Ice pigging is a novel technology using thick ice slurry (a two-phase mixture of ice crystals and freezing point depressant solution) to clean the internal surfaces of pipes or ducts; this mixture displays semi-solid characteristics. When pumped through a pipe, the slurry adopts plug flow, forming an 'ice pig'; slip occurs at the interface with the pipe walls generating high shear stresses; thus able to mobilise and remove sediment residing at the pipe wall. Ice pigs are able to navigate demanding topologies such as vertical falls, diameter changes, orifice plates, heat exchangers, and intrusive instrumentation; they provide a method of removing fouling without the need for dis-assembly, reducing valuable down-time, labour intensive pipe work dismantling, and subsequent manual cleaning. Many decades of nuclear activity here in the UK have produced unique and difficult challenges that require solving at Sellafield, the UK's nuclear waste reprocessing site. The drive to produce plutonium for atomic weapons during the 1950's, with very little foresight towards how the wastes and facilities would be dealt with, has brought about significant challenges. As these facilities are nearing the end of their design lives, the time has come to assess methods of treating these wastes and decommissioning the facilities in a safe, controlled, and cost-effective manner. Ice pigging is one of many technologies being assessed for such a task; this thesis details specific areas of application where experimental work has been conducted. Experimental work conducted in this thesis has: developed a method of characterising the ice pig's sediment removal performance compared to simple water flushing, assessed the ice pig's ability to remove representative sediments, assessed the ice pig's suitability for removing sediment from heat exchangers to restore thermal performance, and analysed the rate of percolation of the driving fluid through the ice pig body, such that the suitability of the ice pig for separating fluids can be established.