ML14358A375
| ML14358A375 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 12/12/2014 |
| From: | Mel Gray Engineering Region 1 Branch 1 |
| To: | Gavutis S C-10 Research & Education Foundation |
| Gray M | |
| References | |
| Download: ML14358A375 (2) | |
Text
From: Gray, Mel Sent: Friday, December 12, 2014 1:44 PM To: sgavutis@ .com Cc: Cook, William; Dentel, Glenn
Subject:
Response to Email from Ms. Sandra Gavutis, Executive Director, C-10 Foundation Regarding NRC Inspection of the Seabrook Station and Structures Affected by ASR Ms. Gavutis, Your email to me on November 12, 2014 included questions regarding a previous email response I provided to Ms. Grinnell of your organization, dated October 16, 2014 (available in the NRCs Agency-wide Documents Access & Management System (ADAMS) under Accession number ML14343A454). Your questions are listed below followed by our responses.
- 1. Referencing your paragraph 6, was the test done in 2010 the same test procedure that was used in 1979?
(That is not clear from your message.) Second, given that the average reduction in the concretes compressive strength was 22%, what was the range of the reduction? (by that we mean, did the reductions range from 20%-
24%, or 2% to 80%, for example).
Response: The standard methodologies used by NextEra staff to obtain and test core samples in 2010 are described in NRC Inspection Report No. 05000443/2011007 dated May 23, 2011 (See ML111360432, page 18). Our inspection report did not identify the test procedures used by NextEra in 1979. A comparison of the 2010 core compressive strength test results to data from 1979 is described in our inspection report as a 21.7%
(approximately 22%) reduction in compressive strength of the concrete. This is a reduction of the average of the 2010 results when compared to the average in 1979. NextEra described the 2010 core strength test results in a document to the NRC dated May 2012. See ML12151A397, Section 3.1.2, page 20 of 182. This document identifies the range of core compressive strength test results from 2010 conducted by Miller Engineering and Testing. The as-tested compressive strength values ranged from 5,690 psi to 3,630 psi (a 7%
- 41% reduction from the original 6,120 psi construction test results), with an average value of 4,790 psi (a 22%
reduction). All of the values exceed the original minimum specified compressive strength of 3,000 psi.
- 2. Referencing paragraph 8: Your message states that contractors for NextEra in 2010 performed the required five-year interval IWL examination of the outer reinforced concrete surface of the containment. Given that the NRC staff did not agree with NextEras initial view that this examination would satisfy their commitment to complete a comprehensive ASR walk down of all reinforced concrete structures potentially affected by ASR, how will re-performing in 2015 the same test satisfy the NRCs requirement? Do you mean NextEras contractors will be performing a different type of or a more extensive surface area test? Can you help us by explicating this, please?
Response: The IWL inspection of the outer concrete surface of the containment structure was performed in late 2010, prior to NextEras implementation of the ASR Walkdown activity. NRC Inspection Report No.
05000443/2012009, dated December 3, 2012, Section 7.2, identifies NRC inspector conclusions that NextEra staff inappropriately credited the 2010 IWL containment inspection as part of their comprehensive station walkdown to identify ASR-affected structures. The inspectors detailed review of the 2010 IWL inspection results and associated visual examination attributes identified that the 2010 IWL exam did not include sufficient examination criteria (i.e., active or pattern cracking) for identification of ASR. NextEra staff entered this issue into their corrective action program under AR 1819069 to augment the scheduled 2015 IWL examination guidance to specifically look for evidence of ASR on the containment reinforced concrete exterior shell.
- 3. Further, still on paragraph 8, your last sentence states that no additional ASR-related inspections or testing of containment have been recommended or imposed by the NRC. Does that mean that the NRC is NOT requiring or recommending core sampling be done? And if not, why not? It would seem clear that if there is crazing/cracking on the surface, there could well be changes in the interior of the concrete that should be investigated. Does that presumption seem correct and reasonable?
1
Response: Core samples taken from the Seabrook containment structure to validate the current evidence of localized areas of ASR have not been required by the NRC. As documented in NRC Inspection Report IR No.
05000443/2012010 (ML13221A172), Section 9.3, the NRC has reviewed and found acceptable the current Prompt Operability Determination for the ASR-affected containment structures. My letter to you dated August 4, 2014 (ML14217A040), addressed a similar question as to whether the NRC was requesting concrete core locations and samples from NextEra staff. While the NRC does not require items such as core locations and samples, our reviews will assure NextEras actions are technically sound and appropriate to address ASR-affected structures at the Seabrook Station. The NRC has concluded the Seabrook ASR-affected safety related structures remain capable of performing their structural safety functions and that these structures represent a non-conforming condition that requires resolution. NextEra has elected to pursue a large scale test program to resolve this condition. We expect that NextEra will need to clearly establish that the results of their large scale test program are representative of actual conditions at Seabrook Station prior to formally submitting the results of their accompanying evaluations to the NRC in accordance with the requirements of 10 CFR 50.59 and 50.90 as applicable to resolve the ASR non-conforming condition.
- 4. If as you say in paragraph 9, ACI 349.3R does not require drilled cores to evaluate the condition of reinforced concrete, would it not be advisable to rewrite ACI 349.3R to take into account the new reality of ASR? Please comment.
ACI 349.3R is a standard established and maintained by the American Concrete Institute (through their standing ACI subcommittee 349) to describe methods and guidance for the evaluating existing safety related concrete structures at nuclear power plants. The committee periodically reviews and updates, as appropriate, this standard for use.
Should you have any additional questions or concerns, please contact Mr. William Cook or myself.
