Radiological Assessment for the Removal of Legacy BPA Power Lines that Cross the Hanford Site Page: 8 of 20
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
inter-facility gross activity guideline values have been established:
Total alpha surface radioactivity: 1,000 dpm/100 cm2
Removable alpha surface radioactivity: 200 dpm/100 cm2
Total beta-gamma surface radioactivity: 4,500 dpm/100 cm2
Removable beta-gamma surface radioactivity: 900 dpm/100 cm2
The inter-facility values cannot usually be applied to electrified wire, because the inter-facility
values weren't derived for such an environment. The electromagnetic attraction of charge
radon daughters over decades results in the long-term buildup of natural radioactive material
on the wire. This is discussed further below.
Potential Means of Contamination and Radionuclides of Concern
The means of contamination are wind transport and biological transport. The wind could have
blown airborne activity from the many facilities and burial grounds. A common biological
vector is bird droppings on poles from birds that have become contaminated with radioactive
material. Contaminated bird nests are an occasional occurrence. Contaminated coyote urine
on the bases of poles is another potential vector.
Given the many possible sources of contamination, it is practical to consider a set of widely
dispersed radionuclides, rather than every possible radionuclide. The radionuclides of concern
were Cs-137, Sr-90, Co-60, U-234, U-235, U-238, Pu-239/240 and Am-241. Sr-90 is an
easily-detectable beta emitter; Cs-137 and Co-60 are easily-detectable gamma emitters; and
U-234, U-235, U-238, Pu-239/240 and Am-241 are all easily-detectable alpha emitters.
Cs-137 serves as a sentinel radionuclide for fission products-signaling the potential
presence of other fission products-because it is the most abundant photon-emitter in the
inter-facility area and has an easily-detectable 662 keV photon. Am-241 is the most
abundant transuranic in the inter-facility area and has a relatively easy to detect 60 keV
photon; it is used as a sentinel radionuclide for transuranics in the inter-facility area.
The BPA transmission lines were divided into three survey units for two reasons: (1) To set
aside a part of the transmission line that has a particularly low chance of contamination as a
background reference area; and (2) to divide the part of the line that runs across the site
between the 100 Area and the 200 Area from the part that runs roughly parallel to the
Columbia River, since they have different potentials for contamination. The background area
to the west is called Survey Unit 1; the part that runs across the site is Survey Unit 2; and the
part that runs roughly parallel to the river is Survey Unit 3. See Figure 1; Map Showing Power
Lines, Survey Units, and Sample Sites.
METHODS AND TECHNIQUES USED TO ASSESS SURFACE RADIOACTIVITY
This section individually describes the methods and techniques used to assess the surface
radioactivity on the components of the electrical transmission lines. The integrating idea, the
Toulmin model of argument, is used to combine the other methods and techniques into an
overall assessment of the likelihood of Hanford-made activity on the components. Examples of
Toulmin diagrams, used to represent Toulmin's model of argument, are shown in the next
10 Nov 13 Draft
Page 5 of 17
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Millsap, William J. & Brush, Daniel J. Radiological Assessment for the Removal of Legacy BPA Power Lines that Cross the Hanford Site, article, November 13, 2013; Richland, Washington. (https://digital.library.unt.edu/ark:/67531/metadc871756/m1/8/: accessed May 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.