Source of new tritium leak at Vermont Yankee still unidentified

Investigation into Tritium Contamination at Vermont Yankee
Feb. 28, 2011 Update

Vermont State Nuclear Advisory Panel (VSNAP)

On February 22, VSNAP met for the first since March 2009, convened at Vernon Elementary School by new Public Service Commissioner Elizabeth Miller. VSNAP is charged with overseeing current and future uses of nuclear power in the state. Most of the meeting focused on the groundwater contamination investigation at Vermont Yankee. The Health Department presented a review of the 2010 Advanced Off-Gas (AOG) building leak, remediation efforts, long-term environmental monitoring, as well as the more recent tritium contamination tracked at groundwater monitoring well GZ-24S. This was followed by reports from Vermont Yankee officials.

The meeting also included presentations on VY docket 7440 for a Certificate of Public Good to continue operating after March 2012, and VY docket 7600 to shut down the plant. A consultant to the Public Service Department gave an update on the comprehensive reliability audit,and a consultant from Fairewinds Associates highlighted reliability issues that were identified in the most recent Public Oversight Panel’s report to the Joint Fiscal Committee. The New England Coalition presented concerns about buried electrical cables that may become submerged in water and degrade. A public comment period followed. About 80 to 100 people attended.

Groundwater contamination near the radwaste building

So far, no source of contamination near the radwaste building has been identified. Vermont Yankee officials have ruled out the stack sump discharge drain line and the second stage AOG delay pipe drain line as sources of low concentrations of tritium near groundwater monitoring well GZ-24S. This well is located near the radwaste building.

Three additional piping runs, sumps and tanks near the radwaste building are still under investigation. The first stage AOG delay pipe drain line is scheduled for testing this week, and the steam packing exhaust drain line is being tested now, but results so far are inconclusive. Changes in the test procedure are being implemented. The standby gas treatment drain line may be tested as early as March 7.

One other explanation is “washout” or “rainout.” This happens when radioactivity in the air is washed out of the air by precipitation. Vermont Yankee is testing snow to see if this is occurring. Vermont Yankee has routinely tested the storm drains, where rain and snow melt end up, for radioactivity including tritium. Tests of the storm drains have been negative for tritium since January 2010. The Health Department has always monitored these storm drain results.

Sampling to start again at former COB drinking water well

On February 26, Vermont Yankee officials reported a delay in preparations for sampling water once again from the Construction Office Building (COB) well. A new internal casing for a new pump had been installed and the first new sample was expected to be obtained on February 25. Vermont Yankee says the problems they are encountering in sampling again are likely due to a full year of inactivity at this well, allowing silt to accumulate in bedrock fractures that feed the well. They expect to have the well ready to sample again on or about March 2.

The COB well is a former drinking water well. It’s about 360 feet deep, and is located in the plume of tritium contaminated groundwater that was created by leaks at the AOG Building. It was taken out of service as a well for drinking water in February 2010. For the past year, the Departments of Health and Environmental Conservation have requested that sampling of this well continue.

The well was subjected to “down-hole geophysical testing” in the spring of 2010, and “packer testing” in the fall of 2010. Both tests were designed to assess the bedrock and water-yielding fractures in the bedrock through which the well was bored. During packer testing in October 2010, water from a low yielding fracture at 200 to 220 feet in depth tested positive for tritium. Subsequently, Vermont Yankee pulled all of its equipment out of the well and stopped testing and sampling it.

Radiochemical analytical results will be shared with the Department of Health, and the Department plans to analyze a split sample from the well.

Groundwater Extraction

According to Vermont Yankee, as of February 10 approximately 325,000 gallons of tritium-contaminated groundwater has been pumped out of the ground, with approximately 13,200 of that total extracted since the restart of that process on December 30, 2010. The two currently operating extraction wells, GZ-22D and GZ-14S, each yield about 0.25 gallons per minute. This is much less than previous groundwater extraction wells. The lower extraction rate is at least partially due to the lower permeability of soils in the area. Groundwater does not move as fast in the soils near GZ-22D and GZ-14S.

Groundwater Monitoring Well Results

The results that follow are as reported by Vermont Yankee for tritium through February 25, 2011. Vermont Yankee has been reporting sample results every day to the Health Department since February 1.

As of this report, 11 out of a total of 31 groundwater monitoring wells are testing positive for tritium. With the exception of wells GZ-14S and GZ-22D, the trends are stable or downward. This includes a downward trend at GZ-24S, which had been at a high of over 9,000 picocuries per liter (pCi/L) on January 20 and is now just barely over the lower limit of detection of approximately 500 pCi/L. The reason for this is unclear. For this week, three wells had an increased tritium concentration compared to the last sample date.

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.

GZ-1: GZ-2: GZ-3: 108,000 on 2/22/11, down from 112,000 on 2/7/11
GZ-4: 94,800 on 2/22/11, up from 70,000 on 1/31/11
GZ-5: GZ-6: GZ-7: 2,280 on 2/22/11, down from 3,610 on 2/7/11
GZ-8: No sample; dry well
GZ-9: GZ-10: GZ-11: GZ-12S: 2,670 on 2/22, down from 3,250 on 2/7/11
GZ-12D: 113,000 on 2/22/11, down from 125,000 on 2/7/11
GZ-13S: GZ-13D: 823 on 2/22/11, down from 955 on 2/7/11
GZ-14S: 426,000 on 2/17, up from 255,865 on 2/10/11
GZ-14D: GZ-15: 100,000 on 2/22/11, down from 108,000 on 2/8/11
GZ-16: GZ-17: GZ-18S: GZ-18D: GZ-19S: GZ-19D: GZ-20: GZ-21: GZ-22D: 344,000 on 2/22/11, up from 308,000 on 2/7/11
GZ-23S: 722 on 2/22/11, up from GZ-24S: 677 on 2/23/11, down from 2,159 on 2/13/11
GZ-25S: GZ-26S: GZ-27S: