Monitoring, investigation of tritium contamination at Vt. Yankee nuclear power station continues

Source: Vermont Department of Health

The Vermont Department of Health has released an update of their continuing investigation and monitoring of tritium contamination found on the site of the Vermont Yankee nuclear power station.

Since the leak was first reported in January, the Health Department has been closely monitoring and reporting on the investigation, stepped up testing of environmental samples, and has been independently analyzing health risk. With assistance from the Agency of Natural Resources, Vermont Emergency Management, and other state agencies, a team of health and environmental experts have been on site regularly as independent analysts.

Vermont Yankee reported in late August that funding for four to five more groundwater monitoring wells has been approved by Entergy, the New Orleans based Corporation which owns the plant, but that the start of drilling is behind schedule. The new wells are to be located next to buried underground pipes that run from the Advanced Off-Gas (AOG) Building to the plant stack. The wells will be used to monitor for potential leaks of radioactive materials.

Plans for this phase of groundwater monitoring also call for testing the COB well, and installing at least two new sampling pumps into the well. The testing, called packer testing, will identify the best locations for the new sample pumps in the 360 foot deep former drinking water well. Packer testing helps verify fractures in the bedrock that provide the greatest amount of drinking water. The new pumps will be used to draw water samples for testing to verify that these drinking water sources remain free of contamination. The COB well has not been used for drinking water since February 25, and there are no plans to use it in the future for anything but a drinking water tritium sampling site. All samples taken from it, to date, have tested below the lower limit of detection (<LLD) for tritium.

The Nuclear Regulatory Commission (NRC) also reported that it has not completed its inspection of the Vermont Yankee groundwater protection program. The NRC has been working with Entergy officials to obtain and review information to complete the inspection the week of September 13. The information needed is being gathered over the coming weeks by Vermont Yankee’s hydrogeological contractors. This includes pressure data that has been logged in each of the on-site wells since their installation, and other groundwater physical and chemical data.

As of August 26, approximately 245,000 gallons of tritium-contaminated groundwater has been pumped out from the site. Vermont Yankee has set a goal of removing 300,000 gallons of contaminated water to help remediate soils. The current concentration of groundwater being removed is in the 76,000 picocurie per liter (pCi/L) range. Over the past five months, three wells have been used for extraction: GZ-EW1, GZ-EW1A and GZ-15. A new extraction well, GZ-EW2, located near GZ-14S, may be operational soon. This new well would make it possible to extract groundwater with tritium concentrations near 370,000 pCi/L.

The groundwater monitoring well results that follow are as reported by Vermont Yankee for tritium. As has been the trend over the past few months, current findings indicate that concentrations of tritium in wells near plant structures, systems and components that may leak and contaminate the groundwater are generally decreasing. Wells near the Connecticut River continue their recent trend of leveling off with tritium concentration, perhaps indicating a peak. To date, gamma spectroscopy and special analyses for hard-to-detect radionuclides have not identified any other nuclear power plant-related radioactive materials in groundwater, drinking water, or river water.

Groundwater Monitoring Well Results

All results for tritium concentrations are expressed in terms of picocuries per liter (pCi/L), or below the lower level of detection (<LLD):

GZ-1: <LLD on 8/2/10
GZ-2: <LLD on 8/2/10
GZ-3: 115,000 on 8/23/10, up from 112,000 on 8/16/10
GZ-4: 33,000 on 8/23/10, up from 30,000 on 8/16/10
GZ-5: <LLD on 8/2/10
GZ-6: <LLD on 8/23/10
GZ-7: 4,700 on 8/25/10, up from 4,000 on 8/18/10
GZ-8: No sample; dry well
GZ-9: <LLD on 8/2/10
GZ-10: <LLD on 8/23/10
GZ-11: <LLD on 8/23/10
GZ-12: 23,000 on 8/16/10, with no change (23,000) on 8/16/10
GZ-13S: <LLD on 8/23/10
GZ-13D: 1,700 on 8/23/10, up from <LLD on 8/16/10
GZ-14S: 370,000 on 8/25/10, up from 353,000 on 8/16/10
GZ-14D: <LLD on 8/23/10
GZ-15: 76,000 on 8/25/10, down from 86,000 on 8/16/10 (as extraction well)
GZ-16: <LLD on 8/23/10
GZ-17: <LLD on 8/2/10
GZ-18: no sampling site yet
GZ-19S: <LLD on 8/2/10
GZ-19D: <LLD on 8/2/10
GZ-20: 3,000 on 8/23/10, up from 2,600 on 8/16/10
GZ-21: 26,000 on 8/23/10, down from 43,000 on 8/16/10

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