ML20217B883
| ML20217B883 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 03/24/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20217B882 | List: |
| References | |
| NUDOCS 9803260205 | |
| Download: ML20217B883 (24) | |
Text
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k UNITED STATES g
j NUCLEAR REGULATORY COMMISSION
- %...../g WASHINGTON, D.C. 3000Nm01 SAFETY EVALUATION BY THE OFFICE OF NUCI FAR REACTOR REGULATION OF THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN REQUESTS FOR RFI IEF NOS. RR-5. RR-19. RR-20. RR-21 RR-23. AND RR-24 VOGTLE Fl FCTRIC GENERATING PLANT. UNITS 1 AND 2 SOUTHERN NUCLEAR OPERATING COMPANY. INC.
DOCKET NOS. 50-424 AND 50-425
1.0 INTRODUCTION
The Technical Specifications (TS) for the Vogtle Electric Generating Plant (VEGP), Units 1 and 2, state that the inservice inspection of the American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (ASME Code) and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i) until the Code Case is published in a future revision of Regulatory Guide 1.147. Section 50.55a(s)(3) states that attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed attematives 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.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-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 edition of Section XI of the ASME Code for the VEGP, Units 1 and 2, second 10-year inservice inspection (ISI) interval is the 1989 Edition.
Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a I
1 9903260205 900324 PDR ADOCK 05000424 G
r request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose altomative requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are 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.
By letter dated May 29,1997, Southem Nuclear Operating Company, Inc. (licensee), submitted attematives to the ASME Code,Section XI regarding its Second 10-Year interval ISI Program Plan Requests for Relief Nos. RR-5, RR-19, RR-20, RR-21, RR-22, RR-23, and RR-24 for VEGP, Units 1 and 2. The licensee provided additionalinformation in its letter dated January 29,1998, and revised Request for Relief No. RR-22 in a second letter dated January 29,1998. The licensee requested that the staff review the attematives required for its up-coming Unit 2 outage contained in Requests for Relief Nos. RR-5, RR 19, RR-20, RR-21, j
RR-22, RR-23, and RR-24.
j 2.0 EVALUATION The staff, with technical assistance from its contractor, the Idaho National Engineering and
- Environmental Laboratory (INEEL), has evaluated the information provided by the licensee in support of its Second 10-Year Interval Inservice Inspection (ISI) Program Plan Requests for Relief Nos. RR-5, RR-19, RR-20, RR-21, RR-22, RR-23, and RR-24 for VEGP, Units 1 and 2.
Based on the results of this review, the staff adopts the contractor's conclusions and i
recommendations presented in the Technical Letter Report (TLR) (attached).
I Request for Relief No. RR-5: ASME Code,Section XI, Examination Category B-G-1, item B6.10 requires 100% surface examination of the reactor pressure vessel (RPV) closure head nuts. In accordance with 10 CFR 50.55a(s)(3)(i), the licensee proposed to perform a VT-1 visual examination of the RPV closure head nuts in lieu of the Code-required surface examination. The licensee stated:
i l
in lieu of the 1989 Edition, Code-required surface examination, the subject RPV Closure Head Nuts will receive a VT-1 visual examination.
The staffs review of the examination requirements for Examination Category B-G-1, indicates that with the exception of the RPV closure head nuts and the closure studs (when removed), all other items in this examination category require VT-1 visual examinations or volumetric examinations (as applicable). Typical relevant conditions that would require corrective action prior to putting closure head nuts back into service would include corrosion, deformed or sheared threads, deformation, and degradation mechanisms (i.e., boric acid attack). Surface 0
examination procedures are typically qualified for the detection of linear type flaws (cracks) with corresponding acceptance criteria for rejectable linear flaw lengths only. When performing surface examinations in accordance with the 1989 Edition of the Code, item B6.10, the surface examination acceptance criteria are not provided, as it was in the course of preparation.
Without clearly defined acceptance criteria, relevant conditions that require corrective measures may not be adequately addressed.
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t l The 1989 Addenda of Section XI, Article IWB-3000, Acceptance Standards, IWB-3517.1, Visual Examination, VT-1, describes relevant conditions that require corrective action prior to continued service of bolting and associated nuts. Included for corrective action in IWB 3517.1, is the requirement to compare crack-like flaws to the flaw standards of IWB-3515 for acceptance. Surface examination acceptance criteria are typically limited to linear type flaws (i.e., cracking, aligned pitting, and corrosion). Because the VT-1 visual examination acceptance criteria include the requirement for evaluation of crack-like indications and other relevant conditions requiring corrective action such as deformed or sheared threads, localized corrosion, deformation of part, and other degradation mechanisms, it is concluded that the VT-1 visual l
examination provides a more comprehensive assessment of the condition of the closure head l
nut and provides assurance of structuralintegrity l
Therefore, the staff concludes that the licensee's proposed attemative VT-1 visual examination provides an acceptable level of quality and safety. In addition, the 1989 Addenda of Section XI changes the requirement for the subject RPV closure head nuts from surface examination to VT-1 visual examination and provides appropriate acceptance criteria. Therefore, the licensee's proposed attemative contained in Request for Relief No. RR-5 is authorized pursuant J
i Request for Relief No. RR-19: ASME Code,Section XI, Examination Category C-F-1, items l
C5.12 and C5.22 and Examination Category C-F-2, items C5.52 and C5.62 require surface and l
volumetric examination as defined by Figure IWC-2500-7. Items C5.42 and C5.82 require surface examination. Longitudinal piping welds require examination for 2.5T from intersecting circumferential welds. In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-524, "Altemative Examination Requirements for Longitudinal Welds in l
Class 1 and 2 Piping,Section XI, Division 1," for Class 2 piping systems as an alternative to the Code requirements.
Although Code Case N-524 applies to both Class 1 and 2 systems, the licensee requested that this attemative only apply to Class 2 systems. ASME Code Section XI requires the examination of longitudinal welds for the langth of 2.5 times the pipe thickness for Class 2 piping welds.
These lengths are measured from the intersection with the circumferential weld. The licensee's l
proposed attemative is to examine only the portions of the longitudinal weld contained within the examination area of the intersecting circumferential weld. This attemative is contained in Code t
Case N-524, which has previously been found acceptable for use at other facilities.
Longitudinal welds are produced during the manufacture of the piping, not in the field as circumferential welds are. Consequently, the welds are fabricated under the strict guidelines specified by the manufacturing standard, which provides assurance of structural integrity.
These welds have also been subjected to the preservice and initial inservice examinations, which provide additional assurance of structural integrity. No significant loading conditions or material degradation mechanisms have become evident to date that specifically relate to longitudinal seam welds in nuclear plant piping. The most critical region of the longitudinal weld is the portion that intersects the circumferential weld. The staff concluded that since this region
, will be eF8 mined during the examination of the circumferential weld, the licensee's attemative provides an acceptable level of quality and safety in that it provides assurance of structural integrity.
Therefsre, the licensee's proposed attemative to use Code Case N-524 for Class 2 systems buntained in Request for Relief No. RR-19 !s authorized pursuant to 10 CFR 50.55a(a)(3)(i).
The use of Code Case N-524 is authorized for Class 2 systems only for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1.147.
At that time, if the licensee continues to implement Code Case N-524, the licensee should follow all provisions in the Code Case, with conditions specified in Regulatory Guide 1.147.
Request for Relief No. RR-20; Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-509 in lieu of the volumetric, surface, or visual examinations of Class 1,2, and 3 integrally welded attachments as required by the Code. By letter dated January 29, 1998, the licensee committed to examine a minimum of 10% of the integrally welded attachments in each piping, pump, and valve item number listed in Code Case N-509, Table IWA-2500-1. These examinations will be distributed among the nonexempt integrally welded attachments in each Class 1,2, and 3 piping systems.
