RS-08-156, Proposed Alternative to 10CFR 50.55a Examination Requirements for Reactor Pressure Vessel Weld Inspections

Proposed Alternative to 10CFR 50.55a Examination Requirements for Reactor Pressure Vessel Weld Inspections

ML083380762
Person / Time
Site:	Clinton
Issue date:	12/03/2008
From:	Simpson P AmerGen Energy Co, Exelon Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-08-156
Download: ML083380762 (7)

Text

www.exeloncorp .com AmerGen Energy Company, LLC An Exelon Company 4300 Winfield Road Warrenville, IL 60555 10 CFR 50 .55a RS-08-156 December 3, 2008 U . S. Nuclear Regulatory Commission ATTN : Document Control Desk Washington, DC 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461

Subject:

Proposed Alternative to 10 CFR 50 .55a Examination Requirements for Reactor Pressure Vessel Weld Inspections In accordance with 10 CFR 50.55x, "Codes and standards," paragraph (a)(3)(i), AmerGen Energy Company, LLC (AmerGen), requests NRC approval of the proposed alternative to American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, Sub Article IWB-2500 to allow reduced requirements for nozzle-to-vessel weld and inner radius examinations . This alternative is requested for the second 10-year interval of the Inservice Inspection Program for the Clinton Power Station (CPS) .

The details of the 10 CFR 50.55a proposed alternative are enclosed as Attachment 1, and the components affected by this request are tabulated in Attachment 2. The NRC provided a Safety Evaluation approving the generic technical basis and acceptability criteria for application of ASME Code Case N-702, "Alternative Requirements for Boiling Water Reactor (BWR) Nozzle Inner Radius and Nozzle-to-Shell Welds,Section XI, Division 1," on December 19, 2007, which AmerGen has followed as detailed in the attached request. The responses to plant specific applicability that this Safety Evaluation requires are included in Attachment 3.

AmerGen requests approval of this request by December 3, 2009, to support planning for the twelfth refueling outage (C1 R12) scheduled for January 2010 . This letter contains no new regulatory commitments.

If you have any questions concerning this letter, please contact Mr. Timothy A. Byam at (630) 657-2804.

Respectfully, F6 Patrick R. Simpson Manager - Licensing Attachment 1 : 10 CFR 50.55a Request Number 4214 Attachment 2: Table of ASME Code Components Affected Attachment 3 : Responses to NRC Plant Specific Applicability

ATTACHMENT I 10 CFR 50 .55a Request Regarding Alternative Provides Acceptable Level Of Quality And Safety (10 CFR 50.55a(a)(3)(i))

Page 1 of 3 10 CFR 50.55a Request Number 4214

1. ASME Code Component(s) Affected Code Class: 1 Component Numbers: Nozzles N1, N2, N3, N5, N6, N7, N8, N9, and N16 (See Attachment 2 for specific nozzle identification numbers)

Examination Category : B-D Item Number: 133.90 and 133.100

==

Description:==

Alternative to Table IWB-2500-1 (Inspection Program B)

2. Applicable Code Edition and Addenda Clinton Power Station (CPS) is currently in its second 10-year inspection interval and complies with the 1989 Edition of Section XI of the ASME Code. Additionally, for ultrasonic examinations,Section XI, Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems," of the 1995 Edition, with the 1996 Addenda, is implemented as required and modified by 10 CFR 50.55a(b)(2)(xv) .

3. Applicable Code Requirement Class 1 nozzle-to-vessel weld and nozzle inner radii examination requirements are given in Subsection IWB, Table IWB-2500-1, "Examination Category B-D Full Penetration Welds of Nozzles in Vessels - Inspection Program B," Item Numbers 133.90 and 133.100, respectively . The method of examination is volumetric . All nozzles with full penetration welds to the vessel shell (or head) and integrally cast nozzles must be examined each interval. All of the nozzles identified in Attachment 2 are full penetration welds .

4. Reason for Request The Class 1 nozzle-to-vessel weld and nozzle inner radii examinations are scheduled for examination prior to the end of the current inspection interval at CPS. The proposed alternative provides an acceptable level of quality and safety and the reduction in scope will provide for a dose savings of about 25 Rem .

