ML17228B294
| ML17228B294 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 10/13/1995 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17228B293 | List: |
| References | |
| NUDOCS 9510200375 | |
| Download: ML17228B294 (5) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 U
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I In 1992, the Nuclear Regulatory Commission'NRC) issued 10 CFR 50.55a(g)(6)(ii)(A) which contains new requirements for'n augmented examination of reactor vessels.
This section requires licensees to implement an augmented examination of "essentially 100X" of the reactor pressure vessel shell welds.
The shell welds are specified in the 1989 Edition of the American Society of Hechanical Engineers (ASHE) Code,Section XI, Table IWB-2500-1, Examination Category B-A, "Pressure Retaining Welds in Reactor Vessel,"
Item Bl.10.
This ASHE classification includes Item Bl.ll, circumferential shell welds, and Item B1.12, longitudinal shell welds.
10 CFR 50.55a(g)(6)(ii)(A)(2) defines "essentially 100X" examination as "more than 90X of the examination volume of each weld."
The schedule for implementation of the augmented inspection is dependent upon the number of months remaining in the 10-year inservice inspection (ISI) interval that was in effect on September 8,
1992.
10 CFR 50.55a(g)(6)(ii)(A)(5) requires licensees unable to completely satisfy the requirements of the augmented reactor vessel examination to propose an alternative that would provide an acceptable level
.of quality and safety.
A licensee may use their proposed alternative when authorized by the Office of Nuclear Reactor Regulation.
In a letter dated April 27, 1995, Florida Power and Light Company (FPL), the
- licensee, presented the results of the last (1983) reactor pressure vessel (RPV) examination for St. Lucie 1 as the basis for this request.
The weld examination coverage obtained on two of three circumferential RPV shell welds, specifically 10-203 (86.8X) and 9-203 (83.5X),
and two of nine longitudinal RPV shell welds, specifically 1-203B (78.8X) and 1-203C (88.3X), did not meet the augmented examination requirements for "essentially 100X" coverage.
The remaining seven RPV shell welds received "essentially 100X" examinations ranging from 90.2X to 100X coverage.
FPL requested authorization for alternative RPV examinations.
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The last automated RPV examination at St. Lucie 1 was performed during the 1983 refueling outage.
The augmented RPV examination required by 10 CFR 50.55a(g)(6)(ii)(A) is planned for the refueling outage currently scheduled to begin April 8,
- 1996, as allowed by 10 CFR 50.55a(g)(6)(ii)(A)(2).
All examination and volume coverage data in FPL's request for authorization is based on the 1983 examinations.
95i0200375 95<0<3 PDR ADOCK 05000335 P
FPL's last examinations were performed from the inside diameter (ID) of the RPV utilizing remote, automated ultrasonic (UT) inspections.
The examination procedures were written to meet the requirements of Section V and Section XI of the ASHE Code and NRC Regulatory Guide 1.150, "Ultrasonic Testing of Reactor Vessel Melds During Preservice and Inservice Examinations,"
Rev.
1, Appendix A.
Scanning the weld volume with the automated UT inspection process was done with several transducer s, including 50/70 bi-modal, 45 and 60 shear
- wave, and 0'ongitudinal wave, to meet the requirements of the ASHE Code,Section V.
The results of these inspections are summarized in Table 1, "Results of St. Lucie 1 Augmented Reactor Pressure Vessel Examinations."
The augmented RPV examination at St. Lucie 1 included 12 welds, 3 circumferential (ASHE Item Bl. 11) and 9 longitudinal (ASHE Item Bl.12),
and resulted in "essentially 100X" coverage for 8 of these welds.
Examination coverage for welds10-203 and 9-203 (circumferential) and 1-203C (longitudinal) was 86.8X, 83.5X, and 88.3X, respectively; below the required value of more than 90X.
Longitudinal weld 1-203B received 78.8X examination coverage due to geometrical limitations.
2.2 m'
s to Exa 'i The licensee cited five specific items that reduced examination coverage:
outlet nozzle integral extensions, inlet nozzle inner blends, materials surveillance capsules, core support lugs, and anti-rotation lugs.
This is consistent with the experience of other licensees who have had limited ID examinations due to similar obstructions.
The greatest limitation to "essentially 100X" coverage occurs at the Upper Shell Longitudinal weld 8 15'1-203B),
where an outlet nozzle integral extension limits coverage to 78.8X.
Specific examination limitation(s) for each shell weld are listed in Table 1; FPL concluded they will not employ outside diameter (OD) examinations based on the following information:
Because of the limited access between the vessel and bioshield wall, conducting the examinations from the external surface for the purpose of investigating the small amount of weld volume missed during the mechanized inside surface examinations would require the destruction of insulation during the removal process, excessive
- manhours, manrem, and substantial costs without providing any substantial increase in the quality and safety of the unit.
2.3 e ectab e
nd'c t'ons i RP She We ds The licensee stated all indications detected during the last RPV examination, in 1983, were acceptable in accordance with ASHE Section XI without analytical evaluation.