Code Case N-509 provides attemative sampling requirements for the examination of Class 1, 2, and 3 integral attachments. The licensee's attemative, as supplemented, includes use of the Code Case with a minimum examination sample of 10% of integral attachments distributed among all nonexempt Class 1,2, and 3 systems and components. The staff concluded that most of the Code examination requirements are based on sampling to ensure the detection of service-induced degradation, extending the sampling philosophy to the integral attachment welds, thus, the licensee's proposed attemative to use the provisions of Code Case N-509
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' provides assurance of structural integrity and thus, an equivalent level of quality and safety for these components. Therefore, the licensee's proposed attemative is authorized pursuant to 10 CFR 50.55a(s)(3)(i). The use of Code Case N-509 is authorized for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1.147.
At that time, if the licensee intends to continue to implement this Code Case, the licensee should follow all provisions in Code Case N-509, with limitations issued in Regulatory Guide 1.147,if any.
Request for Relief No. RR-21: The licensee, pursuant to 10 CFR 50.55a(s)(3)(i), proposed an altemative to the 1989 Edition to use the exemption criteria found in IWC-1222 of the 1989 Addenda of the 1989 Edition of ASME Code Section XI for components within systems other than the Residual Heat Removal, Emergency Core Cooling, and Containment Heat Removal systems. These addenda do not require surface'and volumetric examinations of vessels and their connections in piping 4-inch nominal pipe size (NPS) and smaller for Examination Category C-A, items C1.10, C1.20, and C1.30 (Pressure-Retaining Welds in Vessels) and Examination Category C-C, item C3.10 (Integrally Welded Attachments to Pressure Vessels).
Relief is specifically requested for the following components:
i 5-Regenerative Heat Exchanger (Tag No. 2-1208-E6-001)
Excess Letdown Heat Exchanger (Tag No. 2-1208-E6-002)
Letdown Heat Exchanger (Tag No. 2-1208-E6-003)
Letdown Reheat Heat Exchanger (Tag No. 2-1208-E6-007)
Discharge Dampener (Tag No. 2-1208-V4-002)
I The licensee has requested to use the exemption criteria of IWC-1222 of the 1989 Addenda in lieu of the exemption requirements of the Code of record. In accordar2ce with the 1989 Code, piping NPS 4 and smaller is exempt from examination, but connected components are not. In
' the 1989 Addenda of Section XI, IWC-1222 was revised to exempt vessels, pumps, and valves, and their connections in piping NPS 4 and smaller, with the following note. "In piping is defined as having a cumulative inlet and a cumulative outlet pipe cross-sectional area neither of which exceeds the nominal OD cross-sectional area of the designated size." This exemption is also contained in Code Case N-406-2, Attemative Ruiu for Examination of Class 2 Piping,Section XI, Division 1, which has been approved for general use in Revision 11 of Regulatory Guide 1.147.
The change in the Code described above parallels the logic used for the exemption of Class 1 systems. Specifically, IWB-1220(b)(2) exempts " components and their connections in piping in 1-inch nominai pipe size and smaller," where "in piping"is defined as having one inlet and one outlet pipe, each of which is 1-inch NPS or smaller. The discrepancy between Class 1 and Class 2 systems was recognized by the Code committee, which pattemed the exemption i
criteria for Class 2 in the 1989 Addenda after existing exemption requirements for Class 1 systems.
The staff has concluded that the licensee's attemative, to use the exemption criteria of the 1989 Addenda for the above specified Class 2 systems, provides an acceptable level of quality and safety in that it provides assurance of structuralintegrity. The approach used for the Class 2 exemption criteria found in the 1989 Addenda is similar to that used for exemption of Class 1 systems. In addition, the criteria has been approved by the NRC as part of Code Case N-408-2.
Therefore, the licensee's proposed attemative contained in Re quest for Relief No. RR-21 is i
authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Request for Relief No. RR-22: Pursuant to 10 CFR 50.55a(s)(3)(i), the licensee proposed to use Code Case N-544, Repair and Replacement of Small items, Secton XI, Division 1, in lieu of the repair and replacement requirements of the Code. The licensee proposed that it will comply with the requirements of Code Case N-544 in lieu of IWA-4000 and IWA-7000 except that the subject Code Case will not be applicable to heat exchanger tubing, s"eeves, and welded plugs used for heat exchanger tubes in Class 1, 2, and 3 heat exchangers, including similar steam generator-related components.
The Code requires that repairs and replacements be performed in accordance with IWA-4000 and lWA-7000, respectively. Pursuant to IWA-7400, piping, valves, and fittings NPS 1-inch and smaller are exempt from the requirements of Article IWA-7000. However, Article IWA-4000 has no exemption criteria. >r components NPS 1-inch and smaller. Therefore, som-s licensees may 4
g
, choose to replace rather than repair items to avoid the repair requirements of lWA-4000. In lieu of the repair and replacement requirements of the Code, the licensee proposed to use Code Case N-544.
In accordance with Code Case N-544, piping, valves, and fittings NPS 1-inch and smaller, except for heat exchanger tubing, and sleeves and welded plugs used for heat exchanger tubing, are exempt from both repair and replacement requirements of the Code. The exemption criteria used by the Code Case for items NPS 1-inch and smaller are equivalent to existing Code requirements for the replacement of similar items. Code Case N-544 provides an acceptable level of quality and safety with one exception as noted below.
ASME Code Section XI differentiates between steam generators and heat exchangers by providing separate item numbers. As currently written, Code Case N-544 does not address steam generator tubing, only heat exchanger tubing. Therefore, it appears that steam generator tubing could be exempted from repair and replacement requirements by the Code Case. To address this uncertainty, the licensee has stated that steam generator tubing and similar steam generator-related components will not be included in the scope of this Code Case.
Therefore, the staff concludes that Code Case N-544 with the licensee's revision as noted absve provides an acceptable level of quality and safety in that it provides assurance of structuralintegrity. Therefore, the licensee's proposed attemative contained in Request for Relief No. RR-22, with the clarification provided above, is authorized pursuant to 10 CFR 50.55a(a)(3)(i). The use of the Code Case is authorized for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, if the licensee intends to continue to implement this Code Case, the licensee should follow all provisions in Code Case N-544, with limitations issued in Regulatory Guide 1.147, if any.
Request for Relief No. RR-23: Pursuant to 10 CFR 50.55a(a)(3)(ii), the licensee has requested authorization to use Code Case N-498-1, Altemate Rules for 10-Year Hydrostatic Pressure Testing for Class 1,2, and 3 Systems,Section XI, Division 1. Code Case N-498-1 requires that a VT-2 visual examination be performed in conjunction with system pressure test at nominal operating pressure. Table IWB-2500-1, Examination Category B-P, Table IWC-2500-1, Examination Category C-H, and Table IWD-2500-1, Examination Categories D-A, D-B, and D-C, require system hydrostatic testing of pressure-retaining components in accordance with IWA-5000 once each 10-year interval.
Considering the minimal amount of increased assurance provided by the increased pressure associated with a hydrostatic test versus the pressure for the syst1m leakage test and the hardship associated with performing the hydrostatic test, the staff concludes that compliance with the Section XI hydrostatic testing requirements results in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, the altemative contained in Request for Relief No. RR-23 to use Code Case N-498-1 for Code Class 1,2, and 3 systems is authorized pursuant to 10 CFR 50.55a(a)(3)(ii). The use of this Code Case is
. authorized for the current interval at VEGP, Units 1 and 2, or until the Code Case is approved for general use by reference in Regulatory Guide 1.147. After that time, the licensee must follow the conditions, if any, specified in the regulatory guide.
