ML20216E992
| ML20216E992 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf, Arkansas Nuclear, River Bend, Waterford  |
| Issue date: | 09/04/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20216E981 | List: |
| References | |
| NUDOCS 9709110129 | |
| Download: ML20216E992 (9) | |
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NUCLEAR REEULATCRY CIMMISSION WASHINGTON, D.C. acteHem
\ ***** / SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACT.OR REGULATION ON ASME CODE CASES N-416-1 AND N-532 LQB ARKANSAS NUCLEAR ONE. UNIT 1 DOCKET NOS. 50-313 GRAND GULF NUCLEAR STATION n DOCKET NO. 50-416 ?!
WATERFORD 3 STEAM FLECTRIC STATION P3CKET NO. 50-382 RIVER BEND STATION EQCKET NO. 50-458 ENTERGY OPERATIONS. INC.
1.0 INTRODUCTION
The Technical Specifications for Arkansas Nuclear One, Unit 1, Grand Gulf Nuclear Station, Waterford 3 Steam Electric Station, and River Bend Station, state that the inservice inspection and testing 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 and applicable Addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission orsuant to 10 CFR 50.55a(g)(6)(1). 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when autMben by the NRC, if (i) the proposed alternatives would provide an accetW. Hvel of quality and safety or (ii) compliance with the specified reqAements 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 (includir, supports) shall meet the requirements that become effective subsequent to editions specified in 10 CFR 50.55a(g)(2) and (g)(3),
except the design and access provisions and the preservice examination requirements, set f,rth in the ASME Code,Section XI, " Rules for Inservice Inspecti>a 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 ten-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) on the date twelve 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 next ten-year inservice inspection interval at each nuclear unit of Entergy Operations, Inc. is the 1992 Edition of the ASME Code,Section XI, along with the pressure testing requirements of the 1993 Addenda. The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject 9709110129 970904 ENCL.0SURE PDR ADOCK 05000313 G PDR
to the limitations and modifications listed therein and subject to Commission approval.
Pursuant to 10 CFR 50.55a(g)(5)(iii), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is impractical for its facility, it should be submitted to the Commission in support of that determination. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(1), the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law; will not endanger life, aroperty, or the common defense and security; and are otherwise in the pu)lic interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
By letter dated June 23, 1997, Entergy Operations, Inc. (licensee) requested re-approval for use during the new inspection interval of ASME Section XI Code Case N-416-1, titled " Alternative Pressure Test Pequirement for Welded Repairs or Installation of Replacement Items by Alding Class 1, 2, and 3,Section XI, Division 1", and Code Case N-532, vlternative Requirements to Repair and Replacement Documentation R9quirements and Inservice Summary Report Preparation and Submission as
.<equired by IWA-4000 and IWA-6000," pursuant to 10 CFR 50.55a(a)(3) to be applied to the inservice inspection (ISI) programs for Arkansas Nuclear One, Unit 1, Grand Gulf, Waterford 3, and River Bend.
The staff has reviewed and evaluated the licensee's request and supporting information to use Code Cases N-416-1 and N-532 as proposed alternatives to the Code requirements for each of the above units.
2.0 DISt USSION CODE CASE N-416-1. " ALTERNATIVE PRESSURE TEST RE0VIREMENT FOR WELDED REPAIRS OR INSTALLATION OF REPLACEMENT ITEMS BY WELDING CLASS 1. 2. AND 3
- SECTION XI. DIVISION 1" System / Component Acolicable to Use of Code Calg:
ASME Class 1, 2, and 3 Components Code Reauirement Affected by Use of Code Case:
The 1992 Edition including the 1993 Addenda, ASME Code,Section XI, IWA-4700(a) requires a hydrostatic test to be performed per IWA-5000 after welded repair or replacement of classed components, except those exempted by IWA-4700(b).
IWA-5120 and IWA-5212 requires a pressure test per IWB-5230, IWC-5230, or IWD-5222, as applicable to the system which contains the repaired or replaced components.
.s-Licensee's Basis for Reauul: (As stated)
"requirements Pursuant toto10 CFRhy perform 50.55a(drostatic tests following welded repairs ora)(3)(ii), an replacements to ASME Class 1, 2, or 3 pressure retaining components.