Sincerely, Mel Gray Chief, Engineering Branch 1 Division of Reactor Safety NRC Region I 2
From: Gray, Mel Sent: Friday, December 12, 2014 1:44 PM To: sgavutis@ .com Cc: Cook, William; Dentel, Glenn
Subject:
Response to Email from Ms. Sandra Gavutis, Executive Director, C-10 Foundation Regarding NRC Inspection of the Seabrook Station and Structures Affected by ASR Ms. Gavutis, Your email to me on November 12, 2014 included questions regarding a previous email response I provided to Ms. Grinnell of your organization, dated October 16, 2014 (available in the NRCs Agency-wide Documents Access & Management System (ADAMS) under Accession number ML14343A454). Your questions are listed below followed by our responses.
- 1. Referencing your paragraph 6, was the test done in 2010 the same test procedure that was used in 1979?
(That is not clear from your message.) Second, given that the average reduction in the concretes compressive strength was 22%, what was the range of the reduction? (by that we mean, did the reductions range from 20%-
24%, or 2% to 80%, for example).
Response: The standard methodologies used by NextEra staff to obtain and test core samples in 2010 are described in NRC Inspection Report No. 05000443/2011007 dated May 23, 2011 (See ML111360432, page 18). Our inspection report did not identify the test procedures used by NextEra in 1979. A comparison of the 2010 core compressive strength test results to data from 1979 is described in our inspection report as a 21.7%
(approximately 22%) reduction in compressive strength of the concrete. This is a reduction of the average of the 2010 results when compared to the average in 1979. NextEra described the 2010 core strength test results in a document to the NRC dated May 2012. See ML12151A397, Section 3.1.2, page 20 of 182. This document identifies the range of core compressive strength test results from 2010 conducted by Miller Engineering and Testing. The as-tested compressive strength values ranged from 5,690 psi to 3,630 psi (a 7%
- 41% reduction from the original 6,120 psi construction test results), with an average value of 4,790 psi (a 22%
reduction). All of the values exceed the original minimum specified compressive strength of 3,000 psi.
- 2. Referencing paragraph 8: Your message states that contractors for NextEra in 2010 performed the required five-year interval IWL examination of the outer reinforced concrete surface of the containment. Given that the NRC staff did not agree with NextEras initial view that this examination would satisfy their commitment to complete a comprehensive ASR walk down of all reinforced concrete structures potentially affected by ASR, how will re-performing in 2015 the same test satisfy the NRCs requirement? Do you mean NextEras contractors will be performing a different type of or a more extensive surface area test? Can you help us by explicating this, please?
Response: The IWL inspection of the outer concrete surface of the containment structure was performed in late 2010, prior to NextEras implementation of the ASR Walkdown activity. NRC Inspection Report No.
05000443/2012009, dated December 3, 2012, Section 7.2, identifies NRC inspector conclusions that NextEra staff inappropriately credited the 2010 IWL containment inspection as part of their comprehensive station walkdown to identify ASR-affected structures. The inspectors detailed review of the 2010 IWL inspection results and associated visual examination attributes identified that the 2010 IWL exam did not include sufficient examination criteria (i.e., active or pattern cracking) for identification of ASR. NextEra staff entered this issue into their corrective action program under AR 1819069 to augment the scheduled 2015 IWL examination guidance to specifically look for evidence of ASR on the containment reinforced concrete exterior shell.
- 3. Further, still on paragraph 8, your last sentence states that no additional ASR-related inspections or testing of containment have been recommended or imposed by the NRC. Does that mean that the NRC is NOT requiring or recommending core sampling be done? And if not, why not? It would seem clear that if there is crazing/cracking on the surface, there could well be changes in the interior of the concrete that should be investigated. Does that presumption seem correct and reasonable?
1
Response: Core samples taken from the Seabrook containment structure to validate the current evidence of localized areas of ASR have not been required by the NRC. As documented in NRC Inspection Report IR No.
05000443/2012010 (ML13221A172), Section 9.3, the NRC has reviewed and found acceptable the current Prompt Operability Determination for the ASR-affected containment structures. My letter to you dated August 4, 2014 (ML14217A040), addressed a similar question as to whether the NRC was requesting concrete core locations and samples from NextEra staff. While the NRC does not require items such as core locations and samples, our reviews will assure NextEras actions are technically sound and appropriate to address ASR-affected structures at the Seabrook Station. The NRC has concluded the Seabrook ASR-affected safety related structures remain capable of performing their structural safety functions and that these structures represent a non-conforming condition that requires resolution. NextEra has elected to pursue a large scale test program to resolve this condition. We expect that NextEra will need to clearly establish that the results of their large scale test program are representative of actual conditions at Seabrook Station prior to formally submitting the results of their accompanying evaluations to the NRC in accordance with the requirements of 10 CFR 50.59 and 50.90 as applicable to resolve the ASR non-conforming condition.
- 4. If as you say in paragraph 9, ACI 349.3R does not require drilled cores to evaluate the condition of reinforced concrete, would it not be advisable to rewrite ACI 349.3R to take into account the new reality of ASR? Please comment.
ACI 349.3R is a standard established and maintained by the American Concrete Institute (through their standing ACI subcommittee 349) to describe methods and guidance for the evaluating existing safety related concrete structures at nuclear power plants. The committee periodically reviews and updates, as appropriate, this standard for use.
Should you have any additional questions or concerns, please contact Mr. William Cook or myself.
Sincerely, Mel Gray Chief, Engineering Branch 1 Division of Reactor Safety NRC Region I 2