Request for Relief No. RR-24: Pursuant to 10 CFR 50.55a(s)(3)(ii), the licensee has proposed to use Code Case N-416-1, Altemative Pressure Test Requirements for Welded Repairs or Installation of Replacement items by Welding,Section XI, Division 1. In addition, the licensee proposed to perform surface examinations on the root pass layer of butt and socket welds on the pressure-retaining boundary of Class 3 piping and components.
Section XI of the Code requires a system hydrostatic test to be performed in accordance with IWA-5000 after repairs made by welding on the pressure-retaining boundary. The licensee has proposed the use of Code Case N-416-1 in lieu of the Code requirements. Code Case N 416-1 specifies that NDE of the welds be performed in accordance with the applicable subsection of the 1992 Edition of Section Ill. The Code Case also allows a VT-2 visual examination to be performed at nominal operating pressure and temperature in conjunction with a system leakage test, in accordance with Paragraph IWA-5000 of the 1992 Edition of Section XI.
The staff has determined that nondestructive examination (NDE) performed on Code Class 1 and 2 systems and that hydrostatic pressure tests rarely result in pressure boundary leaks that would not have occurred during system leakage tests. The staff concluded that the added assurance of integrity provided by the hydrostatic test is not commensurate with the associated burden, which typically includes the installation of blanks, cutting and removing supports for access, and removing insulation to prepare and restore the systems, all of which increase radiation exposure for plant personnel.
For Class 3 components, there are no ongoing NDE requirements except for the visual examination for leaks in conjunction with the 10-year hydrostatic test and periodic pressure tests. Therefore, eliminating the hydrostatic test and only performing the system pressure test for Class 3 components is only considered acceptable if an additional surface examination is performed on the root pass layer of butt and socket welds on the pressure-retaining boundary during repair and replacement activities. The licensee has included this revision to Code Case N-416 in its proposed alternative. With this revision, the licensee's proposed attemative provides reasonable assurance of structuralintegrity of the subject Class 3 components.
The staff concluded that compliance with the Code-required hydrostatic testing for welded repairs or replacements of Code Class 1,2, and 3 components would result in hardship or unusual difficulty.without a compensating increase in the level of quality and safety.
Furthermore, the staff concluded that the licensee's proposed attemative provides reasonable assurance of structural integrity of the subject Class 1,2, and 3 components. Therefore, the proposed attemative use of Code Case N-416-1 contained in Request for Relief No. RR-24 is authorized pursuant to 10 CFR 50.55s(a)(3)(ii).
, The use of this Code Case is authorized for the current interval at VEGP, Units 1 and 2, or until the Code Case is approved for general use by reference in Regulatory Guide 1.147. After that time, the licensee may continue to use Code Case N-416-1 with the limitations, if any, listed in Regulatory Guide 1.147.
3.0 CONCLUSION
The staff has reviewed the licensee's submittals and concludes that for Requests for Relief Nos. RR-5, RR-19, RR-20, RR-21, and RR-22, the licensee's proposed attematives to the Code requirements provide an acceptable level of quality and safety. Therefore, the staff concludes that the licensee's proposed attematives contained in Requests for Relief Nos. RR-20, RR-21, and RR-22 are authorized pursuant to 10 CFR 50.55a(s)(3)(i).
For the altamatives contained in Requests for Relief Nos. RR-23 and RR-24, the staff concludes that the Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety, and that the licensee's proposed attematives provide reasonable assurance of structuralintegrity of the subject Class 1,2, and 3 components. Therefore, the licensee's proposed attematives contained in Requests for Relief 1
RR-23, and RR-24 are authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
As previously stated, use of the Code Cases N 544, N-498-1, N-4161, N-524, and N-509 are authorized for tne current interval or until such time as the Code Cases are approved for general use by reference in Regulatory Guide 1.147. After that time, the licensee may continue to use the Code Cases with the limitations, if any, listed in Regulatory Guide 1.147.
Attachment:
Technical Letter Report Principal Contributor: T. McLellan Date:
March 24, 1998 l
1 i
I
TECHNICAL LETTER REPORT ON THE SECOND.10-YEAR INTERVM INSERVICE INSPECTION REQUESTS FOR RELIEF l
EDE SOUTHERN NUCLEAR OPERATING COMPANY VOGTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2 DOCKET NUMBERS: 50424 AND 50425
1.0 INTRODUCTION
Submitted its second 10-year inservice inspection (ISI) program for Vogtle Electric Generating Plant (VEGP), Units 1 and 2. The licensee requested the expedited review of four requests for relief contained in the program (RR-5, RR-19 RR-20, RR-21, RR-23 and RR-24) for implementation in an upcoming outage. Additional information was provided in a letter dated January 29,1998, in response to a Nuclear Regulatory Commission (NRC) request for additionalinformation (RAI). In addition, the licensee submitted a revised version of Request for Relief RR-22, in a second letter dated January 29,1998. Request for Relief RR-22 was previously evaluated, but not authorized in an NRC Safety Evaluation Report dated October 24, 1997, due to concems regarding steam generator tubing and related components, which were not addressed by the Code Case. The Idaho National Engineering and Environmental Laboratory (INEEL) staff has evaluated the information provided by the licensee in support of these requests for relief in the following section.
2.0 EVALUATION The Code of record for the Vogtle Electric Generating Plant, Units 1 and 2, second 10-year inservice inspection intervalis the 1989 Edition of Section XI of the American Society of
)
Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. The information provided by the licensee in support of the requests for relief has been evaluated and the bases for disposition are documented below.
a.
Reauest for Relief No. RR-5 Examination Cateoorv B-G-1. Item B6.10. Reactor Pressure Vessel (RPV) Closure Head Nuts Code Reauirement: Examination Category B-G-1, item B6.10 requires 100% surface examination of RPV closure head nuts.
Licensee's Prooosed Alternative: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to perform a VT-1 visual examination of the RPV closure head nuts in lieu of the Code-required surface examination. The licensee stated:
"In lieu of the 1989 Edition, Code-required surface examination, the subject RPV Closure Head Nuts will receive a VT-1 visual examination."
Attachment
Licensee's Basis for Proposed Alternative (as stated):
" Table IWB-2500-1, Category B-G-1, item B6.10 of the 1989 Addenda to the 1989 Edition of ASME Section XI allows for a VT-1 Visual Examination in lieu of the surface examination required by the 1989 Code.
"The RPV closure head not configuration does not allow for an adequate magnetic particle (MT) examination. The MT method required two directional coverage to detect the surfsce j
flaws. The configuration permits examination in one direction and limits the coverage in the other direction.
"Section XI Code personnel in ISI Optimization performed a survey on bolting which revealed no service-induced cracking. This survey was then used as part of the technical basis for changing the Code-required examination for Category B-G-1, item B6.10. The 2
1989 Addenda and subsequent editions of ASME Section XI changed the examination requirement from a surface examination to a VT-1. Since the change (visual examination) was issued by ASME, the alternative examination should be technically acceptable for determining flaws. The proposed attemative visual examination, VT-1, will provide reasonable assurance the unallowable inservice flaws have not developed in the subject components or that they will be detected and repaired prior to retum of the reactor pressure vessel to service. If relevant indications are detected, attemate surface / volumetric techniques will be performed as necessary. Thus, an acceptable level of quality and safety will have been achieved and public health and safety will not be endangered by allowing the proposed alternative examination in lieu of the Code requirement. Therefore, this request for relief should be granted pursuant to the requirements of 10 CFR 50.55a(a)(3)(i)."
i Evaluation: The Code requires surface examination of the RPV closure head nuts. As an attemative to the Code requirements, the licensee proposed to perform a VT-1 visual examination of the RPV closure head nuts.
