Management of Ukaea Graphite Liabilities

The UK Atomic Energy Authority (UKAEA) is responsible for managing its liabilities for redundant research reactors and other active facilities concerned with the development of the UK nuclear technology programme since 1947. These liabilities include irradiated graphite from a variety of different sources including low irradiation temperature reactor graphite (the Windscale Piles 1 & 2, British Energy Pile O and Graphite Low Energy Experimental Pile at Harwell and the Material Testing Reactors at Harwell and Dounreay), advanced gas-cooled reactor graphite (from the Windscale Advanced Gas-cooled Reactor) and graphite from fast reactor systems (neutron shield graphite from the Dounreay Prototype Fast Reactor and Dounreay Fast Reactor). The decommissioning and dismantling of these facilities will give rise to over 6,000 tonnes of graphite requiring disposal. The first graphite will be retrieved from the dismantling of Windscale Pile 1 and the Windscale Advanced Gas-cooled Reactor during the next five years. UKAEA has undertaken extensive studies to consider the best practicable options for disposing of these graphite liabilities in a manner that is safe whilst minimising the associated costs and technical risks. These options include (but are not limited to), disposal as Low Level Waste, incineration, or encapsulation and disposal as Intermediate Level Waste. There are a number of technical issues associated with each of these proposed disposal options; these include Wigner energy, radionuclide inventory determination, encapsulation of graphite dust, galvanic coupling interactions enhancing the corrosion of mild steel and public acceptability. UKAEA is currently developing packaging concepts and designing packaging plants for processing these graphite wastes in consultation with other holders of graphite wastes throughout Europe. “Letters of Comfort” have been sought from both the Low Level Waste and the Intermediate Level Waste disposal organisations to support the development of these waste disposal strategies. UKAEA is liasing closely with the disposal organisations to ensure that all their concerns are addressed satisfactorily. This paper will describe: i. the varied nature, inventory and history of UKAEA’s graphite liabilities; ii. the options that have been considered for the long-term storage and disposal of UKAEA’s graphite liabilities; iii. the technical issues that have been considered in the development of these options; iv. the recent developments in the consideration of Wigner energy. The paper will summarise the current status and future plans of the UKAEA graphite waste packaging strategies, and describe the interactions with the disposal organisations.