Document Details

Factors in Measuring Beta Activity of Plant Material
Subject Terms:
beta, uranium, isotopes; gamma
Document Location:
DOE INFORMATION CENTER 1 Way, Oak Ridge, TN 37831; Eva Butler; Phone: 865-241-4780; Toll-Free: 800-382-6938, Option 6; FAX: 865-574-3521; Email:
Document Categories:
Specific Material\Uranium; Specific Material\Uranium
Document Type:
Publication Date:
1949 Jan 21
Declassification Date:
1959 Mar 24
Declassification Status:
Document Pages:
Accession Number:
Document Number(s):
Originating Research Org.:
Oak Ridge Y-12 Plant
OpenNet Entry Date:
1998 Jun 16
This report is concerning the factors in measuring beta activity of plant material. The "beta meter" or "Detector C", as used in Y-12, is more properly known as a beta particle counter rate meter and consists of a tubular probe (Geiger-Muller tube) connected to a milliammeter thru an electronic circuit. The beta particles pass thru the walls of the tube and cause an electrical disturbance which registers on the meter. The beta active materials in recycle uranium are not uranium isotopes at all but are Th-234, Th-231 and Pa-234. Some of the problems involved in the calibration of a beta count rate meter for the detection of uranium are (1) A quantity of recycle uranium under the probe of a beta detector could give any meter reading from zero to full scale, depending on the previous history of the recycle uranium; (2) While a beta count rate meter will detect imbedded T, the actual meter reading depends on how deeply the T is imbedded; (3) Geiger-Muller tubes show some response to gamma radiation, and photoelectrons in the tubes produce a disturbance known as background; (4) the reading on a beta rate meter also depends on the geometry of the tube itself; and (5) the beta activity of a sample is proportional to the amount of U-238 present and is independent of the other uranium isotopes, except as they effect the U-238 content. Of these items, the last one is the only one that can be accurately measured and its effect may be small compared with the other factors involved.

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