Review of the examination requirements for Examination Category B-G-1, indicates that with the exception of the reactor pressure vessel closure head nuts and the closure studs (when removed), all other items in this Examination Category require VT-1 visual examirations or volumetric examinations (as applicable). Typical relevant conditions that would require corrective action prior to putting closure head nuts back into service would include corrosion, deformed or sheared threads, deformation, and degradation mechanisms (i.e., boric acid attack). Surface examination procedures are typically qualified for the detection of linear type flaws (cracks) with corresponding acceptance criteria for rejectable linear flaw lengths only. When performing surface examinations in accordance with the 1989 Edition of the Code, Item B6.10, the surface examination acceptance criteria is not provided, as it was in the course of preparation. Without clearly defined acceptance criteria, relevant conditions that require corrective measures may not be adequately addressed.
2
The 1989 Addenda of Section XI, Article IWB-3000, Acceptance Standards, IWB-3517.1, Visual Examination, VT-1, describes relevant conditions that require corrective action prior to continued service of bolting and associated nuts. Included for corrective action in IWB-3517.1 is the requirenent to compare crack-like flaws to the flaw standards of IWB-3515 for acceptance. Surface examination acceptance criteria are typically limited to linear type flaws (i.e. cracking, aligned pitting and corrosion). Because the VT-1 visual examination acceptance criteria include the requirement for evaluation of crack-like indications and I
other relevant conditions requiring corrective action such as deformed or sheared threads, localized corrosion, deformation of part, and other degradation mechanisms, it is concluded that the VF-1 visual examination provides a more comprehensive assessment of the condition of the closure head nut. As a result, the INEEL staff believes that VT-1 visual examination provides an acceptable level of quality and safety. In addition, the 1989 Addenda of Section XI changes the requirement for the subject reactor pressure vessel closure head nuts from surface examination to VT-1 visual examination and provides appropriate acceptance criteria. Therefore, it is recommended that the proposed attemative VT-1 visual examination be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
b.
Reauest for Relief No.19. Use of Code Case N-524. Altemative Examination Reauirements for Lonaitudinal Welds in Class 1 and 2 Pioina. for Examination of Class 2 Pioina Welds I
Code Reauirement: Examination Category C-F-1, items C5.12 and C5.22 and Examination Category C-F-2, items C5.52 and C5.62 require surface and volumetric examination as defined by Figure IWC-2500-7. Items C5.42 and C5.82 require surface examination. Longitudinal piping welds require examination for 2.5T from intersecting circumferential welds.
i Licensee's Procosed Attemativo: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-524, Altemative Examination Requirements for Longitudinal Welds in Class 1 and 2 Piping,Section XI, Division 1, as an alternative to the Code requirements. The licensee stated:
"Southem Nuclear Operating Company will comply with the requirements of ASME Section XI, Code Case N-524 as follows:
l (a) When only a surface examination is required, examination of longitudinal piping welds is not required beyond those portions of the welds within the examination boundaries of the intersecting circumferential welds, and (b) When both surface and volumetric examination are required, examination of longitudinal piping welds is not required beyond those portions of the welds within the examination boundaries of intersecting circumferential welds provided the following requirements are met:
(1) Where longitudinal welds are specified and locations are known, examination requirements shall be met for both transverse and parallel flaws at the intersection of the welds and for that length of longitudinal weld withing the circumferential weld examination volume, and 3
(2) Where longitudinal welds are specified but locations are unknown, or the existence of longitudinal welds is uncertain, the examination requirements shall be met for both transverse and parallel flaws within the entire examination volume of intersecting circumferential welds."
l l
Licensee's Basis for Prooosed Altemative (as statedt
" Code Case N-524 which was approved August 9,1993 by ASME addresses the attemative requirements for surface and volumetric examination requirements of longitudinal piping welds. By implementing the provisions of this ASME Section XI code l
case, personnel radiation exposure, outage examination time, and costs can be significantly reduces at VEGP. A copy of Code Case N 524 is provided as Attachment 1' of this request for relief.
"The proposed attemative testing requirements have been evaluated by the ASME Code Committee and have been deemed acceptable for determining the pressuro boundary integrity of the affected components. The proposed attemative requirements, in accordance with the Code Case, will provide reasonable assurance that unallowable inservice flaws have not developed in the subject welds or that they will be detected and repaired prior to return of the reactor vessel to service. Thus, an acceptable level of quality and safety will have been achieved and public health and safety will no be endangered by allowing the proposed alternative examination in lieu of the Code requirements. Therefore, it is requested that the proposed attemative examinations be authorized pursuant to 10 CFR 50.55a(a)(3)(i)."
Evaluation: ASME Section XI requires the examination of longitudinal welds for the length of 2.5 times the pipe thickness for Class 2 piping welds. These lengths are measured from the intersection with the circumferential weld. The licensee's proposed alternative is to examine only the portions of longitudinal weld contained within the examination area of the intersecting circumferential weld. This alternative is contained in Code Case N-524, Altemative Examination Requirements for Longitudinal Welds in Class 1 and Class 2 Piping, which has previously been found acceptable for use at other facilities.
Longitudinal welds are produced during the manufacture of the piping, not in the field as circumferential welds are. Consequently, the welds are fabricated under the strict guidelines specified by the manufacturing standard, which provides assurance of structural integrity. These welds have also been subjected to the preservice and initial inservice examinations, which provide additional assurance of structural integrity. No significant loading conditions or material degradation mechanisms have become evident to date that specifically relate to longitudinal seam welds in nuclear plant piping. The most critical region of the longitudinal weld is the portion that intersects the circumferential weld. Since this region will be examined during the examination of the circumferential weld, the licensee's alternative provides an acceptable level of quality and safety. Therefore, in accordance with 10 CFR 50.55a(a)(3)(i), it is recommended that the licensee's proposal to implement Ccde Case N-524 be authorized. The use of the Code Case should be Licensee's attachment not included in this report.
4
authorized for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, if the licensee continues to implement this Code Case, the licensee should follow all provisions in Code Case N-524, with conditions specified in the Regulatory Guide, c.
Reauest for Relief No. RR-20. Use of Code Case N-509. Altemative Rules for the Selection and Examination of Class 1. 2. and 3 Intearallv-Welded Attachments.Section XI. Division 1 Code Reauirement The Code requires examination of integrally-welded attachments as
]
specified for Examination Categories B-H, B-K, C-C, D-A, D-B, and D-C. The Code stipulates volumetric or surface examinations, as appropriate, and the extent of examinations.
Licensee's Proposed Attemative: Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee proposes to use Code Case N-509 in lieu of the volumetric, surface, or visual examinations of Class 1,2, and 3 integrally-welded attachments as required by the Code. By letter dated January 29,1998, the licensee committed to examine a minimum of 10% of the integrally welded attachments in each piping, pump, and valve item number listed in Code Case N 509, Table IWA-2500-1. These examinations will be distributed among the non-exempt integrally welded attachments in each Class 1,2, and 3 piping system.. The licensee stated:
"SNC proposes that the following examinations be performed in lieu of the Code-required volumetric, surface, or visual examination on those integrally welded attachments required by Table IWB-2500-1, lWC-2500-1, or IWD-2500-1 in the 1983 Edition, Summer 1983 Addenda of ASME Section XI:
" Surface Examinations:
"Those integrally welded attachments as specifically noted in ASME Code Case N-509, i
"ASME Examination Category B-K, Integral Attachments for Class 1 Vessels, Piping, Pumps and Valves, and "ASME Examination Category C-C, Integral Attachments for Class 2 Vessels, Piping, Pumps, and Valves.
