In formulating this general diffusion theory expression which represents the neutron balance in a nuclear chain reactor the following assumptions were made : (1) the medium through which the neutrons are diffusing has a low neutron capture cross section, (2) the region in which the flux distribute is being described is two or three mean free paths from strong sources and sinks or from a boundary. Certainly, is going to the lattice cell of a receptor, both of the above conditions are violated; fuel elements have a large absorption cross section and most lattice cells are only two or three mean free paths to is over-all sites

Facilities shall be provided in the 221-U Building for removing fuel elements from the casks as placed in the railroad tunnel from the transfer facility and moving the elements to modified existing 10' X 16' X 14' storage tanks in ten existing cells where they will be stored, until scheduled for processing.

A number of Pu-Al and UO2-PuO2 Zircaloy clad capsules have been fabricated for irradiation in the MTR. In addition, a four rod cluster containing Al 8 w/o Pu and Al 12 w/o Si 8 w/o Pu cores has been successfully irradiated and discharged from Loop 3 of the KER. A second four rod cluster is awaiting irradiation and design and fabrication of a seven rod cluster test element is underway.

Basic Studies. Sinterability studies on the isomorphous system UO2-PuO2 have continued. One-half inch diameter X 3/8'' long compacts containing physical mixtures of the two components have been heated in hydrogen. Sintered density as a function of time and temperature has been determined for times of one and eight hours up to 1600 C. In general, there seems to be minima on isothermal plots of density versus composition in the intermediate range 20-40 w/o PuO2. At concentrations greater than 40 w/o PuO2, density increases rapidly with increasing PuO2. In every case pure PuO2, (produced by decomposing plutonium oxalate at at 300 C) sintered to a greater density that ball ball milled PWR grade UO2. The data, for a one hour soak time, and tabulated in percent of the theoretical crystallographic density, can be seen below: