Investigation into Tritium Contamination at Vermont Yankee Nuclear Power Station
Investigation Update
July 26, 2010
Long Term Monitoring
The state’s quality control inspection in June found that water samples used for long-term monitoring are generally being processed, stored and shipped in accordance with industry standards and state expectations. The Health Department is currently awaiting shipment of more than 200 water samples from Vermont Yankee to the Health Department laboratory for confirmatory analysis. We are working to improve the efficiency of the shipping operation at this time.
Quality control inspections have been useful to track sample frequencies, groundwater remediation, and soil remediation and disposal. The inspections have also provided important information for siting new wells, such as siting a sampling station near the centerline of the plume at the edge of the Connecticut River east of well GZ-14. The inspections may also aid in the siting of a new extraction well to enhance contaminated groundwater remediation.
Groundwater Extraction
Vermont Yankee reports that extraction well GZ-EW1A continues to pump out tritium-contaminated groundwater from the soils near the Advanced Off Gas (AOG) building. The latest measurement of tritium concentration of extracted groundwater is 28,000 picocuries per liter (pCi/L). Last week, approximately 162,000 gallons had been extracted, and tritium concentration was measured at approximately 26,000 pCi/L. Vermont Yankee did not update the actual volume of groundwater pumped out as of this week, but weekly increases have been in the 8,000 gallon range. There are no firm plans yet to develop a second extraction well to meet the goal of extracting 300,000 gallons of tritium-contaminated groundwater.
Groundwater Monitoring Well Results
The results that follow are as reported by Vermont Yankee for tritium. As has been true the last few months, concentrations of tritium in wells near structures, systems and components that may leak and contaminate the groundwater are decreasing. These are wells GZ-7, GZ-12, GZ-15, GZ-20 and GZ-21. Wells near the Connecticut River continue their trend since January 2010 to increase in concentration. Wells GZ-3, GZ-4 and GZ-14S continue to increase in tritium concentrations, although more slowly than before. 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. All results are expressed in terms of picocuries per liter (pCi/L), or below the lower level of detection (<LLD):
GZ-1: <LLD on 6/2/10
GZ-2: <LLD on 6/28/10
GZ-3: 150,000 on 7/19/10, down from 155,000 last week
GZ-4: 9,400 on 7/19/10, down from 30,000 last week
GZ-5: <LLD on 6/28/10
GZ-6: <LLD on 7/19/10
GZ-7: <LLD on 7/21/10, down from 2,600 last week
GZ-8: No sample; dry well
GZ-9: <LLD on 6/28/10
GZ-10: <LLD on 7/19/10
GZ-11: 2,200 on 7/19/10, up from 1,400 last week
GZ-12: 47,000 on 7/19/10, down from 64,000 last week
GZ-13S: <LLD on 7/19/10
GZ-13D: 900 on 7/19/10, up from <LLD last week
GZ-14S: 324,000 on 7/21/10, up from 306,000 last week
GZ-14D: <LLD on 7/19/10
GZ-15: 391,000 on 7/19/10, down from 441,000 last week
GZ-16: <LLD on 7/19/10
GZ-17: <LLD on 6/28/10
GZ-18: no well yet
GZ-19S: <LLD on 6/28/10
GZ-19D: <LLD on 6/28/10
GZ-20: <LLD on 7/19/10, down from 2,400 last week
GZ-21: 99,000 on 7/19/10, down from 209,000 last week
Investigation Summary
January 7 - Tritium Contamination Discovered
Vermont Yankee Nuclear Power station notifies the Vermont Department of Health that samples taken in November 2009 from a ground water monitoring well on site (identified as GZ-3) contained tritium. This finding signals an unintended release of radioactive material, and it means that other radioisotopes may have contaminated the environment.
January 11 - Investigation Begins
Vermont Yankee begins its own investigation to identify sources of the tritium and magnitude of contamination, with the Nuclear Regulatory Commission in an oversight role. The Health Department organizes a team of state health and environmental experts to independently monitor, test and report on the investigation, and analyze possible risks and remediation actions.
February 14 - Major Source of Leak Found
A pair of steam pipes inside the Advanced Off-Gas (AOG) pipe tunnel are found to be badly corroded and leaking nuclear steam. The floor drain of this concrete tunnel was found to be clogged with construction debris and mud, which caused condensate from the steam pipes to pool inside the tunnel and leak out at a failed joint. (AOG Building Schematic)
May 14 - Soil Tests Confirm Contamination
Soil testing in the area around the leak has measured concentrations of radioisotopes consistent with a leak of nuclear reactor water. Steadily decreasing tritium concentrations in samples taken from the ground water monitoring wells drilled since January show the movement of tritium contamination in the ground water generally west to east into the Connecticut River. (Monitoring Well Location Map)
May 29 - New Leak Found
Vermont Yankee officials notify the Health Department about a new leak that was identified and stopped on May 28 at the AOG drain line. This occurred as the AOG system was being started up after its refueling outage.
June - Ongoing Investigation
Since the leak was first reported, the Health Department has been closely monitoring and reporting on the investigation, has 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.
This work is ongoing as Vermont Yankee continues its investigation and study of other plant systems and components to identify, repair or remediate similar “extent of conditions” that could result in a leak.
Regular updates presented here are based on information from Vermont Yankee and Entergy officials, and from direct observations and monitoring during site inspections.See Investigation Archive for past updates and information.
Health Advisories & Alerts
- 01/31 - Tritium Leak at Vermont Yankee