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US3786256A
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Method and apparatus for nuclear fuel assay with a neutron source and coincident fission neutron detectors
Assignee: National Nuclear Corp Ltd
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Filing: 1971-11-18
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Granted: 1974-01-15
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Expires: 1991-11-18
Abstract
Abstract A method and apparatus for the non-destructive assay of nuclear reactor fuels. Neutron irradiation of the fuel emits fission neutrons and gammas in groups of two to three neutrons and about five gammas for each fission and these neutrons and gammas are detected in a coincident counting system to obtain a quantitative assay of the fissionable species in the fuel. The proportions of various fissile isotopes in a fuel sample are also detected by coincident counting at a plurality of coincidence levels.
Inventors
- 👤 S Untermyer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 14:10
CPC Classifications
G; G21; G21C; G21C17/00; G21C17/06; G01; G01N; G01N23/00; G01N23/02; G01N23/06; G01N23/09; G01T; G01T1/00; G01T1/16; G01T1/17; G01T1/178; Y; Y02; Y02E; Y02E30/00; Y02E30/30
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
90 words
A method for the non-destructive assay of a nuclear fuel sample comprising the steps of generating source neutrons one at a time for interrogating the sample, irradiating the sample with the source neutrons to fission the fissile elements in the sample for emission of fission neutrons or fission induced gammas in groups of more than two neutrons or gammas, and counting the emitted groups of more than two neutrons or gammas in coincidence to provide a coincident event count rate as an indication of the fissile content of the sample.
Claim 2
Independent Claim
90 words
A method for the non-destructive assay of a nuclear fuel sample comprising the steps of generating source neutrons one at a time for interrogating the sample, irradiating the sample with the source neutrons to fission the fissile elements in the sample for emission of fission neutrons or fission induced gammas in groups of more than two neutrons or gammas, and counting the emitted groups of more than two neutrons or gammas in coincidence to provide a coincident event count rate as an indication of the fissile content of the sample.
Claim 3
Dependent Claim
66 words
The method of claim 1 in which the fuel sample comprises an enlogate fuel rod and the step of irradiating the fuel sample includes advancing the fuel rod in an axial direction, and the step of counting the fission neutrons or gammas is carried out continuously as the rod is advanced to establish a continuous record of the fissile content of local portions of the rod.
Claim 4
Independent Claim
98 words
A method for the non-destructive assay of a nuclear fuel rod by means of three fission neutron detectors comprising the steps of generating an interrogating beam of source neutrons, irradiating a sample area of the rod with the source neutrons to fission neutrons in groups of three or more neutrons or fission induced gammas per fission event, and counting groups of three of the fission neutrons or gammas with said detectors in coincidence to discriminate against the source neutrons and Compton scattering and to provide accurate spatial definition of the sample area along the axis of the rod.
Claim 5
Independent Claim
98 words
A method for the non-destructive assay of a nuclear fuel rod by means of three fission neutron detectors comprising the steps of generating an interrogating beam of source neutrons, irradiating a sample area of the rod with the source neutrons to fission neutrons in groups of three or more neutrons or fission induced gammas per fission event, and counting groups of three of the fission neutrons or gammas with said detectors in coincidence to discriminate against the source neutrons and Compton scattering and to provide accurate spatial definition of the sample area along the axis of the rod.
Claim 6
Dependent Claim
94 words
Apparatus for the non-destructive assay of a nuclear fuel sample including the combination of a source of interrogating neutrons for generating neutrons one at a time, means to position the sample in the path of source neutrons whereby fission events in the fissile elements in the sample radiate fission neutrons or neutron induced gammas in groups of three or more neutrons or gammas per fission event, means to detect the simultaneous radiation of said three or more neutrons or gammas for each fission event, and means to count the detected coincident neutrons or gammas.
Claim 7
Dependent Claim
94 words
Apparatus for the non-destructive assay of a nuclear fuel sample including the combination of a source of interrogating neutrons for generating neutrons one at a time, means to position the sample in the path of source neutrons whereby fission events in the fissile elements in the sample radiate fission neutrons or neutron induced gammas in groups of three or more neutrons or gammas per fission event, means to detect the simultaneous radiation of said three or more neutrons or gammas for each fission event, and means to count the detected coincident neutrons or gammas.
Claim 8
Dependent Claim
23 words
The invention of claim 4 in which a body of neutron moderating material is interposed between the neutron source and the fuel sample.
Claim 9
Dependent Claim
25 words
The invention of claim 4 in which a body of neutron scattering material is interposed between the source of interrogating neutrons and the fuel sample.
Claim 10
Dependent Claim
70 words
The invention of claim 4 in which the means to detect the neutrons or gammas includes at least three radiation detectors positioned to receive the fission neutrons or gammas from the fuel sample, each of the detectors detecting at least one of the neutrons or gammas from each fission event, and the counting means includes counting circuit means to count the number of coincident detections of fission neutrons or gammas.
Claim 11
Dependent Claim
15 words
The invention of claim 7 in which each of the detectors comprise an organic scintillator.
Claim 12
Dependent Claim
20 words
The invention of claim 7 in which a body of Compton gamma shielding material is interposed between said radiation detectors.
Claim 13
Dependent Claim
27 words
The invention of claim 7 in which each of the detectors comprise a neutron sensitive proportional counter, together with a neutron moderating body surrounding the proportional counters.
Claim 14
Dependent Claim
22 words
The invention of claim 10 in which a body of gamma shielding material is interposed between the neutron source and the detectors.
Claim 15
Dependent Claim
21 words
The invention of claim 10 in which a body of gamma shielding material is interposed between the detectors and the sample.
Claim 16
Independent Claim
130 words
A method for determining the respective proportions of at least two fissile materials in a fuel element or other mixture of fissile materials comprising the steps of irradiating the fuel element or other mixture of fissile material with source neutrons to fission the fissile elements in the sample for emission of fission neutrons singly and in groups of two or more neutrons, counting the emitted groups of neutrons in coincidence at at least two levels of coincidence, and comparing the measured count rates for the at least two levels of coincidence with standard count rates for those two levels of coincidence for mixtures containing known proportions of fissile materials to establish the proportions of the at least two fissile materials in the fuel element or other mixture of fissile materials.
Claim 17
Independent Claim
130 words
A method for determining the respective proportions of at least two fissile materials in a fuel element or other mixture of fissile materials comprising the steps of irradiating the fuel element or other mixture of fissile material with source neutrons to fission the fissile elements in the sample for emission of fission neutrons singly and in groups of two or more neutrons, counting the emitted groups of neutrons in coincidence at at least two levels of coincidence, and comparing the measured count rates for the at least two levels of coincidence with standard count rates for those two levels of coincidence for mixtures containing known proportions of fissile materials to establish the proportions of the at least two fissile materials in the fuel element or other mixture of fissile materials.
Claim 18
Dependent Claim
45 words
A method in accordance with claim 13 wherein the fissile elements in the sample also emit gammas singly and in groups of two or more and including the step of counting the emitted gammas as well as neutrons for at least two levels of coincidence.
Claim 19
Dependent Claim
98 words
A method for measuring the respective proportions of a neutron emitting material mixed with a fissile material in a sample comprising the steps of measuring the proportions of fissile material content as in claim 13 and including the steps of counting spontaneous neutron emission rates of the sample at at least two coincidence levels, and comparing the measured count rates for the at least two levels of coincidence with standard count rates for those two levels of coincidence for mixtures containing known proportions of neutron-emitting materials to establish the proportions of various spontaneous neutron-emitting isotopes in the sample.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |