Signatures of fissile materials: high-energy γ rays following fission

Norman, E. B.; Prussin, S.G.; Larimer, R. M.; Shugart, Howard A.; Browne, E.; Smith, Alan Р.; McDonald, R. J.; Nitsche, H.; Gupta, Puja; Frank, Michael I.; Gosnell, T.B.

doi:10.1016/j.nima.2003.10.097

Cited by 80 publications

(44 citation statements)

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“…Interestingly, the density distribution has the same characteristics on any given day. The mean cargo density is just under 0.2 g/cm 3 . This is consistent with the value obtained by dividing the total mass of commodities by the total number of TEU imported to the US (table 3), which predicts that on average, the cargo weight is 6.7 metric tons per TEU, for a density close to 0.2 g/cm 3 .…”

Section: B Imported Commoditiesmentioning

confidence: 96%

“…TEU stands for Twenty Equivalent Unit, and is a unit volume commonly used in the container shipping industry. A TEU represents the known volume of a 6 m (20 feet) container of standard internal dimension 2.35 m wide x 2.4 m high x 5.9 m long, with a volume close to 33.13 m 3 , and a payload of 21.6 metric tons. The total load is 24 metric tons and includes both cargo and container weights.…”

Section: Definitionsmentioning

confidence: 99%

“…[3] [4][5] [6] Within that energy range, 16 N, created through the reaction 19 F(n,a) 16 N, has been identified as the main potential interference since it emits a gamma line at 6.1 MeV. [7] In the last section of the study, we focus on records of commodities identified as containing fluorine.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Recent Manifests for Goods Imported through US Ports

Descalle¹,

Manatt²,

Slaughter³

2006

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Abstract-Several active interrogation techniques are being developed to detect shielded special nuclear materials (SNM) hidden in cargo containers loaded on container ships arriving at US ports. It raises the questions of the types of cargos in which SNM could be hidden, and their impact on detected signatures. Since the definition of a set of "typical" or standard cargos has proven to be difficult, we analyzed shipping manifests for US imports shipped through North American ports collected on 14 days distributed over 12 months. From these data, we generated several distribution functions such as commodity categories, average densities, and packaging types that could be of interest to the cargo scanning community.One of the cargo scanning techniques currently under development at LLNL is based on neutron active interrogation, and relies on the unique signature of beta-delayed gammas emitted by fission products in the 3 to 7 MeV energy range. 19 F(n,a) 16 N, has been identified as the main potential interference for 7 and 9 MeV neutron beams. Estimates of cargo compositions based on manifests identified as containing fluorine are presented.

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Section: B Imported Commoditiesmentioning

confidence: 96%

Section: Definitionsmentioning

confidence: 99%

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Analysis of Recent Manifests for Goods Imported through US Ports

Descalle¹,

Manatt²,

Slaughter³

2006

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“…Second, the two dominant sources of activation counts in the NaI detectors result from thermal neutron activation of the aluminum casing of the detectors (resulting in a 1.779 MeV gamma ray) and of the iodine in the detector itself (a continuum ranging from 443 keV to 2.562 MeV due to beta and gamma decay). Third, a unique signature that spans energies greater than 3 MeV is emitted by the beta decay of the short-lived fission products of fissionable materials [6]; this signature is absent when nonfissionable materials are interrogated. These three features are clearly evident in the spectra shown in Figure 3.…”

Section: Methodsmentioning

confidence: 99%

Outdoor stand-off interrogation of fissionable material with a hybrid coded imaging system

Hutcheson

Phlips

Wulf

et al. 2013

2013 19th IEEE Pulsed Power Conference (PPC)

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A hybrid coded imaging and detection system developed at the U.S. Naval Research Laboratory (NRL) was used for active interrogation measurements with pulsed bremsstrahlung at the Hermes-III facility at Sandia National Laboratories, Albuquerque. This work follows previous experiments performed in 2011 [1] and explores different targets and system conditions to the previous work. The techniques used and challenges encountered during this work are described.

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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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Signatures of fissile materials: high-energy γ rays following fission

Cited by 80 publications

References 0 publications

Analysis of Recent Manifests for Goods Imported through US Ports

Analysis of Recent Manifests for Goods Imported through US Ports

Outdoor stand-off interrogation of fissionable material with a hybrid coded imaging system

Nuclear criticality as a contributor to gamma ray burst events

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