ML050240329

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Request for Relaxation from Nuclear Regulatory Commission Revised Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors
ML050240329
Person / Time
Site: Cook American Electric Power icon.png
Issue date: 01/20/2005
From: Fadel D
Indiana Michigan Power Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
AEP:NRC:5054-03
Download: ML050240329 (13)
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Text

Indiana Michigan Power Company 500 Circle Drive Buchanan, MI 49107 1395 INDIANA MICHIGAN POWER January 20, 2005Janury 0, 0051 AEP:NRC:5054-03 0 CFR 2.202 Docket No: 50-315 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop O-P1-17 Washington, DC 20555-0001 Donald C. Cook Nuclear Plant Unit 1 REQUEST FOR RELAXATION FROM NUCLEAR REGULATORY COMMISSION REVISED ORDER ESTABLISHING INTERIM INSPECTION REQUIREMENTS FOR REACTOR PRESSURE VESSEL HEADS AT PRESSURIZED WATER REACTORS - UNIT I

References:

1) Revised Nuclear Regulatory Commission Order EA-03-009, "Issuance of First Revised NRC Order (EA-03-009)

Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors," dated February 20, 2004.

2) Letter from J. N. Jensen, Indiana Michigan Power Company, to Document Control Desk, U. S. Nuclear Regulatory Commission, "Supplement to Request for Relaxation from Nuclear Regulatory Commission Revised Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors," AEP:NRC:4054-06, dated June 24, 2004.
3) Electric Power Research Institute Document MRP-55, "Materials Reliability Program (MRP) Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials," Revision 1, dated November 2002.

This letter transmits a request for relaxation of requirements contained in the revised Nuclear Regulatory Commission (NRC) Order (Reference 1) regarding

U. S. Nuclear Regulatory Commission AEP:NRC:5054-03 Page 2 inspection of reactor pressure vessel (RPV) heads at pressurized water reactors.

TIhis request applies to Donald C. Cook Nuclear-Plant (CNP) Unit 1.

By Reference 1, the NRC revised its previous order establishing interim inspection requirements for RPV heads at pressurized water reactors.

Section IV.F of the revised order states that licensees proposing to deviate from requirements contained in the order may request that the Director, NRC Office of Nuclear Reactor Regulation, relax those requirements. As permitted by Section IV.F of the revised order, Indiana Michigan Power Company (I&M) is requesting relaxation of requirements regarding the length of RPV head penetration nozzle below the J-groove attachment weld that is required to undergo nondestructive examination during the upcoming Unit 1 refueling outage. For some nozzles, compliance with these requirements would result in hardship or unusual difficulty. Since I&M plans to replace the Unit I RPV head during the subsequent refueling outage (Fall 2006), the remaining service life of the nozzles is only one fuel cycle. Consequently, compliance with the requirement would not provide an increase in the level of quality and safety that compensates for the hardship or unusual difficulty. The requested relaxation is presented in the attachment to this letter.

As noted in the attachment, the requested relaxation is supported by crack growth curves contained in WCAP-141 18-P, Revision 7, which was transmitted to the NRC by Reference 2. The crack growth rate used in WCAP-14118-P, Revision 7 is that recommended in industry report MRP-55 (Reference 3). The NRC has not made a final assessment regarding the acceptability of that report.

In relaxations from the original and revised NRC Order EA-03-009, I&M and other licensees accepted a condition specifying actions to be taken if the NRC finds the crack growth formula in MRP-55 to be unacceptable. I&M accepts the same condition with respect to the relaxation from the revised order proposed in the attachment to this letter. This condition is as follows:

If the NRC staff finds that the crack growth formula in industry report MRP-55 is unacceptable, the licensee shall revise its analysis that justifies relaxation of the Order within 30 days after the NRC informs the licensee of an NRC-approved crack growth formula. If the licensee's revised analysis shows that the crack growth acceptance criteria are exceeded prior to the end of the current operating cycle, this relaxation is rescinded and the licensee shall, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, submit to the NRC written justification for continued operation. If the revised analysis shows that the crack growth acceptance criteria are exceeded during the subsequent operating cycle, the licensee shall, within 30 days, submit the revised analysis for NRC review. If the revised analysis shows that the crack growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, the

U. S. Nuclear Regulatory Commission AEP:NRC:5054-03 Page 3 licensee shall, within 30 days, submit a letter to the NRC confirming that its analysis has been revised. Any future crack growth analyses performed for this and future cycles for RPV head penetrations must be based on an acceptable crack growth rate fornula.

