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 10, 2010

Remotely Operated Vehicle (ROV) Inspection
The remote operated vehicle (ROV) inspection of the AOG pipe tunnel is nearing completion. Inspection of the inside of the AOG pipe tunnel has revealed two specific pipe failures. Both the A and B hydrogen recombiner steam trap drain lines inside the pipe tunnel are corroded and leaking. The A pipe was isolated and the leak stopped on Feb. 14. The B pipe is in a place where it cannot be isolated, and must be kept in service. Plans for a temporary modification are being made to provide both the A and B pipes a complete, leak-free path to the AOG drain tank. Complete modification of both lines is planned for the scheduled April to May 2010 refueling outage. Meanwhile, none of the leakage from the B pipe still in service is leaking into the environment. Any leakage is being routed by the AOG pipe tunnel floor drain to the AOG pit sump.

Groundwater Monitoring Well Testing
Well GZ-10, which had previously showed tritium contamination at 2.5 million picocuries per liter (pCi/l), tested at 525,000 pCi/l on March 9, 2010. Vermont Yankee technicians sampled it on March 8, and results at about 600,000 pCi/l were so much lower than previous days that it could have been an error. With two days of significantly lower concentrations and re-checking testing protocol, Vermont Yankee is now confident of these results.

A new well is also providing new data. This is well GZ-20 located between well GZ-10 and GZ-7, near the condensate storage tank. A sample from this well came in at 624,000 pCi/l. Another new well, GZ-21, on the southern edge of the tritium plume between well GZ-10 and GZ-16, may be providing valid samples by Friday.

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. No on-site or off-site wells show any other radioactive materials related to nuclear power plant operations.

To date, tritium has been detected in seven groundwater monitoring wells, all on-site. 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

Well

Test Result*

GZ-1

<LLD

GZ-2

<LLD

GZ-3

46,000

GZ-4

3,100

GZ-5

<LLD

GZ-6

<LLD

GZ-7

1.115 million

GZ-8

No sample; dry well

GZ-9

<LLD

GZ-10

456,000

GZ-11

<LLD

GZ-12

36,000

GZ-13S

<LLD

GZ-13D

not commissioned yet

GZ-14S

147,000

GZ-14D

<LLD

GZ-15

590,000

GZ-16

<LLD

GZ-17

<LLD

GZ-18

no well yet

GZ-19S

<LLD

GZ-19D

<LLD
GZ-20 624,000

*Results are expressed in picocuries per liter (pCi/l). All of the wells that have shown no contamination have results expressed as "<LLD" (below the lower limit of detection).

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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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