Development of nuclear reactor cores having high power density, long fuel life, and low fabrication costs is the objective of this program sponsored by the AEC. Five tasks are in progress: (1) Task 1A-High Power Density Fuel Development. The number of assemblies has been reduced to seven as a result of the failure of two pellet fuel assemblies. The average burnup of the group operating as of September 1 is 7500 MWD/T. (2) Task 1B-Fuel Fabrication Development. Assembly. Assembly 12S gave positive signals of being a leaker under the multi-type in-core sampler and was declared failed based on the in-core results and visual observation of a cracked rod. Modifications to the instrumented fuel assembly probes were made by removing the failed flow meter rotors to allow continued use of the flux detectors and thermocouples. Flux detectors and thermocouples performed properly after reactor start up. Flux wire tubes were found to be kinked such that their use was prohibited. (3) Task II-Stability, Heat Transfer and Fluid Flow. A series of noise recordings of fluxes, flows, and temperatures has been made at 91 MWt at the Big Rock Point plant. Preliminary analyses of some of the these records were made to obtain …

Quarterly report regarding the activities of the Yankee Core Evaluation Program, the purpose of which is to evaluate the performance of the core used in the Yankee Plant and to compare actual performance with predictions, as well as the revision of designs to address any differences between actual and predicted performance.