ML12200A201

Discussion Points Relayed to-the Licensee After Our Internal Technical Discussion

ML12200A201
Person / Time
Site:	Davis Besse
Issue date:	11/12/2011
From:	Office of Nuclear Reactor Regulation
To:
References
FOIA/PA-2012-0121
Download: ML12200A201 (1)

Text

Discussion points relayed to the licensee after our internal technical discussion 11-12-2011

1. Related to SB-42

a. Compilation of calculations, testing, etc. related to S.B. cracking into a clear and concise report that addressed NRC 3 technical focus questions SB 25, 26, 27

b. Current 12/12/11 completion as part of CR-2011-3346 is not acceptable for justification for earlier startup.

c. NRC needs this clear and concise report with sufficient time for review prior to startup.

2. Request Professors Sozen and Darwin presence on NRC call tomorrow; if unavailable tomorrow, request licensee establish call between the professors and the NRC as early as Monday.

3. Technical concern

a. ACI 349.3R not applicable to laminar cracking

b. 3600 laminar crack does not address Prf. Darwin's concern that circumferential steel be located outside crack region to support the conclusion that "no mode change or operating restrictions" are required.

i. Were the professors aware of the 3600 postulated laminar cracking in upper shield building?

ii. Appear Prof. Darwin stipulates cracking to be outside spliced region.

4. Technical Notes:

a. Top of shield building - 360' around 20' down from the top

i. Challenges Prof. Darwin concern that rebar splices be outside cracked region ii. No ACI standard for evaluation and no licensee structural evaluation

b. Concern that sampling did not eliminate I.F. cracking at top of SB (different undefined failure mechanism Then in the shoulder)

c. Outside shoulder area at top, what is the technical explanation of why the cracking is limited to the outer rebar mat and does not extend through the rebar mat thickness.

d. Any splice in cracked regions require further evaluation - Prof. Darwin

i. Design calc - fully effective rebar, unverified assumption (ACI 349.3R not applicable to laminar cracking)