5. Proposed Alternative and Basis for Use Proposed Alternative:

Pursuant to 10 CFR 50 .55a(a)(3)(i), relief is requested from performing the required examinations on 100% of the identified nozzles. Alternatively, in accordance with Code Case N-702 (Reference 2), CPS proposes to examine a minimum of 25% of the nozzle

ATTACHMENT 1 10 CFR 50.55a Request Regarding Alternative Provides Acceptable Level Of Quality And Safety (10 CFR 50.55a(a)(3)(i))

Page 2 of 3 inner radii and nozzle-to-vessel welds, including at least one nozzle from each system and nominal pipe size . For each of the identified nozzles, both the inner radius and the nozzle-to-shell weld would be examined . As a minimum, the following nozzles would be selected for examination : one of the two 20" recirculation outlet nozzles (i.e., N1); three of the ten 10" recirculation inlet nozzles (i .e., N2); one of the four 24" main steam nozzles (i.e ., N3); one of the two 12" core spray nozzles (i.e., NS); one of the three 10" low pressure coolant injection nozzles (i.e., N6); one of the two 6" head spray nozzles (i.e., N7 and N8) ; one of the two 4" jet pump instrumentation nozzles (i.e., N9); and the vibration instrumentation nozzle (i .e., N16).

Code Case N-702 proposes that visual examination (i .e., VT-1) may be used in lieu of volumetric examination for the nozzle inner radii (i .e ., Item B3.100). Note, however, that CPS is not currently using ASME Code Case N-648-1 on enhanced magnification visual examination and has no plans of using this Code Case in the future . CPS will continue to perform volumetric examinations of all required nozzle inner radii .

Basis for Use:

The Electric Power Research Institute (EPRI) Technical Report 1003557, "BWRVIP-108 :

BWR Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Blend Radii," (Reference 1) provides the basis for Code Case N-702. The EPRI report found that failure probabilities due to a low temperature overpressure event at the nozzle blend radius region and nozzle-to-vessel shell weld are very low (i.e ., < 1 x 10 -6 for 40 years) with or without any inservice inspection .

On December 19, 2007, the NRC issued a Safety Evaluation (SE) approving the use of BWRVIP-108 as a basis for using Code Case N-702 (Reference 3). In Reference 3, Section 5 .0, "Plant Specific Applicability," it states that licensees who plan to request relief from the ASME Code Section XI requirements for RPV nozzle-to-vessel shell welds and nozzle inner radius sections may reference the BWRVIP-108 report as the technical basis for the use of ASME Code Case N-702 as an alternative. However, each licensee should demonstrate the plant-specific applicability of the BWRVIP-108 report to their units in the relief request by showing that the general and nozzle-specific criteria addressed below are satisfied:

(1) The maximum Reactor Pressure Vessel (RPV) heatup/cooldown rate is limited to less than 115 °F/hour ;

(2) For the Recirculation Inlet Nozzles, the following criteria must be met:

a . (pr/t)/CRPV <1 .15

b. [p(roe +rig )/(ro2 -ri2 )]/CNOZZLE<1 .15

ATTACHMENT 1 10 CFR 50 .55a Request Regarding Alternative Provides Acceptable Level Of Quality And Safety (10 CFR 50.55a(a)(3)(i))

Page 3 of 3 (3) For the Recirculation Outlet Nozzles, the following criteria must be met:

a. (pr/t)/CRPV <1 .15

b. [p(roz+rig)/(roz-rig)]/CNOULE<1 .15 Demonstration of how CPS meets the NRC plant-specific applicability is provided in to this letter. Based upon all RPV nozzle-to-vessel shell welds and nozzle inner radii sections meeting the NRC plant-specific criteria, Code Case N-702 is applicable to CPS.

Therefore, use of Code Case N-702 provides an acceptable level of quality and safety pursuant to 10 CFR 50.55a(a)(3)(i) for all RPV nozzle-to-vessel shell welds and nozzle inner radii sections .

6. Duration of Proposed Alternative The proposed alternative is requested to be utilized for the remainder of the CPS second 10-year inspection interval .