I&M requests approval of the proposed alternative by March 23, 2005, to support implementation during the Spring 2005 Unit 1 refueling outage.

T1his letter contains no new regulatory commitments. Should you have any questions, please contact Mr. John A. Zwolinski, Safety Assurance Director, at (269) 466-2428.

Engineering Vice President JW/rdw

Attachment:

Proposed Alternative to Revised U. S. Nuclear Regulatory Commission (NRC)

Order EA-03-009 Regarding Requirements for Nondestructive Examination of Nozzles Below the J-Groove Weld - Unit I c: J. L. Caldwell - NRC Region III K. D. Curry - AEP Ft. Wayne, w/o attachment Director, Office of Nuclear Reactor Regulation J. T. King - MPSC, w/o attachment C. F. Lyon - NRC Washington DC MDEQ - WHMD/HWRPS, w/o attachment NRC Resident Inspector

U. S. Nuclear Regulatory Commission AEP:NRC:5054-03 Page 4 AFFIRMATION 1, Daniel P. Fadel, being duly sworn, state that I am Engineering Vice President of Indiana Michigan Power Company (I&M), that 1 am authorized to sign and file this request with the Nuclear Regulatoiy Commission on behalf of l&M, and that the statements made and the matters set forth herein pertaining to I&M are true and correct to the best of my knowledge, information, and belief.

Indiana Michigan Power Company aniel el Engineering Vice President SWORN TO AND SUBSCRIBED BEFORE ME THIS ~ADAY OF , 2005 NofejlPu liic My Commission Expires ('

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ATTACHMENT TO AEP:NRC:5054-03 PROPOSED ALTERNATIVE TO REVISED U. S. NUCLEAR REGULATORY COMMISSION (NRC) ORDER EA-03-009 REGARDING REQUIREMENTS FOR NONDESTRUCTIVE EXAMINATION OF NOZZLES BELOW THE J-GROOVE WELD - UNIT 1 Submitted in accordance with Revised NRC Order EA-03-009,Section IV.F, Criterion (2):

Compliance with the Order for Specific Nozzles Would Result in Hardship or Unusual Difficulty Without a Compensating Increase in the Level of Quality and Safety References for this attachment are identified in Section 8 below.

1. Components Affected Donald C. Cook Nuclear Plant (CNP) Unit 1 reactor pressure vessel (RPV) head control rod drive mechanism (CRDM) penetrations (79 penetrations).
2. Applicable Document Revised NRC Order EA-03-009 (Reference 1).
3. Applicable Requirement The CNP Unit 1 RPV head is in the moderate susceptibility category as defined in Sections IV.A and IV.B of Revised NRC Order, EA-03-009. Pursuant to Section IV.C(2) of the revised order, the Unit 1 RPV head penetration nozzles must undergo nondestructive examination in accordance with Section IV.C(5)(b) of the revised order during the Spring 2005, Cycle 20 refueling outage. In accordance with Section IV.C(5)(b) of the revised order, the nondestructive examination consists of ultrasonic testing, eddy current, or dye penetrant testing of RPV head penetration nozzle base material and J-groove weld that attaches the nozzle base material to the underside of the head.

The required extent of the ultrasonic testing is stated in Section IV.C(5)(b)(i) of the revised order, which provides the following two options:

Ultrasonic testing of the RPV head penetration nozzle volume (i.e., nozzle base material) from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than 2 inches [see Figure IV-1] [of the revised order]);

OR from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0-inch below the lowest point at the toe of the

Attachment to AEP:NRC:5054-03 Pape 2 J-groove weld (on a horizontal plane perpendicular to the nozzle axis) and including all RPV head penetration nozzle surfaces below the J-groove weld that have an operating stress level (including all residual and normal operation stresses) of 20 ksi tension and greater (see Figure IV-2) [of the revised order]....

The required extent of the eddy current and dye penetrant testing is stated in Section IV.C(5)(b)(ii) of the revised order, which provides the following two options:

Eddy current testing or dye penetrant testing of the entire wetted surface of the J-groove weld and the wetted surface of the RPV head penetration nozzle base material from at least 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than 2 inches [see Figure IV-3] [of the revised order]);

OR from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0-inch below the lowest point at the toe of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) and including all RPV head penetration nozzle surfaces below the J-groove weld that have an operating stress level (including all residual and normal operation stresses) of 20 ksi tension and greater (see Figure IV-4) [of the revised order].

