By Christian Avard |Special to the Vermont Guardian
Posted November 24, 2006
BRATTLEBORO — Vermont Yankee’s nuclear power plant has exceeded the state’s radiation emission limits three times since 1998. But that depends on whose assessments one believes: the state of Vermont’s or company officials’.
According to state standards, Vermont Yankee (VY) exceeded the maximum fence line radiation exposure of 20 millirems annually. A rem is a unit of ionizing radiation equal to the amount that produces the same damage to humans as one roentgen of high-voltage x-rays. A millirem is one-thousandth of a rem.
However, Vermont Yankee officials claim those measurements are inaccurate because they took into account background radiation, not just what the reactor emits. According to their numbers, VY believes they remained within state and federal limits.
The state is now re-evaluating how it monitors the radiation released by the nuclear reactor, and on Nov. 16 the Windham County Regional Commission held a public meeting to answer questions regarding the Vermont Radiological Health Program and its relation to Vermont Yankee’s operation.
Oak Ridge Associated Universities, a group of 80 colleges that studies public safety issues, is now reviewing how and why the plant’s owners and the state came up with different radiation measurements. Last week’s event was an attempt to clear up any misconception the public may have, and clarify the state’s role.
“There have been a lot of questions and discussion about radiation from the plant, at the fence line, etc., and some of those were raised by us,” said Jim Matteau, the commission’s executive director. “But the state has a comprehensive program that may not be fully understood at the local level, and this served as an opportunity for people to learn about the program.”
The Vermont Department of Health conducts 24-hour surveillance of Vermont Yankee, monitoring gamma radiation, particulates, and radioiodine. They take spring and fall samples of wild vegetation, agricultural crops, fish from surrounding bodies of water, sediments from the Connecticut River, as well as soil. In addition, the department conducts monthly tests on locally-produced dairy products and sources of potable drinking water.
Many questions and concerns have arisen from a discrepancy in the way the state and Vermont Yankee calculate radiation doses near the Vernon power station.
The Vermont Guardian first reported the discrepancy back in April 2005 when the state’s departments of health and public service discovered that one of the four monitors at Vermont Yankee’s fence line had readings in excess of state radiation exposure limits.
By the final quarter of 2004, health department measurements at the plant exceeded state limits by as much as 24 percent. According to state regulations, one unit of absorbed radiation equals one unit of radiation dose. However, Vermont Yankee uses an NRC- approved conversion factor that assumes that one unit of absorbed radiation equals 71 percent of a unit of radiation dose.
In an April 8 letter to the Public Service Board, Sarah Hoffman, the director of public advocacy at the Department of Public Service, wrote, “In its testimony before the board, Entergy indicated that the dose at the fence line [after a 20 percent uprate implementation] would comply with Health Department standards. It now appears that Entergy arrived at that conclusion by utilizing a Roentgen-to-rem conversion factor of 0.71 for the greater part of the dose, resulting in a fence line dose of 18.6 millirem above background — and when the Health Department conversion factor is applied, the resultant estimated fence line dose for power uprate exceeds the state limit of 20 millirem per year.”
According to Bill Irwin, Vermont’s chief of radiological health, VY exceeded the state’s 20-millirem limit in 1998 (20.2), 2000 (23.8), and 2004 (24.9).
Entergy Vermont Nuclear, the plant’s owner, disputed the findings and conducted their own calculations, concluding that the measurements were within state limits. While the health department found that Entergy’s method of measurement was “physically and mathematically accurate,” Irwin said, “their method is not acceptable alone to demonstrate compliance to Vermont Department of Health limits.”
To date, it was not yet determined whether the state will redefine how it measures radiation levels emitted by Vermont Yankee. Once an independent report is released in January 2007, a decision will be made.
According to Irwin, the report will likely validate the Vermont Yankee calculation method with a recommended dose conversion factor and a combination of measurements to use to evaluate compliance rather than reliance on only one measurement. Irwin said he hopes the report will also establish sound methods to deal with background radiation in these measurements, quality controls, and a recommended dose conversion factor for dosimeter read-outs. Most of all, Irwin maintained that the state health department and Vermont Yankee will reach a consensus on how future measurements will be made.
However, if any changes are recommended, Irwin said the Legislature will have the final say.
“If they come to consensus and it’s different than what it is now, then it must go to the Legislature,” said Sarah Edwards, P-Brattleboro. “There will be testimony in committee, and a proposal will be made where the governor or the [health department] will bring it to the Legislature and then we will decide if we will accept the old ones or the accepted compromise. I know that many individuals in Windham County want the testing levels to stay where they are now and not be relaxed. My only concern is who knows if the rest of the state will care about it or not. I hope we’ll come up with something that everybody agrees on.”