Investigation into Tritium Contamination at Vermont Yankee Nuclear Power Station

Summary

On January 7, the Vermont Department of Health was notified by Vermont Yankee Nuclear Power Station that samples taken from a ground water monitoring well on site (identified as GZ-3) contained tritium.

Tritium is a radioactive form of hydrogen. It is a by-product of the nuclear fission process in a nuclear reactor, and also occurs naturally in the environment in very low concentrations. Most tritium in the environment is in the form of tritiated water, which easily moves about in the atmosphere, bodies of water, soil and rock.

The finding of tritium in ground water signals that there has been an unintended underground release of radioactive material, and that other radioisotopes may have contaminated the environment.

Vermont Yankee officials are conducting an investigation to identify the source of the tritium, and the magnitude of contamination, with the Nuclear Regulatory Commission (NRC) in an oversight role.

The Vermont Department of Health has stepped up the frequency and number of water and environmental samples tested at the public health laboratory, and is doing independent analyses of health risk. With assistance from a number of other state agencies, a team of health and environmental experts will be on site as independent analysts.

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Investigation Update

March 18, 2010

Recombiner Steam Trap Drain Lines Re-Routed
Temporary modifications to the two failed Advanced Off-Gas (AOG) hydrogen recombiner steam trap drain lines were well underway on March 17. The ‘B train’ has now been temporarily re-routed from its path through the Advanced Off-Gas (AOG) pipe tunnel to the AOG building floor drain system, which empties into the AOG drain tank. Vermont Yankee operators will now prepare the B train to go back into service, and take the A train out of service to make similar modifications. Once both the A and B trains are re-routed, the leak pathway to the AOG pipe tunnel and out into the environment will have been eliminated. A camera will be installed in the AOG pipe tunnel to monitor conditions there.

Second Soil Contamination Study
A second study began March 17 of the soil at the AOG pipe tunnel excavation where a major leak of tritiated water into the environment was identified. This study will evaluate radioactive contaminants in the soil for the length and width of the excavation, measuring concentrations of these contaminants in soil taken from different depths. To start, “core bore” samples of soil will be taken at the surface of the excavation, and at 2 feet and 4 feet below the surface of the excavation. Soils will be analyzed for materials including cobalt-60, manganese-54, zinc-65 and cesium-137. These radioactive metals were identified in the first soil study that was conducted when the excavation first uncovered the leakage pathway on Feb. 26. Split samples will be provided to the Vermont Department of Health Laboratory for independent analysis.

Extraction Well Planned
Planning for a contaminated groundwater extraction well near monitoring well GZ-7 continues. This 6-inch diameter well is scheduled for drilling on March 22. Over time, this well may pump out as much as 300,000 gallons of tritium contaminated groundwater. The extracted water will be treated and stored as radioactive water to be re-used by Vermont Yankee.

Monitoring Well Test Results
Testing by the Vermont Department of Health and Vermont Yankee of on-site and off-site drinking water well samples, as well as water taken from the Connecticut River, continue to show no tritium in excess of the lower limit of detection (<LLD). No on-site or off-site wells show any other radioactive materials related to nuclear power plant operations. The most recent well results reported by Vermont Yankee are listed below. All results are expressed in terms of picocuries per liter (pCi/l), or below the lower level of detection (<LLD).

GZ-1: <LLD
GZ-2: <LLD
GZ-3: 51,000
GZ-4: 2,200
GZ-5: <LLD
GZ-6: <LLD
GZ-7: 1.2 million
GZ-8: No sample; dry well
GZ-9: <LLD
GZ-10: 135,000
GZ-11: <LLD
GZ-12: 78,000
GZ-13S: <LLD
GZ-13D: <LLD
GZ-14S: 180,000
GZ-14D: <LLD
GZ-15: 573,000
GZ-16: <LLD
GZ-17: <LLD
GZ-18: no well yet
GZ-19S: <LLD
GZ-19D: <LLD
GZ-20: 530,000
GZ-21: 1.15 million

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Investigation Site Maps & Diagrams

Monitoring Well Location Map (pdf)
The investigation site map is an aerial photo of the Vermont Yankee power station property. It displays labeled locations of the monitoring wells, station buildings, and other features.

Advanced Off-Gas Building Schematic (pdf)
This 3-D schematic representation shows the AOG Building and related infrastructure within the surrounding excavation area.

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Laboratory Testing & Results

Health Department Laboratory Test Results (pdf)
Independent test results to date for tritium and gamma spectroscopy.

Since Jan. 7, the Vermont Department of Health has stepped up its environmental surveillance of Vermont Yankee by testing water samples taken from drinking water wells and ground water monitoring wells on site at the plant, and in the surrounding area. Water is being sampled at least weekly for independent testing. Other samples, such as soil, milk, river sediment, and vegetation (when available), are being taken for testing as needed.

The Department of Health is using gamma spectroscopy analysis to determine if other radioisotopes, in addition to tritium, are present in samples collected from and around Vermont Yankee site.

Tritium Concentration Graphs (pdf)
These graphs illustrate the concentration over time of tritium in samples collected from certain ground water monitoring wells - those that have produced samples with the highest readings. The data, reported by Vermont Yankee, includes various date ranges depending on when a given well went online for sampling. Environmental Activity is expressed in picocuries per liter (pCi/l) of tritium.

Gamma Spectroscopy

Gamma Spectroscopy is an analytical method used by the Department of Health Laboratory to identify specific radioisotopes in a sample. Gamma spectroscopy measures energies and intensities of gamma radiation emitted from samples to identify specific radioisotopes. Each gamma radiation-emitting radioisotope has unique gamma radiation energies and intensities, like a fingerprint, allowing comparison of sample results to a library of known radioisotopes in the identification process.

Common Natural Gamma Radiation Emitters

Actinium-228

Americium-241

Beryllium-7

Bismuth-212

Bismuth-214

Lead-210

Lead-212

Lead-214

Polonium-210

Potassium-40

Protactinium-234m

Radium-224

Radium-226

Radium-228

Radon-222

Technetium-99

Thallium-208

Thorium-228

Thorium-229

Thorium-230

Thorium-231

Thorium-232

Thorium-234

Uranium-233

Uranium-234

Uranium-235

Uranium-238

Nuclear Facility Gamma Radiation Emitters

Antimony-124

Antimony-126

Barium-140/
Lanthanum-140

Cerium-144/
Promethium-144

Cobalt-56

Cobalt-60

Chromium-51

Cesium-134

Cesium-136

Cesium-137

Iodine-131

Iodine-132

Iodine-133

Iodine-135

Krypton-85

Krypton-88

Manganese-54

Plutonium-239

Plutonium-240

Ruthenium-103

Strontium-85

Strontium-89

Tellurium-132

Xenon-133

Xenon-133m

Xenon-135

Zinc-65

Zirconium-95/Niobium-95

 

 

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Testing Your Drinking Water

Once every week, the Vermont Department of Health Laboratory is testing private drinking water supplies of selected residences near the Vermont Yankee site boundary.

To date, none of these wells have shown evidence of contamination with tritium or other radionuclides that would be associated with a nuclear reactor.

If You Want Your Water Tested

For Vernon residents or others interested in having their private drinking water supplies tested, there are several public health laboratories that will analyze private well water for tritium:

Please contact the laboratories directly for information about sampling bottles, quantity of water needed, turnaround times, and cost.

Additional Water Testing Information

For more information and recommendations about water testing and safety:

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Health Advisories & Alerts

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