Thermal neutron multiplicity measurements using the pyrochemical multiplicity counter at Lawrence Livermore National Laboratory
Book
·
OSTI ID:61364
- Los Alamos National Lab., NM (United States). Safeguards Assay Group N-1
- Lawrence Livermore National Lab., CA (United States)
The pyrochemical multiplicity counter designed and built at Los Alamos has been undergoing tests and evaluation at Lawrence Livermore National Laboratory (LLNL). Measurements have been performed using a variety of plutonium oxide and metal materials. The pyrochemical multiplicity counter uses the information contained in the higher moments of the neutron multiplicity distribution to deduce the three unknowns in the assay problem: {sup 24O}Pu-effective mass, ({alpha},n) neutron rate, and self-multiplication. This is an improvement over conventional neutron coincidence counting, which must rely on some estimate of the ({alpha},n) neutron rate or self-multiplication to deduce an assay result. Such conventional techniques are generally unsatisfactory for impure materials for which these quantities are unknown. The authors present the assay results obtained with the pyrochemical multiplicity counter and discuss the procedures necessary to produce good assay results. Using these procedures, they have obtained assay accuracies of 1%--2% for oxide materials in 1/2 hour measurement times. They also compare these results to those that would have been obtained using conventional neutron assay techniques and discuss the correlations they have observed between assay results and the ratio of total neutron counts in the different rings of the pyrochemical counter.
- OSTI ID:
- 61364
- Report Number(s):
- CONF-930749--
- Country of Publication:
- United States
- Language:
- English
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