Monitoring a sample containing a neutron source
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Abstract
The invention considers the frequency distributions of singles, doubles and triple neutron emission events from a sample under assay. The count rates are equated to mathematical functions related to the spontaneous fission rate, self-induced fission rate, detection efficiency and c,n rate with probability distribution assigned to each of those factors, the value of the product of all the probability distributions being increased to give an optimised solution and so provide a value of the spontaneous fission rate which is linked to the mass of the neutron source. The technique aims to provide increased accuracy and certainty compared with neutron coincidence counting based techniques.
21 Citations
41 Claims
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1-12. -12. (canceled)
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13. A method of monitoring a sample containing a neutron source in which:
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i) signals from a plurality of neutron detectors are analyzed and the count rates for single, double and triple incidence of neutrons on the detectors are determined;
ii) the single, double and triple count rates are equated to a mathematical function related to the spontaneous fission rate, self-induced fission rate, detection efficiency and α
,n reaction rate;
iii) a probability distribution is assigned to each of the spontaneous fission rate, the self-induced fission rate, detection efficiency and α
,n reaction rate and each of the counting rates to provide a probability distribution factor for any given value, wherein the probability distribution assigned to,the single, double, and triple count rates is a first distribution, the spontaneous fission rate is a second distribution, the self-induced fission rate is a third distribution, the detector efficiency is a fourth distribution, the α
,n reaction rate is a fifth distribution;
iv) and the value of the product of all the probability distribution factors is increased to give an optimized solution and so provide a value for the spontaneous fission rate which is linked to the mass of the neutron source. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of monitoring a sample containing a neutron source having a neutron source mass, comprising:
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analyzing signals from a plurality of neutron detectors;
determining a single incidence neutron count rate (R1), a double incidence neutron count rate (R2), and a triple incidence neutron count rate (R3) associated with the neutron source based upon the analyzing;
equating the single, double and triple incidence neutron count rates to a mathematical function related to a spontaneous fission rate (FS), a self-induced fission rate (M), a (α
,n) reaction rate (α
) and a detection efficiency (ε
);
assigning a probability distribution to each of the spontaneous fission rate, self induced fission rate, the detection efficiency, the α
,n reaction rate and each of the counting rates;
obtaining probability distribution factors for a set of trial values;
calculating an overall value of a product of all the probability distribution factors; and
varying one or more of the trial values so as generate a maximal overall value for the product of all probability distribution factors, the value of the spontaneous fission rate being taken, wherein that value for the spontaneous fission rate is linked to the neutron source mass. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A method of monitoring a sample containing a neutron source in which:
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i) signals from a plurality of neutron detectors are analyzed and the count rates for single, double, and triple incidence of neutrons on the detectors are determined;
ii) the single, double, and triple count rates are equated to a mathematical function related to the spontaneous fission rate, self induced fission rate, detection efficiency and α
,n reaction rate;
iii) a probability distribution is assigned to each of the spontaneous fission rate, the self induced fission rate, detection efficiency, and α
,n reaction rate and each of the counting rates to provide a probability distribution factor for any given value;
iv) and the value of the product of all the probability distribution factors is increased to give an optimized solution and so provide a value for the spontaneous fission rate which is linked to the mass of the neutron source. - View Dependent Claims (37, 38, 39, 40, 41)
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Specification