A more accurate and penetrating method to measure the enrichment and mass of UF6 storage containers using passive neutron self-interrogation

Conference · Fri Jan 01 00:00:00 EST 2010

OSTI ID:1011482

Menlove, Howard O ^[1]; Swinhoe, Martyn T ^[1]; Miller, Karen A ^[1]

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1. Los Alamos National Laboratory

This paper describes an unattended mode neutron measurement that can provide the enrichment of the uranium in UF{sub 6} cylinders. The new passive neutron measurement provides better penetration into the uranium mass than prior gamma-ray enrichment measurement methods. The Passive Neutron Enrichment Monitor (PNEM) provides a new measurement technique that uses passive neutron totals and coincidence counting together with neutron self-interrogation to measure the enrichment in the cylinders. The measurement uses the neutron rates from two detector pods. One of the pods has a bare polyethylene surface next to the cylinder and the other polyethylene surface is covered with Cd to prevent thermal neutrons from returning to the cylinder. The primary neutron source from the enriched UF{sub 6} is the alpha-particle decay from the {sub 234}U that interacts with the fluorine to produce random neutrons. The singles neutron counting rate is dominated by the {sub 234}U neutrons with a minor contribution from the induced fissions in the {sub 235}U. However, the doubles counting rate comes primarily from the induced fissions (i.e., multiplication) in the {sub 235}U in enriched uranium. The PNEM concept makes use of the passive neutrons that are initially produced from the {sub 234}U reactions that track the {sub 235}U enrichment during the enrichment process. The induced fission reactions from the thermal-neutron albedo are all from the {sub 235}U and provide a measurement of the {sub 235}U. The Cd ratio has the desirable feature that all of the thermal-neutron-induced fissions in {sub 235}U are independent of the original neutron source. Thus, the ratio is independent of the uranium age, purity, and prior reactor history.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1011482
• Report Number(s): LA-UR-10-03040; LA-UR-10-3040; TRN: US1102179
• Resource Relation: Conference: INMM 51 Annual Meeting ; July 11, 2010 ; Baltimore, MD
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
97 MATHEMATICS AND COMPUTING
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
ALBEDO
CONTAINERS
COUNTING RATES
DECAY
ENRICHED URANIUM
FISSION
FLUORINE
MONITORS
NEUTRON SOURCES
NEUTRONS
POLYETHYLENES
STORAGE
THERMAL NEUTRONS
URANIUM