The operation of nuclear fuel reprocessing plants generates a radioactive effluent containing nitrate salts as the major constituent. This waste must be disposed of safely and economically, and to achieve this aim the Japan Atomic Energy Agency (JAEA) is developing a cement based encapsulation method to immobilise this waste. Non-radioactive development work has been performed at both small and large-scale (up to 200 litres) to investigate the optimum cement formulation. The results from these studies demonstrate that nitrate waste that has been concentrated by evaporation of the water to a predetermined level can be successfully encapsulated up to a waste loading corresponding to 50 wt% sodium nitrate. It has been identified that high concentrations of bicarbonate ions in the effluent can have a detrimental effect on the strength of the cement encapsulated waste; however, provided this concentration is controlled, successful encapsulation of the effluent is still achieved.