" Visual Examinations:
"ASME Examination Category D-A, Integral Attachments for Class 3 Vessels, Piping, Pumps and Valves."
Licensee's Basis for Reauestino Relief (as stated):
"On November 25,1992, ASME issued Code Case N-509 (copy provided as Attachment 1 to this request for relief): which approved a set of attemative rules for the selection and examination of Class 1,2, and 3 Integrally Welded Attachments,Section XI, Division 1.
This Code Case has not been formally endorsed by inclusion in NRC Regulatory Guide included in licensee's submittal, but not in this report.
5
1 1.147 but has been euthorized by the NRC for use previously at VEGP and other plants.
ASME Section XI Code Case N-509 was approved by the NRC for use at VEGP during the l
First Ten-Year Interval as addressed in NRC correspondence dated March 8,1996 and August 13,1996 for VEGP-1 and 2, respectively. (
Reference:
First Ten-Year interval Requests for Relief RR-61 for VEGP-1 and 2.)
l Code Case N-509 provides an attemative sampling which will retain an acceptable level of quality and safety for Class 1,2, and 3 integrally welded attachments. Since approval was granted by ASME, the attemative requirements should be technically acceptable for determining flaws and authorized pursuant to 10 CFR 50.55a(s)(3)(i) provided a minimum of 10% of the total number of integral attachments in all Class 1,2, and 3 systems are examined. A VEGP-1 study was performed previously that compared the number of integrally welded attachment examinations required under the present ASME Section XI scope (based on the requirements of the 1983 Edition of ASME Section XI with Summer 1983 Addenda which was the code of reference for the First Ten-Year Interval) versus the number of integrally welded attachment examinations required under ASME Code Case N-509. The study shown in Attachment 2 [shown below] to the request for relief, and indicated that at least 10% of the present ASME Section XI integrally Welded Attachment scope for piping will be examined when ASME Code Case N-509 is implemented. Since Units 1 and 2 are similar at VEGP, the results of the VEGP-1 study will be typical for VEGP-2. By implementing the attemative examinations, cost savings, personal radiation dose, and outags time can be realized by SNC for VEGP-1 and 2."
VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 (TYPICAL FOR UNIT 2)
ASME CODE CASE N-509 STUDY l
Scope Class 1 Class 2 Class 3 Total Present 0
103 329 432
-N-509 0
9 37 46 Exams Saved 0
94 292 386 i
Evaluation: The licensee proposed to apply the requirements of Code Case N-509 in lieu of the Code requirements for the examination of integrally-welded attachments on Class 1, 2, and 3 piping and components Code Case N-509 provides alternative sampling l
requirements for the examination of Class 1,2, and 3 integral attachments. The licensee l
also committed to supplement the Code Case with a minimum examination sample of 10%
l of integral attachments distributed among all non-exempt Class 1,2, and 3 systems and components. Considering that most of the Code examination requirements are based on sampling to ensure the detection of service-induced degradation, extending the sampling philosophy to the integral attachment welds will provide an equivalent level of quality and safety for these components. Therefore, it is recommended that the licensee's proposed attemative be authorized pursuant to 10 CFR 50.55a(a)(3)(i). The use of the Code Case should be authorized for the current interval or until such time as the Code Case is
]
6
T e
published in a future revision of Regulatory Guide 1.147. At that time, if the licensee intends to continue to implement this Code Case, the licensee should follow all provisions L
in Code Case N-509, with limitations issued in Regulatory Guide 1.147, if any.
i d.
Reauest for Relief No. RR-21. lWC-1220. Class 2 Comoonents Exemot from Examination Code Reauirement: IWC-1220, Components Exempt from Examination, contains the exemption criteria for Class 2 components. lWC-1222 contains the requirements for 1
components within systems other than the Residual Heat Removal (RHR), Emergency Core Cooling (ECC), and Containment Heat Removal (CHR) systems. In accordance with IWC-1222, components exempt from the surface and volumetric examination requirements of IWC-2500 are as follows:
(a) Vessels, piping, pumps, valves, and other components NPS 4 and smaller.
(b) Component connections NPS 4 and smaller (including nozzles, socket fittings, and other connections) in vessels, piping, pumps, valves, and other components of any size.
(c)
Vessels, piping, pumps, valves, and other components of any size in systems or portions of systems that operate (when the system function is required) at a pressure equal to or less than 275 psig and at a temperature equal to or less than 200*F.
(d) Piping and other components of any size beyond the last shutoff valve in open ended portions of systems that do not contain water during normal plant operating conditions.
Licensee's Prooosed Alternative: Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee has proposed to use the exemption criteria found in IWC-1222 of the 1989 Addenda of the 1989 Edition of ASME Section XI for components within systems other than the RHR, ECC, and CHR systems. This Addenda does not require surface and volumetric examinations of vessels and their connections in piping 4-inch nominal pipe size (NPS) and smaller for Examination Category C-A, items C1.10, C1.20, and C1.30 (Pressure-Retaining Welds in Vessels) and Examination Category C-C, Item C3.10 (integrally Welded Attachments to Pressure Vessels). Relief is specifically requested for the following components:
Regenerative Heat Exchanger (Tag No. 2-1208-E6-001)
Excess Letdown Heat Exchanger (Tag No. 2-1208-E6-002)
Letdown Heat Exchanger (Tag No. 2-1208-E6-003)
Letdown Reheat Heat Exchanger (Tag No. 2-1208-E6-007)
Discharge Dampener (Tag No. 2-1208-V4-002)
The licensee stated:
"These exemptions exclude the applicable vessels from the surface and volumetric examinations required by IWC-2500. The remainder of the Code-required examinations j
(i.e., pressure tests) would be performed to assure that an acceptable level of safety and quality is maintained for the applicable components."
7
Licensee's Basis for Reauestina Relief (as stated):
"Subarticle IWC-1220 of the 1989 Addenda of ASME Section XI allowed the exemption of selected components from the surface and volumetric examination requirements of IWC-1220 [ Table IWC-2500-1]. The 1996 Addenda of ASME Section XI also includes these exemptions in IWC-1220. The NRC granted these exemptions to VEGP in the first interval through correspondence dated March 8,1996 and August 13,1996 for VEGP-1 and 2, respectively.
"These exemptions will be allowed when the newer Addenda and Editions of the Code are authorized in 10 CFR 50.55a. SNC sees no benefit in performing examinations on components which the Code has determined can be exempted. The other requirements in the Code are therefore acceptable to assure an acceptable level of safety or quality. It is impractical to perform examinations which do not provide a compensating increase in the level of safety or quality.
