ML12054A701
| ML12054A701 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 08/01/2011 |
| From: | Conte R NRC Region 1 |
| To: | Conte R NRC Region 1 |
| References | |
| FOIA/PA-2012-0119 | |
| Download: ML12054A701 (10) | |
Text
Conte, Richard From: Conte, Richard Sent: Monday, August 01, 2011 11:26 AM To: Conte, Richard
Subject:
Cliffords Comments on TIA Draft 5 FW: Message from R1-2019K501 Attachments: SKMBT_50111080111220.pdf For hold From: rlscanbnrc.gov [1]
Sent: Monday, August 01, 2011 12:23 PM To: Conte, Richard
Subject:
Message from R1-2019K501 1.
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- 0 UNITED STATES
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NUCLEAR REGULATION I COMMISSION 0REGION 475 All ndale Road _*
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MEMORANDUM T# ert A. on, ty Director sonr olicy and Rulemaking nt r Nuclear Reactor Regulation
- ifce pp FROM: s Clifford, Deputy Director
~ (PDivision of Reactor Projects SUBJE REQUEST FOR TECHNICAL ASSISTANCE SEABROOK STATION ALKALI-SILICA REACTION Region I requests evaluate technical the potential conseq enc-c' ra ofonNuclear from the Office tance alka-ic (Rdegradatioi :f-a-eefe*(NRR)
Reactor Regulation to y---->+* J
-re ated concrete structure at Seabrook Sation, based on a re . e minar (o en) _'t.*+
Tunnel and Penetration Room) in light of a recently discovered degradation mechanism.
Additional Task Interface Agreements~may be nec..essaryfor a review of the.inal operability .. Deleted: assistance determination results for the control buiiting and for other buildings also exhibiting the-A-SR . . Deleted: the problem.
Background
NextEra (the licensee) analyzed concrete core samples from the interior surface of exterior walls of the Control Building as part of their assessment to support renewal of their license. In August 2010, tests undertaken as a part of the core sample analysis reported a change in material properties. The analysis reported the presence of an (ASR) in core samples taken from chronically wet walls below grade, with eductions reported inthe c mpessve ...... ...
strength and modulus of elasticity from that expected. NextEra evaluated these parametric reductions to determine the impact on the design basis of the Control Building. By their process, the licensee performed an immediate and prompt operability determination (POD) and concluded, preliminarily, that the Control Building was operableb ith reduced strength ........ Deleted: within the limits of the design basis__
reserves to design capacity. although NextEra continued to evaluate the extent of this condition for five other safety related buildings.
The other five buildings for which concrete core samples were taken were: Equipment Vault (housing ECCS equipment including that for Residual Heat Removal (RHR)], RCA (Radiological Controls Area) Walkway, Emergency Feedwater Building, Emergency Diesel Generator (EDG)
Building, and the Containment Enclosure Building. As of June 30, 2011 there are two open.
prompt operability determinations, one for the Control Building and one for the other five buildings collectively. The licensee found additional evidence of ASR in four of thefiveother ...... Deleted: these buildings and they evaluated that information in a separate immediate and prompt operability
R. Nelson -"2 V2 determination using the same evalua ion tec niques as for the Control Building - the evaluation is al -onsidered-prelim arv or o e . Ba d on NRC internal discussions, it appears that the a6lculation methods and correlatio sedbmay not be valid in light of the ASR problem.
