The Savannah River Site has the majority of the United States' supply ofneptunium currently stored in an acid solution in one of their canyonfacilities. A program is being developed that could be utilized to ship thismaterial, as glass, to Oak Ridge National Laboratory where the Np could beleached from the glass, purified by ion exchange and made into targetmaterial for the production of Pu-238. Ion exchange purification dictates nomaterial be in the leachate making the isolation of the Np difficult. Wehave developed a process using thorium as a surrogate for Np that couldimmobilize the Np into a soda borosilicate glass for shipment. To achieverecovery of the Np, the glass can be phase separated prior to leaching withnitric acid. Phase separation would produces a Np-rich sodium-borate phaseand a Si-rich phase similar to a Vycor® glass. The nitric acid selectivelyattacks the sodium-borate phase allowing high Np recovery in a solution thatcontains only sodium and boron. These can be easily separated from Np by ionexchange. Essentially all of the silicon which would interfere with ionexchange by precipitation is retained in the Vycor®-type phase. Thistechnology may also be applied to other actinides stored in relatively puresolutions.

This paper will report the optimization of variables for maximizing Th (a Npsurrogate) recovery while minimizing Si release. Th solubility in glass,heat treatment conditions and leaching parameters will be discussed.Transmission Electron Microscopy (TEM) with energy dispersive spectroscopy(EDS) data will be included to show phase separation after heattreatment.