Fission Signatures for Nuclear Material Detection

Gozani, T.

doi:10.1109/tns.2009.2015309

Cited by 42 publications

(34 citation statements)

References 10 publications

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“…This begs the question whether the fission delayed gamma rays can also be measured with this detector along with the prompt neutrons from thermal and epithermal fissions. Fission delayed gamma rays are a very strong fission signature (about 7 gammas per fission) with a roughly exponentially decreasing intensity with energy and a relatively slow decrease with time [26,27]. The lack of distinct strong spectral features allows measurements with lowresolution detectors such as plastic or liquid scintillators [28][29][30].…”

Section: Feasibility Of Detecting Fission Delayed γ Raysmentioning

confidence: 99%

Neutron kinetics in moderators and SNM detection through epithermal-neutron-induced fissions

Gozani¹,

King²

2016

Nuclear Instruments and Methods in Physics Research Section A:

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Section: Feasibility Of Detecting Fission Delayed γ Raysmentioning

confidence: 99%

Neutron kinetics in moderators and SNM detection through epithermal-neutron-induced fissions

Gozani¹,

King²

2016

Nuclear Instruments and Methods in Physics Research Section A:

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“…Not only does the initial gamma distribution depend on the fissile isotope but the time profile of the delayed gamma spectrum also changes with isotope (El-Wahab 1982). The changes are not dramatic resulting in a reasonably predicable profile for a single pulse event sufficient for detection of special nuclear materials (Gozani 2009, Norman et al 2004). Initiation of a critical configuration in an accretion disk could have a variety of these combinations present including variable assembly rates.…”

Section: Fast and Thermal Fission Of Different Isotopes (Initial And mentioning

confidence: 99%

Nuclear criticality as a contributor to gamma ray burst events

Hayes¹

2013

Astrophys Space Sci

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-Most gamma ray bursts are able to be explained using supernovae related phenomenon. Some measured results still lack compelling explanations and a contributory cause from nuclear criticality is proposed. This is shown to have general properties consistent with various known gamma ray burst properties. The galactic origin of fast rise exponential decay gamma ray bursts is considered a strong candidate for these types of events. BackgroundThe Oklo uranium mine in South Africa is a place where the natural abundance of U235 was found to be consistently less than the 0.72% found everywhere else on the planet (with the remainder of the uranium being almost entirely U238). It was not until the excess isotopic distribution from the stable fission product decay nuclides was found that it was realized this was an ancient natural nuclear reactor (Cowan 1976). Because the half life of U235 is almost an order of magnitude smaller than that of U238, the ratio of U235 to U238 increases in reverse time. By going back far enough in time, the abundance of the two nuclides would become comparable. With sufficiently enriched uranium in the soil, addition of moisture from rain would then provide the necessary moderation for the earth to sustain a natural nuclear chain reaction until the heat would drive away the water and return the system to a subcritical state. This process is believed to have occurred over a billion years ago in central Africa (Fujii et al. 2000).If the Oklo reactor occurred naturally as a result of uranium created in supernovae (SN) events, it is not incredible to think that it could occur prior to accumulation into planetary form from other SN events. In other words, just after the SN creation of the uranium and transuranic isotopes, most of the already radioactive elements created will quickly decay into stable atoms leaving these fissile and fissionable isotopes close to their original abundance. Even if a large fraction of the Pu239 (which is fissile with a moderately long half life of just over 24 ka) were to decay away, there would still be almost the initial amount of U233 (which is fissile with a moderately long half life of just under 0.2 ma) with only a negligible fraction of the U235 having decayed away. If a gravitational accumulation of the SN excreta were to occur within some few years, a longer list of potential fissile isotopes could be present in the material including Pu241, Am243, Cm243, Cm245, Cm247, etc while the majority of the radioactive elements would still have decayed into stable isotopes. This presents a dynamic reactivity dependency in terms of the fissile nuclides generated which would be strongly dependent on the initial isotopic distribution source term.The model presented here has the potential to explain some of the highly varied nature of a portion of measured gamma ray bursts (GRBs). These include the random nature of the events in terms of their parametric values and ranges. Specifically many measured values of energy and time distributions, pulsing, and afterglows ...

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“…2. [5,23,24] Both complementary and orthogonal fission signatures that can be used. However, while the coupling of individual fission signatures (e.g.…”

Section: The Need To Assess Multiple Signatures (The Limitations mentioning

confidence: 99%

Addressing different active neutron interrogation signatures from fissionable material

Chichester

Seabury

2009

2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC)

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-In a continuing effort to examine portable methods for implementing active neutron interrogation for detecting shielded fissionable material research is underway to investigate the utility of analyzing multiple time-correlated signatures. Time correlation refers here to the existence of unique characteristics of the fission interrogation signature related to the start and end of an irradiation, as well as signatures present in between individual pulses of an irradiating source. Traditional measurement approaches in this area have typically worked to detect die-away neutrons after the end of each pulse, neutrons in between pulses related to the decay of neutron emitting fission products, or neutrons or gamma rays related to the decay of neutron emitting fission products after the end of an irradiation exposure. In this paper we discus the potential weaknesses of assessing only one signature versus multiple signatures and make the assertion that multiple complimentary and orthogonal measurements should be used to bolster the performance of active interrogation systems, helping to minimize susceptibility to the weaknesses of individual signatures on their own. Recognizing that the problem of detection is a problem of low count rates, we are exploring methods to integrate commonly used signatures with rarely used signatures to improve detection capabilities for these measurements. In this paper we will discuss initial activity in this area with this approach together with observations of some of the strengths and weaknesses of using these different signatures.

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Fission Signatures for Nuclear Material Detection

Cited by 42 publications

References 10 publications

Neutron kinetics in moderators and SNM detection through epithermal-neutron-induced fissions

Neutron kinetics in moderators and SNM detection through epithermal-neutron-induced fissions

Nuclear criticality as a contributor to gamma ray burst events

Addressing different active neutron interrogation signatures from fissionable material

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