The critical mass of 94-239 and the corresponding critical dimensions of homogeneous mixtures of 94-239 with various moderating media been calculated as a function of the concentration of 94. A simple transformation makes the figures applicated to92-235. the results are in essential agreement with the preliminary estimated made independently by Oppenheimer and Serber. The problem of the stability of a chain reaction in solution and questions of protection are discussed.

When a slug has been displaced from its normal position the thickness of the water film is decreased over part of the surface, and higher temperatures may be expected where the film is thin. The experimental data necessary for an exact calculation is incomplete, but some approximate estimates ae made here with special assumption concerning the heat transfer coefficient h as a function of the angle p from the point where the water film is thinnest. Variation in water bulk temperature around the annulus due to poor mixing is not considered here.

Abstract. Some rather idealized considerations are given regarding the depth a warped rod presses into the ribs at the places of contact. It appears that this distance may, under some conditions, be of the order of 70 times greater than for a straight rod resting uniformly on the ribs.

Abstract. the Laplacian of a beryllium metal lattice with 3.3 kg of uranium metal per cell and a volume ratio of 17.2 was measured in the removable region of the CP-2 machine. the sandwich effect with different moderators made interpretation of the observations very uncertain. The best result found was Be = 407 x 10(-6) cm(-2).