"These added exemptions would apply to several components which are in high dose rate
. areas. The most significant of these components is the regenerative heat exchanger. A conservative whole body dose in the range of one to two Rem is a reasonable estimate for examining the regenerative heat exchanger. The dose rate surveys for the regenerative heat exchanger indicate a contact dose rate of two to three Rem / hour and a dose rate at eighteen inches away from the heat exchanger of one to one-and-one-half (1 to 1-1/2)
Rem / hour. The estimated stay time to perform the Code-required examinations on the regenerative heat exchanger is one hour. Such exposure is contrary to the principles of ALARA to perform examinations on components without a compensating increase in safety or quality. For the reasons discussed above, SNC has determined that implementation of the Code requirements is impractical. Therefore, SNC requests that the proposed attemative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Evaluation
- The licensee has requested to use the exemption criteria of IWC-1222 of the 1989 Addenda in lieu of the exemption requirements of the Code of record. In accordance with the 1989 Code, piping NPS 4 and smaller is exempt from examination, but connected components are not. In the 1989 Addenda of Section XI, IWC-1222 was revised to exempt vessels, pumps and valves, and their connections in piping NPS 4 and smaller, with the following note. "In piping is defined as having a cumulative inlet and a cumulative outlet j
pipe cross-sectional area neither of which exceeds the nominal OD cross-sectional area of the designated size." This exemption is also contained in Code Case N-408-2, Attemative Rules for Examination of Class 2 Piping,Section XI, Division 1, which has been approved for general use in Revision 11 of Regulatory Guide 1.147, Inservice inspection Code Case Acceptability-ASME Section XI, Division 1.
The change in the Code described above parallels the logic used for the exemption of Class 1 systems. Specifically, IWB-1220(b)(2) exempts " components and their connections in piping in 1-inch nominal pipe size and smaller", where "in piping"is defined as having one inlet and one outlet pipe, each of which is 1-inch NPS or smaller. The discrepancy between Class 1 and 2 systems was recognized by the Code committee, which pattemed the exemption criteria for Class 2 in the 1989 Addenda after existing exemption requirements for Class 1 systems.
8
The INEEL staff has reviewed this request and concludes that the licensee's attemative, to use the exemption criteria of the 1989 Addenda for the above specified C! ass 2 systems, will provide an acceptable level of quality and safety. The approach used for the Class 2 -
exemption criteria found in the 1989 Addenda is similar to that used for exemption of Class 1 systems. In addition, the criteria has been approved by the NRC as part of Code Case N-408-2. Therefore, it is recommended that the licensee's proposed attemative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
- e. Reauest for Relief RR-22. Use of Code Ca== N-544. Renair and Realacement of Small j
ltems.Section XI. Division 1 Code Requirement The Code requires that repairs and replacements be performed in accordance with IWA 4000 and IWA-7000, respectively.
Licensee's Pronosed Altemative: Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-544, Repair and Replacement of Smallitems,Section XI, Division 1, in lieu of the repair and replacement requirements of the Code. The licensee stated:
"Southem Nuclear Operating Company will comply with the requirements of Code Case N-544 in lieu of IWA 4000 and IWA-7000 except that the subject code case will not be applicable to heat exchanger tubing, sleeves, and welded plugs used for heat exchanger tubes in Class 1,2, and 3 heat exchangers, including similar steam generator-related components."
Licensee's Basis for Reauesting Relief (as stated):
"ASME Section XI Code Case N-544 was issued on August 24,1995 and provides an alternative to the requirements of IWA-4000 and IWA-7000 when a repair or replacements is performed on piping, valyes and fittings 1-inch NPS and smaller. A copy of the code case is provided as Attachment 1 to this request for relief. The provisions of this code case were added to IWA4131 and IWA-4132 in the 1995 Addenda to ASME Section XI.
"The 1989 Edition of ASME Section XI Code provides an exemption for replacement items 1-inch NPS and smaller from the requirements of IWA-7000, but repairs to such items are not similarly exempted. Therefore, a repair to an item is subject to more restrictive requirements than replacing an item. Code Case N-544 allows application of the attemative requirements for replacement to all repair and replacement activities. The ASME Code Committee evaluated the proposed attematives contained in the Code Case and determined that they are acceptable for repair and replacement activities on piping _
(including tubing with certain exceptions), valves, and fittings 1-inch NPS and smaller.
Components to which exceptions were applied are identified in Paragraphs -1300 and -1400 of Code Case N-544. Specifically the exceptions include heat exchanger tubing, sleeves, and welded plugs for heat exchanger tubing for Class 1,2, and 3 systems. In addition, SNC considers steam generator tubing, sleeves, and welded plugs, used for plugging steam generator tubes to be heat exchanger-related components. Therefore, Code Case N-544 will not be applicable to the steam generators nor to other Class 1,2, and 3 heat exchanger tubing, including sleeves and welded plugs for heat exchanger tubing. The steam generator tubes will contint M be inspected in accordance with the requirements of VEGP Technical Specification 5.5.9, Steam Generator (SG) Tube Surveillance Program', including any tube 9
s, plugging requirement as a result of inspection performed. Any necessary repairs of steam generator tubes or those of other Class 1,2, and 3 heat exchangers will be repaired in i
accordance with the requirements of the 1989 Edition of ASME Section XI. SNC has
{
determined that implementauon of the code case (with exceptions noted herein conceming heat exchangers and steam generators) will not affect the level of quality and safety, nor decrease the margin of public health and safety. To ensure that the level of quality and safety is maintained, SNC will perform repair / replacement activities for 1-inch NPS and smaller using various existing approved procedures and/or programs which establish control on the planning, work control, quality assurance / quality control, and implementation of work
- packages, "While the cost savings associated with Code Case N-544 have not been quantified as a Cost Beneficial Licensing Action item, its implementation is consistent with the intent to eliminate non-beneficial work activities and their associated costs. Therefore, it is requested that the proposed attemative be authorized pursuant to 10 CFR 50.55a(s)(3)(i).
Evaluation: The Code requires that repairs and replacements be performed in accordance with IWA-4000 and IWA-7000, respectively. Pursuant to IWA-7400, piping, valves and j
fdtings NPS 1-inch and smaller are exempt from the requirements of Article IWA-7000.
1 However, Article IWA-4000 has no exemption criteria for components NPS 1-inch and
)
smaller. Therefore, some licensees may choose to replace rather than repair items to avoid the repair requirements of IWA-4000, in lieu of the repair and replacement requirements of the Code, licensee proposed to use Code Case N-544, Repair and Replacement of Small items.
In accordance with Code Case N-544, piping, valves, and fittings NPS 1-inch and smaller, except for heat exchanger tubing, and sleeves and welded plugs used for heat exchanger tubing, are exempt from both repair and replacement requirements of the Code. The exemption criteria used by the Code Case for items NPS 1-inch and smaller is equivalent to existing Code requirements for the replacement of similar items. Therefore, the INEEL staff believes that Code Case N-544 provides an acceptable level of quality and safety with one exception. The ASME Section XI Code differentiates between steam generators and heat exchangers by providing separate item numbers. As currently written, the Code Case does not address steam generator tubing, only heat exchanger tubing. Therefore, it appears that steam generator tubing could be exempted from repair and replacement requirements by the Code Case. To address this uncertainty, the licensee has stated that steam generator tubing and similar steam generator-related components will not be included in the scope of this Code Case. Therefore, it is recommended that the licensee's proposed alternative, with the clarification provided above, be authorized pursuant to 10 CFR 50.55a(a)(3)(i). The use of the Code Case should be authorized for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, if the licensee intends to continue to implement this Code Case, the licensee should follow all provisions in Code Case N-544, with limitations issued in Regulatory Guide 1.147, if any.
10
f.
Reauest for Relief No. RR-23 Reauest for Authorization to use Code Case N-498-1.
Attemale Rules for 10 Year Hvdrostatic Pressure Testina for Class 1. 2. and 3 Svstems.
Section XI. Division 1 Code Requirement Table IWB-2500-1, Examination Category B-P, Table IWC-2500-1, Examination Category C-H, and Table IWD-2500-1, Examination Categories D-A, D-B and D-C, require system hydrostatic testing of pressure-retaining components in accordance with IWA-5000 once each 10-year interval.
