Trial manufacture of bismuth loop

In a basic study using a molten bismuth as a coolant of reactor, the authors made an attempt to manufacture an out-pile loop with graphite, and succeeded in making the loop of no-leakage of bismuth. In this report, the outline of the structure of this loop was shown. The loop was charged with bismuth by pressurizing the sumptank with nitrogen gas. In operation, the bismuth was pumped by means of a mechanical pump to III, II and I vessels and a flow meter. Temperature of bismuth metal was controlled at 550℃ (usual) and 700℃ (maximum), and was read with chromel-alumel and platinum-platinum, rhodium thermocouples set in 28 points of this loop. Individual piping runs and vessels were wrapped with hot plates of nichrome heater. The total power supplied to groups of these heaters were maximum 20.12 kW. The pipe consisted of two parts. An inner tube (bismuth piping) was surrounded by hot plate of nichrome heater and an outer tube was surrounded by thermal insulator. In order to protect the inner tube from being oxidized by air, graphite powder was packed between these tubes and nitrogen gas was let flow through this powder. (author)