Radiological Assessment for the Removal of Legacy BPA Power Lines that Cross the Hanford Site Page: 4 of 20
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Radiological Assessment for the Removal of Legacy BPA Power Lines that Crossed the
Hanford Site - 14039 (Draft)
William J. Millsap *, Daniel J. Brush *
* Mission Support Alliance
This paper discusses some radiological field monitoring and assessment methods used to
assess the components of an old electrical power transmission line that ran across the Hanford
Site between the production reactors area (100 Area) and the chemical processing area (200
Area). This task was complicated by the presence of radon daughters-both beta and alpha
emitters-residing on the surfaces, particularly on the surfaces of weathered metals and metals
that had been electrically-charged. In many cases, these activities were high compared to the
DOE Surface Contamination Guidelines, which were used as guides for the assessment. These
methods included the use of the Toulmin model of argument-represented using Toulmin
diagrams-- to represent the combined force of several strands of evidences, rather than a single
measurement of activity, to demonstrate beyond a reasonable doubt that no or very little
Hanford activity was present and mixed with the natural activity. A number of forms of evidence
were used: the overall chance of Hanford contamination; measurements of removable activity,
beta and alpha; 1-minute scaler counts of total surface activity, beta and alpha, using
"background makers"; the beta activity to alpha activity ratios; measured contamination on
nearby components; Nal gamma spectral measurements to compare uncontaminated and
potentially-contaminated spectra, as well as measurements for the sentinel radionuclides, Am-
241 and Cs-137 on conducting wire; comparative statistical analyses; and in-situ measurements
of alpha spectra on conducting wire showing that the alpha activity was natural Po-210, as well
as to compare uncontaminated and potentially-contaminated spectra.
Bonneville Power Administration (BPA) owned an electrical transmission line with several
conductors that crossed the Hanford Site and which had been in operation for seven decades.
See Figure 1 for a map of the transmission line. This transmission line was being replaced with
a new line following a somewhat different routing across the site. BPA wished to dispose of
many of the components of the old transmission line as uncontaminated material, and, in
particular, it wished to recycle the metal, especially the large amount of valuable bare, copper
conductor. There were about 30 miles of three-phase copper conducting wire and about 10
miles of three-phase aluminum wire. The metal was estimated to be worth about $1.5 million.
To support this plan, BPA asked the Mission Support Alliance (MSA), a Hanford contractor, to
assess the likelihood that the components of the transmission line were contaminated with
radionuclides from Hanford, and if so, was the contamination likely to exceed the DOE Surface
MSA planned and implemented a detailed survey of the components of the transmission line.
The following components were surveyed: wooden poles (two per structure); the cross arms
that braced the two poles for each structure; the electrical insulators; and the conductors.
Figure 2 shows a photograph of typical poles, a cross arm and insulators. The types of
surveys performed were alpha radioactivity and beta-gamma radioactivity scan surveys; 1-
minute scaler counts for both alpha and beta-gamma radioactivity (these measure the actual
count in one minute, rather than a count rate); removable radioactivity surveys for both alpha
and beta-gamma radioactivity; in-situ alpha spectrometry on the conducting wire; and in-situ
gamma spectroscopy on the conducting wire. Conducting wire samples were cut into short
pieces, laid side-by-side on a wooden board to form "wire sheets." Radiological
10 Nov 13 Draft
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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/m1/4/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.