Licensee's Proposed Attemative: Pursuant to 10 CFR 50.55a(a)(3)(ii), the licensee has requested authorization to use Code Case N-498-1, Allemate Rules for 10-Year Hydrostatic Pressure Testing for Class 1, 2, and 3 Systems,Section XI, Division 1. The licensee stated:
"Southem Nuclear Operating Company proposes to perform an attemative examination delineated in Code Case N-498-1 as an option to performing Code-required hydrostatic tests. Code Case N-498-1 requires that a VT-2 visual examination be performed in conjunction with system pressure test at nominal operating pressure."
Licensee's Basis for Reauesting Relief (as stated):
"Southem Nuclear Operating Company has determined that hydrostatically testing represents a hardship with little benefit. Hardships are generally encountered with the
{
performance of hydrostatic testing performed in accordance with the Code. For example, since hydrostatic test pressure would be higher than nominal operating pressure, hydrostatic testing frequently requires significant effort to set up and perform. The need to use special equipment and the need for individual valve lineups can cause the testing to impact maintenance / refueling outage schedules.
" Piping components are designed for a number of loadings that would be postulated to occur under the various modes of plant operation.Section XI hydrostatic testing only subjects the piping components to a small increase in pressure over design pressure and, therefore, does not present a significant change to pressure boundary conditions.
Accordingly, hydrostatic pressure testing is primarily regarded as a means to enhance leakage detection during the examination of components under pressure, rather than solely as a measure to determine the structuralintegrity of the components.
"The ASME Subcommittee Working Group on Pressure Testing concluded that no additional benefit is gained by conducting the existing system hydrostatic tests in place of the attemate rules which require a leak test at nominal operating pressure. The conclusion -
of the group was that hydrostatic testing does not necessarily verify structural integrity and, in fact, the slight'y higher test pressure currently called for in the Code could result in operational difficulties as well as extended outages and increased costs. Industry experience has demonstrated that leaks are not discovered as a result of hydrostatic test pressures propagating a pre-existing flaw through-wall. This experience indicates that leaks in most cases are being found when the system is at normal operating pressure. This is mainly due to the fact that hydrostatic pressure testing is infrequently performed, while system leakage tests at normal operating pressures are conducted a minimum cf once each maintenance / refueling outage for Class 1 systems, and each 40-month inspection period for Class 2 and 3 systems. In addition, leaks may be identified during system walkdowns by plant operators.
11 1
'o "The use of Code Case N-498, Attemative Rules for 10-Year System Hydrostatic Testing for Class 1 and 2 Systems, was previously approved by the NRC in Regulatory Guide 1.147, l
Revision 11. The attemative rules for Code Class 1 and 2 in Code Case N-498-1 are j
unchanged from N-498. Code Case N-498-1 added an attemative to the 10-year system hydrostatic tests required for Class 3 systems by Table IWD-2500-1, Categories D-A, D-B, or D-C to the Class 1 and 2 attematives included in Code Case N-498. Code Case N-498 was found to be acceptable because the attemative provided adequate assurance and because compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality or safety.
"Southem Nuclear Operating Company has determined that the attemative rules of ASME Code Case N-498-1 provide reasonable assurance of the structuralintegrity of the Code system. Consequently, an acceptable level of quality and safety will be maintained by allowing the proposed attemative examination as an option to the Code requirement."
Evaluation
- The Code requires the performance of a system hydrostatic test once per interval in accordance with the requirements of IWA-5000 for Class 1,2, and 3 pressure-retaining systems. In lieu of the Code-required hydrostatic testing requirements, the licensee has requested authorization to use Code Case N-498-1, Altemative Rules for 10-Year System Hydrostatic Testing for Class 1, 2, and 3 Systems, dated May 11,1994.
The system hydrostatic test, as stipulated in Section XI, is not a test of the structural integrity of the system but rather an enhanced leakage test.8 Hydrostatic testing only subjects the piping components to a small increase in pressure over the design pressure, therefore, piping dead weight, thermal expansion, and seismic loads present far greater challenges to the structural integrity of a system. Consequently, the Section XI hydrostatic pressure test is primarily regarded as a means to enhance leak detection during the examination of components under pressure, rather than as a method to determine the structuralintegrity of the components. In addition, the industry experience indicates that l
leaks are not being discovered as a result of hydrostatic test pressures causing a preexisting flaw to propagate through the wall. In most cases leaks are being found when the system is at normal operating pressure.
Code Case N-498, Attemative Rules for 10-Year System Hydrostatic Testing for Class 1 and 2 Systems, was previously approved for general use on Class 1 and 2 systems in Regulatory Guide 1.147, Rev. 9. For Class 3 systems, Revision N-498-1 specifies l
requirements identical to those for Class 2 components (for Class 1 and 2 systems, the attemative requirements in N-498-1 are unchanged from N-498). In lieu of 10-year hydrostatic pressure testing at or near the end of the 10-year interval, Code Case N-498-1 l
requires a VT-2 visual examination at nominal operating pressure and temperature in conjunction with a system leakage test performed in accordance with paragraph IWA-5000 of the 1992 Edition of Section XI.
Class 3 systems do not normally receive the amount and/or type of nondestructive examinations that Class 1 and 2 systems receive. While Class 1 and 2 system failures are relatively uncommon, Class 3 leaks occur more frequently and are caused by different failure mechanisms. Based on a review of Class 3 system failures requiring repair during
- 3. S. H. Bush and R. R. Maccary, " Development ofin-Service Inspection Safety Philosophy for U.S.A. Nuclear Poner Plants," ASME,1971 12 l
l
)
s, l
the last 5 years,' the most common causes of failures are erosion-corrosion (EC),
microbiological!y-induced corrosion (MIC), and general corrosion. In general, licensees have implemented programs for the prevention, detection, and evaluation of EC and MIC; i
therefore, Class 3 systems receive inspection commeneurate with their functions and expected failure mechanisms.
1 System hydrostatic testing entails considerable time, radiation dose, and dollar resources.
i The safety assurance provided by the enhanced leakage gained from a slight increase in system pressure during a hydrostatic test may be offset or negated by the necessity to gag or remove Code safety and/or relief valves (placing the system, and thus the plant, in an off-normal state), erect temporary supports in steam lines, and expend resources to set up testing with special equipment and gages. Therefore, performance of system hydrostatic testing represents a considerable burden for the licensee.
Giving consideration to the minimal amount of increased assurance provided by the increased pressure associated with a hydrostatic test versus the pressure for the system leakage test and the hardship associated with performing the hydrostatic test, the INEEL staff finds that compliance with the Section XI hydrostatic testing requirements results in hardship and/or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, it is recommended that the use of Code Case N-498-1 for Code Class 1, 2, and 3 systems be authorized pursuant to 10 CFR 50.55a(a)(3)(ii). The use of this Code Case should be authorized for the current interval at VEGP, Units 1 and 2, or until the Code Case is approved for general use by reference in Regulatory Guide 1.147. After that time, the licensee must follow the conditions, if any, specified in the regulatory guide.
- g. Reauest for Relief No. RR-24. Use of Code Case N-416-1. Attemative Pressure Test Reauirements for Welded Renairs or Installation of Reolacement items bv Weldina.
Section XI. Division 1 Code Reauirement: Section XI, Paragraph IWA-4400, Pressure Test, requires a system hydrostatic test in accordance with lWA-5000 after repairs by welding on the pressure-retaining boundary.
Following welding, the Code requires volumetric examination and/or surface examination (depending on wall thickness) of repairs or replacements in Code Class 1 and 2 systems, but only requires a surface examination of the final weld pass in Code Class 3 piping components. There are no ongoing nondestructive examination (NDE) requirements for Code Class 3 components except for VT-2 visual examination for leaks in conjunction with the 10-year hydrostatic tests and the periodic pressure tests.
