Initial recovery of the magnox reprocessing plant following a loss of reductant feed in the solvent extraction process - 14429

A recent event in the Magnox Reprocessing Plant involved the loss of reductant feed to a contacting vessel and required the plant to be shutdown. The criticality team attended the site out-of-hours to facilitate the production of a recovery plan. This initial recovery plan involved manual dosing of the contactor with reductant but was heavily dependent upon initial information regarding the length of time the maloperation had been occurring. Key assumptions fundamental to maintaining criticality safety during the planned recovery were clearly highlighted in the assessment that was written to support the operation, which allowed informed decisions to be made regarding the adequacy of the plan, once further information emerged suggesting the fault had been ongoing for much longer than originally assumed and therefore the amount of Pu in the contactor was much higher than initially thought. (author)