Solutions

The technology used worldwide for treating radioactive waste is "vitrification," an immobilization process in which the waste is melted to form a borosilicate glass. GSI has developed and patented two novel enhanced vitrification technologies, one for high-level radioactive waste (HLW) and one for high-alkaline low-activity radioactive waste (LAW). A third GSI patent relates to novel mineral encapsulation methods.

Based on mineralogical concepts, our enhanced vitrification technologies design the borosilicate glass so that its' structure closely replicates that of natural glass. This significantly improves the waste loading (the amount of waste immobilized in a given volume) in the final vitrified product, which leads to substantial cost savings. In addition, our technology is cleantech, significantly reducing the volume of the treated waste that is then stored and eventually deposited in underground repositories. Our glass technologies use the same equipment as state-of-the-art vitrification processes, while satisfying both the processing requirements and waste form acceptance criteria for glasses produced in vitrification melters. They can therefore be used in vitrification facilities that are operative today.

"Mineral encapsulation" is an alternative technology to vitrification, in which HLW is encapsulated within a mineral and a surrounding rock matrix. This provides four barriers against leaching and diffusion of the radionuclides. Barrier 1 involves integrating the HLW in a mineral. Barrier 2 protects the immobilizing mineral from leaching and diffusion by a physical-chemical covering with a 30-50 micron non-radioactive mineral layer. A 30 micron covering provides approximately 200,000 years protection and a 50 micron covering provides protection for approximately 1 million years. Barrier 3 involves surrounding the above in a rock matrix, in which more HLW is incorporated. The immobilizing minerals and surrounding rock are comprised primarily of the same components as the host rock. Thus the ground water approaches chemical equilibrium and will be almost non-reactive to the waste product (Barrier 4). In addition to the substantially increased safety, mineral encapsulation also enables up to twice as much HLW to be incorporated than does standard vitrification. Due to the increased viscosity of the final product, mineral encapsulation cannot use the same liquid-fed ceramic melter used for vitrification. Rather, it is an "in-can" process, meaning that it would be heated and cooled in its' final canister.

Both our enhanced vitrification technologies and mineral encapsulation immobilize liquid HLW. GSI has a fourth technology that immobilizes solid HLW. In this technology, the HLW is almost fully crystallized and forms immobilizing minerals. The final waste form is a dense ceramic containing the immobilizing minerals, with a waste loading greater than 90 wt%. As with mineral encapsulation, this is also an "in-can" process, with a one-stage heating and cooling process.

Hanford Waste Treatment Plant

GSI's enhanced vitrification suits HLW projects throughout the world, including the planned Waste Treatment Plant at Hanford in Washington State. In 2003, GSI completed a successful industrial scale pilot testing of its' enhanced vitrification technology in the Forschungszentrum Karlsruhe. Our technology immobilized 34.5 wt% of Hanford HLW simulant (i.e. a 34.5 wt% waste loading), in contrast to a 25 wt% waste loading which is the maximum attained by DOE. We have subsequently successfully immobilized other Hanford HLW simulants at laboratory scale (representing over 90 vol% of the Hanford HLW), reaching waste loadings ranging between 40 and 55 wt%, an increase of 15-30 wt% above the 25 wt% waste loading currently achieved by DOE.

GSI Laboratory Test Results Using Other Hanford Waste Compositions*

Batch	Total Mass	Principal Components	Maximum Expected Waste Loading**	Waste Loading Achieved by GSI	Crystallinity at 11500C [after 3 days at 9500C]
69 (from Cluster #1)	2,349	Al, Na, Si	35 wt%	43 wt%	0 vol% [0.5 vol%]
56 (from Cluster #2)	1,749	Bi, P	40 wt%	55 wt%	0 vol% [0.2 vol%]
35 (from Cluster #3)	1,647	Al, Zr	35 wt%	40 wt%	>0.3 vol% [2 vol%, avg. crystal size <10um]
46 (from Cluster #4)	1,395	Na, Al, U	40 wt%	45 wt%	0.2 vol% (<1vol%)
53 (from Cluster #5)	1,384	Na, Al, Bi	40 wt%	50 wt%	0 vol% (<0.5 vol%)
87 (from Cluster #6)	947	Na ,Al	40 wt%	50 wt%	~0.3 vol% (<0.5 vol)
34 (from Cluster #7)	678	Na ,Al	35 wt%	50 wt%	0 vol% (<0.1 vol%)
48 (from Cluster #8)	506	Na, Al	35 wt%	40%	0 vol% (<0.1 vol%)
20 (from Cluster #9)	426	Zr	35 wt%	40 wt%	<0.3 vol% [2 vol%, avg. crystal size <10um]
15 (from Cluster #10)	232	Na, Mn	40 wt%	45 wt%	<0.5 vol% [<1.5 vol%
Total	11,313 (out of 12,385 found in all 17 Clusters) (>91vol%)

*Waste compositions taken from Tanks Focus Area HLW Melter Study Report (July 2001).
** Maximum achieved ~25 wt%

Enhanced vitrification is suited for Hanford high-alkaline low-activity radioactive waste (LAW) as well. The limiting factor in Hanford's LAW vitrification is the high sodium concentration. The amount of sodium incorporated in the final glass is expressed in terms of wt% sodium loading. DOE has achieved a 20 wt% sodium waste loading. Using the same simulant as DOE, GSI has reached a 25 wt% sodium waste loading.

Idaho National Laboratory (INL)