Preliminary experiments have been conducted to evaluate the use of the nuclear reactions Li6 (n,α)H3 and O16(H13,n)F18 to determine the thickness of oxide films on metals. Sheets of thin paper and of aluminum, imbedded in powdered LiF, were irradiated with pile neutrons at a flux of 6 x 10^11 n/cm^2/sec and counted with an end-window proportional counter. A saturation activity of 1.87 hr F18 of 150 dis/min per microgram of oxygen was observed in the paper, but radioactivity due to impurities masked F18 in the aluminum. It is concluded that a 1 A (0.01 μgm/cm^2) oxide film thickness may be measured by a neutron irradiation at a flux of 10^14 n/cm^2/sec but chemical separation of induced radioactivity from the bulk metal is essential.

Quarterly progress report discussing activities related to the Vallecitos Boiling Water Reactor (VBWR) and related facilities.

Experiments in the controlled melting of irradiated fuel specimens, particularly of the APPR, STR, and MTR types have confirmed that prolonged heating in air at temperatures in excess of the melting point results in the release of a large portion of the radioactivity. On the other hand, a moderate amount of heating in air or steam sufficient only to melt a specimen results mainly in the partial volatilization of the rare gases; the halogens, iodine and bromine; and the alkali metals, cesium and rubidium. In the presence of air or water vapor, strontium and other fission products are not released. At trace concentration of fission products, slow melting of the APPR plate at 1525 C in air or steam effected the release of 50 percent of the rare gases, 33 percent of the iodine, 9 percent of the cesium and traces of strontium. After 25% burn-up, the cesium value increased to about 60 percent. Aluminum alloy of the MTR type, also at trace concentration, upon melting at 700 C released up to 2 percent of the iodine, 10 percent of the rare gases, and negligible portions of other fission products. Zirconium alloy of the STR type after 15 percent burn …