ML061010696

Groundwater Tritium Investigation Slides

ML061010696
Person / Time
Site:	Braidwood
Issue date:	12/20/2005
From:	Exelon Nuclear
To:	Office of Nuclear Reactor Regulation
References
FOIA/PA-2006-0115, FOIA/PA-2010-0209
Download: ML061010696 (15)

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Braidwood Station Groundwater Tritium Investigation i 2 0

December 20, 2005

Agenda reI A-M Nuclear

• Introduction - Scott Humbard

• Braidwood Site Overview - John Moser Safety of the Public - John Moser

- Status of Investigation - Scott Sklenar

• Long Term Plan - John Moser

• Summary -John Moser 2

Braidwood Site Overview ExeIa Nuclear

• Approximately 4500 acre site with 2500 acre cooling lake

• Tritium generated in reactor coolant from reactor operation

• Circulating water system transfers heat to cooling lake Continuous make-up and blowdown between cooling lake and Kankakee River Vacuum breakers used in blowdown line to prevent damage due to water surges in pipe when flow changes 3

CI-c Ct Braidwood Site Overview I

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• Liquid effluent management

• No tritium (or other liquid radioactive effluents) being released into blowdown line flow until pipe confirmed to be leaktight liquid effluent storage capacity being supplemented with temporary storage tanks 4

Ci Safety of the Public E xeI cni Nuclear

• Groundwater sampling identified elevated concentrations of tritium in the shallow groundwater

• Drilled over 100 monitoring wells onsite and offsite to determine extent of tritium migration

• Tested 14 private wells of residents north (downgradient) of the site Thirteen private wells measured less than 142 picocuries per liter (pCi/L)

I Three readings from one private well were 1151,1524,1367 pCi/L

• Calculated radiation associated with highest private l o0 well reading is 0.3 millirem per year

• Results of private well sample analysis have be n communicated to residents 5

C7-Status of Investigation Nuclear Regional Geology

• Fine grained uniform sand - ranges in thickness 15 to 35 feet

• Regional clayey till - averages 20 feet thick

• Bedrock formations comprising shales, coal, silt stones, limestone, and sandstones

• Uppermost aquifers - uniform sand and bedrock sandstone Man-made Features

• Coal mining operations

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• Borrow pits

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Status of Investigation EXeI An Nuclear HvdroloQy

• Shallow groundwater flows toward the north

• Geologic barriers exist to vertical downward migration

• Deep bedrock groundwater also flows to the north

• Interaction of groundwater with surface water bodies 7

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Status of Investigation fl Nuclear Extent of Tritium Plume

• Shallow water-bearing sand

• Surface water bodies

• Deeper water-bearing sand

• Bedrock aquifer 8

Status of Investigation

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Nuclear Potential Sources, Transport of Tritium

• Existing evidence indicates the source of the tritium is the blowdown line

• Further investigations focused to confirm whether source is current leak(s), historic spills, or a combination

• Potential transport mechanisms Influence of pond on tritium transport Jkp

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• -l Status of Investigation Exe -

m Nuclear Regional Investigation

• Historical review of coal mines and local quarries

• Review of historical aerial photographs

• Survey of public and private drinking water systems north of site

• Development of regional hydrogeologic cross-sections 10

Status of Investigation i" SIM Nuclear Field Investigation

• Two onsite shallow sand wells

• 21 onsite deeper sand wells

• 1 0 offsite shallow wells

• 12 offsite deep wells

• Synoptic round of water level measurements

• Comprehensive round of groundwater samples

• Will sample selected wells weekly

• Installing staff gauges in surface water bodies 11

Status of Investigation axe is n

Nuclear Blowdown Line Integrity

• Periodic surveillance of blowdown line vacuum breaker valves to verify no leakage December 9, 2005 surveillance confirmed no leakage

• Special acoustic monitoring test being

.performed on blowdown pipe to determine if pipe has underground leak

- Sensor ("microphone") attached to umbilical cable inserted in pipe; water flow pulls sensor through pipe to identify location of leak

- Test scheduled to be completed December 30, 2005 12

Status of Investigation XeI:Tfs.

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• Data evaluation and reporting Evaluate data from field investigations and pipeline integrity test in order to:

• Determine source or sources

• Define lateral and vertical extent of plume

• Evaluate risk to human health and environment

• Develop appropriate future actions including monitoring

• Prepare summary documents of evaluations for regulatory review

• Establish periodic informational update meetings 13

Long Term Plan 1(eI 4

Nuclear Project underway to significantly reduce overall liquid tritium discharge from Braidwood Reduce tritium production through enhanced reactor core design Optimize management of tritium inventory in reactor operations Enhance gaseous release capability Research tritium separation technology 14

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Summary in Nuclear

• Investigation and actions in progress to minimize the risk to human health and the environment e Long term approaches to minimize liquid tritium effluent are being pursued

• We remain committed to open communication with stakeholders 15