NextEra's planned actions are two-fold: 1) to follow their operability determination process; and,
- 2) to follow the guidance in NEI 95-10, "Industry Guiqeline for Implementing the Requirements of 10 CFR Part 54- The License Renewal Rule," to velop an aging management program to support the license renewal application. Possible outc: es to the PODs are: 1) restored conditions (which may not be possible); 2) resolved con ions ý.... jse as is _byprocedure change Deleted: or incorporate or Action Request (AR. disposition aprsroveda; r 3)c urnticensingbasisC-LB- ------ eeterd revise revised (e.g. 10 ..*"CFR 50.59
...... .. - .. ...evaluation... ... : . ... ... -.---- -: : - ---
... : ,- . The
... ....licensee
... .... has
... ... .. . .. .. I- -- t
- elet.. th e pt--co- ndition r~
b posted on the rex nternal website their operability determination process for reference (EN- .Deleted: whicehe ondign cn AA-203-1001 ,. 1 on Certrec Document Tab List) "l,
- w " ad
.2" TheY proposal related to 'cense renewal was described in a letter dated April 14, 2011, under the response to NRC requ st for additional information B.2.1.31-1 (Agencywide Documents Access and Management S stem (ADAMS) Accession No. ML11108A131). This letter ,
- o,'
describes periodic reviews fo \operability as information is developed to support the aging management review. At the ti e, the proposal included another analysis (termed "final" by ,N, NextEra) of the impact of ASR o. t e current licensing and design basis, including the extent of \.-
the condition, to be completed by e 2011. Since that letter and as noted above, the control building POD was kept open and a immediate and POD were completed for the other five .
building core sample results.
On June 29, 2011, the NRR Division of Lt ense Renewal issued another "Request for Additional Information" (ADAMS Accession No. ML11 B8A338) related to key aspects of NextEra's comprehensive plan for assessing the ASR p blem for the Structures Monitoring Program including that for the Fuel Handling Building an Containment ("Followup RAI B2.1.31-1, . ,-h#
B2.1.31-4, and B2.1.28-3). The response to this*tter is due on or about August 13, 20"10 nditJtv-
&bot1a reflect a comprehensive plan for determinin petbility/functionality of affected ings along with plans for the development for aging manag ey review and program.
With respect to Part 50 requirements, Region I reviewed t NextEra current Structures Monitoring Program and found a violation of the maintenanc rule for the control building. The finding is described in detail in NRC Inspection Report 050004 /2011002 (ADAMS Accession No. ML111330689). More details related to the newly discovere SR issue are also documented in NRC Inspection Report 05000443/2011007 (ADA Accession No. ML111360432), which was issued as part of a license renewal inspe 'on. The cover letter for the latter report notes that the aging management review for the ASR i ue is not complete and that there is a need for a continuing review in the Part 50 and 54 areas. e staffs of Region2ý Ow and NRR (Division of Engineering and License Renewal) have been 0 .ce --- - Deleted: working closely together January 2011 to ensure that the Part 50 and ...
54 .. .. .. ... .. .. .. ........... Deleted:agency De et d:ag nc
. Deleted: this matter in unison and speaks ,th The below listed documents were made available for review on the licensee' ertrec' internal one voice website. These documents reflect current NextEra view of operability for the on ro Building - .
and the associate tunnel and penetration room. The "Certrec" system was set up in order ' -..
addree 4s~tr,. e.-ated ~te-e, documents bein@-§ad- bt.ic-tBh.-o; @ .A- c " ,
.federe-gevemrmentT;r;emses. Please inform Region I and NextEra if the document is to be printed, for review purposes, prior to doing so.
R. Nelson 3
- 1. (No. 2 on Certrec Document Library Tab List) C-S-1-10159 CALC_000, Rev. 0, 'B' Electrical Tunnel Transverse Shear Evaluation Supplement to Calculation CD-20
- 2. (No. 4 on Certrec Document Library Tab List) C-S-1-10150 CALC_000, Rev. 0, Effects of Reduce Modulus of Elasticity - 'B' Electrical Tunnel Exterior Walls
- 3. (No. 5 on Certrec Document Library Tab List) CD-20-CALC, UE Control and Deisel Generator Building Design of Material and Walls below grade for Electrical Tunnel and A ,
the Control Building (Original Design Calculation)
- 4. (No. 6 on Certrec Document Library Tab List) Action Request (AR) 581 34 Prompt Afrd Operability Determination Reduceq Concrete Properties Bel w ade inB' Electrical Tunnel Exterior Walls. . - L4 Also, before the startup/f Seabrook from a refueling outage in May 2011, on April 27, 2011, "I NRR Division of Engi!ering provided support by reviewing the following document - AR No. c 1644074 which ae reduction in modulus of elasticity in light of concrete core A"stin using a 10 CFR 50.59 screening process (note that this AR will be o Ce r6 it is related to No. 10 on Certrec Document Library Tab List, Enclosure Bldg and Con rol Bldg MSP - Design Change Package Description No. EC-272057, Rev. 000, Concrete Modulus of Elasticity Evaluation which also refers to AR No. 581434 for the Control Building (noted above). While the screening process was questioned by NRC staff, NRR DE provided a list of questions as
",.boted in the attachment (with one question being withdrawn - question No. 7.)
