Experimental Work at Harwell on the Injection of Sodium into Liquid Steel

The equipment and experimental technique used to inject molten sodium beneath the surface of molten steel (and subsequently molten uranium dioxide) are described. The results of an exploratory experiment, in which 2 g of sodium at 380 deg. C were injected into 54 g of steel at 1530 deg. C, are outlined. A violent reaction occurred, apparently as a result of a vapour explosion, and a number of pulses were recorded by a force transducer. A preliminary examination of the steel debris is reported. In conclusion: The injection of ∼2 g of sodium at ∼380 deg. C beneath the surface of ∼54 g of steel at 1530 deg. C resulted in a vapour explosion. A series of three pulses (perhaps more) at intervals of ∼6 ms were observed; the peak amplitude was at least 600 N (equivalent to a pressure of ∼20 bar on the base of the crucible). The steel was highly dispersed giving material of predominant particle size ∼500 μ and calculated surface area ∼13.5 cm2 g-1; the particles were almost spherical but some had a small indentation on their surface. The apparatus operated very well, especially considering its rudimentary nature and the speed with which it was assembled. Nevertheless experience of the first experiment showed that many improvements are desirable. (a) Interpretation of the pulses recorded by the force transducer was difficult and would be facilitated by the use of a strong crucible and by a redesigned pillar. (b) Instrumentation on the injector would enable tM and tI to be determined and would permit the injection timing to be related to the pulse record, thus giving a measure of the dwell time. (c) The closed circuit television needs to be linked to a video tape recorder. (d) The recording instrumentation should have a better resolution so that short pulses are not lost or inaccurately recorded; a multichannel tape recorder may be desirable. (e) Direct measurement of the surface area of the debris should be carried out using an existing technique (BET low temperature gas adsorption using Xe133)