Summary: Purpose of the investigation is to improve the peripheral welding of the brazed joint at the top of aluminum-sheathed fuel slugs by forming the can over the top of the cap and welding the resulting center opening. This investigation looked at the applicability of the inert-gas-shielded, consumable electrode process, using commercially available equipment, for producing a weld closure in spun-over fuel cans. Using commercially available sigma welding equipment, no practical combination of welding conditions was found which resulted in satisfactory leak-tight closures in spun-over canned fuel slugs. It is recommended that plug welding of spun-over closures by the sigma welding process be dismissed from consideration for start-up at the Savannah River Plant.

From abstract: "An ionization chamber of the integrating type was built that could detect a tritium leak rate of 10[^-13] cc per second within a few minutes, after a gas-collecting period of 16 hours. Electronic circuitry was avoided by using a quartz fiber voltmeter to indicate the rate of discharge of the chamber."

From abstract: "Background material leading to the development of the metal quality of reactor-grade thorium is given. The metal should be sound and of uniform hardness, free of internal cracks and inclusions, and corrosion resistant. It should contain only small amounts of natural uranium, thorium oxide, and elements that act as reactor poisons. Because of their effect upon metal quality, various methods for the production of thorium are discussed. Use of consumable electrode arc melting as the final step has contributed much to the production of thorium of excellent quality for reactor use."