"---1'iicensee Position To date, within the limitations of their testing, NextEra has determined that none of the seismic _ .IJVJ. '
category I structures tested have been found to be outside their design basis. The Seabrook decadesignand licensing basis t._v hieh-t~ie-licen e e ted4heee-datez .iatioa&ie-tecmented* D (,,
4i nin UFSAR Section 3.8. 0fextEra is Gat-e-e-teehe -leet ieFfm-l -t-mee _, .. ,W ."
like y in the final operability determination currently scheduled for September 30, 2011. A ,
comprehensive plan is expected on or about August 13, 2011, in response to NRC letter of June
,, _. 29, 2011, as noted above.
e licensee is also planning an apparent cause review for the maintenance rule violation note J, o'VP , , -
0above. Corrective actions include a comprehensive walkdown of all structures with suspected ASR condition in accordance with a revised structures monitoring program procedure that /
- meets the latest ACl standard in the area (ACI 349.3R:02). This has been completed for the control building, containment enclosure building, and the containment but the completion date I for the other buildings hac,.not been formulated._ _F urther they plana rotcausee of -e Deleted: s ASRsLitshould be comrrleted i _r4corporatioen-in*rc planned March 201 ngineeting Evaluation f e abo... .. 1 In light of the newly discovered ASR issue, it appears that NextEra technical reviewers are developing new insights for what key aspects must be addressed in the final operability dAMA1 0 ---
determination for any building with evidence of ASR. NextEra is considering NRC staff questions to date and has hired consultants in this area. n order for Region I to indeendently' eermine °prailty of the'control iuirinaffected-"Y-e ASR problem (as a test case to applied to other structures), we need to independently develop a comprehensive set of issues to I a* (C7) be addressed in the final operability determination in our oversight of the licensee's process and their new insights gained. 1, rf' f,
,.//
R. Nelson 4 Requested Actions J egion I requests that NRR evaluate the adeauacy of NextEr'scontrol building operabilitv. _..... ..-.Deleted: reviewed for adequacy
,p ' etermination that is currently open with particular fou he bon below listed key tecq* . .,. Deleted: the posted documents on the Certrec Auestions. The licensee has provided a set of documents notedlonothe-referenc--rtI. Internal website supporting the control building website above but the NRR review should not be limited to those documents. Regli ('1'Electrical Tunnel and Penetration room) operability determination with particular facilitate ensuring. that additional documents, as needed, are on the website or, as necessary, by an onsite inspection. NRR's determination should enable the staff to confirm that there is j/easonable assurance of continued _operability gien the concrete degradation identified due to . ( Deleted provid a ASR for the control building. In the course of this review, Region I requests that NRR specifically identify any concerns with the assumptions, methodologies, or calculations, etc
.alon with the regulatory or other basis of each concern; and, notify Region I immediately if l NRR finds that reasonable any of the assurance reviewed documents of continued for the-buadtha operagb.l~yýt control building do not provide pg.-As-wR;m.m.,,,t eh'response*5 *.,j, L-t4~*-
. the TIA should include a e-nently developed comprehensive set of iss s-to be addressed in the final opera*ei eerina i o-BEit o Iusto further ln.,/.
k assess the licensee's process and their new insights gained for all buildings with ev ence of "
ASR.
t c
- 1. Do the referenced questions represent a comprehensive list of issues that need to be addressed in the final operability determination for the Control Building, given the current view of operability by NextEra? ,z Discussion: The reference questions are those listed in the attachment of this document L'Y 7 J 4 1]' , "
and those questions posted in the NRC RAI request for additional information [(ADAMS J_ . I.
