Multivariate High Order Statistics of Measurements of the Temporal Evolution of Fission Chain-Reactions

Mattingly, John

doi:10.2172/814036

Cited by 3 publications

(3 citation statements)

References 15 publications

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“…This could be due to fission products after neutron emission not being exactly 180 degrees apart. Mattingly's higherorder statistics development [15] allowed the quantitative determination of the fraction of californium fission counted in these types of chambers and showed that 4% of the fissions were not counted. This was determined by measuring the ratio of contributions to G 23 associated with the californium detection to G 23 , which contains contributions from undetected californium fissions.…”

Section: Californium Source Driven Noise Analysis Measurementsmentioning

confidence: 99%

Subcritical Californium Source Drive Noise Analysis Measurements With Unreflected Uranium (93.15) Hydride

Mihalczo

2021

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On July 6, 1989, subcritical californium source-driven noise analysis (CSDNA) measurements were performed with bare uranium hydride cylindrical assemblies at the Los Alamos National Laboratory Critical Experiments Facility in KIVA 1. Three configurations of ~7.5 cm radius-enriched (93.15 wt. % 235 U) uranium hydride with a density of ~10 g/cm 3 cylinders were assembled with uranium hydride heights of ~11, ~14, and ~16 cm. The uranium hydride (~2 and ~3 cm high) was in thin-welded stainless steel cans. The neutron multiplication factors obtained on-line from the measured ratios of spectral densities were 0.942 ± 0.002, 0.917 ± 0.003, and 0.867 ± 0.004 for uranium hydride heights of ~16, ~14, and ~11 cm., respectively. Neutron multiplication factors for these three configurations calculated by Los Alamos National Laboratory Monte Carlo methods were 0.952 ± 0.005, 0.922 ± 0.005, and 0.860 ± 0.005, all of which are in good agreement with the measurements. The break frequency noise analysis data could be fitted to obtain the prompt neutron decay constant at all subcritical states. Some data presented in this report are from notes that are not in the logbooks. A discussion of the two different point kinetics theories of the measurements that illustrated the deficiencies of the rigorous theory at low neutron multiplication factors (k eff < 0.80) is given in an Appendix. These measurements may be the only configuration of unreflected, highly enriched uranium hydride configuration assembled. The presence of hydrogen diluted the uranium density, decreasing the reactivity, but this is offset by slowing down the neutron energy to the energy ranges of higher-fission cross sections. Extrapolations to delayed critical indicate that adding one more 3 cm can and one more 2 cm can would result in the unreflected cylindrical system being slightly above critical with a critical mass of ~37 kg, which is considerably less than the critical mass of an unreflected and unmoderated highly enriched uranium metal sphere. An unreflected, highly enriched uranium hydride sphere would have a critical mass less than 37 kg.

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Section: Californium Source Driven Noise Analysis Measurementsmentioning

confidence: 99%

Subcritical Californium Source Drive Noise Analysis Measurements With Unreflected Uranium (93.15) Hydride

Mihalczo

2021

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“…Thus, all the PMT bases that are shipped with the detectors must be modified in-house to operate with positive voltages. 11 Likewise, the ORTEC 556 detector power supplies can source either positive or negative voltages. To select positive voltage on this power supply, turn the polarity selector screw on the rear of the power supply to the positive position as shown in Figure 2.8.…”

Section: Detectors and Associated Electronicsmentioning

confidence: 99%

Nuclear Materials Identification System Operational Manual

Chiang¹

2001

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“…Thus, the third order correlation function including the Cf source channel may be used to separate the effects of Cf neutrons and inherent source neutrons. This may allow the separation of the effects of 240 Pu and 239 Pu and thus provide a estimate of the Pu isotopics 16 .…”

Section: Higher Order Correlationsmentioning

confidence: 99%

Oak Ridge Multiple Attribute System (ORMAS) for Pu, HEU, HE, Chemical Agents, and Drugs

Mihalczo¹

2001

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Multivariate High Order Statistics of Measurements of the Temporal Evolution of Fission Chain-Reactions

Cited by 3 publications

References 15 publications

Subcritical Californium Source Drive Noise Analysis Measurements With Unreflected Uranium (93.15) Hydride

Subcritical Californium Source Drive Noise Analysis Measurements With Unreflected Uranium (93.15) Hydride

Nuclear Materials Identification System Operational Manual

Oak Ridge Multiple Attribute System (ORMAS) for Pu, HEU, HE, Chemical Agents, and Drugs

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