ML17160A084

Slides from Nrc/Pg&E Public Meeting on Humboldt Bay Plant Decommissioning and License Termination Dated November 19, 2014

ML17160A084
Person / Time
Site:	Humboldt Bay
Issue date:	11/19/2014
From:	Pacific Gas & Electric Co
To:	NRC Region 1
References
Download: ML17160A084 (31)

Text

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L ~~~~~~~~~~~~~

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• Agenda 2

• HBPP Decommissioning Status and Schedule

• Gardian System

• Caisson Removal Retaining Wall Option

• CSM Wall Description and Characterization Plans

• Potential L TP Changes

• L TP Approval Schedule

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Decommissioning Status and Schedule

• Unit 2 excavation and remediation nearing completion

• Hot shop above grade demolition complete

• SAS building above grade demolition complete

• Currently removing RPV cut "windows"

• Spent fuel pool liner removal progressing 3

Decommissioning Status and Schedule (Cont'd)

• Gardian system installed for soil processing

• Discharge canal isolated from the bay

• Ground water treatment and pre-treatment system operational

• Soil management facility complete and in use

• Final site permit and Remedial Action Plan nearly ready for submittal 4

• &~ 2015 Schedule Milestones

• July 2015

• May 2015 Discharge Canal Remediation Complete Pre-Trenching Complete

• January 2016 Complete Water Cutoff Wall 5

Hot Shop Demolition 6

• &~ ~ SAS Building Demolition 7

Soil Management and Pre-treatment 8

Facilities I

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9 Groundwater Treatment Facility

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• s Sheet Pile for Canal Isolation

11 Gardian System Installation

12 Unit 2 Remediation

13 Waste Shipment

Gardian System TBD

• System previously used at Big Rock Point

• Contains 4 Canberra In-Situ Object Counting System (ISOCS) characterized detectors.

• A complete Validation and Verification (V&V) of each detector's characterization file has been completed as part of pre-operational system testing.

• The Big Rock Point Technical Basis Document (TBD) has been revised for Humboldt Bay Power Plant specifics.

• The TBD will be submitted to NRC for review.

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Caisson Removal Retaining Wall

• Outer water cutoff wall with excavation to remove SFP and install sheet piling for lower caisson removal is the feasibility study provided to CPUC

• Contractor proposed a different alternative using CSM (Cutter Soil Mix) technology but award was bounded by feasibility approach

• PG&E is considering different configurations of CSM option

• CSM alternative may be used in addition to water cutoff wall from the surface for caisson removal 15

CSM Installation Water/Bentooite Injected Loosens ~

and Sizes Soil Water/Cement Injected

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Foons CSM Wall Equ1>fnent Side View 16

17 Cutter Soil Mix (CSM) Machinery

. &r CSM Cutter Head 18

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. s CSM Installation

. &r Water/Soil Excess Removal 20

21 Completed Panel

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• Discharged Material 22

CSM Wall with Ring Steel x 2.8 S<:IL 1111 p

q *- o o* (

.)

El.. 6 El. 1 El.. 16 El.

El. 4 El. 56 El.

El.. 16 El. a

-t io* c::H rr 01 ** I-23

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• Potential CSM Wall Example Diagram 110' C~LL WITH 3 METER THICK WALL

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rei=ITTER OF REACTOR AND CAISSON 24

Reasoning for Potential CSM Wall

• Prevents un-shored excavations

• Installed completely from ground level

• Minimizes on-site excavation equipment

• Reduces volume of material to be handled

• Encompasses the spent fuel pool 25

• &~

• Challenges to CSM Wall Installation

• Wall construction utilizes displaced soils as part of the construction material

• CSM wall will be left in place at license termination

• Residual activity within the CSM wall will potentially affect future groundwater dose 26

CSM Wall Soil Sampling Geo probe sampling in soils around where CSM wall will be placed

~- Soil impacted by CSM wall 27

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Calculating Future Groundwater 28 Dose

• Core bore sampling could assess the activity inventory in the CSM wall to remain and characterize soil outside of the wall

• A basement fill model could be used to determine the potential dose contribution to groundwater from the CSM wall

• The dose contribution from the CSM wall would have to be included with any other dose pathways in demonstrating the area meets the License Termination Rule of 25 mrem/yr plus A LARA

NRC Approvals Requirement

1) If no activity found in soil, no approval required.

2) If activity less than soil DCGL, treat wall as soil and no approval required.

3) If activity greater than soil DCGL, use a basement fill model to determine potential dose to groundwater pathway.

For number 3, PG&E would submit a request to the NRC for approval of the basement fill model methodology. Supporting technical information will be provided in a Technical Based Document (TBD) requiring NRC approval.

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L TP Approval Schedule

• Any Outstanding NRC Items Needing Resolution to Approve L TP Revision 1?

• Projected Date for NRC Approval 30