7. Precedents A similar request was approved for use at Duane Arnold Energy Center on August 29, 2008 (Reference 4).

8. References 1 . EPRI Technical Report 1003557, "BWRVIP-108: BWR Vessel and Internals Project Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Blend Radii,"

dated October 2002

2. ASME Boiler and Pressure Vessel Code, Code Case N-702, "Alternative Requirements for Boiling Water Reactor (BWR) Nozzle Inner Radius and Nozzle-to-Shell Welds,Section XI, Division 1," dated February 20, 2004

3. Letter from Matthew A. Mitchell (NRR), to Rick Libra, BWRVIP Chairman, "Safety Evaluation of Proprietary EPRI Report, 'BWR Vessel and Internals Project, Technical Basis for the Reduction of Inspection Requirements for the Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Inner Radius (BWRVIP-108),'" dated December 19, 2007

4. Letter from Lois James (NRR) to Richard L. Anderson (Duane Arnold Energy Center), "Duane Arnold Energy Center - Safety Evaluation for Request for Alternative to Reactor Pressure Vessel Nozzle to Vessel Weld and Inner Radius Examinations (TAC NO. MD8193)," dated August 29, 2008

Attachment 2 Table of ASME Code Components Affected Page 1 of 2 IDENTIFICATION WELD DESCRIPTION Code Item Number NUMBER Category N1A 20" Recirculation Outlet Nozzle N1A to B-D B3.90 Vessel Weld N1A-IRS 20" Recirculation Outlet Nozzle N1A Inner B-D 83.100 Radius N1B 20" Recirculation Outlet Nozzle N 1 B to B-D 83.90 Vessel Weld N 1 B-IRS 20" Recirculation Outlet Nozzle N 1 B Inner B-D 83.100 Radius N2A 10" Recirculation Inlet Nozzle N2A to B-D 83.90 Vessel Weld N2A-IRS 10" Recirculation Inlet Nozzle N2A Inner B-D 83.100 Radius N2B 10" Recirculation Inlet Nozzle N2B to B-D B3.90 Vessel Weld N213-IRS 10" Recirculation Inlet Nozzle N2B Inner B-D 83.100 Radius N2C 10" Recirculation Inlet Nozzle N2C to B-D B3.90 Vessel Weld N2C-IRS 10" Recirculation Inlet Nozzle N2C Inner B-D 83.100 Radius N2D 10" Recirculation Inlet Nozzle N2D to B-D B3.90 Vessel Weld N2D-IRS 10" Recirculation Inlet Nozzle N2D Inner B-D B3.100 Radius N2E 10" Recirculation Inlet Nozzle N2E to B-D B3.90 Vessel Weld N2E-IRS 10" Recirculation Inlet Nozzle N2E Inner B-D 83.100 Radius N2F 10" Recirculation Inlet Nozzle N2F to B-D B3.90 Vessel Weld N2F-IRS 10" Recirculation Inlet Nozzle N2F Inner B-D 83.100 Radius N2G 10" Recirculation Inlet Nozzle N2G to B-D B3.90 Vessel Weld N2G-IRS 10" Recirculation Inlet Nozzle N2G Inner B-D 83.100 Radius N2H 10" Recirculation Inlet Nozzle N2H to B-D B3.90 Vessel Weld N2H-IRS 10" Recirculation Inlet Nozzle N2H Inner B-D 83.100 Radius N2J 10" Recirculation Inlet Nozzle N2J to Vessel B-D B3.90 Weld N2J-IRS 10" Recirculation Inlet Nozzle N2J Inner B-D 83.100 Radius N2K 10" Recirculation Inlet Nozzle N2K to B-D B3.90 Vessel Weld

