ML23255A005
| ML23255A005 | |
| Person / Time | |
|---|---|
| Site: | Clinch River, 99902056 |
| Issue date: | 09/13/2023 |
| From: | Allen Fetter Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML23255A005 (1) | |
Text
9/11/2023
NRC Public Meeting
TVA Clinch River Project
CRN-1 Reactor Building Excavation
September 13, 2023
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Agenda Introductions Clinch River Nuclear (CRN) Site
Background
Expected Activities/Benefits Exemption Request Schedule Conclusion Questions/Comments
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Background
- InpreparingtheCRN-1sitefornuclearconstruction,TVAintendstoexcavateforthe BWRX-300ReactorBuildinginadvanceofreceivingtheConstructionPermit(CP).
- Per10CFR50.10(a)(2)(v),excavationonitsownisnotconsideredtofallintothe definitionofconstruction.
- Toensureworkersafetyduringexcavationandfacilitateconstructionactivities,an initialgroundsupportsystemisexpectedtobeinstalledforerosioncontrolpriorto andduringexcavation.
- Initialgroundsupportsystemservesnofunctioninthecompletedconstruction.
- Proposedinitialgroundsupportfeaturesareinfeasibletoremoveandareplannedto beabandonedinplace.
- TVAhasnotyetauthorizedthedeploymentofanSMR.Nonetheless,thesediscussions andeffortsregardingexcavationactivitieswillenableTVAtomoveforwardinatimely manner,ifandwhenadecisionismadetobuildanSMR.
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Initial Ground Support System
The following items may be installed as part of theinitial ground support system:
secant piles or steel piles through the soil overburden and weathered rock, if required, rock bolts to secure unstable rock blocks and create a safe and stable excavation, as required, wire mesh and a thin, non-structural sprayed-gunitelining to stabilize and protect exposed rock walls, horizontal gravity drains to manage groundwater, as required, pressurized grout to seal any notable areas of water entry.
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Benefits of Excavation prior to CP Issuance Reduces risk and improves schedule by completing excavation prior to CP issuance and commencement of construction activities:
Additional subsurface information can be provided to the NRC to consider before the CP is issued.
Allows the extensive geotechnical mapping and surveys to be performed on a more controlled schedule when it is separated from the primary construction schedule.
Identification of any critical features like discontinuities, shear zones, faults, karst features, or potentially unstable blocks will help improve the design of the permanent ground support system prior to construction.
Optimizing the schedule for demonstrationof new nuclear plants is imperative to enabling TVA to consider SMRs throughout the TVA Power Service Areas to support TVAs carbon emission reduction aspirations (e.g. net-zero by 2050).
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Expected Excavation Activities
- 1. Sitepreparationactivities
- 2. Installationoffieldinstrumentation
- 3. Excavationthroughthesoiloverburdenandweatheredrock.
- 1)slopedexcavationusingconventionalearthmoving equipment,
- 2)secantpilesorsteelpilesinstalledandkeyedintothe bedrock1.
- 4. Constructionoftemporarycranepads.
- 5. Linedrillingaroundtheperimeteroftheshaftexcavation.
1If installed will be abandoned in place.
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Expected Excavation Activities
6.Excavatingthroughthebedrockwillbecompletedin8-12deeplifts.
- 1)Controlleddrillingandblasting,
- 2)Expandingchemicalgrouting,and
- 3) Rock Hammer 7.Temporaryde-wateringsystems,suchaspumpsand sumpsandtemporarywellsorwellpoints,willbe employedduringshaftexcavation. Areasofnotable waterentrywillbesealedviaanengineeredpressure groutingprocessorlocalizedwatercollectionsystem1.
1If installed will be abandoned in place.
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Expected Excavation Activities
8.Geologicalmappingoftherockwallswillbecompleted duringtheexcavationmeetingtherequirementsof NRCInspectionManual88131.Theinspectionofthe shaftwallswillbeperformedastheshaftprogressesin lifts.
9.Naturalvoidsorpoorqualityrockidentifiedduring theexcavationprocessorexposedinthewallsoflifts willbeevaluatedand,whenrequired,stabilized.This stabilizationmayincluderockreinforcement(i.e.rock bolts)ortreatmentwithgrout1.
1If installed will be abandoned in place.
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Expected Excavation Activities
10.Wiremeshreinforcement,incombinationwitha non-structuralsprayed-guniteliningwillbeinstalled ontherockface1.Incaseswhereseepageisnotedin thebedrock,horizontalgravitydrains1 and/orweep holeswillbeinstalledsothatthewaterdoesnot deterioratethesprayed-gunitelining.
11.Thefinalfoundationlevelatthebaseoftheexcavation willbecleanedandmappedinadditiontothewallsof thefinallift.Ifanyanomalousissuesarediscovered, additionalgeotechnicalinvestigationswillbe performedinaccordancewithRG1.132.
1If installed will be abandoned in place.
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TVA is considering submitting an exemption request to provide regulatory certainty in moving forward with excavation prior to CP Issuance.
It is not expected that an NRC environmental impact statement or environmental assessment will be required for approval of an exemption request as it would meet the criteria of 10 CFR 51.22(c)(25).
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Construction Permit Issuance
20222023202420252026 Q1Q2Q3Q4Q1 Q2Q3Q4Q1Q2Q3 Q2Q3Q4Q4Q1Q2Q3Q4 Q1
NRC Acceptance CPA Approval Review
Prepare ER NRCReview ER
Submit NRC Approval of Exemption Exemption Request Request Prepare NRC Review Excavation TVA NEPA
- As communicated previously, TVA has not yet authorized the deployment of an SMR. Nonetheless, receiving an exemption from 10 CFR 50.10(c) will provide regulatory certainty from NRC moving forward for excavation activities which would enable TVA to move forward in a timely manner, if and whena decision is made to build an SMR.
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Conclusion
- The RB excavation is of critical importance to the CRN-1 construction schedule and cannot be conducted without installation of the initial ground support system.
- If excavation for CRN-1 is delayed until issuance of the CP, it is anticipated the demonstration of constructing and licensing an SMRwould be delayed over one year, hence delaying the availability of carbon-free electricity generation.
- Anexemption request would satisfy the necessary elements of 10 CFR 50.12(a) and 10 CFR 50.12(b), as well as satisfy the requirements for a categorical exclusion in accordance with 10 CFR 51.22(c)(25).
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