Licensee's Proposed Altemative: Pursuant to 10 CFR 50.55a(a)(3)(ii), the licensee has proposed to use Code Case N-416-1, Attemative Pressure Test Requirements for Welded Repairs or Installation of Replacement items by Welaing,Section XI, Division 1. The licensee stated:
"Southem Nuclear Operating Company proposes to perform attemative examinations delineated in ASME Code Case N-416-1, with augmented exams for Class 3 piping and
- 4. Documented in Licensee Event Repor1s and the Nuclear Plant Reliability Data System databases.
13
'o components, in lieu of Code-required hydrostatic tests. These attemative examinations are as follows:
1.
" Perform nondestructive examinations in accordance with the methods and acceptance criteria of the applicable subsection of the 1992 Edition of ASME, Section Ill.
2.
" Perform a VT-2 visual examination of the welds in conjunction with the system leakage test using the 1992 Edition of ASME Section XI.
3.
" Perform surface examinations on the root pass layer of butt and socket welds on the pressure-retaining boundary of Class 3 piping and components.
4.
"The nondestructive examinations and pressure tests shall be documented on an Owner's Report for Repairs or Replacements, Form NIS-2.
Licensee's Basis for Raouestina Relief (as stated):
"ASME Section XI Code Case N-416-1 which is provided as Attachment 1 to this request 5
for relief was issued on February 15,1994. This Code Case has not formally endorsed by inclusion in NRC Regulatory Guide 1.147 but has been authorized by the NRC for use previously at VEGP and other plants. ASME Section XI Code Case N-416-1 was approved by the NRC for use at VEGP during the First Ten-Year Interval as addressed in NRC correspondence dated March 8,1996 and August 13,1996 for VEGP-1 and 2, respectively.
- Southem Nuclear Operating Company has determined that hydrostatically testing post-repair / installation welds represents a hardship with little benefit. Hardships are generally encountered with the performance of hydrostatic testing performed in accordance with the Code. For example, since hydrostatic test pressure would be higher than nominal operating pressure, hydrostatic testing frequently requires significant effort to set up and perform. The need to use special equipment and the need for individual valve lineups can cause the testing to impact maintenance / refueling outage schedules.
" Piping components are designed for a number of loadings that would be postulated to occur under the various modes of plant operation.Section XI hydrostatic testing only subjects the piping components to a smallincrease in pressure over design pressure and, therefore, does not present a significant change to pressure boundary conditions.
Accordingly, hydrostatic pressure testing is primarily regarded as a means to enhance leakage detection during the examination of components under pressure, rather than solely j
as a measure to determine the structural integrity of the components.
"The ASME Subcommittee Working Group on Pressure Testing concluded that no additional benefit is gained by conducting the existing system hydrostatic tests in place of the attemate rules which require a leak test at nominal operating pressure. The conclusion of the group was that hydrostatic testing does not necessarily verify structural integrity and, in fact, the slightly higher test pressure currently called for in the Code could result in operational difficulties as well as extended outages and increased costs.
l included in license's submittal, but not in this report.
14
- c
" industry experience has demonstrated that leaks are not discovered as a result of hydrostatic test pressures propagating a pre-existing flaw through-wall. This experience indicates that leaks in most cases are being found when the system is at normal operating pressure. This is mainly due to the fact that hydrostatic pressure testing is infrequently performed, while system leakage tests at normal operating pressures are conducted a minimum of once each maintenance / refueling outage for Class 1 systems, and each 40-month inspection period for Class 2 and 3 systems, in addition, leaks may be identified during system walkdowns by plant operators.
"Southem Nuclear Operating Company has determined that the nondestructive examinations and their associated acceptance criteria provide assurance of the structural integrity of the weld. The proposed alternative examinations will provide reasonable assurance that unallowable flaws are not present in the subject welds. Consequently, an acceptable level of quality and safety will be achieved and public health and safety will not be endangered by allowing the proposed alternative examination in lieu of the Code requirement."
Evaluation: Section XI of the Code requires a system hydrostatic test to be performed in accordance with IWA-5000 after repairs made by welding on the pressure-retaining boundary. The licensee has proposed the use of Code Case N-416-1 in lieu of the Code requirements. Code Case N-416-1 specifies that NDE of the welds be performed in accordance with the applicable subsection of the 1992 Edition of Section 111. The Code Case also allows a VT-2 visual examination to be performed at nominal operating pressure and temperature in conjunction with a system leakage test, in accordance with Paragraph IWA-5000 of the 1992 Edition of Section XI.
The 1989 Editions of Sections ill and XI are the latest Code edn,vns referenced in 10 CFR 50.55a. The NRC staff previously compared the system pressure test requirements of the 1992 Edition of Section XI to those of the 1989 Edition. In summary:
1)
The test frequencies and the pressure conditions associated with these tests have not changed; 2)
The hold times have either remained unchanged or increased; 3)
The terminology associated with the system pressure test requirements for all three Code classes has been clarified and streamlined; and 4)
The NDE requirements for welded repairs remain the same.
Piping components are designed to withstand the loading mechanisms that are postulated to occur under the various modes of plant operation. Hydrostatic testing subjects the piping
)
components to a small increase in pressure over the design pressure and, therefore, does i
not present a significant challenge to pressure boundary integrity. Accordingly, hydrostatic i
pressure testing is primarily regarded as a means to enhance leak detection during the examination of components under pressure rather than a measure of the structuralintegrity of the components.
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Considering the NDE performed on Code Class 1 and 2 systems and that the hydrostatic pressure tests rarely result in pressure boundary leaks that would not have occurred during system leakage tests, the INEEL. staff believes that the added assurance of integrity provided by the hydrostatic test is not commensurate with the associated burden, which typically includes the installation of blanks, cutting and removing supports for access, and removing insulation to prepare and restore the systems, all of which increase radiation exposure for plant personnel.
For Class 3 components, there are no ongoing NDE requirements except for the visual examination for leaks in conjunction with the 10-year hydrostatic test and periodic pressure tests. Therefore, eliminating the hydrostatic test and only performing the system pressure test for Class 3 components is only considered acceptable if an additional surface examination is performed on the root pass layer of butt and socket welds on the pressure-retaining boundary during repair and replacement activhies. The licensee has included this condition in their attemative which is, therefore, accepts ble.
In summary, compliance with the Code-required hydrostatic testing for welded repairs or replacements of Code Class 1,2, and 3 components would result in a hardship without a j
compensating increase in the level of quality and safety. Therefore, it is recommended that I
the proposed attemative, use of Code Case N-416-1, be authorized pursuant to 10 CFR 50.55a(a)(3)(ii). The use of this Code Case should be authorized for the current interval at VEGP, Units 1 and 2, or until the Code Case is approved for general use by reference in Regulatory Guide 1.147. After that time, the licensee may continue to use Code Case N-416-1 with the limitations, if any, listed in Regulatory Guide 1.147.
3.0 CONCLUSION
The INEEL staff has reviewed the licensee's submittals and concludes that for Requests for i
Relief 5,19,20,21 and 22, the licensee's proposed attematives to the Code requirements provide an acceptable level of quality and safety. Therefore, it is recommended that these proposed alternatives be authorized pursuant to 10 CFR 50.55a(a)(3)(i). For Request for Relief 23 and 24, it is concluded that the Code requirements would result in hardship without a compensating increase in the level of quality and safety. Therefore, it is recommended that these proposed attematives be authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
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