Study of neutron noise from reflected, metal assemblies with criticality safety applications in mind
The author studied the statistics of detected neutrons that leaked from four subcritical reflected, enriched-uranium assemblies, to explore the feasibility of developing a criticality warning system based on neutron noise analysis. The calculated multiplication factors of the assemblies are 0.59, 0.74, 0.82, and 0.92. The author studied three possible discriminators, i.e., three signatures that might be used to discriminate among assemblies of various multiplications. They are: (1) variance-to-mean ratio of the counts in a time bin (V/M); (2) covariance-to-mean ratio of the counts in a common time bin from two different detectors (C/M); and (3) covariance-to-mean ratio of the counts from a single detector in two adjacent time bins of equal length, which the author calls the serial-covariance-to-mean ratio (SC/M). The performances of the three discriminators were not greatly different, but a hierarchy did emerge: SC/M greater than or equal to V/M greater than or equal to C/M. An example of some results: in the neighborhood of k = 0.6 the ..delta..k required for satisfactory discrimination varies from about 3% to 7% as detector solid angle varies from 19% to 5%. In the neighborhood of k = 0.8 the corresponding ..delta..ks are 1% and 2%. The noise analysis techniques studied performed well enough in deeply subcritical situations to deserve testing in an applications environment. They have a good chance of detecting changes in reactivity that are potentially dangerous. One can expect sharpest results when doing comparisons, i.e., when comparing two records, one taken in the past under circumstances known to be normal and one taken now to search for change.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6339983
- Report Number(s):
- UCRL-93219; CONF-8508105-1; ON: DE85017273
- Resource Relation:
- Conference: DOE subcritical reactivity measurements workshop, Albuquerque, NM, USA, 26 Aug 1985; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FISSILE MATERIALS
MULTIPLICATION FACTORS
MEASURING METHODS
SUBCRITICAL ASSEMBLIES
ALARM SYSTEMS
CRITICALITY
DISCRIMINATORS
NEUTRON DETECTION
NEUTRON DETECTORS
NOISE
REACTIVITY
DETECTION
ELECTRONIC CIRCUITS
EXPERIMENTAL REACTORS
FISSIONABLE MATERIALS
MATERIALS
MEASURING INSTRUMENTS
RADIATION DETECTION
RADIATION DETECTORS
REACTORS
RESEARCH AND TEST REACTORS
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