ML13016A464

Lr - Shield Building Draft RAIs

ML13016A464
Person / Time
Site:	Davis Besse
Issue date:	12/19/2012
From:	Office of Nuclear Reactor Regulation
To:	Division of License Renewal
References
Download: ML13016A464 (4)

Text

Davis-BesseNPEm Resource From: CuadradoDeJesus, Samuel Sent: Wednesday, December 19, 2012 10:56 AM To: dorts@firstenergycorp.com Cc: custerc@firstenergycorp.com; Davis-BesseHearingFile Resource

Subject:

Shield Building Draft RAIs Attachments: Draft RAIs - Davis-Besse 12-18-2012 (2 DRAIs).docx

Steve, Attached are the revised draft RAIs. Please let me know if no clarification is needed and Ill proceed to issue the RAIs formally

Regards, Samuel Cuadrado de Jesús Project Manager Projects Branch 1 Division of License Renewal U.S. Nuclear Regulatory Commission Phone: 301-415-2946 Samuel.CuadradoDeJesus@nrc.gov 1

Hearing Identifier: Davis_BesseLicenseRenewal_Saf_NonPublic Email Number: 3988 Mail Envelope Properties (377CB97DD54F0F4FAAC7E9FD88BCA6D0B86551FD20)

Subject:

Shield Building Draft RAIs Sent Date: 12/19/2012 10:56:28 AM Received Date: 12/19/2012 10:56:30 AM From: CuadradoDeJesus, Samuel Created By: Samuel.CuadradoDeJesus@nrc.gov Recipients:

"custerc@firstenergycorp.com" <custerc@firstenergycorp.com>

Tracking Status: None "Davis-BesseHearingFile Resource" <Davis-BesseHearingFile.Resource@nrc.gov>

Tracking Status: None "dorts@firstenergycorp.com" <dorts@firstenergycorp.com>

Tracking Status: None Post Office: HQCLSTR01.nrc.gov Files Size Date & Time MESSAGE 415 12/19/2012 10:56:30 AM Draft RAIs - Davis-Besse 12-18-2012 (2 DRAIs).docx 24045 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

Shield Building Monitoring Program Follow-up DRAIs Follow-up DRAI B.2.43-2

Background:

By letter dated November 20, 2012, the applicant responded to an RAI regarding the proposed monitoring methods for the Shield Building (SB) cracking. The RAI response indicates that the proposed inspection sample size of 20 core bores will cover the three areas of cracking (flute shoulders, upper 20 of the building, and the steam line penetrations) and is adequate to identify any changes in the laminar cracking, without further impulse response testing during the period of extended operation.

Issue:

As part of evaluating the applicants plan for monitoring the SB cracking with core bores, the staff needs to understand the technical basis for the size of the sample. For example, is the sample based purely on statistics or is it based on the long term effect of the concrete cracks on the ability of the reinforcement to carry design loads and the safety significant of the cracking.

In an earlier RAI response, dated April 5, 2012, it was indicated that the structural impact of the cracking would be determined via testing. A summary description of the test results and discussion of how the test results demonstrate that the sample size is sufficient has not been provided.

Request:

Provide a discussion of the technical basis for the adequacy of the sample size. If the sample size was based on laboratory testing, provide a summary of the testing. Include an explanation of the testing completed as well as the results, and how this information relates to the structural capacity of the shield building and supports the adequacy of the sample size.

Follow-up DRAI B.2.43-3

Background:

By letter dated November 20, 2012, the applicant responded to an RAI regarding the scope of the proposed Shield Building Monitoring Program. The RAI response notes that there were four conditions required to cause the SB laminar cracking and that the SB is the only plant structure that has all of these conditions. The response further states that the design features of all other concrete structures within the scope of license renewal prevent the occurrence of similar cracking, and this was verified via core bores and impulse response testing of an Auxiliary Building wall, which was a bounding location.

Issue:

1. The staff believes that testing to verify cracking did not occur in other structures should be conducted on a structure comparable to the SB. It is not clear to the staff why the Auxiliary Building is considered a comparable structure to the SB, since the wall that was tested was coated while the SB was uncoated. A comparable structure should have as many characteristics that match the SB as possible (e.g., similar rebar density, similar wall thickness, similar environmental exposure, lack of coating).

2. In past RAI responses, the applicant has explained that some other structures within the scope of license renewal have exterior coatings; however, they are not relied upon to prevent sub-surface laminar cracking. In addition the coatings are not included in the scope of license renewal.

Request:

1. Explain why the Auxiliary building is comparable to the SB, or identify other comparable structures and provide technical justification for why testing is unnecessary on those structures or how it will be verified that cracking has not occurred in those structures.

The response should identify any uncoated structures within the scope of license renewal.

2. Identify which coatings are included in the scope of license renewal and the acceptance criteria that will be used for those coatings. Provide technical justification for excluding the coatings that are not within license renewal.