ML21235A104

Letter to Natalie Treat, Executive Director, C-10 Research and Education Foundation, from Chairman Hanson Questions Raised with Commissioner Baran Regarding Safety Concerns at Seabrook Station

ML21235A104
Person / Time
Site:	Seabrook
Issue date:	09/16/2021
From:	Christopher Hanson NRC/Chairman
To:	Treat N C-10 Research & Education Foundation
Poole J, NRR/DORL/LPLI, 415-2048
Shared Package
ML21221A234	List: ML21235A104
References
CORR-21-0067, LTR-21-0226
Download: ML21235A104 (4)

Text

1. REGoe UNITED STATES

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? a WASHINGTON DC. 205550001 e

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%*o CHAIRMAN September 16,2021 Ms.Natalie H.Treat Executive Director C-10 ResearchandEducation Foundation 11Chestnut Street Amesbury, MA 01913

Dear Ms.Treat:

OnbehalfoftheU.S.Nuclear Regulatory Commission (NRC), Iamresponding to your dated letter August 9,2021, inwhich yourequested responses toseveral questions and concerns alkali-silica about reaction atSeabrook Station, Unit No. 1 (Seabrook). Responses tothe specific questionsinyourletter areenclosed.

your Iappreciate letter andcontinued interestintheNRC's oversight atSeabrook. If youhave additional questions orneedmoreinformation, please contact Justin Poole, Project Manager, ofNuclear Office Reactor Regulation, at301-415-2048 orJustin.Poole@nrc.gov.

Sincerely, s .

( . s ,

Christopher T.Hanson

Enclosure:

Asstated

U.S.Nuclear Regulatory Commission Responses toQuestions intheAugust 9,2021, Letter Question 1 Because so much isunknown about therate ofASR[alkali-silica reaction) expansion,why doesn't NRCrequire theuseoferror bars inmodeling its progression?This isonearea where independent experts could beofassistance toquantify themargin oferror.Wedon't knowwhere we areonthecurve. That iscause forconcern by C-10 andDr. Saouma; itshould beofequal concern to NextEra andtheNRC. Indeed, determination ofthe out-of-plane expansion relies ontheavailabilityof concrete cores saved during construction, andthe empirical curve torelatedegradation ofelastic modulus with expansion. Thuswe have tworelated questions:

a)Howmanyconstruction cores have been saved over thepast 40years? We would like toknowunder which protocol were they collected (how many cores percast cubicyard), under which conditions (temperature andrelative humidity) have they been stored,andhowmanyhave been savedfrom theconcrete cast inthe containment buildingfrom thebase tofive feet aboveground-themost criticalsegment ofthebuilding? A picture ofthose cores would goa long wayin assuaging ourconcerns.

b)Howconfident areyouinusing thecalibration curve? Can youquantify its 90%confidence levelinterms oftheassociated uncertainties (calibration curve, empirical relationshipbetween compressive strength andelastic modulus, representativeness oftheclosest core toanarbitrary location of sudden ASR expansion)? Ultimately,howtall would youexpect the error barsto be?

There isnoNRCrequirement tosave theinitial construction cylinders ("cores")beyond testing theoriginal conducted during construction. Thelicensee collected wetconcrete samples actual during construction pours ofeach structure, andstandard cylinders werecast and tested inaccordance withapplicableAmerican Society for Testing andMaterials standards atspecified times(e.g.,

7 days, 28days), asrequired bytheconstruction codes ofrecord (American ConcreteInstitute 318-71, "Building CodeRequirements for Reinforced Concrete," forother category1 structures, andthe1973 Edition of American Society of Mechanical Engineers Boiler andPressure Vessel CodeSection III, Division 2,for containment). TheNRCdoesnotmaintain constructionrecords; thelicensee maintains these records onsite for future reference anduse, asnecessary. Whenextensometers areinstalled inreinforced concrete structures atSeabrook, coresremoved from theplace where theextensometer will belocated aretested; anythrough expansion thickness todate isthen determined using themethodology approved bytheNRCin LicenseAmendment No.159(Agencywide Documents Access andManagement System (ADAMS) Accession No.ML18204A291).

Asdetailed intheNRCsafety evaluation for that license amendment, theNRCstaff foundthatthelicensee's useofthecalibration curve provided reasonable assurance of adequateprotection ofthepublic health andsafety. While neither thelicensee northeNRC staff placed a quantified confidence level, orerror bars, onthecalibration curve (i.e.,

the correlation"),

"modulus-expansion a conservative modulus reduction factor was appliedtothe curve calibration toaccount for uncertainty. Additionally, aspart ofLicense Amendment No.

