Environmental Engineering Reference
In-Depth Information
From the 1980s, the local indigenous people of the Déline First Nation began to voice
concerns about the state of the abandoned mine and to draw conclusions related to the in-
cidence of cancers in their community to the mine. In 1999, the Canadian federal govern-
ment began to investigate the site and between 2001 and 2004 worked with the Déline as
part of the Canada/Déline Uranium Table (CDUT) to fully characterize the environmental
conditions at the mine. This study also considered the potential for human exposure to ra-
diation during the transport of uranium ore across Great Bear Lake and up the Mackenzie
River to Fort McMurray. Local Déline indigenous people were employed in this work, but
records do not show they worked at the mine.
The CDUT survey found that some parts of the exposed tailings contained uranium
series radionuclides up to 37,000 Bq/kg. Gamma radiation levels at the site varied from
naturalbackground(100-150nGy/hour)to740nGy/hour(anGy,ornanoGy,is10 -9 gray).
Water samples from Great Bear Lake in close vicinity to the mine showed slight elevation
of trace metals, but fish from the lake carried no detectable body burdens.
The CDUT report paid particular attention to the potential exposure of Déline workers
involved in the Northern Transportation Route. Oral histories referred to exposure to
“yellow powder”. This was originally assumed to be yellowcake (uranium concentrate).
However, yellowcake was only produced at Port Radium from 1958 to 1960 and was
shippedoutindrumsbyair(notbytheNorthernTransportationRoute).Theyellowpowder
referred to in the oral reports probably referred to sulphur powder shipped to the mine site
from 1950 to 1960 for use in the acid leach plant. A dose reconstruction was carried out for
the CDUT to estimate historical radiation exposures to 35 Northern Transportation Route
workers and their families. The average dose estimated for the ore transport workers was
76 mSv/year. The cumulative doses during the period of employment varied from 27 to
3,015 mSv. The study reported that based on the radiation doses calculated in the dose re-
construction, 1-2 cancer deaths would be expected amongst the 35 ore transport workers,
in addition to the 9-10 cancer deaths that would “normally” be expected in a similar, non-
exposed group of 35 people. Radiation doses to family members who lived near Port Radi-
um or along the transportation route were estimated to be similar to background doses.
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