Accession No. MI111 78A338) dated June 29, 2011, related to key aspects of NextEra's comprehensive plan for assessing the ASR problem for the Structures Monitoring Program 0)0
( -2",
including that for the Fuel Handling Building and Containment (Followup RAI B2.1.31-1, .,- OV 62.1.31-4, and B2.1.28-3)]. Ifthe issues are initially considered comprehensive, please give consideration to the below additional views produced by the regional technical staff. Ifthe , d.
CL-issues are not considered comprehensive, then identity those additional issues to be .IJAO 21.V0A*I "
included with consideration to those listed below along with regulatory or other basis for the 44,d-",-. ,,-
concern. An example would be the need for Poisson ratio calculations on core samples because there are assumed numbers in the UFSAR or stiffness damage tests because of -
applicable ACI standard requires it in the current licensing basis. ' . .'v,,'v'-. ,
- 2. What is the importance of tensile strength measurements on core samples, and distinguish its.mportance for testing related to the control building vs. the containment structure? ....... - .... Deleted: that Discussion: No tensile strength testing is being performed on the concrete core samples .q-* f and this question was raised in the RAI request for information in terms of how shear . -6 capacity is being determined. However, the Region I staff believe that the specific
-" cJ)AO '6 sr)t .
parameter of tensile strength of concrete may not be sufficiently accurate and therefore -
relevant in a constrained structure aloheASR cad is transferred to the rebar. Deleted: afte Available research in this area appears to be conflicting. For example, using ASTV , (,6AAA /
standards, the reported tensile values can vary from real values by up to +/-40% and, as one ( / " /. } /?
researcher said, "...can hardly be assumed to be a material property ." Prior to transfer, the pressure contribution appears to be minimal (on the order of less than 5% of the rebar yield based on preliminary research of literature). Other papers including the UFSAR for A .sD containment assume concrete in reinforced systems provide no tensile strength./ 4 ,*e/d
-C)-0
R. Nelson 5 Considerable research may be needed in order to independent establish a regulatory or other basis in this area.
1 'Review of the splitting-test standards from a fracture mechanics point of vieW", C. Rocco, G. V.Guinea, J. Planas, and M.Elicesh Facultad de Ingenierla, Universidad Nacional de la Plata, La Plata, Argentina, Departamento de Ciencia de Materiales, Universidad Polit~cnica de Madrid, Madrid, Spain, 5 September 2000
- 3. What is the importance of obtaining key parameter test data by conducting confined (tri-axial) core testing?
Discussion: A core sample with ASR does not represent the forces contained in the structure because for this test, in particular, elastic rebound is not considered. For split tensile tests on core samples, the frictional influences in the test itself are not accommodated. The frictional losses are further exacerbated by the standard laboratory practice of placing plywood on opposing faces of the tensile specimen to stop it from rolling off the test stand, thus restraining axial expansion of the sample.
- 4. Because the original design basis assumes no ASR is present during the design life of the structure, what are the specific original design assumptions affected by the presence of ASR that are not clearly evident in the UFSAR design basis?
Discussion: For example several calculation methods such as the relationship between compressive strength and modulus of elasticity to shear capacity and shear force are used in the seismic analysis. These assumed relationships may not be valid with ASR present in the structure.
- 5. What is the appropriate ACI standard to be used for degraded concrete core sampling assessing in-situ degradation for the control building (locations, numbers, frequency of sampling in the future, etc)?
