To examine the conditions brought about upon initiation of core spraying, a 36-rod assembly was heated to different temperatures and then spray cooled. The runs were made at atmospheric pressure using two kinds of assemblies, both made up of heater rods of 15 mm outer sheath diameter, arayed into 6x6 lattice accommodated in a 119 x 119 mm2 channel, but with heated lengths of 1, 500 and 2, 500 mm.
From these experiments following results were obtained:
(1) The surface of the exposed fuel rod after loss of coolant accident can be considered close to adiabatic state.
(2) The cooling water streams down the surface of the heater rods in the form of water film. If the wall surface temperature is quite high, water film is blown off the heated wall surface at a certain point along the rod (wet front), where the temperature is about 150°C. This wet front progresses slowly downward along the rod.
(3) The speed of downward progress of the wet front was measured, and an empirical equa- tion obtained.
(4) After commencement of spraying, the heat transfer coefficient of the portion of rod not yet reached by the wet front is approximately equal to that after attainment of steady state in dry-out condition.

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The ray analysis method is applied to the problem of γ-ray streaming through multibend cylindrical ducts. In this application, the total path length of a γ-ray photon through the shielding material is determined by calculating one by one the positions of the intersections between the straight line representing the direction of photon travel and the surfaces of the shield or of the wall of the bent duct, as the photon passes from duct into wall and out of wall into duct.
Based on this procedure of calculation, two computer programs have been prepared for the estimation of collision-free and total γ-ray doses as well as single and total scattered γ-ray doses behind a shield with multibend cylindrical duct.
The results of calculation with these programs are compared with the experimental values obtained by Shure and Marshall, and fairly good agreement is obtained.

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Neutron wave propagation in both non-multiplying and multiplying media is treated on the basis of the monochromatic telegrapher's equation. This approach makes it possible to take account of the aspects related to wave characteristics.
Using the Green function of the telegrapher's equation, the transient behavior of neutron waves propagating in a finite homogeneous medium is investigated. It is found that wave pro-pagates in three different ways depending upon the size and nuclear properties of the medium. The asymptotic solutions of the telegraper's equation are next investigated. The dispersion re-lations of non-multiplying and multiplying media are derived.

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The diffusive separation of ³⁶A/⁴⁰A isotope mixture in an axisymmetric supersonic jet was analyzed numerically with account taken of the pressure diffusion in the jet.
An approximate equation is proposed which gives the diffusion flux of the lighter compo-nent into the peripheral stream as a function of cut and Mach number.
The experimental results presented by Becker, et al. are found to be in fairly good agree-ment with the results of calculation by the proposed equation.

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In the present experiment, the effects of differences in the weight ratio between the epoxy resin and curing reagent, and in the radiation dose on the amount of residual fringe patterns were studied in detail. The specimens contained 12, 16, 20 and 25 (weight) parts of curing reagent for 100 parts of epoxy resin, and the radiation dose was varied in steps of 0.53 × 10⁸, 1.16 × 10⁸, 1.92 × 10³ and 3.17 × 10⁸ R on the average. The optical and mechanical properties of epoxy resin were also compared between non-irradiated and irradiated specimens for: Photo-elastic sensitivity, modulus of elasticity, Poisson's ratio and Rockwell's hardness. The relation-ship between the chemical and radiation crosslinking was obtained in an endeavor to throw light on the reason why the amount of residual fringe patterns depended on the epoxy resin/ curing reagent weight ratio and on the radiation dose. It was also shown that the change and disturbance in the patterns depended on optical creep, time edge-effect and on the generation of gases by irradiation.

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This paper deals with heat transfer in a fluid, with uniformly distributed internal heat source, flowing upwards through a vertical tube. Measurements were made of the temperature distribution in both laminar and turbulent flow, and both with and without heat transfer at wall. Heat generation within the fluid was brought about by passing an electrical current through the working fluid, which was an aqueous solution of sodium chloride. The experi-mental results were compared with analytical calculations.
Free convection, which occurs and is superimposed on the movement by forced convection, flattens the fluid temperature distribution in laminar flow through thermally insulated vertical tube. In turbulent flow with heat transfer to wall, the temperature distribution near the wall is affected considerably by the outgoing heat flux.

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