1152 K
29 pp.
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TitleRadiocarbon from Pile Graphite; Chemical Methods for Its Concentrations
Author(s)Arnold, J. R.; Libby, W. F.
Publication DateOctober 10, 1946
Report NumberCC-3643
Unique IdentifierACC0334
Other NumbersOSTI ID: 4350390
Research OrgArgonne National Laboratory, Lemont, IL
Contract NoW-31-109-ENG-38
Sponsoring OrgU.S. Atomic Energy Commission (AEC)
Other InformationDeclassified Feb. 16, 1957
SubjectChemistry; Carbon 14; Carbon Dioxide; Chromium Oxides; Control; Counters; Diffusion; Enrichment; Gases; Graphite; Irradiation; Labeled Compounds; Measured Values; Oxidation; Oxygen; Qualitative Analysis; Radiations; Reactors; Surfaces; Wigner Effect
Related Web PagesWillard Libby, Radiocarbon, and Carbon Dating
AbstractSamples of pile graphite, irradiated in a test-hole at Hanford for 15 months, have been assayed for radioactive C{sup 14} yielding 0.38 ± 0.04 microcuries per gram. At this level of activity, the pile graphite contains very valuable amounts of C{sup14}. The relation between the above assay and the probable average assay of pile graphite is discussed, and it is concluded that the latter is almost certainly above 0.3 microcuries/gram. Controlled oxidation of this graphite, either with oxygen at ~750șC, or with chromic acid "cleaning solution" at room temperature, yields early fractions which are highly enriched in C{sup 14}. Concentrations of 5-fold with oxygen, and 50-fold with CrO{sub 3}, have been observed. The relation between the observed enrichment and the Wigner effect is discussed, and a mechanism accounting for the observations put forward. According to this, about 25% of the stable carbon atoms in the lattice have been displaced by Wigner effect, a large fraction of which have healed by migrating to crystal edges. All the C{sup 14} atoms have been displaced, and the same fraction of these migrate to the edges. The enrichment then results from surface oxidation, in the oxygen case. Predictions are made on the basis of this hypothesis. A technique of counting radioactive CO{sub 2} in the gas phase is described.
1152 K
29 pp.
View Document 

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