The Development of High Purity Tantalum and Alloys for Liquid Plutonium Containment in LAMPRE I

Abstract

By combining arc casting and electron beam melting, spectroscopically pure tantalum and alloys, suitable for containment of molten Pu-Fe alloys, were produced. The 0.1% W alloy was used for the first LAMPRE loading. The effects of a large number of additives on the corrosion resistance of tantalum were tested. Additions of up to 10% tungsten gave increasing endurance. Specimens of tantalum irradiated with neutrons until 3% converted to tungsten were stitl satisfactory in mechanical properties for reactor use. Either tungsten or the traces of yttrium remaining after arc melting can raise the one-hour recryatatlization temperature of tantalum by 400 deg C. Effects of internal strain, critical strain and precipitation hardening in tantalum alloys were studied. High-temperature annealed tantalum had superior corrosion resistance, while impact extruded and ironed material was better than deep-drawn metal. Mechanical tests on tantalum with added interstitial elements showed that their presence to the extent expected in LAMPRE would be unlikely to weaken the tantalum. Evidence was found that oxygen promotes plutonium attack on tantalum. Small amounts of hydrogen, nitrogen and carbon had no effect on corrosion. (auth)