Background radiation for Pacific NW cities

["Dukelow, James S Jr" <jim.dukelow@pnl.gov>]

As a partial, but mostly unsatisfactory, response to Jonathan Wiles question of
14 July --

Because of geology, Spokane is a region of fairly high radon and the rest of the
state of Washington and Portland are low to medium radon areas.  Although much
of the nation's weapons plutonium was produced in the Tri-Cities, environmental
Pu levels are higher west of the Cascades (Portland and Seatlle), because they
are dominated by rain-out of Pu from bomb testing in the 40s through the 60s.
Those of us in the ever-brown corner of the Evergreen State don't suffer that
much from rainfall.  Interestingly, levels of some radionuclides in the Columbia
River are higher upstream from Hanford than downstream, for reasons that are not
completely clear.   Some springs along the Hanford shore of the Columbia contain
higher than EPA drinking water standard levels of strontium-90, but levels of
all radionuclides in the main flow of the Columbia are well below drinking water
standards, which is nice, since that is what we drink in the Tri-Cities.

I did a modest search for web sites that would document the above folklore,
without success.  The Washington State Departments of Health and Ecology web
sites seemed to be innocent of any information about background radiation,
although richly supplied with information about I-131 releases from Hanford that
decayed away 40 to 55 years ago.

The maps referred to in replies by Baker and Frame show: 1) Spokane as a region
of high radon, but medium uranium, thorium, potassium, and terrestrial gamma, 2)
the Tri-Cities with medium radon, low potassium, and low to medium uranium,
thorium, and terrestrial gamma, 3) Portland similar to the Tri-Cities, and 4)
Seattle with low radon, uranium, thorium, and terrestrial gamma, but high
potassium levels.  Certain aspects of the way the maps are presented on the web
site leaves some residual uncertainties about the levels, particularly for
Seattle, where the color used to represent shorelines (with which Puget Sound is
richly supplied) is the same as the color used to represent high levels of the
radionuclide.

High radon on the USGS map is greater than 4 pCi/liter for average residence, so
by the usual conversion, radon background for Spokane would be around 800
mrem/year.

Altitudes for Portland and Seattle are effectively sea level, the Tri-Cities
sits at about 400 feet, and Spokane at about 2200 feet.

Best regards.

Jim Dukelow
Pacific Northwest National Laboratory
Richland, WA
jim.dukelow@pnl.gov

These comments are mine and have not been reviewed and/or approved by my
management or by the U.S Department of Energy.
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