4. Reason for Request

Indiana Michigan Power Company (I&M) is proposing an alternative to the above requirements for the upcoming Unit 1 Cycle 20 refueling outage because, for certain CRDM nozzles, compliance with the revised order would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

As shown on the sketch included in this attachment, the outside surface of the bottom of all CRDM nozzles is threaded with a relief at the top of the threads. The threads and -relief extend for approximately 0.75 inches above the bottom of the nozzle. To reduce personnel radiation exposure, the nozzles are typically inspected using remotely operated ultrasonic and eddy current testing equipment. Ultrasonic testing of the threaded portions of the nozzle is not practical, since it could produce multiple reflections and tip diffraction signals, resulting in scans that are difficult or impossible to read. To the best of I&M's knowledge, an ultrasonic probe capable of obtaining readable scans of threaded portions of the nozzle is not available. The eddy current probe used for nozzle inspections is not capable of examining the threaded surfaces. Development, qualification, and implementation of an eddy current probe capable of examining the threaded surfaces would result in a significant testing period and significant expense.

Attachment to AEP:NRC:5054-03 Page 3 Although dye penetrant testing of threaded surfaces is possible, it would require that personnel be located under the RPV head to manually perform the surface cleaning and penetrant testing operations. I&M estimates that dye penetrant testing threaded surfaces would result in a personnel radiation exposure of approximately 300 to 700 person-millirem per nozzle. Therefore, the portion of the nozzle below the J-groove weld that can be inspected without significant radiation exposure to personnel is that portion from the bottom of the J-groove weld (including the toe of the weld) to the top of the threads and relief. This distance is referred to as the remotely inspectable distance in the following discussions.

Due to the geometry involved in the vertical nozzles penetrating the hemispherical RPV head, the minimum remotely inspectable distance occurs on the "downhill" side of each nozzle, i.e., the side opposite the RPV vertical centerline. The table included in this attachment provides dimensional data for the downhill and uphill sides of the nozzles. This data is based on the results of a previous inspection, performed prior to issuance of the original NRC order. The data is a best estimate by personnel reviewing ultrasonic scan recordings. As shown in the table:

  • Dimensional data is available for 64 of the 79 CRDM penetrations.
  • For 44 of the 64 nozzles that have dimensional data available, the remotely inspectable distance on the downhill side of the nozzle is less than the criterion of 1.0 inch plus the distance that the nozzle has an operating stress level of 20 ksi tension and greater, as specified in the second options of Section IV.C(5)(b)(i) and Section IV.C(5)(b)(ii) of the revised order.
  • The minimum remotely inspectable distance for the 44 nozzles that have dimensional data available but have a remotely inspectable distance less than the criteria specified in the order is 0.369 inches. This occurs on Penetration 63. Thie remotely inspectable distance for the remainder of those 44 nozzles is greater than 0.6 inches.
  • There is no reliable dimensional data available for 15 of the 79 nozzles. These nozzles were previously inspected using eddy current testing, which does not provide reliable data regarding the location of the tip of the J-groove weld.

I&M plans to replace the Unit 1 RPV vessel head during the Fall 2006 refueling outage, which is the next outage following the upcoming Cycle 20 refueling outage. As described below, the expenditure of outage time, resources, and personnel radiation exposure to inspect threaded areas of the nozzle in order to comply with the 1.0 inch plus 20 ksi criterion specified in the second options of Section IV.C(5)(b)(i) and Section IV.C(5)(b)(ii) of the revised order would not provide a compensating increase in the level of quality and safety for the one fuel cycle of remaining RPV service life.

Attachment to AEP:NRC:5054-03 Page 4

5. Proposed Alternative and Basis l&M proposes that the extent of RPV penetration nozzle inspections below the J-groove weld specified in Sections IV.C(5)(b)(i) and IV.C(5)(b)(i) of the revised order be as follows:

All CRDM nozzles shall be inspected to the maximum extent possible by remote ultrasonic and/or eddy current testing below the J-groove weld, i.e., down to the top of the thread relief. For the 15 nozzles for which dimensional data is not available, inspection shall extend to at least 0.5 inches below the lowest point on the toe of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis).

Basis CNP specific calculations demonstrate that a postulated 100 percent through-wall axial flaw, with its upper tip at the bottom of the inspection area specified in the proposed alternative, would not propagate to the toe of the J-groove weld prior to replacement of the Unit 1 RPV head. These calculations are illustrated by the crack growth curves in Figures 6-12 through 6-20 of WCAP-14118-P, Revision 7, which was transmitted to the NRC by Reference 2.

