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This report summarizes the knowledge base on the iron-enriched basalt (IEB) waste form developed at the Idaho National Engineering Laboratory (INEL) during 1979-1982. The results presented discuss the applicability of IEB in converting retrieved transuranic (TRU) waste from INEL's Radioactive Waste Management Complex (RWMC) into a vitreous/ceramic (glassy/rock) stable waste form suitable for permanent disposal in an appropri_te repc_sitory, such as the Waste Isolation Pilot Plant (WIPP) in New Mexico. Borosilicate glass (BSG), the approved high-level waste form, appears unsuited for this application. Melting the average waste-soil mix from the RWMC produces the IEB composition and attempting to convert IEB to the BSG composition would require additions of substantial B20 3,Na, and SiO2 (glass frit). IEB requires processing temperatures of 1400 to 1600°C, depending upon the waste composition. Production of the IEB waste form, using Jouleheated melters, has proved difficult in the past because of electrode and refractory corrosion problems associated with the high temperature melts. Higher temperature electric melters (arc and plasma) are available to produce this final waste form. Past research focused on extensive slag property measurements, waste form leachability tests, mechanical, composition, and microstructure evaluations, as well as a host of experiments to improve production of the waste form. Past INEL studies indicated that the IEB glass-ceramic is a material that will accommodate and stabilize a wide range of heterogeneous waste materials, including long rived radionuclides and _;crap metals, while maintaining a superior level of chemical and physical performance characteristics. Controlled cooling of the molten IEB and subsequent heat treatment will produce a glass-ceramic waste form with superior leach resistance. Recommended future work includes studies on 1) the retention and dissolution of TRU oxides in the IEB slag in solid solution with zirconia or equivalent, 2) the disposition af the high vapor pressure metals, including Cs, Pb, and Hg, 3) the controlled cooling process necessary to obtain the appropriate fine-grained crystalline structure necessary for minimum leaching of radionuclides and toxic substances, 4) processing with plasma-torch and/or arc-heated melters in an attempt to overcome process temperature-related problems experienced with the Jouleheated melter, and to detect at lab scale any r'_'_;or: processing problems.

Inertial confinement by heavy ion beams is the most promizing approach to future generation of electrical energy. Activities in Europe concentrate at present on some key issues, the generation of intense heavy ion beams and the interaction of these beams with matter. After the completion of a systems study and some work on fundamental issues like ion stopping in fully ionized dense plasma, during the last decade, two aspects characterize the directions of future research: (1) The heavy ion synchrotron and cooler ring facility SIS/ESR at GSI is being commissioned these days and will allow a number of new experiments in the fields of high intensity beam dynamics and beam target interaction. With this facility beam instabilities at high space charge density can be investigated and dense plasmas can be produced u p to temperatures of several tens of electron volts. (2) New accelerator scenarios based on non-Liouvillean techniques, which allow current multiplication without increasing the phase space volume, are being investigated and may greatly influence the situation of heavy ion drivers. Plasma processing has t h e advantages o f h i g h l y e f f i c i e n t d e s t r u c t i o n ; smaller throughput, r e a c t o r , and a u x i l i a r y equipment; lower c a p i t a l costs; p o r t a b i l i t y ; h i g h l y s t a b i l i z e d waste forms; f a s t s t a r t u p and shutdown; closed system design; and c o m p e t i t i v e processing c o s t f o r mixed wastes. major disadvantages are r e l a t i v e l y h i g h energy costs; t h e assumption t h a t energy cost i s t h e o v e r r i d i n g economic f a c t o r ; l i m i t e d R&D funding t o develop t h e plasma engineering science (e.g., compared t o combustion science); and l i m i t e d experience of engineering f i r m s w i t h plasma processing systems. and a u x i l i a r y h e a t i n g methods. advantages f o r c e r t a i n types o f m a t e r i a l s and d e s i r e d products, b u t as i n combustion, s u f f i c i e n t time, temperature, and turbulence (mixing) are r e q u i r e d t o perform the d e s t r u c t i o n and recombination i n t o d e s i r a b l e products. The engineering science aspects o f these methods w i l l be discussed i n some d e t a i l as r e g a r d i n g gas phase r e a c t i o n s , s l a g chemistry, and f i n a l waste form c h a r a c t e r i s t i c s . Present plasma processing science p a r a l l e l s t h e e a r l y days o f combustion science. To o b t a i n e f f i c i e n t plasma processing methods, research i s r e q u i r e d i n : 1. Plasma processing science regarding e l e c t r i c a l , thermodynamic, t r a n s p o r t , chemical r e a c t i v i t y , and p h y s i c a l p r o p e r t i e s 2. Plasma process energy t r a n s f e r t o enhance energy e f f i c i e n c y 3 . Plasma process chemical r e a c t i o n s t o enhance d e s t r u c t i o n e f f i c i e n c y 4 . Plasma process electromagnetic e f f e c t s t o reduce energy losses, enhance mixing, and promote se1 e c t i v e chemical r e ...

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.

The iron-enriched basalt (IEB) waste form, developed at the Idaho National Engineering Laboratory a decade ago, was modified by adding sufficient TiO 2 and ZrO 2 to develop zirconolite (ZrCaTi 2 O 7 ) crystals in addition to those crystals that normally form in a cooling basalt. Zirconolite is an extremely leach-resistant mineral with a strong affinity for actinides. Zirconolite crystals containing uranium and thorium that have endured more than 2 billion years of natural processes have been found. On this basis, zirconolite is considered an ideal host crystal for transuranic elements in wastes.Zirconolite crystals were developed in laboratory melts of IEB which contained 5 wt % each of TiO 2 and ZrO 2 and were slow-cooled in the 1200-1000C range. Actinide surrogates were incorporated into zirconolite rather than precipitated in residual glass. Zirconolite crystals should stabilize and immobilize dilute transuranics (TRUs) found in heterogeneous low-level wastes as effectively as they do in the Synroc used for high-level wastes. Synroc requires hot-pressing equipment but zirconoiite may be precipitated from a cooling basaltic melt.