1CAN011101, Response to Request for Additional Information, Regarding the Request for Alternative ANO1-R&R-013, Repairs to the Pressurizer Instrumentation Penetrations

Response to Request for Additional Information, Regarding the Request for Alternative ANO1-R&R-013, Repairs to the Pressurizer Instrumentation Penetrations

ML110070413
Person / Time
Site:	Arkansas Nuclear
Issue date:	01/06/2011
From:	Pyle S Entergy Operations
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
1CAN011101
Download: ML110070413 (5)

Text

Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802 Tel 479-858-4710 Stephenie L. Pyle Acting Manager, Licensing Arkansas Nuclear One 1CAN011101 January 6, 2011 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

SUBJECT:

Response to Request for Additional Information Regarding the Request for Alternative ANO1-R&R-013 Repairs to the Pressurizer Instrumentation Penetrations Arkansas Nuclear One, Unit 1 Docket No. 50-313 License No. DPR-51

REFERENCES:

1. Entergy letter to NRC dated April 5, 2010, Fourth 10-Year Inservice Inspection Interval Request for Alternative ANO1-R&R-013 (1CAN041002)

2. Entergy letter dated April 12, 2010, Supplemental Information to Fourth 10-Year Inservice Inspection Interval Request for Alternative ANO1-R&R-013 Repairs to the Pressurizer Instrumentation Penetrations (1CAN041004)

Dear Sir or Madam:

In Reference 1, Entergy Operations, Inc. (Entergy) requested approval of alternatives, pursuant to 10 CFR 50.55a(a)(3)(i), to the requirements associated with repair of components of the Arkansas Nuclear One, Unit 1 (ANO-1) Pressurizer.

Entergy proposed to repair the penetration by installing a welded pad using Ambient Temperature Temper Bead (ATTB) welding in accordance with ASME Code Case N-638-1.

As an alternative to performing the Code Case N-638-1 surface and ultrasonic examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the completed weld has reached ambient temperature, Entergy proposed performing the surface and ultrasonic examinations at least 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the third weld layer is completed.

Following initial NRC review of the referenced letter, the NRC provided individual requests for additional information (RAI) via emails dated April 6 and April 7, 2010. Reference 2 provided the Entergy responses to the RAIs. The NRC also requested the analyses performed to verify

1CAN011101 Page 2 of 2 the maximum postulated flaw that bounds the range of flaw sizes be provided to the NRC. This information was provided via Reference 2 as well.

In email dated October 13, 2010, the NRC determined that additional information / clarification was required to complete their review. The attachment to this letter provides the response to the requested information.

This letter contains no new commitments.

If you have any questions or require additional information, please contact me.

Sincerely, Original signed by Stephenie L. Pyle SLP/rwc

Attachment:

Responses to Request for Additional Information - Request for Alternative ANO1-R&R-013 cc: Mr. Elmo Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 U. S. Nuclear Regulatory Commission Attn: Mr. Kaly Kalyanam MS O-8 B1 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. Bernard R. Bevill Arkansas Department of Health Radiation Control Section 4815 West Markham Street Slot #30 Little Rock, AR 72205

ATTACHMENT 1CAN011101 Responses to Request for Additional Information Request for Alternative ANO1-R&R-013

Attachment to 1CAN011101 Page 1 of 2 Responses to Request for Additional Information Request for Alternative ANO1-R&R-013

1. On page 8, question no. 10, of the licensees letter of response to the staff Request for Additional Information (RAI) dated April 12, 2010, the licensee stated in part, These nine penetrations consist of seven penetrations that are one-inch (nominal pipe size) nozzles that are attached to the pressurizer with a partial penetration weld located at the inside surface of the pressurizer. The other two penetrations consist of a 1.5-inch diameter thermowell that is attached to the pressurizer with a partial penetration weld located at the inside surface of the pressurizer, and a smaller thermowell that was installed through a spare penetration that was originally a one-inch nozzle similar to the other seven discussed above. Please clarify the sentence underlined/bold. Is this the 10th nozzle? Please explain.

RESPONSE

In reviewing the April 12, 2010, the confusion concerning the total the number of penetrations is noted. Clarification as to the total number of penetrations is provided below.

As noted in the April 12, 2010, submittal there was nine (9) unmitigated Alloy 600/82/182 instrument penetrations related to the Arkansas Nuclear One, Unit 1 pressurizer at the beginning of the last refueling outage. All nine penetrations were modified during that outage.

• The 1.5 thermowell nozzle was attached to the pressurizer by a partial penetration weld on the inside surface of the pressurizer.

• Six (6) 1 nozzles (level taps, spares, vent and sample tap, sample tap) were attached to the pressurizer by a partial penetration weld on the inside surface of the pressurizer.

• Two (2) previously repaired nozzles (1 thermowell [TE-1002A/B] and 1 level tap

[RC-1001A/B]) had outside diameter pads replaced with resistant material and the nozzles were also replaced using resistant material. It should be noted that TE-1002A/B is one nozzle and RC-1001A/B is one separate nozzle.

There is no 10th nozzle, just the nine described above.

2. Flaw evaluation document ANO-34Q-326, pages 4, 5, and .. talk about Self Similar Crack Growth assumption and indicates that this assumption is a conservative approach.

Please describe underlying nature of Self Similar Growth and state why this assumption is considered conservative approach.

Attachment to 1CAN011101 Page 2 of 2

RESPONSE

Self-similar crack growth means that the crack aspect ratio (depth-to-length) remains constant as the crack propagates. The crack front retains its shape as it grows into the base metal, thus, the term 'self-similar' crack growth. For the small bore nozzle in calculation ANO-34Q-326, an initial flaw is postulated in the pressurizer J-groove weld.

The initial postulated crack front is assumed to take the shape of the boundary of the J-groove weld at its interface with the pressurizer base metal. Assuming self-similar growth, two larger flaws are postulated, retaining the shape of the initial flaw, as illustrated in Figure 1 of calculation ANO-34Q-326.

The self-similar crack growth assumption is conservative because the stress intensity factor (K) is not uniform along the crack front. Because of the non-uniform distribution of K along the crack front, the crack is unlikely to propagate in a self-similar manner, but rather would tend to show more growth at the location of maximum K. By assuming that it grows self-similarly, the crack growth calculated based on the maximum K along the crack front is essentially being conservatively applied to the entire crack front to determine the next crack size.

3. Was buttering applied/used between the J-groove attachment weld and the pressurizer carbon steel shell at the nozzle location?

RESPONSE

A review of a Nuclear Steam Supply System vendors documentation and plant drawings noted that a weld butter was not used between the J-groove attachment weld and the pressurizer carbon steel shell at the nozzle location in the construction of the welds.