These crack growth curves support the proposed alternative as follows.

As shown in the table included in this attachment, the minimum remotely inspectable distance for the 64 nozzles for which dimensional data is available is 0.369 inches. This occurs on the downhill side of Penetration 63, which is located in the row with a head angle of 38.6 degrees. Figure 6-16 of WCAP-14118-P, Revision 7, shows that a flaw located with its upper tip at 0.369 inches below the toe of the J-groove weld on the downhill side of Penetration 63 would take approximately 2.1 effective full power years (EFPY) to reach the weld. I&M expects the existing RPV head to be in service for no more than 1.38 EFPY following the Cycle 20 refueling outage inspection. Therefore, the proposed alternative' would provide over 0.7 EFPY of margin against flaw propagation to the toe of the J-groove weld for Penetration 63. The margin for the remaining 63 nozzles would be significantly greater.

Figure 6-14 of WCAP-14118-P, Revision 7, is the crack growth curve for the downhill side of the row of nozzles having a head angle of 26.2 degrees. This is likely the most limiting row, or close to the most limiting row of nozzles with respect to crack growth. The crack growth curve of Figure 6-14 shows that a flaw located with its upper tip at 0.5 inches below the toe of the J-groove weld would take approximately 4.1 EFPY to reach the weld.

Therefore, an inspection that extends 0.5 inches below the toe of the J-groove weld would likely provide over 2.7 EFPY of margin against flaw propagation to the weld for any row in which there are nozzles without available dimensional data.

Duration of the Proposed Alternative The proposed alternative will apply during Unit 1 Fuel Cycle 20.

Attachment to AEP:NRC:5054-03 Page 5

7. Precedents The reason for this request, the proposed alternative, and its basis are similar to those for relaxations approved for CNP Unit 2 (Reference 3), Salem Nuclear Generating Station Unit 1 (Reference 4), and San Onofre Nuclear Generating Station Units 2 and 3 (Reference 5).
8. References
1. Revised NRC Order EA-03-009, "Issuance of First Revised NRC Order (EA-03-009)

Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors," dated February 20, 2004.

2. Letter from J. N. Jensen, I&M, to Secretary, Office of the Secretary of the Commission, NRC, "Supplement to Request for Relaxation from Nuclear Regulatory Commission Revised Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors," AEP:NRC:4054-06, dated June 24, 2004.
3. Letter from R. H. Ruland, NRC, to M. K. Nazar, l&M, 'Donald C. Cook Nuclear Plant, Unit 2 - Relaxation of the Requirements of First Revised Order (EA-03-009) Regarding Reactor Pressure Vessel Head Inspections Dated February 20, 2004 (TAC no. MC3074),"

dated September 27, 2004 (ML042510444).

4. Letter from C. F. Holden, NRC, -to R. A. Andersen, PSEG Nuclear, "Salem Nuclear Generating Station, Unit No. 1 - Evaluation of Relaxation Request No. S1-RR-13-B21, Re: First Revised Order (EA-03-009) Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized-Water Reactors (TAC No. MC0967),"

dated May 5,2004 (ML041190161).

5. Letter from H. N. Berk-ow, NRC, to H. B. Ray, Southern California Edison Company, "Relaxation of the Requirements of Order EA-03-009 Regarding Reactor Pressure Vessel Head Inspections, San Onofre Nuclear Generating Station (SONGS), Units 2 and 3 (TAC Nos. MC1542 and MC1543)," dated March 19, 2004 (ML040840128).

Attachment to AEP:NRC:5054-03 Page 6 Bottom of Unit 1 Reactor Vessel Head Penetration Nozzle (Not to Scale) 4k J-groove Weld 0.75 In.

Bottom of Nozzle I RPV Head Inside Surface

  • Dimension 'A' represents the remotely inspectable distance below J-groove weld. Available values for dimension WA for each nozzle are provided in the table following this sketch.

Attachment to AEP:NRC:5054-03 Page 7 Donald C. Cook Unit 1 Reactor Vessel Head Penetration Nozzle Data Penetration Head Downhill Uphill Distance Remotely No. Angle Remotely Remotely Below Inspectable Inspectable Inspectable J-groove Distance Distance Distance Weld to 20 Meets (Dimension ksi, 1 inch +

"A" on 20 ksi Sketch) Criterion?

