Large Shielded Packages for Decommissioning Waste

Following earlier work (Price and Lafontaine, 1985) a further study of large shielded packages for decommissioning waste was initiated in September 1986, funded in part under the second five year joint action programme of the Commission of the European Communities (CEC). A methodology was developed which considered all the factors and constraints affecting the design of a package over its total life-cycle. It involved five interactive tasks, viz: A the effect of manufacture on design of large transport packages for decommissioning waste; B a survey of transport hazards and constraints; C the constraints of disposal on package design; D package design/ performance criteria; and   E the assessment of proposed package designs.   The investigations were carried out jointly by the Winfrith Technology Centre (WTC), Ove Arup and Partners (OAP) and Windscale Laboratory (WL), with the Safety and Reliability Directorate Culcheth (SRD), acting as consultant, and a comprehensive report on the work is in preparation.   The status of decommissioning operations in the Federal Republic of Germany (FRG), France and the United Kingdom (UK) was established as these countries have large civil nuclear power programmes in the European Community.   Initially the factors affecting package design were examined. The study of large reinforced concrete packages was led by the Windscale Laboratory, which is already involved in the decommissioning of the Windscale Advanced Gas-Cooled Reactor. The work on ferrous packages was led by WTC. Task B, carried out by OAP, involved desk and route studies of transport hazards as well as the definition of regulatory and physical constraints. Reference routes in the FRG, France and the UK were selected for detailed survey. This gave an estimate of accident probabilities for ten transport accident scenarios. In carrying .out Task C the following aspects were examined by WTC:   i the radionuclide inventory required to be disposed;  ii the estimation of the toxicity of the leachate from packages; iii disposal implications of the radionuclide inventory; iv the constraints imposed by disposal sites; v the effect of cement formulation on the migration of key radionuclides; vi the corrosion behaviour of ferrous metals; and vii gas production from a package. Tasks A, B and C were data collection tasks which fed into the two final tasks of the study, Package Design Criteria and the Assessment of Package Designs, led by OAP.