[en] ANSTO waste form development for high-level radioactive waste is directed towards practical applications, particularly problematic niche wastes that do not readily lend themselves to direct vitrification. Integration of waste form chemistry and processing method is emphasised. Some longstanding misconceptions about titanate ceramics are dealt with. We have a range of titanate-bearing waste form products aimed at immobilisation of tank wastes and sludges, actinide-rich wastes, INEEL calcines and Na-bearing liquid wastes, Al-rich wastes arising from reprocessing of Al-clad fuels, Mo-rich wastes arising from reprocessing of U-Mo fuels, partitioned Cs-rich wastes, and ⁹⁹Tc. Waste form production techniques cover hot isostatic and uniaxial pressing, sintering, and cold-crucible melting, and these are strongly integrated into waste form design. Speciation and leach resistance of Cs and alkalis in cementitious products and geo-polymers are being studied. Recently we have embarked on studies of candidate inert matrix fuels for Pu burning. We also have a considerable program directed at basic understanding of the waste forms in regard to crystal chemistry, dissolution behaviour in aqueous media, radiation damage effects and optimum processing techniques. (authors)

[en] Cementitious material is the most commonly used encapsulation medium for low and intermediate level radioactive waste. This paper focuses on the aqueous durability of a Materials Testing Reactor (MTR) cementitious wasteform - a possible candidate for the proposed intermediate level waste management facility in Australia. A series of medium term (up to 92 months) durability tests, without leachate replacement, were conducted on samples of this wasteform. The wasteform was made from cement, ground granulated blast furnace slag and a simulated waste liquor. The compressive strength (39 MPa) was typical of MTR cement waste-forms and well above that required for handling or storage. The wasteform was an inhomogeneous mixture containing calcite, a calcium silicate hydrate phase, hydrotalcite and unreacted slag particles. After leaching for 92 months the crystallinity of the calcium silicate hydrate phase increased. The majority of the releases of Ca, Si, Al, Sr, S, Na and K was reached within 4 days of leaching, with the maxima i.e. the highest concentrations in the leachates, occurring at 3 months for Ca, Al, Sr, S, Na and K, and at 1 month for Si. For the longer leach periods (6 months and 3 months respectively) there was a slight reduction in concentration in the leachates, and these levels were similar to those for the longest period of 92 months, suggesting steady-state conditions prevailing after 3 to 6 months of leaching. The highest releases of matrix elements were for Na (37%), K (40%) and S (16%). Releases for elements such as Ca, Na, Al and Sr were similar in magnitude to those reported by the UKAEA in earlier MTR studies. After leaching for 92 months there was an alteration layer about 80 μm deep where calcium has been depleted. Na, K and Sr showed signs of diffusion towards the outer part of the cement samples. (authors)