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

Abstract

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 comparedmore » to characterize the contributions resulting from multiplication, time-of-flight, and scattering.« less

Authors:
 [1];  [1];  [1]
  1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
OSTI Identifier:
1020774
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: INMM 51st Annual Meeting, Baltimore, MD (United States), 11-15 Jul 2010
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Pena, Kirsten E., McConchie, Seth M., and Mihalczo, John T. Prompt Neutron Time Decay in Single HEU and DU Metal Annular Storage Castings. United States: N. p., 2010. Web.
Pena, Kirsten E., McConchie, Seth M., & Mihalczo, John T. Prompt Neutron Time Decay in Single HEU and DU Metal Annular Storage Castings. United States.
Pena, Kirsten E., McConchie, Seth M., and Mihalczo, John T. 2010. "Prompt Neutron Time Decay in Single HEU and DU Metal Annular Storage Castings". United States.
@article{osti_1020774,
title = {Prompt Neutron Time Decay in Single HEU and DU Metal Annular Storage Castings},
author = {Pena, Kirsten E. and McConchie, Seth M. and Mihalczo, John T.},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/1020774}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jul 11 00:00:00 EDT 2010},
month = {Sun Jul 11 00:00:00 EDT 2010}
}

Conference:
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