Investigation into Tritium Contamination at Vermont Yankee Nuclear Power Station

Investigation Update

October 12, 2012

Test results from both the Health Department Laboratory and its contract laboratory report that neither tritium nor gamma-emitting radioactive materials were detected in the COB well samples taken on September 17. The split samples were received by the Health Department from Vermont Yankee on September 26.

October 3, 2012

Vermont Yankee sampled the Construction Office Building (COB) well on September 17. Tritium results, reported by Vermont Yankee’s contract laboratory, were all less than the detection limit for all three samples. The detection limits reported were between 511-530 picocuries per liter for tritium.

The Health Department received split samples on September 26. These samples will be tested by the department for tritium, gamma-emitting and hard-to-detect (iron-55, nickel-63 and strontium-90) radionuclides. Results of the samples will be available on our website after the tests are complete.

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Investigation Summary

January 7, 2010 - 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, 2010 - 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, 2010 - 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, 2010 - 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, 2010 - 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 2010 - 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.

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About the Investigation Updates

The updates presented here are based on information from Vermont Yankee and Entergy officials, and from direct observations and monitoring during site inspections.

Update Archive
See the Investigation Archive for past updates and information.

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Health Advisories & Alerts

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