ML072640492

TMI Tritium Update 08/07 - Slide Presentation

ML072640492
Person / Time
Site:	Three Mile Island
Issue date:	08/14/2007
From:	Exelon Nuclear
To:	NRC/FSME
Widmayer D, ACNW, 301-415-7366
References
WL-130
Download: ML072640492 (24)

Text

Tritium Update Three Mile Island Londonderry Township, Pennsylvania August 14, 2007

Objectives

• Geology/Hydrogeology

• Fleetwide Tritium Assessment

• Mass Flux Calculations

• Additional Data (2006/2007)

• Actions Taken

• Path Forward

Site Location N

N Site Photo

Geology Shale Gettysburg Formation 60 Shallow Bedrock Bedrock Shale Gettysburg Formation 100 Deep Bedrock Silts and Sands deposited on top of rock surface Glacial Outwash 25 Native Overburden Crushed rock Backfill 0 to 40 Backfill Overburden Description Name Depth (feet)

Sub-Unit Unit

Auxiliary Building Pit Elevation 253 +/-

Construction Photo

Reactor Foundation Shelf Tendon Gallery Reactor Leveling Mat - Elevation 269 +/-

Auxiliary and Fuel Building Leveling Mat - Elevation 275.5 +/-

Auxiliary Building Pit Construction Photo

Geologic Cross-Section WEST EAST

Hydrogeologic Units ND to 24,200 Moderate permeability Shallow Bedrock Bedrock ND to 14,000 Moderate permeability Deep Bedrock ND to 28,100 Minimal Native Overburden ND to 33,100 High permeability Backfill Overburden Range of Tritium Concentrations (pCi/L)

Flow Characteristics Sub-Unit Unit

Regional Groundwater Flow No groundwater flow from island beneath river to the mainland.

WEST EAST

Fleetwide Tritium Investigation

• Identification of Areas for Further Evaluation

• Installation of Additional Monitoring Wells and Staff Gauges

- 59 previously existing wells, but many wells screened in both overburden/backfill and bedrock

- Installed 31 new formation-specific wells to better understand lateral and vertical distribution of tritium and evaluate potential sources

• Groundwater and Surface Water Sampling

• Data Evaluation and Hydrogeologic Report

N Site Map with New Wells

• Groundwater Flow

- Overburden and bedrock groundwater flows outward from the center of the island toward the Susquehanna River

- Industrial wells capture a significant portion of the bedrock groundwater

• Tritium

- No tritium or radionuclides were detected in surface water

- Tritium was not detected in groundwater at concentrations greater than the USEPA drinking water standard of 20,000 pCi/L

- Tritium concentrations ranged from 223 +/-114 pCi/L to 13,500 +/-1,390 pCi/L

- Only 11 of the 58 groundwater samples contained tritium at concentrations greater than 1,000 pCi/L Fleetwide Tritium Assessment Results

Overburden Groundwater Map N

Bedrock Potentiometric Map N

Tritium Isoconcentrations in Overburden N

Tritium Isoconcentrations in Shallow Bedrock N

E-W Cross-Section with Tritium Isoconcentrations WEST EAST

N-S Cross-Section with Tritium Isoconcentrations South North

Mass Flux to River

• To quantify the amount of tritium entering the river, mass flux calculations were completed

• The results show that 0.05 Ci/year of tritium is entering the river from groundwater

Additional Data

• Groundwater samples collected in November 2006 and 2007

- Results are consistent with Fleetwide Tritium Results with the exception of RW-2

• Focused investigation around RW-2 to investigate potential leak

- Samples collected frequently (weekly) in 2007 at 9 wells

- New spike in RW-2 identified (see next slide)

- Leak found and under repair

RW Tritium Results for 2007 0

5,000 10,000 15,000 20,000 25,000 30,000 35,000 March April May June July August September Tritium (pCi/L)

Action Taken

• Ongoing periodic monitoring of select wells

• REMP sampling

• Identification of potential sources

- Focused investigations to determine if source is ongoing

- E.g., RW-2

• Continued operation of the industrial supply wells, which capture the majority of tritium at the island

Path Forward

• Groundwater and surface water sampling for tritium

• Periodic updates of mass flux calculations to river

• Open and frequent communications with regulatory agencies

• Evaluate groundwater results for evidence of leaks

- If evidence, further evaluate the area and potential sources

- Fix leaks, if identified

• Pumping of industrial supply wells, which serve to capture the majority of tritium on the island