Discussion: While this is an issue raised in the attachment, we need to know the regulatory or other basis for the use of either of two applicable standards or other more appropriate standard. One standard is ACl 228 used by NextEra for correlation to Renetration . . Deleted: SYZ resistance probe data and the other is ACI 214 (version 1965 is referenced in the UFSAR section 3.8.2.4., It should be further noted that a later revision of ACl 214 (ACI-214.R-03) Deleted: WXYZ provides for additional sampling in order to achieve a 95% confidence level. The ACI 228 appears to be met by NextEra but it requires less sampling. - These standards were- ..... . Deleted: former requires tess core samples developed for general design and construction of concrete structures for non-nuclear than the latter bercause the later standard is establishing a 95' %confidence level. NextEra applications. Technical research may be needed in order to determine their relevance for has chosen the fo'rmer or the least amount of nuclear application in which the structures are heavily reinforced with rebar. This leads to sampling.
the next set of questions.
- 6. What is the complete set of aboratory tests for cre sampling including_aproprate parameters obtained along with laboratory................................................................
test conditions ........... ............ .... { Deleted; ptease-- Duringthe Denletduing thecouptet cours pleas Identify the complet of this review, ness of the Deleted: Ing of Discussion: Also, during the course of this review, please identify the need for,an in_ situ ".( ee:.,
testing of control building conditions including appropriate parameters to be obtained suc . Deleted: completeness of as temperature and humidityalong with test .................
........... now and in the conditions for................. future. Also,.................
.................. Deleted: obtaned De leted : obta ine
R. Nelson 6 provide guidance on where and how much rebar should be exposed in order to assess the effect on rebar from the ASR issue.
- 7. What is the effect of the alkali-silica reaction degradation on the current and future ability of the control building to respond to design basis loads, including seismic events?
Discussion: NextEra is planning new modeling of the building loads including seismic. A review of the seismic analysis codes is beyond the current capability of the Region I technical staff. This review should include an assessment of the need to analyze the foundations alone vs. the response of a whole structure when just the foundation is degraded.
Coordination This request was discussed between Richard Conte and Michael Modes (RI), and Meena Khanna, George Thomas, and Barry Miller (NRR) during a final conference call on ...... The TIA was accepted with an agreed upon preliminary draft response date within 45 days and a final response of 90 days after receipt. The purpose of the preliminary draft response is to communicate issues early to NextEra during the course of a followup inspection in this area.
References http://ims.certrec.com (No. 2 on Certrec Document Library Tab List) C-S-1-10159 CALC_000, Rev. 0, 'B' Electrical Tunnel Transverse Shear Evaluation Supplement to Calculation CD-20 (No. 4 on Certrec Document Library Tab List) C-S-1-10150 CALC_000, Rev. 0, Effects of Reduce Modulus of Elasticity - 'B' Electrical Tunnel Exterior Walls (No. 5 on Certrec Document Library Tab List) CD-20-CALC, UE Control and Deisel Generator Building Design of Material and Walls below grade for Electrical Tunnel and the Control Building (Original Design Calculation)
(No. 6 on Certrec Document Library Tab List) Action Request (AR) 581434 Prompt Operability Determination Reduced Concrete Properties Below Grade in 'B' Electrical Tunnel Exterior Walls.
