NUCLEAR MAGNETIC RESONANCE STUDIES OF NEUTRON-IRRADIATED FLUORIDES, ESPECIALLY LITHIUM FLUORIDE
Thesis/Dissertation
·
OSTI ID:4727211
The decomposition of LiF produced by neutron irradiation in reactors was studied by nuclear magnetic resonance (NMR) techniques. Several sets of crystals and powdered samples were irradiated at a variety of temperatures from 26 to 150 deg C, for total neutron doses between 10/sup 15/ and 2 x 1O/sup 19/ nvt. After irradiation, distinctive lines were found superimposed upon the characteristic NMR spectrum of LiF. By a detailed study of their properties, the additional lines were shown to be due to F/sup 19/ nuclei in a gaseous F phase and to Li/sup 7/ nuclei in a metallic Li phase. It was concluded that irradiation causes some decomposition of LiF into its elements, L and F, and that many of the halogen defects are present as F gas in tiny cavities rather than as isolated irterstitials in the lattice. In discussing the results, the role of halogen gas was emphasized; the observation of metallic Li supports the conclusions of previous studies which indicated the presence of colloidal Li. NMR lines representing colloidal Li were observed in only 2 specimens; both of these had received doses greater than 10/sup 19/ nvt and contained large gas concentrations. A weak line in the Li/sup 7/ NMR spectrum (frequency shift of (1.6 plus or minus 0.3) x 10/sup -4/ with respect to the ionic Li resonance! was tentatively identified as due to Li metal in the metastable face-centered cubic phase. Exploratory experiments on NaF and CaF/sub 2/ demonstrated that a fast-neutron irradiation of 10/sup 19/ nvt can, on occasion, produce F gas concentrations comparable to those found for LiF. This result shows that decomposition is not limited to LiF. (M.P.G.)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-016111
- OSTI ID:
- 4727211
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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· Phys. Rev. Letters
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OSTI ID:4303970