Due to the additional preparation required to safely accomplish the required hydrostatic tests (at pressures above normal operating levels) after welded repairs and replacements on Code Class 1, 2, and 3 components, these tests present unusual difficulties and hardship situations for Entergy Operations' nuclear facilities.
Some of the specific problems typically encountered when preparing and performing hydrostatic tests include:-
- Complicated or abnormal valve line-ups in order to properly vent, fill, and isolate the component requiring testing.
- Relief valves with setpoints lower than the hydrostatic test pressure must be gagged or removed and blind flanged. This process requires the draining and refilling of the system both prior to the test and prior to system restoration.
- Valves that are not normally used for isolation (e.g., normally open pump discharge valves) are often required to provide pressure isolation for an elevated pressure hydrostatic test. These valves frequently require time consuming seat maintenance in order to obtain a leak tight pressure boundary.
- The radiation exposure to plant personnel involved in hydrostatic tests is high in-comparison to operational pressure testing due to the large amount of time required to prepare the volume for testing (i.e., installing relief valve gags, performing appropriate valve line-ups, completing valve maintenance, filling and venting, etc.).
The alternative pressure tests permitted by Code Case N-416-1 fulfill the same purpose as a hydrostatic pressure test, i.e., a check for component / system leakage. No leakage detection benefit-is gained from the added challenge to the piping system provided by an elevated pressure hydrostatic test as compared to:a system leakage test. The stresses experienced during a hydrostatic test may not include stresses caused by thermal and oaerational transients due to normal system operation; therefore, tie accumulated stress experienced during hydrostatic testing may actually be less than the total stress
. experienced during a system leakage test. Thus, if a through wall-leakage path exists, leakage during a system leakage test may be more evident."
Licensee's Proposed Alternative to Code Reauirement: (As stated)
"After welded repairs or installation of replacement items by welding, the following alternative requirements will be met in lieu of performing the hydrostatic pressure test required per paragraph IWA-4700, IWA-5120, and IWA-5212:
(1) NDE shall be performed in accordance with the methods and acceptance criteria of the applicable Subsection of the 1992 Edition of Section III.
(2) Prior to or immediately upon return to service, a visual examination (VT-2) shall be performed in et,njunction with a system leakage test, using the 1992 Edition of Section XI, in accordance with paragraph IWA-5000, at nominal operating pressure and temperature.
(3) Use of this Alternative shall be documented on an NIS-2 Form or an NIS-2A Form per Code Case N-532.
(4) Additional surface examinations shall be performed on the root (pass) layer of butt and socket welds of the pressure retaining boundary of Class 3 components when a surface examination of the final weld is required by (1) above.
(5) If additional requirements related to Code Case N-416-1 are imposed in a future revision of Regulatory Guide 1.147, they will be adopted in addition to items (1) through (4), above.
These requirements are specified in Code Case N-416-1 as approved by the Board of Nuclear Codes and Standards, with the additional provisions of (4) and (5) above. The commitment in item (4) is consistent with the limitation for Code Case N-416-1 listed in draft Revision 12 to Regulatory Guide 1.147, " Inservice Inspection Code Case Acceptability, ASME Section Division 1," and with Entergy Operation's previous approvals to use this code case.
Based on the above, Entergy Operations has concluded that compliance with the Code as written would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety above that provided for in Code Case N-416-1.'
3.0 EVALUATION In lieu of hydrostatic pressure testing for welded repairs or installation of replacement items by welding, Code Case N-416-1 allows a system leakage test using the 1992 Edition of ASME Code,Section XI, in accordance with paragraph IWA-5000, at nominal operating pressure and temperature. This code case also specifies that the non-destructive
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examination (NDE) of welds be performed in accordance with the applicable Subsection of the 1992 Edition of ASME Code,Section III.
The latest edition of ASME Code,Section XI and Section III, referenced in 10 CFR 50.55a, is the 1989 Edition. The staff has compared the system pressure test requirements of the 1992 Edition of Section XI to those of the 1989 Edition and determined that the 1992 Edition of the Code imposes a more uniform set of system pressure test requirements for Code Class 1, 2, and 3 systems. The terminology associated with the system pressure test requirements for all three code classes have been clarified and streamlined. The test frequency and test pressure associated with these tests have not been changed. The hold time for the test has either remained unchanged c,r increased. The corrective action with respect to removal of bolts from a leaking bolted connec-tion, however, has been relaxed in the 1992 Edition which has been accepted by the staff in previous safety evaluations. Nevertheless, the NDE requirements of post-weld repair, however, remain the same in both versions of the Code. Therefore, the staff finds that the requirements of the 1992 ASME Code,Section XI, as referenced in Code Case N-416-1 are equivalent to those of the 1989 ASME Code,Section XI.
