A system for depositing fragmented ice in vertical wire mesh cylindrical baskets. A pneumatic system moves the ice in a stream of air to the basket being filled through a flexible hose which has at its free end a precipitator unit or ice-air separator with a discharge opening at its bottom end. To fill a basket, the precipitator unit is moved down through the top of the basket with the discharge opening at the bottom. The ice is separated from the air in the precipitator unit, and the air is discharged upwardly and a body of ice accumulates and closes the discharge opening. The precipitator unit is moved upwardly in the basket at a rate depending upon the rate of delivery and accumulation of ice. During that upward movement the bottom lip around the discharge opening is always below the level of the accumulated ice so that the ice at the opening and beneath it is quiescent. Positioned adjacent the basket wall around the discharge opening is an annular heater which melts a small amount of the ice at the lip. The subcooled condition of the adjacent ice produces recongealing or refreezing so as to sinter together the ice fragments which are in contact with the basket wall. That produces a composite shell formed by the sintered shell of ice adhered to the basket wall. The immediate effect of the shell is to assist in preventing the loss of ice particles through the basket wall, even though the shell may not be a solid layer of ice. The shell also increases the resistance to the discharge of air through the discharge opening of the precipitator unit so that the air is forced upwardly and it flows at a slow rate and does not carry ice particles with it. The cylindrical shell also tends to reduce sublimitation of the ice so as to preserve the enclosed ice. The system is particularly useful in providing ''''permanent '''' bodies of borated ice in an atomic energy power plant for the absorption of radiation and heat in the event of an explosion.