An Analysis Technique for Active Neutron Multiplicity Measurements Based on First Principles

Conference · Mon Aug 13 00:00:00 EDT 2012

OSTI ID:1048837

Evans, Louise G ^[1]; Goddard, Braden ^[1]; Charlton, William S ^[1]; Peerani, Paolo ^[2]

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1. Los Alamos National Laboratory
2. European Commission, EC-JRC-IPSC

Passive neutron multiplicity counting is commonly used to quantify the total mass of plutonium in a sample, without prior knowledge of the sample geometry. However, passive neutron counting is less applicable to uranium measurements due to the low spontaneous fission rates of uranium. Active neutron multiplicity measurements are therefore used to determine the {sup 235}U mass in a sample. Unfortunately, there are still additional challenges to overcome for uranium measurements, such as the coupling of the active source and the uranium sample. Techniques, such as the coupling method, have been developed to help reduce the dependence of calibration curves for active measurements on uranium samples; although, they still require similar geometry known standards. An advanced active neutron multiplicity measurement method is being developed by Texas A&M University, in collaboration with Los Alamos National Laboratory (LANL) in an attempt to overcome the calibration curve requirements. This method can be used to quantify the {sup 235}U mass in a sample containing uranium without using calibration curves. Furthermore, this method is based on existing detectors and nondestructive assay (NDA) systems, such as the LANL Epithermal Neutron Multiplicity Counter (ENMC). This method uses an inexpensive boron carbide liner to shield the uranium sample from thermal and epithermal neutrons while allowing fast neutrons to reach the sample. Due to the relatively low and constant fission and absorption energy dependent cross-sections at high neutron energies for uranium isotopes, fast neutrons can penetrate the sample without significant attenuation. Fast neutron interrogation therefore creates a homogeneous fission rate in the sample, allowing for first principle methods to be used to determine the {sup 235}U mass in the sample. This paper discusses the measurement method concept and development, including measurements and simulations performed to date, as well as the potential limitations.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: DOE Graduate Fellowship Program
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1048837
• Report Number(s): LA-UR-12-24054; TRN: US1204313
• Resource Relation: Conference: INMM 53rd Annual Meeting ; 2012-07-15 - 2012-07-19 ; Orlando, Florida, United States
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
42 ENGINEERING
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ABSORPTION
ATTENUATION
BORON CARBIDES
CALIBRATION
CROSS SECTIONS
EPITHERMAL NEUTRONS
FAST NEUTRONS
FISSION
GEOMETRY
LANL
LINERS
MULTIPLICITY
NEUTRONS
PLUTONIUM
SHIELDS
SPONTANEOUS FISSION
URANIUM
URANIUM ISOTOPES