Formulas are developed for the angle between any two vectors lying in a plane through the origin of reciprocal space. The application of these formulas for computing the counter and crystal angles for the collection of data with a counter-- diffractometer in the equatorial plane is developed, and a suitable computer program, written in FORTRAN without format suitable for an IBM 1620 computer, is described.

A comprehensive investigation of the spectrophotometric determination of beryllium with Chrome Azurol S is described. At pH 4.6, and in the presence of EDTA, only Cr-3+ and F1- ions interfere seriously. A molar absorptivity of 4060 at 569 mu has been found for the complex, with a standard deviation of plus or minus 0.4 per cent at the 25 omega g beryllium level. Chrome Azurol S has several advantages over Berillon II, which is widely used for the spectrophotometric determination of beryllium.

Empirical methods are given for calculating reactivity changes in HIFAR with changes in fuel loading, poison concentration, and temperature variations. The procedures are derived from the analysis of typical operating programs, reinforced by analogue computer analysis of variation of the important fission product poisons Xenon 135 and Samarium 149.

Satisfactory dense crack—free dispersions of spheroidal UO2 — ThO2 particles in BeO can be produced by "co-sintering", a process in which unsintered particles are hydrostatically pressed in BeO and the dispersion is sintered in one step, the large voids and cracks in dispersions of fully sintered particles in BeO following sintering are related to mismatched sintering shrinkage between the two phases; they are probably indicative of a high interfacial energy between the two phases. Co—sintering has been used for individual fabrication of specimens for irradiation testing, but is not immediately applicable to large scale fabrication of fuel element shapes, Possible modifications of the method are discussed.

Uranium and thorium beryllides and their solid solutions were prepared by reaction-sintering, reaction—pressing and arc—melting of mixed metal powders. The major difficulties of preparation were the large swellings accompanying reaction without pressure and the loss of beryllium at temperatures above 1200 — 1300ºC, the reaction—pressing method suffered least from these difficulties and yielded the purest and most dense products.