Degrees Inches Inches Inches Yes/No 1 0 Not Available Not Available 1.08*

2 8.0 1.39 2.192 Yes 3 8.0 1.44 2.233 Yes 4 8.0 1.47 2.170 Yes 5 8.0 1.32 2.016 Yes 6 11.4 Not Available Not Available 7 11.4 Not Available Not Available 8 11.4 Not Available Not Available 9 11.4 Not Available Not Available 10 16.2 Not Available Not Available 11 16.2 Not Available Not Available 12 16.2 Not Available Not Available 13 16.2 Not Available Not Available 14 18.2 Not Available Not Available Assume 1.08 15 18.2 1.08 2.649 based on Yes 16 18.2 Not Available Not Available distance for 0 17 18.2 1.16 2.689 degree row. Yes 18 18.2 Not Available Not Available 19 18.2 1.47 2.939 Yes 20 18.2 Not Available Not Available 21 18.2 1.08 2.744 Yes 22 23.3 1.16 3.092 Yes 23 23.3 1.16 3.023 Yes 24 23.3 0.689 2.958 No 25 23.3 1.119 3.004 Yes 26 24.8 0.919 3.219 No 27 24.8 1.039 3.214 No 28 24.8 1.239 3.277 Yes 29 24.8 0.649 3.179 No 30 26.2 0.809 3.076 No 31 26.2 j 1.16 3.210 0.831* Yes

Attachment to AEP:NRC:5054-03 Page 8 Donald C. Cook Unit 1 Reactor Vessel Head Penetration Nozzle Data Penetration Head Downhill Uphill Distance Remotely No. Angle Remotely Remotely Below Inspectable Inspectable Inspectable J-groove Distance Distance Distance 'Weld to 20 Mleets (Dimension ksi, 1 inch +

"A" on 20 ksi Sketch) Criterion?

Degrees Inches Inches Inches Yes/No 32 26.2 0.959 3.350 No 33 26.2 0.689 3.197 No 34 26.2 1.319 3.277 0.831* Yes 35 26.2 1.159 3.607 Yes 36 26.2 1.079 3.489 Yes 37 26.2 0.919 3.431 No 38 30.2 0.839 3.561 No 39 30.2 0.839 3.876 No 40 30.2 0.879 3.359 No 41 30.2 0.879 3.606 No 42 30.2 0.999 3.741 No 43 30.2 0.959 3.799 No 44 30.2 0.809 3.618 No 45 30.2 0.809 3.709 No 46 33.9 0.769 3.878 No 47 33.9 0.769 3.886 No 48 33.9 0.879 4.116 Assume 0.831 No 49 33.9 0.809 3.985 based on No distance for 50 35.5 0.609 4.038 26.2 degree No 51 35.5 0.689 4.114 row. No 52 35.5 Not Available Not Available 53 35.1 0.649 3.899 No 54 35.1 0.879 4.112 No 55 35.1 0.919 4.067 No 56 35.1 0.799 3.960 No 57 35.1 0.879 3.994 No 58 36.3 0.689 4.142 No 59 36.3 0.729 4.039 No 60 36.3 1.039 4.327 Yes 61 36.3 0.959 4.191 No

I Attachment to AEP:NRC:5054-03 Page 9 Donald C. Cook Unit I Reactor Vessel Head Penetration Nozzle Data Penetration Head Downhill Uphill Distance Remotely No. Angle Remotely Remotely Below Inspectable Inspectable Inspectable J-groove Distance Distance Distance Weld to 20 Meets (Dimension ksi, 1 inch +

"A" on 20 ksi Sketch) Criterion?

Degrees Inches Inches Inches Yes/No 62 38.6 0.809 4.193 No 63 38.6 0.369 3.954 No 64 38.6 0.809 4.389 No 65 38.6 0.749 4.299 0.529* No 66 38.6 0.569 4.369 . No 67 38.6 1.119 4.597 Yes 68 38.6 0.689 4.387 No 69 38.6 0.879 4.314 No 70 44.3 Not Available Not Available 71 44.3 0.609 4.733 0.508* No 72 44.3 0.999 5.191 No 73 44.3 0.769 5.069 No 74 48.7 0.819 5.979 No 75 48.7 0.819 6.259 No 76 48.7 0.699 5.739 0 515* No 77 48.7 0.819 6.099 . No 78 48.7 1.019 6.059 Yes 79 48.7 1.059 6.179 Yes

  • Based on Figures B-I through B-9 of WCAP-141 18-P, Revision 7.
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