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

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%*o CHAIRMAN September 16,2021 Ms.Natalie H.Treat Executive Director C-10Research andEducation Foundation 11Chestnut Street

Amesbury, MA01913

DearMs.Treat:

Onbehalf oftheU.S.Nuclear Regulatory Commission (NRC),

Iamresponding to yourletter dated August 9,2021,inwhichyourequested responses toseveral questions and concerns about alkali-silica reaction atSeabrook

Station, Unit No.1(Seabrook). Responses tothespecific questions inyourletter areenclosed.

Iappreciate yourletter andcontinued interest intheNRC's oversight atSeabrook.

If youhaveadditional questions orneedmoreinformation, please contact Justin Poole, Project

Manager, Office ofNuclear Reactor Regulation, at301-415-2048 orJustin.Poole@nrc.gov.

Sincerely, s

. (.

s Christopher T.Hanson

Enclosure:

Asstated

U.S.Nuclear Regulatory Commission Responses toQuestions intheAugust9,2021,Letter Question 1

Becauseso much isunknownabouttherateofASR[alkali-silica reaction) expansion,why doesn't NRCrequire theuseoferror barsinmodeling its progression?This isoneareawhereindependent experts could beofassistance toquantify the margin oferror.Wedon't knowwhereweareonthecurve.

That iscauseforconcern by C-10 andDr.Saouma;itshould beofequal concern to NextEra andtheNRC.

Indeed, determination oftheout-of-plane expansion relies ontheavailabilityof concrete coressavedduring construction, andthe empirical curve torelate degradation ofelastic modulus withexpansion.

Thuswe havetworelated questions:

a)

Howmanyconstruction cores have been savedoverthepast40years?We wouldlike toknowunder which protocol were theycollected (how manycores percastcubic yard),

underwhich conditions (temperature andrelative humidity) havetheybeenstored, andhowmanyhave been savedfromtheconcrete cast inthecontainment building fromthebasetofive feet aboveground-themost critical segment ofthebuilding?

A picture ofthose cores wouldgoalongwayin assuaging ourconcerns.

b)Howconfident areyouinusing thecalibration curve? Can youquantifyits 90%confidence level intermsoftheassociated uncertainties (calibration curve, empirical relationship between compressive strength andelastic

modulus, representativeness oftheclosest coretoanarbitrary locationof sudden ASR expansion)?

Ultimately, howtall wouldyouexpect theerror barsto be?

ThereisnoNRCrequirement tosavetheinitial construction cylinders("cores")beyond theoriginal testing conducted during construction.

Thelicensee collected wetconcrete samples during actual construction pours ofeachstructure, andstandard cylinders werecastand tested inaccordance with applicable American Society forTesting andMaterials standards atspecified times(e.g.,

7days, 28days),

asrequired bytheconstruction codesofrecord (American Concrete Institute 318-71, "Building CodeRequirements forReinforced Concrete,"

for other category 1structures, andthe1973Edition ofAmerican Society ofMechanical Engineers Boiler andPressure Vessel CodeSection

III, Division 2,forcontainment).

TheNRCdoesnotmaintain construction records; thelicensee maintains these records onsite forfuture reference

anduse, asnecessary.

Whenextensometers areinstalled inreinforced concrete structures atSeabrook, cores removed fromtheplace wheretheextensometer will belocated aretested; anythrough thickness expansion todateisthendetermined using themethodology approved bytheNRCin License Amendment No.159(Agencywide Documents AccessandManagement System (ADAMS)

Accession No.ML18204A291).

Asdetailed intheNRCsafety evaluation forthat license amendment, theNRCstaff found that thelicensee's useofthecalibration curveprovided reasonable assurance of adequate protection ofthepublic health andsafety.

Whileneither thelicensee northeNRC staff placed aquantified confidence

level, orerror

bars, onthecalibration curve(i.e.,

the "modulus-expansion correlation"),

aconservative modulus reduction factor wasapplied tothe calibration curve toaccount foruncertainty.

Additionally, aspartofLicense Amendment No.

Enclosure

- 2 159, theNRCimposed alicense condition that thecurve becorroborated with actual field measurements andobservations asadditional plant-specific databecomeavailable.