http:/Iportal.nrc.gov/edo/ri/EB1/Shared%20Documents/Forms/AlIItems.aspx Docket No. 50-443 CONTACT: Michael Modes, DRS (610) 337-5198
R. Nelson 7 ML111610530 SUNSI Review __ Complete DOCUMENT NAME: G:\DRS\Engineering Branch 1\-- MModes\TIA Seabrook ASR Draft 2.docx Publicly Available Non-Publicly Available Sensitive Non-Sensitive To recelye a oopyof 'lis dcument Indicate Inthe concurrenoe bx 'CV Copy whot U ttohi/encl; 1, gf=oy th aace/ond 'N = No pop OFFICE RI DRS RI DRS RI DRP RI DRS RI DRP NAME MModes RConte ABurritt PWilson DRoberts DATE 06/ /11 06/ /11 06/ /11 06/ /11 06/ /11
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R. Nelson 8 Attachment DE/EMCB Comments on AR1644074 Evaluation of Containment Enclosure Building (CEB)
(4-27-11)
- 1. An important effect of reduction in elastic modulus (Ec) of concrete due to ASR is a reduction in stiffness (axial, flexural, shear) of the affected areas relative to the stiffness of the unaffected areas. This would result in redistribution of forces in the global response of the structure under design loads due to changes in the relative stiffness of the affected and unaffected areas from that considered in the original global structural analyses of the CEB using the SAG computer code. Further, since the ASR degradation is in the lower areas of the CEB, the reduction in elastic modulus could affect the boundary conditions assumed in the original analysis at the junction of the basemat and the CEB wall. Note that FSAR Section 3.8.4.4.a states, in part, that 'Lateral forces are transferredto the foundation mats primarilyby the action of shear walls; some load is also transferredby means of flexural action of the wall, all of which are rigidly attachedat the mat." Also refer to pages 11 and 12 of Calculation C-S-1-10150. The AR1644074 Evaluation does not address the effect of the reduced modulus on the global response of the structure. It assumes that the forces and moments in the different elements of the structure under design loads remains the same and only evaluates the local sections (concrete stresses, strains and flexural capacity) for the reduced modulus, which are based on forces and moments from the original structural analysis.
- 2. The AR1644074 Evaluation does not evaluate the effect of the reduced modulus on the shear capacity of the affected area.
- 3. The AR1644074 Evaluation does not address the effect of the reduced modulus on the potential changes in the natural frequencies of the CEB structure, which could have effect the response of the structure to seismic load.
- 4. The AR1644074 Evaluation of the local section does not evaluate the effect of reduced modulus on stress and strain in the rebar. The strain in the rebar could go beyond the yield strain. From page 47 of Calc CE-4 referenced in the evaluation for element 255, the stress in the hoop reinforcement is 61.493 ksi, which is already beyond yield.
- 5. The AR1644074 Evaluation of the local section is based on element 255, which is 27" thick and appears to be outside the area affected by ASR. The areas affected by ASR appear to be at the lower elevations of the CEB which are 36" thick. A critical element in the affected area needs to be evaluated. Further, note that the forces and moments in element 255 could increase based on Comment 1 above, and thereby further affect concrete and rebar stresses and strains in element 255.
- 6. The AR1644074 Evaluation does not explicitly evaluate the effect of the reduced modulus on the flexural capacity of affected local sections, but makes reference to Calc
R. Nelson C-S-1-10150 performed for the electrical tunnel. The effect on flexural capacity of the affected Section of the CEB should be explicitly evaluated since the effect of the reduced modulus on moment capacity of a section is a function of the amount of reinforcement in the section, the section dimensions and material properties. The CEB wall reinforcement, dimensions and material properties appear significantly different from that of the electrical tunnel.
- 7. On page - of the AR Evaluation, tIs stated that "The roducti*n in Ec 74,6nF "auses the neutral axis of the baianced cencrete and rFenfOrcing steol cootion to shift toWard the tension reinforcing steel." it appears that the reduction in Ec would tend to cause the noutral axis to shift toward the extrcme comprescion fibor that the tension reinforcing steekjPeF T Per George Thomas telecon of June 9, 2010 with R. Conte.
- 8. To have any level of statistical validity, the number of cores used in an evaluation should be at least 3. The AR1644074 Evaluation uses results based on only 2 core tests of the ASR affected area.
- 9. What are the strain levels at the reported values of concrete compressive strength and elastic modulus from core tests reported in Table 1 of AR1644074? Does petrographic examination of the cores indicate ASR through the thickness of the wall.
- 10. The AR1644074 evaluation should include a problem statement description of the condition being evaluated and its preliminary extent (at least based on visual inspection) for the structure in question so that an outside reviewer can understand what is being evaluated.