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

Site Photo N

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

Construction Photo Auxiliary Building Pit Elevation 253 +/-

Construction Photo Auxiliary and Fuel Building Auxiliary Building Pit Leveling Mat - Elevation 275.5 +/-

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

Geologic Cross-Section WEST EAST

Hydrogeologic Units Unit Sub-Unit Flow Characteristics Range of Tritium Concentrations (pCi/L)

Backfill High permeability ND to 33,100 Overburden Native Overburden Minimal ND to 28,100 Shallow Bedrock Moderate permeability ND to 24,200 Bedrock Deep Bedrock Moderate permeability ND to 14,000

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

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

Site Map with New Wells N

Fleetwide Tritium Assessment Results

• 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

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 North South

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 35,000 30,000 25,000 Tritium (pCi/L) 20,000 15,000 10,000 5,000 0

March April May June July August September

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