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Nuclear Update 2 – Studies in Pembroke, Ontario yield worrisome new findings about Tritium

Tritium dynamics in soils and plants grown under three irrigation regimes at a tritium processing facility in Canada [from CNSC - Canadian Nuclear Safety Commission-Jan. 2016]

Abstract: The dynamics of tritium released from nuclear facilities as tritiated water (HTO) have been studied extensively, with results incorporated into regulatory assessment models. These models typically estimate organically bound tritium (OBT) for calculating public dose since OBT itself is rarely measured.

Higher-than-expected OBT/HTO ratios in plants and soils are an emerging issue. To support the improvement of models, an experimental garden was set up in 2012 at the SRB Technologies (SRBT) tritium processing facility in Pembroke, Ontario to characterize the circumstances under which high OBT/HTO ratios may arise. Soils and plants were sampled weekly to coincide with detailed air and stack monitoring. The design included a plot of native grass/soil, contrasted with sod and vegetables grown in barrels with commercial topsoil under natural rain and either low- or high-tritium irrigation water. Air monitoring indicated that the plume was present infrequently at concentrations of up to about 100 Bq/m3 (the garden was not in a major wind sector). Mean air concentrations during the day on workdays (HTO 10.3 Bq/m3, HTO 5.8 Bq/m3) were higher than at other times (0.7–2.6 Bq/m3). Mean tissue-free water tritium (TFWT) in plants and soils and OBT/HTO ratios were only very weakly or not at all correlated with releases on a weekly basis. TFWT was equal in soils and plants and in above- and below-ground parts of vegetables. OBT/HTO ratios in above-ground parts of vegetables were above 1 (1.5–1.8) when the main source of tritium was from high-tritium irrigation water. Ratios were below 1 (0.4–0.6) in below-ground parts of vegetables when irrigated with high-tritium water, and above 1 (1.3–2.8) in vegetables rain-fed or irrigated with low-tritium water. In contrast, OBT/HTO ratios were very high (9.0–13.5) when the source of tritium was mainly from the atmosphere. TFWT varied considerably through time as a result of SRBT’s operations; OBT/HTO ratios showed no clear temporal pattern in above- or below-ground plant parts. Native soil after ∼20 years of operations at SRBT had high initial OBT that persisted through the growing season; little OBT formed in garden plot soil during experiments. High OBT in native soil appeared to be a signature of higher past releases at SRBT. This phenomenon was confirmed in soils obtained at another processing facility in Canada with a similar history.

This study’s insights into variation in OBT/HTO ratios are of regulatory interest, and should be incorporated in assessment models to help design relevant environmental monitoring programs for OBT.

To obtain a copy of the abstract’s document, please contact us at cnsc.information.ccsn@canada.ca or call 613.995.5894 or 1.800.668.5284 (in Canada). When contacting us, please provide the title and date of the abstract.

January 2015?   Levels of tritium in soils and vegetation near Canadian nuclear facilities releasing tritium to the atmosphere: implications for environmental models. From the Abstract: "Concentrations of organically bound tritium (OBT) and tritiated water (HTO) were measured over two growing seasons in vegetation and soil samples obtained in the vicinity of four nuclear facilities and two background locations in Canada. At the background locations, with few exceptions, OBT concentrations were higher than HTO concentrations: OBT/HTO ratios in vegetation varied between 0.3 and 20 and values in soil varied between 2.7 and 15. In the vicinity of the four nuclear facilities OBT/HTO ratios in vegetation and soils deviated from the expected mean value of 0.7, which is used as a default value in environmental transfer models. Ratios of the OBT activity concentration in plants ([OBT]plant) to the OBT activity concentration in soils ([OBT]soil) appear to be a good indicator of the long-term behaviour of tritium in soil and vegetation. In general, OBT activity concentrations in soils were nearly equal to OBT activity concentrations in plants in the vicinity of the two nuclear power plants. [OBT]plant/[OBT]soil ratios considerably below unity observed at one nuclear processing facility represents historically higher levels of tritium in the environment. The results of our study reflect the dynamic nature of HTO retention and OBT formation in vegetation and soil during the growing season. Our data support the mounting evidence suggesting that some parameters used in environmental transfer models approved for regulatory assessments should be revisited to better account for the behavior of HTO and OBT in the environment and to ensure that modelled estimates (e.g., plant OBT) are appropriately conservative."

QUOTATIONS:

“Tritium is no big deal. All it can do is destroy a DNA molecule.” – a health physicist, Oak Ridge National Laboratory, 1977 

Nobody Can Undo the Doo Doo from a Candu, let alone contain it. “Tritium, the radioactive sibling of hydrogen, is created by fissioning inside a CANDU reactor. They use heavy water. Heavy water then becomes radioactive water. Chemically there is no way to separate radioactive water from stable water. Because Lake Ontario water provides the coolant water, it becomes populated with radioactive water before it is released back into the Lake. Lake Ontario is now a tritium dump.” ~ Tim Seitz

“Tritium is bad for sperm.” ~ Diane D’Arrigo (NIRS or Nuclear Information & Resource Service)

“There’s been new research documenting cancer & other health maladies in people who live near nuclear plants. Nuclear plants need not undergo an accident to kill. They emit “routine releases” of radioactive poisons including xenon, krypton & tritium because nuclear plants are not sealed. Once, nuclear scientists spoke of a “threshold dose” of radiation & maintained that below that there was no harm. Now it is acknowledged that any amount of radioactivity can lead to illness & death. The Radiation & Public Health Project has documented rates of cancer significantly higher for distances of up to 40 miles around nuclear plants.” – Karl Grossman, in the Preface to his book Cover Up: What You Are Not Supposed to Know About Nuclear Power (available free on-line)

“How do tritium spills happen in a CANDU nuclear station? It’s not rocket science; it’s plumbing. It’s pipes, & they leak.”Jeff Brackett, Tritium Awareness Peterborough

** much of the content for this page has been lifted from another blog site, with permission

** many great quotations about nuclear emergency planning/causes of Fukushima disaster