The adequacy ofthecalibration curve, along with theuseoferror

bars, wasconsidered bythe Atomic Safety andLicensingBoard,andtheBoard found that thelicensee's approach tothe corroboration study (withouttheuseoferror bars) provided reasonable assurance ofadequate protection (Atomic Safety andLicensing BoardInitial Decision LBP-20-9 (slip op.at167-70)

(ADAMS Accession No. ML20254A339);

Atomic Safety andLicensing BoardMemorandum and

Order, LBP-20-12(slip.

op.at10)

(ADAMS Accession No.ML20322A417)).

Question 2:

HowcantheNRCincrease transparency about whatinspectors seeattheplant, in particular, withregard toASR?

IfNRCinspections donotidentify findings ofmore-than-minor significance, theagency's practice isgenerally todocument the inspection

inabrief, straightforward

manner, usually consisting ofasentence ortwodescribingthe subject oftheinspection.

WhenNRCinspections identify performance issues that involve findings orviolations ofmore-than-minorsignificance, theinspectors document agency activities andconclusions ingreater

detail, following a

systematic process.

Inspectors alsodocument observations andminor violations inaccordance with theNRC'sEnforcement Manual andapplicableinspection manualchapters.

Forexample, themostrecent Seabrook inspection report (ADAMS Accession No.ML21222A126) provided several suchobservations andadescription ofNextEra'sASR monitoring-related activities, as well asobservations anddocumentation ofaminor violationrelated toseveralother inspections conducted during thequarter.

AstheNRCstaff conducts its ongoing inspections atSeabrook, agency inspectors will continue todocument their inspection results consistent withagency policy insufficient detail sothat stakeholders canadequately followNRC inspection activities andregulatory conclusions.

Inspection reports will continue tobepublicly available inthe NRC'sADAMSat

. Membersof the publiccanalso signuptoreceive notice ofplant-specific public documents asthey becomeavailable at Question 3:

Underwhatcircumstances might theagency revisit Seabrook's concrete aging management program?

TheNRChasanumberofprocesses toalert theagency tonewinformation that may trigger further consideration ofalicensee's aging management program (AMP).

Forexample, information gathered through inspections ofthelicensee's activities, reviews ofplant operating experience, ortheresults ofresearch activities could promptareview ofanAMP.Additionally, theNRC'sregulation at10CFR2.206 permits anyperson topetition theNRCtomodify,

suspend, orrevoke

alicense, orforanyother action asmaybeproper.

Withrespect toSeabrook specifically, Seabrook's ASRAMPinthecurrent license includes requirements forthelicensee tomonitor plant-specific andindustrywide operating experience, including applicable ongoing industry studies andresearch, update theprogram as necessary.

Theseprovisions arediscussed intheNRCstaff's safety evaluation report for 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 that thelicensee

- 3 is not properly implementingitsprograms ormeeting license conditions, thentheNRCcantake actions toincrease inspections andoversight.

Thestaff documented theresults oftheNRC's mostrecent inspection that included anASRsampleinSeabrook

Station, Unit No.1,Integrated Inspection Report No.

05000443/2021002, dated August 11,2021(ADAMS Accession No.ML21222A126).

Question 4:

After whatyou've learned intheSeabrook

case, wouldyousupport thedevelopment of NRCregulationsgoverning concretetesting, andmorescrutiny ofother material-aging issues?

TheNRCcontinues tobelieve thatcompliance withtheexisting regulations in10CFR Part50,"Domestic licensing ofproduction andutilizationfacilities,"

and10CFRPart54,aswell asinspection andrelated activities under theNRC'sReactor Oversight Process provide reasonable assurance that concrete degradation duetoASR,orother material-aging

issues, will bemanaged suchthat affected safety-related structures atnuclear powerplants will remain capable ofperforming their intended functions.

Existing NRCregulations require licensees to monitor theperformance andcondition ofsafety-related structures andtoaddress conditions adverse toquality (including significant degradation) inamanner sufficient toprovide reasonable assurance that intended functions will be maintained.

NRCregulations areintended toprovide generic rules orrequirements.