ML20211F511
| ML20211F511 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/23/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20211F508 | List: |
| References | |
| NUDOCS 9908300349 | |
| Download: ML20211F511 (5) | |
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UNITEC STATES 3.) ' C NUCLEAR REGULA 'ORY COMMlGSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FIRST 10-YEAR INTERVAL INSERVICE INSPECTION PLAN REQUEST FOR RELIEF RR-ENG-30 STP NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT. UNIT 2 DOCKET NO. 50-499
1.0 INTRODUCTION
. Inservice inspection (ISI) 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 pursuant to 10 CFR 50.55a(6)(g)(i). The regulation at 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed Sternatives would provide an acceptable level of quality and safety or (ii) compliance with the ipecified 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
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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. For South Texas Project, Unit 2 (STP), the applicable edition of Section XI of the ASME Code for the first 10-year ISI interval is the 1983 Edition through summer 1983 Addenda.
2.0 DISCUSSION I
i By letter dated March 15,1999, STP Nuclear Operating Company (licensee), submitted Request for Relief RR-ENG-30, seeking relief from the requirements of the ASME Code,Section XI, for STP Unit 2. The information provided by the licensee in support of the request for relief from Code requirements has been evaluated and the basis for disposition is documented below.
9908300349 990823 PDR ADOCK 05000499 G
2-2.1 Reauest for Relief No. RR-ENG-30 ASME Code,Section XI, Table 2500-1, Examination Category B-B, requires volumetric examination of the specified primary head welds; and Table IWC-2500-1, Examination l
Category C-A, C-B, and C-C, requires volumetric and/or surface examination of specified secondary shell and head welds and other examination areas (e.g., nozzle inside radius section).
1 Pursuant to 10 CFR 50.55a(a)(3)(ii), the South Texas Project requests relief for the current ISI interval from the Section XI examination requirements for the specified steam generator welds and other examination areas noted (with name and identification number) below:
Steam Generator 2C primary head welds:
Circumferential weld no. SG-2C-SR1 (channel head cap to support ring)
Tubesheet to head weld no. SG-2C-SR2 (support ring to tube plate)
Steam Generator 2-A secondary shell and upper head welds:
Circumferential tubesheet to shell weld no. SG-2A-S1 (tube plate to stub barrel)
Circumferential shell weld no. SG-2A-S2 (stub barrel to lower shell section A)
Circumferential shell weld no. SG-2A-S3 (lower shell section A to lower shell section B)
Circumferential shell weld no. SG-2A-S4 (lower shell section B to transition cone)
Feedwater nozzle to shell weld no. SG-2A-FW10 (feedwater nozzle to stub barrel)
Feedwater nozzle inside radius section no. SG-2A-FW10-lR (inside radius section)
Main steam nozzle to head weld no. SG-2A-MS8 (upper head to steam outlet nozzle)
Integral attachment no. SG-2A-TR12 (Trunnion B) 2.2 Licensee's Basis for Reauestina Relief (as stated) i Pursuant to 10CFR50.55a(a)(3)(ii), the South Texas Project requests relief from the Section XI examination requirements for the specified steam generator welds and other examination areas for the current inservice inspection (ISI) interval. Compliance with these requirements would result in a hardship without a compensating increase in the level of quality and safety. Performance of these examinations will serve no useful purpose because the South Texas Project Unit 2 steam generators are currently scheduled to be replaced during the 2RE09 refueling outage in the fall of 2002. Prior to and during the Unit 2 steam generator replacement outage, the South Texas Project will perform baseline ISI examinations on applicable replacement steam generator welds, steam generator connection and rerouted piping welds, and new and modified component supports. If the Unit 2 steam generators are not replaced prior to or during the fall 2002 refueling outage, the South Texas Project will perform the Section XI NDE
[ nondestructive examination) addressed in this relief request during that outage.
The ISI examinations of the welds and other examination areas in the Class 1 portion of the Unit 2 steam generators were scheduled for all four steam generators. The two primary head welds in Steam Generator 2C specified above are the only Class 1 steam generator welds remaining to be examined in the current inspection interval. A total of thirty other Class 1 steam generator welds and other examination areas have previously
4 been examined in the current IS! interval with acceptable results. Of these thirty previous examinations, sixteen were performed in Period 1, twelve were performed in Period 2, and two were performed in Period 3. Included in these previous examinations are those performed on welds in the other three Unit 2 steam generators corresponding to the two Class 1 welds specified above. The South Texas Project believes these inspections are sufficient to demonstrate the structural integrity of the Unit 2 steam generator primary head welds until the steam generators are replaced in the fail of 2002.
