Metallurgy Division Quarterly Report for January, February, and March 1954

Abstract

The second core for EBWR is planned to consist of thoria-urania pellets enclosed in tube sheets, similar to the Borax-IV loading which is now-under test. Higher temperature and strength requirements for the EBWR, however, make necessary the substitution of tube sheet material different than the aluminum alloy used for Borax-IV. Zircaloy-2 is a possible choice for tube sheet material, but extrusion of this material, unlike the aluminum, would be expected to be very difficult. Alternate methods, including rolling and expansion, are being tried. These take the form of bonding two Zircaloy-2 plates together by rolling, but leaving lengthwise strips of unbonded areas which later can be expanded into tubes pneuinatically. Efforts to date have been unsuccessful in establishing proper conditions for the intermittent bonding.

An Evaluation of Data on Zirconium-Uranium Alloys

“…and oil quenched 94 to 96 w/o uranium alloys showed no lines that could not be assigned t o alpha uranium (73). precipitate, presumably epsilon (73).…”

“…precipitate, presumably epsilon (73). zirconium a r e evidently the most potent in improving the 100 C (212 F ) c o r r o s i o n r e s i s t a n c e of uranium.…”

“…Corrosion r a t e s have been found to decrease as the general quality of the metal improves(72). Corrosion resistance appears to be improved somewhat by gamma quenching (73) with rates of -3 . 3 mg/(cm2) ( h r ) reported, a s compared with -4.9 mg/(cm2) ( h r ) for alpha-annealed uranium.…”

“…More than 50 ppm nitrogen, titanium, o r aluminium, or more than several hundred ppm carbon, result in early failure (73). other hand, it is believed that zirconium corrodes rather rapidly unless small amounts (approximately 500 ppm) of iron, o r nickel, a r e present.…”