Improving iron-enriched basalt with additions of ZrO{sub 2} and TiO{sub 2}

Abstract

This report describes the results of a "proof-of-principle" study that examined the results of cooling of small IEB4 melts in a laboratory furnace to precipitate zirconolite crystals and that examined the ability of these crystals to incorporate lanthanides as actinide surrogates. This work was performed to determine the advantages, if any, of adding ZrO 2 and TiO 2 to IEB before committing additional resources to an IEB4 study. Melt additions of 0.5% each of CeO 2, Eu203, Gd203, Nd203, and Sm203 were made to an IEB reference composition and to an IEB4 composition for the purpose of comparing the behavior of each waste form composition when crystallization took place in the 1200-1000°C range. Lanthanide oxides were precipitated in the residual glass phase of the IEB melt in a manner analogous to UO 2 and PuO 2, as had beea observed in our previous studies. But the lanthanides were concentrated from 0.5% each to nearly 8% in the zirconolite in the IEB4 melt. These results were F:omising and additional study is warranted. Future studies should investigate: (1) development of zirconolite in melts of the various expected waste compositions, (2) more suitable ratios of TiO 2 and ZrO 2 as well as useful ranges of concentration, (3) crystallization behavior below 1000°C, (4) crystallization behavior as influenced by the environment in the carbon electrode arc furnace, (5) partition coefficients of lanthanides (and " actinides) between crystals and the residual glass phase, (6) the capability of zirconolite to capture uranium, thorium, and TRU elements, and (7) the leaching characteristics of IEB4 in appropriate aqueous media.

Graphite electrode arc melter demonstration Phase 2 test results

“…Examination of the nominal 800-lb slag monoliths from the BWID Phase 1 demonstration melting tests revealed that the cores of the molds, which underwent a slower cooling rate, were primarily crystalline. In fact, the targeted final waste form for the Phase 1 tests was the iron enriched basalt, which was crystalline by design (Reimann and Kong 1993). Thus, to call these materials glass would have been incorrect.…”

Advanced Mixed Waste Treatment Project melter system preliminary design technical review meeting

“…Additives such as soil have been included in some cases as a buffer to adjust the slag chemistry. There has been much work done to characterize the waste streams, evaluate the properties of the slag with and without soil additions, and descriie some of the final waste form options (Reimann lm, Eddy et al 1% Grandy, Eddy, andAnderson 1993a and1993b;and Reimann and Kong 1993 …”