The dependence of the resonance integral for thorium upon geometry and thorium temperature has been determined through reactivity coefficient measurements performed in the Hanford Test Pile. The geometry dependence was investigated using thorium cylinders of various diameters in the form of solid elements and shells. The temperature dependence (Doppler broadening) was studied by heating thorium elements and permitting them to cool while observing the change in pile reactivity.

The Plutonium Recycle Test Reactor is heavy water moderated with a heavy or light water reflector contained by a complex aluminum vessel called a Calandria. ( See Figure 1). Construction of this vessel started in August, 1958, at a large West Coast vendor's plant and was completed at Hanford in December, 1959. The fabrication problems associated with a high integrity welded aluminum vessel were generally unrealized prior to this period. This report covers the fabrication of the Calandria and lists recommendations for improving the design and reducing the cost.

Applications of sheathed (metal) thermocouples may require in many instances, the insertion of the thermocouple thermal junction into an area that must be hermetically sealed to the outside. This same area usually contains highly reactive heat transfer medium such as an eutectic alloy of sodium and potassium of sodium alone. When fissionable materials are being irradiated, fission products that are driven off would also be present and must be contained under varying temperatures and pressures.