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The effects of ``water mixing`` pieces on the axial flux distributions and reactivities of the K Reactors are discussed in this report. Two mixing piece configurations in the K piles are compared to provide a basis for determining the optimum configuration with respect to rupture control, reactivity cost and temperature cycling effects.

Studies are under ray in Chemical Research and Development to-provide the technical ``know-how`` necessary to calcine Purex 1WW and safely store the solid product. The solid product can be stored as the particulate solid from the calciner or, after further treatment, as a solid matrix or melt. In this regard, Chemical Research is studying a PO{sub 4}BO{sub 2} melt. This document presents expected fission product heat generation rates in the solid product, shows the effect of various variables on heat transfer in the stored solid, and emphasizes certain items for further study. Also a vault cooling method is suggested for further study.

The equipment and experiments performed to measure the thermal-neutron- flux distribution in a fuel assembly of an experimental loop mock-up of a gas:cooled reactor at the Battelle Research Reactor (BRR) are described. The loop was located adjacent to the core of the BRR and contained one fuel assermbly composed of seven flat fuel plates each containing approximately 29.5 g of U/sup 235/. The plates consisted of a core 0.050 in. thick of UO/sub 2/ dispersed in Type 347 stainless steel and clad on each side with 0.005 in. of Type 347 stainless steel. The measurements showed that with the present design of the loop system an average thermal-neutron flux of 4.09 x 1O/sup 12/ neutrons/(cm/sup 2/)(sec) or a power generation of 45 kw in the assembly can be conveniently obtained. The ratio of the peak thermal-neutron flux to average thermal flux in the entire element was found to be 1.87. At any horizontal cross section, thermal-flux depression from the edge of the element to the center of less than a factor of two was observed for the final loopcore arrangement. (auth)