ML14246A605
| ML14246A605 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 09/03/2014 |
| From: | Mel Gray Engineering Region 1 Branch 1 |
| To: | Grinnell D C-10 Foundation |
| Gray M | |
| References | |
| Download: ML14246A605 (2) | |
Text
From:
Gray, Mel To:
Heater, Keith Cc:
Cook, William; Dentel, Glenn; Barkley, Richard
Subject:
FW: Response to your email to me dated August 5, 2014 regarding the Seabrook Station Attachments:
Scan.pdf Add to ADAMS.
From: Gray, Mel Sent: Wednesday, September 03, 2014 9:45 AM To: 'Debbie Grinnell' Cc: Sheehan, Neil; Diane Screnci; William Cook
Subject:
Response to your email to me dated August 5, 2014 regarding the Seabrook Station I am responding to your email to me dated August 5, 2014 (see below), that included an internal NRC email (attached) dated November 17, 2011, describing discussions involving an NRC branch chief and NextEra managers involving concrete cores taken by NextEra from Seabrook structures. The email indicates the branch chiefs understanding that NextEra staff sent fifteen cores to a lab in Illinois for compressive strength testing and NextEra staff retained five core samples.
When the attached email was written in November 2011, NextEra was developing plans to conduct testing of large scale ASR affected specimens at the University of Texas to address the Seabrook ASR issue. The NRC staff was maintaining awareness of NextEras plans and developing our own plans for continued oversight of NextEras activities. The NRC branch chief who authored the attached email identified one possible approach involving the NRC taking possession of five cores and conducting independent material property testing. The branch chief requested alternate views from other NRC staff and managers.
Ultimately the NRC determined inspection at Seabrook Station and at NextEra contractor facilities where the fifteen cores were tested was appropriate. Our review of these activities and conclusions is described in NRC Inspection Report 05000443/2011010 Related to Alkali-Silica Reaction Issue in Safety-Related Structures, dated March 26, 2012 (ADAMS M1120480066).
The NRC did not taken possession of the five cores mentioned in the email you provided nor has the NRC directed what testing, if any, is warranted for these or any other cores.
Your email also provided your views related to the need for core testing for tensile strength.
The NRC has neither recommended testing of cores nor the large scale testing program NextEra is currently implementing. Rather our reviews to date have determined, based on bounding assumptions regarding the effect of ASR, that safety related structures at the Seabrook Station affected by ASR remain capable of performing their intended safety functions. Should NextEra elect to use the results of their large scale test program, or implement another approach to resolve the non-confirming ASR condition, the methodology and results will be subject to NRC review. We would expect that if NextEra submits the results of their large scale testing program as a basis for resolution of this non-conforming condition consistent with 10CFR50.59 and/or 10CFR50.90, NextEra will need to clearly establish that the test results are representative of conditions at the Seabrook Station.
Finally, I would note that although your email indicated the cores were taken from the (Seabrook) containment, I do not believe this is the case. Our inspection report referenced
above (page 3) indicates the fifteen cores were removed from the Seabrook Control Building electrical tunnel. My staff is not aware of any cores taken from the Seabrook, tri-axially reinforced containment structure.
Sincerely, Mel Gray Branch Chief, Engineering Branch 1 NRC Region 1 Office From: Debbie Grinnell Sent: Tuesday, August 05, 2014 9:04 AM To: Gray, Mel Cc: sandra
Subject:
Hello Mel, In order to confirm that ASR is occurring or is not occurring in containment after areas have been visually identified and recorded as ASR they have, a core must have been taken. It should have occurred. Could we have the results of the confirmation that ASR is present in the containment building from a core. Thank you.
My reference that cores were taken from containment that were held back and not tested for tensile strength was incorrect. There were 15 cores taken and sent to a certified lab in Illinois for compression strength only. See the attached. Five were held back as the decision NOT to do tensile strength was made. Where are they and have you asked to have them tested for tensile strength. If not, why not.
Within the same email exchange is this statement It has been established in literature that ASR reduces the tensile strength of concrete more rapidly than it reduces compressive strength. According to NRC Abdul Sheikh: Concrete shear strength is a function of its tensile strength. With the concrete being cracked, the tensile and shear strength of concrete will be appreciably different from the code specified values based on compression strength. In the design of perimeter walls, shear strength of concrete is an important consideration. The capacity of anchor bolts and embeds in concrete walls are based on shear(tensile) strength of concrete. Embeds located in cracked walls may not be capable of resisting design loads.
A clear NRC engineering rational to test for tensile strength as well as several other properties. When are you going to listen to your own staff? Are you or are you not going to require testing for the key properties your staff have stated should be done?
Thank you, Debbie T%ahnk you,