ML102450690

Groundwater Tritium Investigation

ML102450690
Person / Time
Site:	Braidwood
Issue date:	12/20/2005
From:	Exelon Nuclear
To:	Office of Information Services
References
FOIA/PA-2010-0209
Download: ML102450690 (44)

Text

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-;EA,4ý7 Braidwood Station Groundwater Tritium Investigation December 20, 2005

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Agenda Exelý5ns,\

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

f Braidwood Site Overview Exe Iiiz:n I...

Nuclear o 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

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Braidwood Site Overview

-Nuclear e 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

A* N Safety of the Public 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 (pCi/L) private wells measured less than 142 picocuries per liter

. Thirteen °o\

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

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

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

N Status of Investigation Nuclear Regional Geology

" Fine grained uniform sand - ranges in thickness from 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 bedroc (

sandstone Man-made Features

" Coal mining operations

• Borrow pits /ýV

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Status of Investigation Eeo.,o Nuclear Hydrology

" 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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ffimm Status of Investigation kxeml o-nm Nuclear Extent of Tritium Plume

" Shallow water-bearing sand

" Surface water bodies

" Deeper water-bearing sand

• Bedrock aquifer 8

Status of Investigation txeli:n, 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

t-Status of Investigation n,,'A Nuclear Regional Investigation

• Historical review of coal mines and local quarries

• Review of historical aerial photographs e Survey of public and private drinking water systems north of site

• Development of regional hydrogeologic cross-sections 10

7 Status of Investigation Exe I nsm Nuclear Field Investigation

• Two onsite shallow sand wells

• 21 onsite deeper sand wells o 10 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 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 Nuclear

" 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

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Long Term Plan E elo

• Nuclear Project underway to significantly reduce overall liquid tritium discharge from Braidwood

- Reduce tritium production through enhanced reactor core design 7 Optimize management of tritium inventory in reactor operations

- Enhance gaseous release capability

- Research tritium separation technology 14

Exelon B ddeiNude-ar Braiedwood Generating Station

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Radiation and Sources of Internal Dose Eli A. Port, CHP, CIH, P.E...

What is Tritium (H-3) ?

° An isotope of Hydrogen with two neutrons 2

How much H-3 is in the environment ?

• Cosmic rays produce 4,000,000 curies per year

• The total tritium in the environment is about 70,000,000 curies 4

arial Radiloactive Mtra QuniYof e Traditional u. .ocurie (pCt)

• Sub-unit- P!

• oComparison -12 Ci or a trillionth of a curie

-1 pCi 0 5

Sources of Radiation Natural 292 mrem

- Radon 200 mrem

- Cosmic ray 27 mrem

- Rocks and Soil 30 mrem

- Food and drink 35 mrem AverageTotal

Background

Radiation Man-made 65 mrem 357 mrem/year

- x-rays 40 mrem

- Nuclear med 13 mrem

- Consumer products 10 mrem

- Research 2 mrem 6

EPA Drinking Water Limit

• 20,000 pCi/I

• At this concentration, drinking 2 liters of water per day will result in a dose 4 mrem per year 7

Tritium in Well Water

• The highest concentration of tritium found in a well supplying drinking water is:

1,524 pCi/i 9 At this concentration, drinking 2 liters per day will result in 0.3 mrem per year.

8

Other Sources of Internal Dose 9

Dose from C-14

" The concentration of C-14 in natural carbon is 7 pCi/g

• Human Reference Diet = 300 g carbon/day

" Resulting in 1.9 mrem per year from carbon in food 10

7 N Potassium-40 (K-40) Dose

• The concentration of K-40 in natural potassium is 820 pCi/g

• Human Diet = 2 -.5 g/day

• Resulting in a K-40 dose between 10 mrem per year and 25 mrem per year 11

Annual Dose from K-40 In Specific Foods 0 1 banana per day = 2.6 mrem

• 1 8 oz. glass of orange juice per day = 2.5 mrem

• 1 medium baked potato per day = 4.3 mrem 1 cup Total raisin bran per day = 1.8 mrem

° 1 double burger sandwich per day = 2.9 mrem

• 1 large order of fries per day = 4.7 mrem

• 1 cup cantaloupe per week = 0.4 mrem

° 1 cup spinach per week =0.6 mrem

° 6 oz halibut fillet per week = 0.7 mrem 12

Smoking

• The average annual dose from Po-210 in tobacco.is 2000 mrem

• Hot spots (bronchial bifurcations) may

.receive up to 16,000 mrem per year 13

Biological Effects

• We know that radiation may cause damage in tissue

• No effects have been found from low doses, under 10,000 mrem

° To be conservative, limits are set below doses where effects -are detected 14

• I-N Questions 99 P

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