Prompt Neutron Time Decay in Single HEU and DU Metal Annular Storage Castings

Conference · Sun Jul 11 00:00:00 EDT 2010

OSTI ID:1020774

Pena, Kirsten E. ^[1]; McConchie, Seth M. ^[1]; Mihalczo, John T. ^[1]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Previous measurements of highly enriched uranium (HEU) storage castings performed by Oak Ridge National Laboratory (ORNL) at the Y-12 National Security Complex showed a prompt neutron time decay that is not exponential. These measurements showed that multiple time constants originating from multiplication, time-of-flight, scattering in the assembly and room return could be associated with this prompt neutron decay. In this work, the contribution not associated with neutron multiplication was investigated via measurements with a depleted uranium (DU) casting. The measurements at ORNL used an annular (5.0-in OD, 3.5-in ID, 6.0-in H) DU casting with a time-tagged 252Cf source, centered vertically on the axis, and four closely coupled 1 1 6-in.-long plastic scintillators with -in.- thick lead shielding adjacent to the outer surface of the casting. This setup was identical to the configuration used in the previously performed measurements with HEU castings at Y-12. The time correlation between fission events and detections in the plastic scintillators was measured, as well as the time distribution of coincidences between multiple detectors within a 512-ns time window. The measurement results were then compared to MCNP-PoliMi calculations and the previous HEU measurements. Time constants from decay fits to the HEU and DU data were compared to characterize the contributions resulting from multiplication, time-of-flight, and scattering.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1020774
• Resource Relation: Conference: INMM 51st Annual Meeting, Baltimore, MD (United States), 11-15 Jul 2010
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
36 MATERIALS SCIENCE
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CASTING
CASTINGS
CONFIGURATION
DECAY
DEPLETED URANIUM
DISTRIBUTION
FISSION
HIGHLY ENRICHED URANIUM
NEUTRONS
ORNL
PLASTIC SCINTILLATORS
PROMPT NEUTRONS
SCATTERING
SHIELDING
STORAGE
Nuclear Criticality Safety Program (NCSP)
Highly Enriched Uranium (HEU) Storage Castings
Prompt Neutron Time Decay
Measurements
Depleted Uranium (DU) Casting