[cdn-nucl-l] Hot tumbleweed

["Brown, Morgan" <brownmj@AECL.CA>]

>From http://www.newscientist.com/newsletter/news.jsp?id=ns228434

When the wind blows
Beware tumbleweeds . . . they may have strayed into a radioactive pond 


MIGRATING ducks and stray tumbleweeds have been contaminated with
radioactivity after landing fleetingly in ponds of waste water at a nuclear
facility in the US. The news raises questions about the practice of leaving
such ponds open to the elements.

In the mid-1990s, staff at the Idaho National Engineering and Environmental
Laboratory (INEEL) realised that tumbleweeds were able to "blow into
waste-water ponds, and wash up on shore and blow out again", says Ronald
Warren, an independent environmental monitoring expert who is contracted to
scrutinise radioactivity at INEEL. "The tumbleweeds blew against the
[2-metre high] fence where they built up, forming a ramp other weeds could
climb over," he says.

In a two-year study, Warren and his colleagues measured how much radiation
the tumbleweeds took with them from two waste ponds near a US Navy test
reactor. The team found that the tumbleweeds, which were mostly Russian
thistle (Salsola kali), carried out a total of 66 megabecquerels of
radiation and spread it over a 32-hectare area.

"The activity from those tumbleweeds made a relatively small, around 15 per
cent, increase to the activity due to global fallout in that area," he says.
Risk to humans is slight since the nearest house is 42 kilometres away and
the tumbleweeds travelled less than a kilometre. 

Nonetheless, INEEL has taken action. "They've now made the fence higher and
they go out and collect tumbleweeds and bury them," Warren says. Growing
shrubs near the ponds has also hampered the tumbleweed.

But birdlife is not so easily thwarted. In research yet to be published,
Warren says he has found 21 species of migratory duck that fly over
INEEL--and some take a rest stop in the waste ponds. Warren says the duck's
radiation levels wouldn't harm you, even if you ate a whole one. "The
maximum radiation dose you'd get would be less than you'd get from a dental
X-ray," he says. 

This does not reassure everyone. "I haven't a clue why they don't cover the
ponds with any kind of net," says Margaret Stewart of the Snake River
Alliance, an anti-nuclear pressure group based in Idaho. "It seems like a
sensible kind of thing to do if you're trying to keep birds out." But an
INEEL spokesman maintains that radionuclide concentrations are so low in the
ponds that birds would face more risk of death from entanglement in netting.


Britain had its own problem with birds in 1999, when researchers found that
pigeons visiting contaminated buildings at the Sellafield nuclear complex
were concentrating radioactivity in their droppings in the nearby village of
Seascale.

More at: Journal of Environmental Radioactivity (vol 54, p 361)

Paul Marks 


From New Scientist magazine, 31 March 2001.