.
Code Case N-460, which was approved for use by the NRC in RG 1.147, Revision 17, states that a reduction in examination coverage due to interference by another component or part geometry for any ASME Class 1 or Class 2 weld is acceptable provided that the reduction is less than 1O percent (i.e., greater than 90 percent examination coverage is obtained).
Licensee's Relief Request For the subject welds, the licensee calculated a surface examination coverage of approximately 50 percent. Coverage was limited due to the proximity of the support structure for the pump motor to the weld and the flange bolting on the pump casing. The licensee is requesting relief from ASME BPV Code, Section XI, Table IWC-2500-1, Item C6.10, which requires 100 percent surface examinations for pump casing welds.
Burden Caused by Compliance The licensee stated that increasing the surface examination coverage would require a redesign of the pump flange and pump motor support and room to allow for additional space around the weld.
Licensee's Basis for Relief The licensee stated that in addition to the surface testing achieved, VT-2 examinations are performed on the subject weld every outage and leakage testing every ISi period.
NRC Staff Evaluation
The proximity of the support structure for the pump motor to the weld and the flange bolting on the pump casing were the predominant limitations that prevented the licensee's UT from achieving essentially 100 percent coverage of the ASME BPV Code-required volume.
Therefore, the NRG staff finds that achieving essentially 100 percent coverage is impractical.
Increasing the examination coverage would require a redesign of the pump flange and pump motor support, resulting in a very substantial capital cost and extended outage time. Therefore, compliance with the ASME BPV Code requirements to perform the required examinations would place a burden on the licensee.
The NRG staff considered whether the licensee's proposed alternative provided reasonable assurance of structural integrity and leak tightness of the subject weld based on: (1) the examination coverage achieved and (2) safety significance of unexamined volumes (e.g., the presence or absence of known active degradation mechanisms and essentially 100 percent coverage achieved for similar welds in similar environments subject to similar degradation mechanisms).
The licensee stated that approximately 50 percent coverage was obtained for this examination.
In evaluating the licensee's proposed alternative, the NRC staff assessed whether it appeared that the licensee obtained the maximum coverage achievable. The NRC staff has reviewed the information provided and determined that the licensee made every effort to obtain maximum coverage.
The NRC staff evaluated the safety significance of the unexamined volumes of weld. The nozzle elbow is SA-234 {carbon steel), the weld is likely E7018 (tow carbon steel) or similar, and the flange is SA-350 (carbon steel). Consistent with NUREG-0313, these materials are considered to be resistant to sensitization and IGSCC.
Additionally, the licensee stated in the submittal that leakage tests are performed each refueling outage. The purpose of the surface examinations is to identify cracks that penetrate through the thickness of the welded component. These cracks would also be detected by the leakage tests performed by the licensee. The leakage tests, the coverage obtained with no relevant indications identified, and the resistance of the materials to sensitization and IGSCC provide reasonable assurance of structural integrity and leak tightness of the subject weld.
Based on the above, the NRC staff concludes that the ASME BPV Code requirement is impractical, the imposition of the ASME BPV Code required inspections would result in a burden to the licensee, and the licensee's examination coverage provides reasonable assurance of structural integrity and leak tightness of the subject weld
4.0 CONCLUSION
As set forth above for Relief Requests ISl-RR-13, ISl-RR-14, ISl-RR-18, ISl-RR-19, ISl-RR-23, and ISl-RR-24, the NRC staff finds that it is impractical for the licensee to comply with the ASME BPV Code, Section XI, requirements, the proposed inspection provides reasonable assurance of structural integrity and leak tightness of the subject welds, and granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were
imposed on the facility. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants relief requests for ISl-RR-13, ISl-RR-14, ISl-RR-18, ISl-RR-19, ISl-RR-23, and ISl-RR-24 for HNP, Units 1 and 2, for the fourth 10-year ISi Interval, which commenced on January 1, 2006, and ended on December31, 2015.
All other ASME BPV Code, Section XI, requirements for which relief was not specifically requested and authorized herein by the NRG staff remain applicable, including third-party review by the Authorized Nuclear lnservice Inspector.
Principal Contributor: Alan Huynh, NRR Date: October 26, 2017
. ML17279A045 OFFICE NRR/DORULPL2-1/PM NRR/DORULPL2-1/PM NRR/DORULPL2-1/LA NAME MOrenak RH all KGoldstein IPBlechman forl DATE 10/16/17 10/25/17 10/16/17 OFFICE NRR/DE/EPNB/BC* NRR/DORULPL2-1/BC NAME DAllev MMarklev DATE 9127117 10/26/17