Passive neutron assay of plutonium by multiplicity counter technique: theory and practice
The multiplicity counter technique for passive neutron assay of plutonium (Pu) is discussed in detail. The detected neutron pulse train generated by neutron emitting isotopes of a plutonium sample is analysed by the Euratom Time Correlation Analyser (Ispra-type multiplicity counter). An equivalent point source is considered for the interpretation model. The Plutonium mass of a sample with known isotopic composition is derived, based upon the shift register concept using the sample multiplication, and detector efficiency as parameters. Using the multiplicity counter technique, theoretical predictions of the multiplicity distributions are derived again using as parameters the sample multiplication, and detector efficiency. Measured and calculated multiplicity distributions are then compared. Expressions defining the theoretical predictions of the multiplicity distributions are based upon probability considerations and are fully derived. The multiplicity counter technique was tested by assaying 53 Pu cans. The measured data were analysed by the multiplicity counter technique comparing measured and calculated multiplicity distributions. Finally most of the cans were analysed by the destructive technique: the agreement with neutron multiplicity analyses was always within 3% to 4%. Computer codes in FORTRAN are included for some of the most interesting numerical calculations. The discussions are completed by numerical exercises.
Bibliographic Reference: EUR 16462 EN (1996) 75pp., FS
Availability: Available from the Public Relations and Publications Unit, JRC Ispra, I-21020 Ispra (IT), Fax: +39-332-785818
Record Number: 199611513 / Last updated on: 1997-01-27
Original language: en
Available languages: en