Enclosure

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159, theNRCimposed a license condition that the curve becorroborated with actualfield measurements andobservations asadditional plant-specific data become available. The adequacy ofthecalibration curve, along with theuseoferror bars, wasconsidered bythe Atomic Safety andLicensing Board, andtheBoard found that thelicensee's approach tothe corroboration study (without the useoferror bars) provided reasonable assurance ofadequate protection (Atomic Safety and Licensing Board I nitial Decision LBP-20-9 (slip op.at 167-70)

(ADAMS Accession No. ML20254A339); Atomic Safety andLicensing Board Memorandum and Order, LBP-20-12(slip. op.at10) (ADAMS Accession No.ML20322A417)).

Question 2:

HowcantheNRCincrease transparency about whatinspectors seeattheplant, in particular, with regard toASR?

IfNRCinspections donotidentify findings ofmore-than-minor significance, theagency's practice isgenerally todocument theinspection ina brief, straightforward manner, usually consisting ofa sentence ortwodescribingthe subject oftheinspection. WhenNRCinspections identify performance issues thatinvolve findings orviolations ofmore-than-minor significance, theinspectors document agency activities and conclusions in greater detail, following a systematic process. Inspectors also document observations andminor violations inaccordance with theNRC's Enforcement Manual andapplicableinspection manual chapters. For example, the mostrecent Seabrook inspection report (ADAMS Accession No. ML21222A126) provided several such observations anda description ofNextEra'sASR monitoring-related activities, as well asobservations anddocumentation ofa minor violationrelated toseveral other inspections conducted during thequarter. AstheNRCstaff conducts its ongoing inspections atSeabrook, agency inspectors willcontinue todocument their inspection results consistent with agency policy insufficient detail sothat stakeholders canadequately followNRC inspection activities andregulatory conclusions. Inspection reports will continue tobepublicly available inthe NRC's ADAMSat . Members of the publiccanalso sign uptoreceive notice ofplant-specific public documents asthey becomeavailable at Question 3:

Under whatcircumstances might theagency revisit Seabrook's concrete aging management program?

TheNRChasa number ofprocesses toalert theagency tonewinformation thatmay triggerfurther consideration ofa licensee's aging management program (AMP). Forexample, information gathered through inspections ofthelicensee's activities, reviews ofplant operating experience, ortheresults ofresearch activities could prompt a review ofanAMP.Additionally, theNRC's regulation at10CFR2.206 permits anyperson topetition theNRCtomodify, suspend, orrevoke a license, orfor anyother action asmaybeproper.

With respect toSeabrook specifically, Seabrook's ASRAMPinthe current license includes requirements for thelicensee tomonitor plant-specific andindustrywide operating experience, including applicable ongoing industry studies andresearch, update theprogram as necessary. These provisions arediscussed intheNRCstaff's safety evaluation reportfor Seabrook license renewal (ADAMS Accession No.ML18362A370). TheNRCstaff continues to monitor Seabrook's implementation ofits ASRprograms andrelated license conditions through inspections under theReactor Oversight Process. Ifinspection results indicate thatthelicensee

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is not properly implementing its programs ormeeting license then conditions, theNRCcantake actions toincrease inspections andoversight. Thestaff documented theresults oftheNRC's mostrecent inspection that included anASRsample inSeabrook Station, UnitNo.1,Integrated Inspection Report No.05000443/2021002, dated August 11,2021(ADAMS Accession No.ML21222A126).

Question 4:

After whatyou've learned intheSeabrook case, would yousupport thedevelopmentof NRCregulations governing concrete testing, andmorescrutiny ofother material-aging issues?

TheNRCcontinues tobelieve thatcompliance with theexisting in10CFR regulations Part 50,"Domestic licensingofproduction andutilization and10CFRPart facilities," 54,aswell asinspection andrelated activities under theNRC'sReactor Process Oversight provide reasonable assurance that concrete degradation duetoASR,orother material-aging issues, will bemanaged such affected that safety-related structures atnuclear powerplants willremain capable ofperforming their intended functions. Existing NRCregulations licensees require to monitor theperformance andcondition ofsafety-related structures andtoaddress conditions adverse toquality (includingsignificant degradation) ina manner sufficient toprovide reasonable assurance that intended functions will be maintained. NRCregulationsareintended toprovide generic rulesorrequirements.