Cesium in the Biosphere: Guest Post by Stewart Farber

Stewart Farber
MSPH

Air Pollution and Dosimetry

Starting in 1972, for about 3 years, as a Public Health scientist and air pollution control specialist, I was responsible for upgrading and reviewing the Radiological Environmental Monitoring Program data from VY (and other Yankee plants) and generating periodic summary reports to the NRC.

In 1975, I was responsible for getting approval for a multi-million dollar centrally located state-of-the-art, greatly enhanced environmental lab. This lab was far more advanced than the labs of any of the then-current commercial contractors.  The lab was established as the Yankee Atomic Electric Co. Environmental Lab in Westboro, MA. Vermont Yankee management were willing to share in the substantial expense of setting up this advanced facility. This lab analyzed radiological environmental samples from VY, as well as Maine Yankee, Yankee-Rowe, and Seabrook (and misc. other plant samples) and performed personnel dosimetry services for these nuclear plants for over 25 years.

Meteorological Monitoring

I proposed upgrading the meteorological monitoring program at all Yankee plants in 1974, including VY. To its credit, VY willingly, despite the cost, supported installation of a 300' meteorological tower (vs. 120'). This met tower had  more advanced met instrumentation, and a computerized data acquisition system to digitize wind speed, wind direction, and temperature at 3 elevations so it could be reviewed from a central facility on a routine basis. This made met parameters available remotely in the event of an emergency, in order to assist in emergency planning. VY recognized the value of having good met and environmental radiological data and willingly shared in the costs this required. The sponsor companies and staff at VY deserve substantial credit.

A comment follows on the variability of environmental radioactivity of nuclear fission isotopes as a cautionary note on jumping to conclusions about environmental radioactivity based on limited sampling, something which VT politicians with an agenda often used against VY to negatively influence public opinion and advance their short-sighted agenda.

Wood Ash and Cs

Wood burning fireplace

In 1990 I took a sample of wood ash from burning hardwoods in my fireplace at a vacation home I had in Warren, VT (which is 130 miles distant from VY in Vernon, VT) and had it analyzed for radioactivity level by sensitive gamma spectroscopy at the Yankee lab. Wood ash is the end product of burning roughly 100 to 300 pounds of wood to yield 1 pound of ash, so ash concentrates what minerals are in the wood to yield a sample that can serve as a very sensitive indicator of natural environmental radioactivity and potential contamination from man-made isotopes . This sample from Warren, VT as would be expected, contained very high levels of the natural isotope K-40 (half life= 1.2 billion years), multiple isotopes of the U-238 (half life 4.5 billion years) decay chain, and multiple isotopes of the Th-232 (half life= 14 billion years) decay series. These are primordial isotopes present in the environment; they are residual from the Big Bang. In addition, this sample contained very high, and quite surprising, levels of the nuclear fission product Cs-137 residual from atmospheric nuclear bomb testing by the US and USSR which ended in 1963.

This initial sample of wood ash from Warren, VT contained 15,000 pCi/kg ash of Cs-137 --the highest level of Cs-137 the Yankee Lab had ever seen in any background environmental sample analysis. I asked VY staff (and other nuclear facilities across the US) to submit a wood ash sample gamma spec analysis after the initial measurement in Warren was so surprisingly high. The wood ash sample from trees grown near VY was analyzed showing a Cs-137 level of about 1,500 pCi/kg ash --10% of the level of fallout Cs-137 seen 130 miles distant!!!! This demonstrated how variable man-made nuclear isotope fallout can be in the environment. This has NOTHING to do with a nuclear plant: a nuclear plant releases essentially zero levels of Cs-137 and Sr-90 in airborne releases.

Cs lower near Vermont Yankee

Many years later after 2011, anti-nuclear politicians like Governor Shumlin in VT, set out with their agenda to make VY look bad because slight differences in Sr-90 (present throughout the environment residual from open air bomb testing) were seen in a few fish near the plant and upriver from VY. A few isolated environmental measurements mean very little. As was seen with the wood ash measurements mentioned above, the Cs-137 level in wood ash near VY in 1990 was 1/10th the level measured 130 miles away in Warren.

This difference was not likely due to major differences in fallout from past bomb testing in Central vs. Southern VT but due to soil chemistry factors between the two locations. Can you imagine what some environmental activist charlatans might do and demand if Cs-137 levels in trees was 10 times higher near VY vs. 130 miles away, rather than the other way around as is actually the case?

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Steward Farber holds a degree in chemistry from Brown University, and an MS Public Health from UMass Amherst.  Farber originally submitted this post as a two-comment set on my blog post Cinco de Bye-O at Vermont Yankee. However, I felt this knowledgeable and extensive comment deserved its own post.  You might also want to look back at the original post, where Farber's writing gathered two more comments. One was about the different uptake of Cs by different tree species, and and the second comment was about pulses of radionuclides that are released in forest fires.