2.4 FPL presented the following alternative examinations:
The extent of examination volume achieved ultrasonically and the alternate scans performed (see Examination Coverage Table Attachment B) coupled with the system pressure tests provide assurance of an acceptable level of quality and safety.
As an alternative, FPL proposes the following:
1.
Periodic system pressure tests per Category B-P, Table IWB 2500-1.
2.
Conduct essentially 100X mechanized (automated) ultrasonic examinations to the extent practical on all reactor pressure vessel welds from the inside surface.
3.
Conduct a 50/70'i-modal ultrasonic examination of the inner 25 percent t.
A special bi-modal scan of the cladding-base metal interface and 1/4 t under the cladding.
This scan shall not be factored into the coverage calculations, except to augment weld examinations where clad roughness exhibited near surface noise.
4.
Conduct a full vee 45'hear wave examination to the extent practical to compensate for recorded limitations.
5.
Employ as they become available additional examinations, inspections, and/or techniques that would provide a
substantial increase in the examination of areas currently missed under current examination techniques.
FPL's justification for an alternative examination is based upon the results of the last RPV examination, conducted in 1983.
FPL's inspection results indicate that the automated UT examinations of the RPV were conducted to the extent practical.
The ID examinations achieved "essentially 100X" coverage for 8 of the 12 RPV shell welds.
Three of the remaining four welds (10-203, 9-203, and 1-203C) were close to meeting the regulatory requirement for more than 90X of the examination volume of each weld.
The remaining longitudinal weld (1-203B).= received 78.8X coverage due to an outlet nozzle integral extension obstructing the remote inspection tooling.
FPL chose a conservative method to calculate weld coverage and performed additional examinations in an attempt to detect under-clad and near-surface indications.
The augmented RPV examination is scheduled for the spring 1996 refueling outage.
The licensee would be expected to obtain in 1996 the same or greater coverage as obtained in 1983.
Examination from the OD surface would potentially allow St. Lucie 1 to meet the "essentially lOOX" examination requirement for welds10-203, 9-203, 1-
- 203C, and 1-203B.
However, geometrical obstructions which prevented full coverage from the ID may interfere with an OD examination.
In addition, an OD examination would require destruction of the insulation installed on the RPV.
Preparation, insulation removal, inspection, insulation replacement, and cleanup from this type of examination would result in significant accumulated personnel dose.
The additional weld volume examined that may be obtained from examination from the OD would be small in comparison to the welds already examined from the ID.
All indications detected in 1983 with the ID examinations have been acceptable to ASHE Section XI without analytical evaluation.
The results from examination of a significant portion of the weld volume indicate that the vessel is not experiencing any safety-significant degradation.
3.0 CONC USIO Based on the information submitted, the staff concludes that, pursuant to 10 CFR 50.55a(g)(6)(ii)(A)(5), the licensee's proposed alternative, i.e.
examination of the accessible volume from the ID surface to the augmented RPV examination requirements of 10 CFR 50.55a(g)(6)(ii)(A) provides an acceptable level of quality and safety.
After performing the augmented RPV examination, FPL should notify the NRC in writing of the actual examination coverage obtained.
Table 1.
Results of St. Lucie 1 Augmented Reactor Pressure Vessel Examinations.
Keld Item No.
Descri tion Covera e'imitation 9-203 Bl.ll Intermediate Shell to Lower Shell Circumferential 10-203 Bl.ll Lower Shell to Lower Head Circumferential 86.8X 83.5X Core support and anti-rotation lu s Materials surveillance capsules 8-203 Bl.ll Upper Shell to Intermediate Shell Circumferential 100X N/A 3-203A Bl. 12 Lower Shell Lon itudinal 8
135'-203B B1.12 Lower Shell Lon itudinal 8 225 3-203C Bl. 12 Lower Shell Lon itudinal 8
15'-203A Bl. 12 Intermediate Shell Lon itudinal 8
15'-203B B1.12 Intermediate Shell Lon itudinal 8 135 2-203C B1.12 Intermediate Shell Lon itudinal 8 225 1-203A B1.12 U
er Shell Lon itudinal 8 255 1-203B B1.12 U
er Shell Lon itudinal 8 15 1-203C Bl.12 U
er Shell Lon itudinal 8
135'5X 94.2X 95X 91.6X 91.6X 90.2X 91.6X 78.8X 88.3X Anti-rotation lu s and flow skirt Haterials surveillance ca sules Anti-rotation lu s and flow skirt Near surface interface noise Near surface interface noise Haterials surveillance ca sules Inlet nozzle inner blend Outlet nozzle inte ral extension Inlet nozzle inner blend
'Overall claimed coverage.
45 full vee path scan obtained complete coverage of the near surface volume.
45'nd 70 full vee path scan obtained effectively 100X coverage of the near surface volume.
These volumes effectively examined during the Nozzle-to-Shell weld examinations.