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 the nominal operating pressure, hydrostatic pressure testing frequently requires significant effort to set up and perform. The need to use special equipment, such as a temporary attachment of test pumps and gages', and the need for individual valve lineups can cause the testing to be on a critical path.
Piping components are designed for a number of loadings that would be postulated to occur under the various modes of plant operation.
Hydrostatic testing only subjects the piping components to a small increase in pressure over the design pressure and, therefore, does not present a significant challenge to pressure boundary integrity.
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 structural integrity of the components.
The industry experience has demonstrated that leaks are not being discovered as a result of hydrostatic test pressures propagating a pre-existing flaw through the walls. The experience, however, indicates that leaks in most cases are being found when the system is at normal operating pressure. This is largely due to the fact that hydrostatic pressure testing is required only upon installation and then once every 10-year inspection interval, while system leakage tests at nominal operating pressures are conducted a minimum of once each refueling outage for Class 1 systems and each 40-month inspection period for 1
Class 2 and 3 systems. In addition, leaks may be identified by plant operators during system walkdowns which may be conducted as often as once a shift.
Following completion of welding, the Code requires volumetric examination of repairs or replacements in Code Class 1 and 2, but requires only a surface examination of the final weld pass in Code Class 3 components. There are no other 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.
Consiaering the NDE performed on Code Class 1 and 2 systems and considering that the hydrostatic pressure tests rarely result in pressure boundary leaks that would not occur during system leakage tests, the staff believes that increased assurance of the integrity of Class 1 and 2 welos is not commensurate with the burden of performing hydrostatic testing. However, considering the nature of NDE requirements for Code Class 3 components, the staff does not believe that elimination of the hydrostatic pressure testing while only performing system pressure testing is an acceptable alternative to hydrostatic testing unless additional surface examinations are performed on the root pass layer of butt and socket welds on the pressure retaining boundary of Class 3 components when the surface examination method is used in accordance with Section III.
For clarification, it should be noted that, consistent with the code case requiring the performance of NDE in accordance with the methods and acceptance criteria of the 1992 Edition of Section III, the scope of examination should also be in accordance with the 1992 Edition of Section III. The additional surface examination of the root layer of Class 3 pressure retaining welds should be performed only when those pressure retaining welds are required to have a surface examination performed in accordance with the 1992 Edition of Section III. For those Class 3 welds receiving radiography in lieu of a surface examination in accordance with Section III, no additional surface examination of the root layer needs to be performed.
4.0 CONCLUSION
The staff concludes that compliance with the code hydrostatic testing requirements for welded .*epairs or replacements of Code Class 1, 2, and 3 components would result in hardships without a compensating increase in the level of quality and safety. Accordingly, the licensee's proposed alternative to use Code Case N-416-1 with the additional
-surface examinations to be performed on the root pass layer of butt and socket welds on the pressure retaining boundary of Class 3 components J
when the surface examination method is used in accordance with Section III is authorized for Arkansas Nuclear One, Unit 1 Grand Gulf, Waterford 3 and River Bend Station, pursuant to 10 CFR 50.55a(a)(3)(li).
Use of Code Case N-416-1, with the additional surface examination as noted above, is authorized for the duration of the next ten-year ISI interval at the above nuclear plants until such time as the code case is approved by reference in Regulatory Guide 1.147. At that time, if the licensee intends to continue to implement this code case, the licensee must follow all provisions in Code Case N-416-1 with limitations issued in Regulatory Guide 1.147, if any.
5.0 DISCUSSION CODE CASE N-532. " ALTERNATIVE RE0VIREMENTS TO REPAIR AND REPLACEMENTS DOCUMENTATION RE0VIREMENTS AND INSERVICE
SUMMARY
REPORT PREPARATION AND SUBMISSION AS RE0VIRED BY IWA-4000 AND IWA-6000" System /Comoonent Aeolicable to Use of Code Case:
Class 1, 2, and 3 Components Code Reauirement Affected by Use of Code Case: (As stated)
"IWA-6200 requires the preparation of Inservice Inspection (ISI) Summary Reports which contain completed Form NIS-1, "0wner's Report for Inservice Inspection" and Form NIS-2, " Owner's Report for Repair and Repl acement" . In accordance with IWA-6240, the ISI Summary Report is required to be submitted to the enforcement and regulatory authorities having jurisdiction at the plant within 90 days of the completion of the inservice inspections conducted each refueling outage.
