We have designed leaching systems for experiments on several kinds of solids, including glassy debris from underground nuclear explosions at Nevada Test Site (puddle glass), refractory compositions for retention of radioactive nuclear reactor waste, and spent reactor fuel. The system used on puddle glass has a continuously variable flow rate from 13 to 460 cm/sup 3//d, a temperature range from 25 to 75/sup 0/C, operating capacity for up to 20 simultaneous experiments, and one-pass operation with continuous exposure of samples to fresh solution. Results obtained on puddle glass are in qualitative agreement with those on silicate glasses designed for isolation of nuclear reactor waste.

During this report period, a decision was made to defer the construction of the 50 MT Si/year Experimental Process System Development Unit (EPSDU) until FY 1980, and in the meantime to construct and evaluate, at full scale, four critical units of the EPSDU. The fluidized bed, zinc vaporizer, by-product condenser, and electrolytic cell have been combined with auxiliary units, capable of supporting 8-hour batchwise operation, to form the Process Development Unit (PDU), which is scheduled to be in operation by October 1, 1979. The design of the PDU and objectives of its operation are discussed. Pending completion of the PDU, work has continued in the area of experimental support. A wetted-wall condenser has been constructed in which zinc chloride, introduced in excess of that condensed, is used to wash down the unreacted zinc and residual silicon accumulated as fine-particle solids. Improvements in the experimental electrolytic cell have led to power efficiencies around 40%, thus substantiating the pertinence of the Bureau of Mines experience with pure zinc chloride as a basis for what can be expected with the zinc chloride/zinc/silicon slurry of the present application. (WHK)

The results are presented of an examination of 17 samples obtained from various components of the subject geothermal heating system. The samples obtained for this study were selected to represent the several materials of construction and equipment ages of the various components in this system. For purposes of this report, the samples have been grouped into three categories by material: ferrous, non-ferrous and non-metallic. Failures in these components have taken the form of leakage at solder joints, tubing perforation, scaling, or valve seizure. Most components evaluated in this examination have been in service for 14 years. This work documents these failures, discusses their causes and recommends possible remedial action.