Extrapolated experimental critical parameters of unreflected and steel-reflected massive enriched uranium metal spherical and hemispherical assemblies

Rothe, R.E.

doi:10.2172/658339

Cited by 14 publications

(11 citation statements)

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“…The shells have a bulk density of 18.664 g/cm 3 and an isotopic content listed in Table I. 20 Each individually numbered shell is hemispherical in shape, and each consecutive pair of shells (1-2, 3-4, etc.) represents two nearly identical hemispheres that form one spherical shell.…”

Section: A Experimentsmentioning

confidence: 99%

“…The HEU target was simulated using the isotopic contents listed in Table I and the spatial dimensions for each shell. 20 For the EJ309 organic liquid scintillators, a density of 0.959 g/cm 3 and an atomic composition of 9.85% H and 90.15% C by weight were assumed. 22 Conversion of neutron interactions into light output pulses for the 2-inch detectors utilized the exponential model described in Reference 23, which was then tailored to produce light output spectra that matched experimental results.…”

Section: B Simulationmentioning

confidence: 99%

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Spectroscopic fast neutron transmission imaging in a treaty verification setting

2018

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Measurements of the geometric configuration of objects and their material composition are needed for nuclear treaty verification purposes. We experimentally demonstrate a simple method based on monoenergetic fast neutron transmission to realize crude imaging of the geometric configuration of special nuclear material, confirm its fissionable content, and obtain information on its approximate fissile mass. In the experiment, we used monoenergetic neutrons from D(d, n)3He and T(d, n)4He reactions and a linear array of liquid scintillation detectors to perform spectroscopic neutron imaging of up to 13.7 kg of highly enriched uranium in a spherical geometry. We also show an example of detection of material diversion and confirm the presence of fissionable material based on the measurement of high-energy prompt fission neutrons, including estimating the quantity of material from the comparison of measured and predicted fission neutron emission rate. The combination of crude imaging and fissionable material detection and quantification in a simple approach may be attractive in certain treaty verification scenarios.

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Section: A Experimentsmentioning

confidence: 99%

Section: B Simulationmentioning

confidence: 99%

Spectroscopic fast neutron transmission imaging in a treaty verification setting

2018

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“…The HEU source chosen for this study are the Rocky Flats HEU shells (6). This configuration of HEU is unclassified and available at the DAF at the NNSS for possible future measurements.…”

Section: Geometry Of Interestmentioning

confidence: 99%

Gamma/neutron time-correlation for special nuclear material characterization %3CU%2B2013%3E active stimulation of highly enriched uranium.

Marleau

Nowack

Clarke

et al. 2013

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A series of simulations and experiments were undertaken to explore and evaluate the potential for a novel new technique for fissile material detection and characterization, the timecorrelated pulse-height (TCPH) method, to be used concurrent with active stimulation of potential nuclear materials. In previous work TCPH has been established as a highly sensitive method for the detection and characterization of configurations of fissile material containing Plutonium in passive measurements. By actively stimulating fission with the introduction of an external radiation source, we have shown that TCPH is also an effective method of detecting and characterizing configurations of fissile material containing Highly Enriched Uranium (HEU). The TCPH method is shown to be robust in the presence of the proper choice of external radiation source. An evaluation of potential interrogation sources is presented. 4 ACKNOWLEDGMENTS

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“…Rocky Flats Shells[3].5.1.1 The Rocky Flats HEU ShellsThe Rocky Flats Shells are a set of nesting hemispherical HEU metal shells that were manufactured for critical experiments at the Rocky Flats facility in Colorado in the 1960s[2]. There are 80 shells in total, numbered sequentially from the smallest to largest diameters: the odd-numbered shells stack to form one half of a sphere and the even-numbered shells stack to form the other half.…”

mentioning

confidence: 99%

“…The total mass for all 32 shells is 116,446 g. The isotopic composition of the Rocky Flats Shells from measurements performed in 1971 is shown in Table 5.2. The average density of the HEU is 18.65 g/cm 3[2].The shells will be unmoderated and unreflected such that the neutron spectrum will remain relatively hard; i.e., the neutrons will be within the fast energy regime. Compared to a total mass of 22.1 to 53.6 kg for the HEU cylinders studied in Chapter 4, the Rocky Flats Shells contain more mass at around 116 kg for the symmetrical case.…”

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confidence: 99%

Analysis of the Temporal Response of Coupled Asymmetrical Zero-Power Subcritical Bare Metal Reactor Systems

Klain

2017

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The behavior of symmetrical coupled-core systems has been extensively studied, yet there is a dearth of research on asymmetrical systems due to the increased complexity of the analysis of such systems. In this research, the multipoint kinetics method is applied to asymmetrical zeropower, subcritical, bare metal reactor systems. Existing research on asymmetrical reactor systems assumes symmetry in the neutronic coupling; however, it will be shown that this cannot always be assumed. Deep subcriticality adds another layer of complexity and requires modification of the multipoint kinetics equations to account for the effect of the external neutron source. A modified set of multipoint kinetics equations is derived with this in mind. Subsequently, the Rossi-alpha equations are derived for a two-region asymmetrical reactor system. The predictive capabilities of the radiation transport code MCNP6 for neutron noise experiments are shown in a comparison to the results of a series of Rossi-alpha measurements performed by J. Mihalczo utilizing a coupled set of symmetrical bare highly-enriched uranium (HEU) cylinders. The ptrac option within MCNP6 can generate time-tagged counts in a cell (list-mode data). The list-mode data can then be processed similarly to measured data to obtain values for system parameters such as the dual prompt neutron decay constants observable in a coupled system. The results from the ptrac simulations agree well with the historical measured values. A series of case studies are conducted to study the effects of geometrical asymmetry in the coupling between two bare metal HEU cylinders. While the coupling behavior of symmetrical systems has been reported on extensively, that of asymmetrical systems remains sparse. In particular, it appears that there has been no previous research in obtaining the coupling time constants for asymmetrically-coupled systems. The difficulty in observing such systems is due in part to the iii v List of Tables viii List of Figures x

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Extrapolated experimental critical parameters of unreflected and steel-reflected massive enriched uranium metal spherical and hemispherical assemblies

Abstract: DISCLAIMER d m w h e d b y t h e I d a h o N~d E n g i n e a i n g a n d E n~t a l~, a l t h o u g h t h e w o r k w a s~~e d a t R o c k y F l a t s ,~l~. .

Cited by 14 publications

References 0 publications

Spectroscopic fast neutron transmission imaging in a treaty verification setting

Spectroscopic fast neutron transmission imaging in a treaty verification setting

Gamma/neutron time-correlation for special nuclear material characterization %3CU%2B2013%3E active stimulation of highly enriched uranium.

Analysis of the Temporal Response of Coupled Asymmetrical Zero-Power Subcritical Bare Metal Reactor Systems

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