Attachment 2 Table of ASME Code Components Affected Page 2 of 2 IDENTIFICATION WELD DESCRIPTION Code Item Number NUMBER Category N2K-IRS 10" Recirculation Inlet Nozzle N2K Inner B-D B3.100 Radius N3A 24" Main Steam Nozzle N3A to Vessel B-D B3.90 Weld N3A-IRS 24" Main Steam Nozzle N3A Inner Radius B-D B3.100 N3B 24" Main Steam Nozzle N3B to Vessel B-D B3.90 Weld N313-IRS 24" Main Steam Nozzle N3B Inner Radius B-D B3.100 N3C 24" Main Steam Nozzle N3C to Vessel B-D B3.90 Weld N3C-IRS 24" Main Steam Nozzle N3C Inner Radius B-D B3.100 N3D 24" Main Steam Nozzle N3D to Vessel B-D B3.90 Weld N3D-IRS 24" Main Steam Nozzle N3D Inner Radius B-D B3.100 N5A 12" Core Spray Nozzle N5A to Vessel Weld B-D B3.90 N5A-IRS 12" Core S ray Nozzle N5A Inner Radius B-D B3.100 N5B 12" Core Spray Nozzle N5B to Vessel Weld B-D B3.90 N513-IRS 12" Core Spray Nozzle N5B Inner Radius B-D B3.100 N6A 10" Low Pressure Core Injection Nozzle B-D B3.90 N6A to Vessel Weld N6A-IRS 10" Low Pressure Core Injection Nozzle B-D B3.100 N6A Inner Radius N6B 10" Low Pressure Core Injection Nozzle B-D B3.90 N6B to Vessel Weld N613-IRS 10" Low Pressure Core Injection Nozzle B-D B3.100 N6B Inner Radius N6C 10" Low Pressure Core Injection Nozzle B-D B3.90 N6C to Vessel Weld N6C-IRS 10" Low Pressure Core Injection Nozzle B-D B3.100 N6C Inner Radius N7 6" Top Head Spray Nozzle N7 to Vessel B-D B3.90 Weld N7-IRS 6" To Head Spray Nozzle N7 Inner Radius B-D B3.100 N8 6" Top Head Spare Nozzle N8 to Vessel B-D B3.90 Weld N8-IRS 6" To Head Spare Nozzle N8 Inner Radius B-D B3.100 N9A 4" Jet Pump Instrumentation Nozzle N9A to B-D B3 .90 Vessel Weld N9A-IRS 4" Jet Pump Instrumentation Nozzle N9A B-D B3.100 Inner Radius N9B 4" Jet Pump Instrumentation Nozzle N9B to B-D B3.90 Vessel Weld N913-IRS 4" Jet Pump Instrumentation Nozzle N9B B-D B3.100 Inner Radius N16 Vibration Instrumentation Nozzle to Vessel B-D B3.90 Weld N16-IRS Vibration Instrumentation Nozzle Inner I B-D B3.100 Radius

Attachment 3 Responses to NRC Plant Specific Applicability Page 1 of 1 1 . The maximum Reactor Pressure Vessel (RPV) heatup/cooldown rate is limited to less than 115 °F/hour .

This criterion is met by adherence to Clinton Power Station Technical Specification 3 .4.11, "Reactor Coolant System Pressure/Temperature Limits,"

Surveillance Requirement 3.4 .11 .1 which requires verification that the Reactor Coolant System heatup and cooldown rates are limited to less than or equal to 100 °F in any one hour period and, less than or equal to 20 °F in any one hour period during RPV pressure testing .

2. For the Reactor Recirculation Inlet (N2) Nozzles (pr/t)/C R PV must be less than 1 .15, where :

p = normal RPV pressure = 1025 psig r = RPV inner radius = 110 .19 inches t = RPV wall thickness = 6.1 inches CRPV = 19332 Result : (pr/t)/CRPV = 0.96

3. For the Reactor Recirculation Outlet (N1) Nozzles, (pr/t)/C RPV must be less than 1 .15, where :

p = normal RPV pressure = 1025 psig r = RPV inner radius = 110.19 inches t = RPV wall thickness = 6.1 inches CRPV = 16171 Result : (pr/t)/CRPV = 1 .14 4 . For the Reactor Recirculation Inlet (N2) Nozzles [p(ro2 +rig )/(ro2-ri2 )]/CNOZZLE must be less than 1 .15, where:

p = normal RPV pressure = 1025 psig ro = nozzle outlet radius = 11 .69 inches ri = nozzle inner radius = 5.81 CN077 LE = 1637 Result : [p(ro2 + rig)/(ro2 - ri2 )]ICNOZZLE = 1 .04

5. For the Reactor Recirculation Outlet (N1) Nozzles [p(ro2+rig)/(ro2-ri2 )]/C NOZZLE must be less than 1 .15, where :

p = normal RPV pressure = 1025 psig ro = nozzle outlet radius = 16 .3125 inches ri = nozzle inner radius = 9.0 inches CNOZZLE = 1977 Result : [p(ro2 + rig)/(ro2 - rig)]/CNOZZLE = 0.97