US3786257A
Expired / Lapsed
US
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Nuclear failed fuel detection system
Assignee: Westinghouse Electric Corp
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Filing: 1971-08-12
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Granted: 1974-01-15
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Expires: 1991-08-12
Abstract
Abstract A system is disclosed which utilizes multiple radiation detectors to establish the isotopic or pseudo isotopic (weighted average of several isotopes) content of radiation sources on a continuous on-line basis. A specific application which utilizes this principle is a failed fuel monitor which continuously monitors the delayed neutron and gamma activity emanating from the primary coolant of a nuclear reactor. Employing two neutron detectors, the system has the ability to distinguish between activity from failed fuel and from fuel rod surface contamination. Applying a technique to compensate for activity build-up in the primary coolant loop, the system makes it possible to interpret the signals even during power transients. The provision of a third detector responsive to the gamma radiation emitted from the primary coolant in the reactor coolant loop enables the system to distinguish between enlarged cladding failures in already failed fuel rods and additional fuel failures.
Inventors
- 👤 H Weiss
- 👤 R Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:54
CPC Classifications
G; G21; G21C; G21C17/00; G21C17/02; G21C17/04; G21C17/044; G21C17/047; Y; Y02; Y02E; Y02E30/00; Y02E30/30
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
103 words
A nuclear failed fuel detection system for detecting the presence of fission products due to failed fuel within the coolant medium of a nuclear reactor comprising: a first detector responsive to the radioactivity within the reactor coolant medium after the radioactivity has decayed for a first delay period; a second detector responsive to the radioactivity in the reactor coolant medium after the radioactivity has decayed for a second delay period; means for taking the ratio of the signals received from said second and first detectors respectively; and means for subtracting from said ratio, the component value of the ratio attributable to surface contamination.
Claim 2
Dependent Claim
103 words
A nuclear failed fuel detection system for detecting the presence of fission products due to failed fuel within the coolant medium of a nuclear reactor comprising: a first detector responsive to the radioactivity within the reactor coolant medium after the radioactivity has decayed for a first delay period; a second detector responsive to the radioactivity in the reactor coolant medium after the radioactivity has decayed for a second delay period; means for taking the ratio of the signals received from said second and first detectors respectively; and means for subtracting from said ratio, the component value of the ratio attributable to surface contamination.
Claim 3
Dependent Claim
26 words
The apparatus of claim 1 including means for compensating said first and second detector signals for the residual build-up of radiation within the reactor coolant medium.
Claim 4
Dependent Claim
22 words
The apparatus of claim 1 wherein said first and second detectors are responsive to the neutrons emitted from the reactor coolant medium.
Claim 5
Dependent Claim
31 words
The apparatus of claim 3 including a gamma detector responsive to the gamma radiation emitted from the reactor coolant medium after the gamma radiation has decayed for a third delay period.
Claim 6
Dependent Claim
24 words
The apparatus of claim 4 wherein said third delay period is selected to allow the N-16 gamma radiation to decay to a negligible level.
Claim 7
Dependent Claim
15 words
The apparatus of claim 4 wherein said third delay period is approximately one hundred seconds.
Claim 8
Dependent Claim
64 words
The apparatus of claim 3 wherein said first delay period iS selected to allow the N-17 activity and short lived groups of delayed neutron emitters, having half lives less than five seconds, to decay to a negligible level and said second delay period is selected to obtain a signal in said second detector which significantly differs from the signal received from said first detector.
Claim 9
Dependent Claim
18 words
The apparatus of claim 3 wherein said first and second delay periods are 60 and 120 seconds, respectively.
Claim 10
Dependent Claim
23 words
The apparatus of claim 1 wherein said first and second detectors are responsive to the gamma radiation emitted from the reactor coolant medium.
Claim 11
Dependent Claim
50 words
The apparatus of claim 9 wherein said first delay period is selected to allow the N-16 gamma radiation to decay to a negligible level and said second delay period is selected to obtain a signal in said second detector which significantly differs from the signal received from said first detector.
Claim 12
Dependent Claim
14 words
The apparatus of claim 9 wherein said first delay period is one hundred seconds.
Claim 13
Dependent Claim
31 words
The apparatus of claim 9 including a neutron detector responsive to the neutron actively emitted from the reactor coolant medium after the neutron activity has decayed for a third delay period.
Claim 14
Dependent Claim
38 words
The apparatus of claim 12 wherein said third delay period is selected to allow the N-17 activity and short lived groups of delayed neutron emitters, having half lives less than five seconds, to decay to a negligible level.
Claim 15
Dependent Claim
13 words
The apparatus of claim 12 wherein said third delay period is 60 seconds.
Claim 16
Independent Claim
112 words
A method for detecting the presence of fission products due to failed fuel within the coolant medium of a nuclear reactor comprising the steps of: a. measuring the radioactivity emitted from the reactor coolant medium after the radioactivity has decayed for a first delay period; b. measuring the radioactivity emitted from the reactor coolant medium after the radioactivity has decayed for a second delay period; c. taking the ratio of the radioactivity measurements received in steps (b) and (a), respectively; d. establishing the value of said ratio attributable to surface contamination in the absence of failed fuel; and e. subtracting the value of said ratio attributable to surface contamination from said ratio.
Claim 17
Independent Claim
112 words
A method for detecting the presence of fission products due to failed fuel within the coolant medium of a nuclear reactor comprising the steps of: a. measuring the radioactivity emitted from the reactor coolant medium after the radioactivity has decayed for a first delay period; b. measuring the radioactivity emitted from the reactor coolant medium after the radioactivity has decayed for a second delay period; c. taking the ratio of the radioactivity measurements received in steps (b) and (a), respectively; d. establishing the value of said ratio attributable to surface contamination in the absence of failed fuel; and e. subtracting the value of said ratio attributable to surface contamination from said ratio.
Claim 18
Dependent Claim
20 words
The method of claim 15 wherein steps (a) and (b) measure the neutron activity emitted from the reactor coolant medium.
Claim 19
Dependent Claim
48 words
The method of claim 16 including the steps of: measuring the gamma radiation emitted from the reactor coolant medium after the gamma radiation has decayed for a third delay period; and detecting an increase in said neutron measurements in the absence of an increase in said gamma measurements.
Claim 20
Dependent Claim
29 words
The method of claim 15 including the step of compensating the measurements obtained in steps (a) and (b) for the residual build-up of radiation within the reactor coolant medium.
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 |