David J. Devlin

PARTICULATE CAPTURE OF PLUTONIUM BY HIGH GRADIENT MAGNETIC SEPARATION WITH ADVANCED MATRICES

A high performance superconducting magnetic separator is being developed for near single particle retrieval from low concentration field collected samples. Results show that maximum separation is obtained when the effective matrix element diameter approaches the diameter of the particles to be captured. Experimentally, we were able to capture very dilute levels of 0.2 to 0.8 μm PuO2 particles with dodecane as a carrier fluid. The development of new matrix materials is being pursued through the deposition of nickel dendrites on an existing stainless steel matrix material. The new materials are promising for the submicron collection of paramagnetic particles. Results indicate that these new matrices contain a high number of capture sites for the paramagnetic particles. We have also derived a force-balance model that uses empirically determined capture cross section values. The model can be used to optimize the capture cross section and thus increase the capture efficiency. This enables the prediction of high gradient magnetic separator performance for a variety of materials and applications.

CAPTURE AND RETRIEVAL OF PLUTONIUM OXIDE PARTICLES AT ULTRA-LOW CONCENTRATIONS USING HIGH-GRADIENT MAGNETIC SEPARATION

A high-gradient magnetic separation system has been developed for capture and retrieval of ultra-low plutonium oxide concentrations. The application of advanced matrix materials and improved methodology has demonstrated the effective collection and recovery of submicron paramagnetic actinide particles with particle concentrations as low as 10−23 M. Incorporation of multiple passes during recovery of magnetically captured particles improves the system mass balance. Activity balances for plutonium were verified with stringent sampling protocols. Collection and recovery values demonstrate that 99% of the submicron plutonium oxide particles can be accounted for when recycle loops are incorporated into capture and recovery circuits, magnetically captured particles are released by sonication, carrier fluids are organically based, and longer matrix lengths are utilized.

Target Fabrication of Opacity Experiments on Z for Weapons Science Applications

Abstract Opacity data are very important in high energy density physics experiments. Recent targets of alternating layers of either Al2Te3 or Mg/Sn with a CH tamper have been made for obtaining these data. These targets are geometrically simple in the half-moon configuration of the metal compound coating to the pure CH tamper but require stringent procedural requirements to fabricate to the purity requirements. These specific targets require mass ratios of elements that proved to be difficult to obtain while also having the requirement of being pinhole-free and oxygen-free.

Magnetic Separation for Nuclear Material Surveillance

A high performance superconducting magnet is being developed for particle retrieval from field collected samples. Results show that the ratio of matrix fiber diameter to the diameter of the captured particles is an important parameter. The development of new matrix materials is being pursued through the controlled corrosion of stainless steel wool, or the deposition of nickel dendrites on the existing stainless steel matrix material. We have also derived a model from a continuity equation that uses empirically determined capture cross section values. This enables the prediction of high gradient magnetic separator performance for a variety of materials and applications. The model can be used to optimize the capture cross section and thus increase the capture efficiency.