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"A series of thermal neutron diffusion length measurements has been made on non-multiplying lattice of lead-cadmium alloy rods in D2O. One-inch diameter rods in square lattice spacing of 4, 9, 6, 9, and 12 inches were used. Excellent agreement was found between theoretical and experimental values of the diffusion length. The analysis o the diffusion length measurement required a correction for the epithermal neutrons entering the exponential tank. These epithermal neutrons provided a distributed source of thermal neutrons upon slowing down in the lattice."

None

A preliminary study has been made of a solid homogeneous reactor for stationary power plant application. The core consists of graphite spheres impregnated with uranium and thorium, and the coolant is bismuth. This concept possible offers advantages over other solid fuel reactor systems with respect to simplification of core structure, fuel fabrication and fuel handling, and reduction of fuel inventory external to the reactor. From the results of this preliminary study, it appears that the potential cost of electric power from this reactor is competitive with that from other reactor systems which have been proposed for the same application. The Po210 produced in the coolant presents a decontamination problem, but is also possibly a valuable by-producgt.

The following progress report describes the examination of elements removed in comparison to a previous study on the power facility reactor operations.

"The purpose of this report is to examine the safety aspects of PNPF restart on continued operation, after completion of the core cleanup and system modifications."

Quarterly report with the objectives of evaluating, producing, and maintaining of an up-to-dat set of basic nuclear data; producing and evaluating of multigroup constants; and the improvement of present day methods of neutronic calculations as relates to microscopic and macroscopic nuclear data, for unclassified research sponsored by the U.S. Atomic Energy Commission during FY 1968.

Annual report with the objectives of evaluating, producing, and maintaining an up-to-date set of basic nuclear data; producing and evaluating multigroup constants; and improving of present day methods of neutronic calculations as related to microscopic and macroscopic nuclear data, for unclassified research sponsored by the U.S. Atomic Energy Commission during FY 1968.