IWA-4900 reiterates the requirement to complete NIS-2 forms for repairs and replacements."
Licensee's Basis for Reauest:
basis that it provides an accep) table level of quality and Code safety. Pursuant to 1 Case N-532 provides an alternative to the current ASME Section XI repair and replacement documentation requirements, as well as regulatory reporting requirements relating to inservice inspection. This alternative will reduce the resources required to prepare NIS-2 forms and prepare and submit the ISI Summary Report currently required by the Code after each refueling outage. This is a significant reduction in the administrative burden required by ASME Code,Section XI, IWA-6000.
By use of this code case, the licensee will prepare an "0wner's Activity Report" on Form OAR-1 upon completion of each refueling outage providing the following information:
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i e aa abstract of all examinations and tests performed during the outage; a listing of item (s) with f1r.ws or relevant conditions that required evaluation to determine acceptability for continued service; and
- an abstract of repairs, replacements, and corrective measures perfomed due to an item containing a flaw or relevant condition that exceeded acceptance criteria.
Each Form OAR-1 prepared during an inspection period would be available onsite for NRC's review and would be submitted to the NRC at the end of an inspection period, The licensee states that the corrective measures to be reported in the Form OAR-1, will include the code required activities such as repairs and replacements -instead of routine maintenance activities such as tightening threaded fittings to eliminate-leakage, replacing valve packing due to unacceptable packing leakage, adjusting and realigning supports, etc.
The licensee considers the alternative documentation and reporting-requirements cf Code Case N-532 to be a reasonable alternative and an improvement to existing requirements. Because the use of this alternative only affects documentation and reporting requirements, the licensee considers this alternative to provide an acceptable level of quality and safety.
Licensee's Pronosed Alternativs Criteria:
Entergy Operations will use Code Case N-532 in its entirety with the clarification stated above regarding the provision in paragraph 2(c) of '
the Code._ Case for reporting corrective measures.
6.0 EVALUATION The-staff reviewed the alternative documentation requirement of Code Case N-532 and determined that the use of the code case would still require preparation of the REPAIR / REPLACEMENT CERTIFICATION RECORD, FORM NIS-2A. The completed Form NIS-2A shall be certified by.an Authorized Nuclear Inservice Inspector (ANII) as defined in ASME Code,Section XI, IWA-2130 and shall be maintained by the Owner. - Furthermore, the OWNER'S ACTIVITY _ REPORT FORM, OAR-1 shall also be prepared and certified by an ANII upon completion of each refueling outage. The staff noted that=
each OAR-1 form shall contain an abstract of applicable examinations and tests, a list of. item (s)-with flaws-or relevant conditions that require evaluation to determine acceptability for continued service, an abstract of repairs, replacements and corrective measures performed as a result of unacceptable flaws or relevant conditions. Hence, the information provided in the documentation pertaining to the use of Code Case N-532, k
4 can be used in the same manner to assess the safety implications of code activities performed during an outage. The review using the information as prescribed by the code case will, therefore, provide the same or improved level-of safety as reviews that may have been conducted using the older reporting requirements. In addition, more detailed information may bo requested by the staff if it is deemed necessary.
7.0 CONCLUSION
The staff has determined that the proposed alternative documentation requirement of the code case would provide an acceptable level of quality and safety as that of the 1992 Edition of the ASME Code,Section XI, subsections IWA-4900 and IWA-6200. Therefore, the use of Code Case N-532 is authorized pursuant to 10 CFR 50.55a(a)(3)(1) at Arkansas Nuclear One, Unit 1, Grand Gulf, Waterford 3 and River Bend nuclear stations during the next inspection interval. The licensee is authorized to use Code Case N-532 until such time as the code case is included in a future revision of Regulatory Guide 1.147. At that time, the licensee must follow all provisions and any limitations that may be descri.ed in Regulatory Guide 1.147 concerning the use of Code Case N-532.
Principal Contributor: D. Wigginton Date: September 4, 1997
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