All ISI examinations of the welds and other examination areas in the Class 2 portion of the Unit 2 steam generators were scheduled on Steam Generator 2A, as allowed by Section XI. Of the twelve Class 2 ISI welds and examination areas in Steam Generator 2A, four have been examined during the current ISI interval with acceptable results.
Included in these four previous steam generator inspections was NDE of: (1) the transition cone to upper shell circumferential weld; and (2) the upper shell to upper head circumferential weld. Additionally, during the current ISI interval NDE has been performed with acceptable results on several other Class 2 vessel welds of the same type and configuration (i.e., same examination category and item number) as those specified above for which South Texas Project is requesting relief. These additional NDE, summarized in Table 1 below, were performed on other Unit 2 vessel welds (ie.,
RHR [ residual heat removal] Heat Exchanger and Regenerative Heat Exchanger) as well as on Class 2 steam generator and other vessel welds in Unit 1. These thirty-eight ISI welds and other examination areas in Class 2 vessels are summarized in Table 1 for each examination category and item number applicable to the eight welds and other examination areas for which South Texas Project is requesting relief. The South Texas Project believes these inspections are sufficient to demonstrate the structural integrity of the secondary shell and upper head welds and other examination areas of the Unit 2 steam generators until they are replaced in the fall of 2002.
l Table 1 i
Summary of Completed ISI Examinations on Unit 1 and Unit 2 I
Class 2 Vessel Welds of the Applicable Examination Category and item Number Number of Unit 2 Class 2 Number of Units 1 and 2 and Vessel Welds and Examination Class 2 Vessel Welds and Section XI Examination Areas Addressed by This Relief Examination Areas Alreal-Category & ltem Number Request Examined This ISI intert 4 Examination Category C-A i
item Number C1.10 3
9 Item Number C1.30 1
4 Examination Category C-B ltem Number C2.21 2
12 Item Number C2.22 1
1 Examination Category C-C ltem Number C3.10 1
12 Totals 8
38
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This relief request applies only to the NDE methods specified in the attached lists. All other Section XI examinations and tests applicable to the South Texas Project steam generators will be performed within the current ISI interval in accordance with the South Texas Project Ten Year ISI Plan, unless relief has been obtained by an approved relief request.
2.3 Licensee's Proposed Alternative Examination (as stated)
The Section XI code requirernent for visual (VT-2) examination for leakage during system pressure tests in accordance with Examination Category B-P (primary side) and C-H (secondary side) will be met for all South Texas Project steam generators in the current ISI interval. These inspections for leakage help assure the structural and leak-tight integrity of the entire pressure boundary of all South Texas Project steam generators.
3.0 EVALUATION The Section XI examinations of Class 1 and Class 2 steam generator welds and other examination areas performed each ISI interval serve two purposes. First, the NDE results provide assurance of continuing structuralintegrity of these welds and adjacent base material.
Second, the NDE results provide documentation of the "NDE signature" of the examination volume or area (e.g., geometric reflectors, acceptable flaws) with current NDE technology that can be used for comparison with future ISI examination resuus. STP noted that it performed NDE previously in the current interval on steam generator and other similar vessel welds, along with the system pressure tests and inspections for leakage, and that these previous exams provide an adequate demonstration of the structuralintegrity of the Unit 2 steam generators.
The licensee estimates that its staff and contractor personnel will absorb at least five to six person-rem of radiation dosage during performance of the code-required examinations. In addition to the direct radiation dosage that will be incurred by craft and NDE personnel, the removal of the secondary side insulation on steam generator 2A may produce airborne contamination due to entrained dust within the insulation, and that the removed insulation will not be reusable. The licensee noted that the Unit 2 steam generators are being replaced and if the Unit 2 steam generators are not replaced prior to or during the fall 2002 refueling outage, it will perform the Section XI NDE addressed in the relief request during that outage.
The staff determined that imposition of the Section XI examination requirements for the specified steam generator welds and other examination areas would result in hardship on the licensee without a compensating ir) crease in the level of quality and safety. Furthermore, the staff determined that the previous NDE of other steam generator and vessel welds, by other steam generator ISI tests, and inspections in the current interval provide reasonable assurance of structural integrity of the subject welds. Therefore, the licensee's proposed alternative contained in Request for Relief RR-ENG-30 is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
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4.0 CONCLUSION
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On the basis of its review, the staff concludes that compliance with the Section XI examination l
requirements for the specified steam generator welds and other examination areas would result l
in hardship or unusual difficulty without a compensating increase in the level of quality and i
. safety. Furthermore, the staff concludes that the previous NDE of other steam generator and vessel welds, other steam generator ISI tests, and inspections in the current interval provide reasonable assurance of structuralintegrity of the subject welds. Accordingly, the licensee's proposed alternative contained in Request for Relief No. RR-ENG-30 is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
Principal Contributor: T. McLellan Date:
August 23, 1999 L