Legacy Ponds and Silo Wastes

The accident at Fukushima in Japan has led to the generation of large volumes of High Dose Spent Adsorbents (HDSA) which are currently stored on site but need to be immobilised in a solid waste form before being permanently disposed of. The majority of the radionuclides in HDSA are Cs and Sr with relatively short half-lives so that the level of performance of the waste form is not as demanding as for usual vitrified High Level Waste. The process used to immobilise the HDSA wastes should be simple, low cost and low temperature to preclude Cs and Sr volatilisation, and should produce a waste form that does not form hydrogen over timescales of hundreds of years via radiolysis when in contact with water. This project will examine options using low temperature routes where low-melting temperature glasses are used to vitrify the HDSA. This project will develop the processing route and characterise the waste forms produced using inactive Cs and Sr radionuclides in the UK and active ones in Japan. Characterisation will be based on the use of X-ray diffraction, thermogravimetric and calorimetric methods, infrared measurements and electron microscopy techniques and long term stability examined using leach testing.