Summarized here are the results of exponential experiments conducted at elevated temperatures on rod lattices of slightly-enriched UO2 moderated by D2O-H2O mixtures. The fuel rods, 4%-enriched UO2 swaged in stainless steel, were 0.476-inch OD by 0. 016-inch wall. The non-moderator-to-moderator volume ratio was 1. 006. The two moderator compositions studied were light water {0% DjO) and a D2O-H2O mixture containing 81.5 mole % D2O. The experimental facility and techniques are described. Material buckling values derived from radial and axial flux measurements are summarized below. 0% D2O
This report describes the thermal activation method for measuring P28 in heterogeneous slightly enriched U02 lattices and gives resulls for 12 water-moderated lattices. The technique has three primary advantages over conventional U238 cadmium-ratio measurements: (1) uranium activities are measured by chemically processing the irradiated fuel to avoid problems associated with the use of U238 foils, (2) cadmium-covered uranium measurements are eliminated to avoid cadmium perturbations, and (3) P28 is obtained directly, rather than by subtracting one from the cadmium ratio, to avoid large errors when the cadmium ratio approaches unity. The technique compares total absorptions in U238 to thermal absorptions in an intermediate material, usually dysprosium, having a
3-1. Facility for Small Lattice Experiments 3-8 3-2. Assembly Plan (4.02%-Enriched U0 2 Experiments). :. .. . 3-9 3-3. Assembly Elevation (4.02%-Enriched U0 2 Experiments) .. 3-10 3-4. Core Tank and Buffer Region (4.02%-Enriched U0 2 Experiments). 3-11 3-5. Test and Buffer Region Plan (UO z-Th0 2 Experiments).. .. 3-12 3-6. Test and Buffer Region Elevation (U0 2-Th0 2 Experiments) 3-13 3-7. Test Insert (4.02%-Enriched U0 2 Experiments) 3-14 3-8. Unloaded Test Region (4.02%-Enriched UO z Experiments) • •■ • 3-15 3-9.. Void Can (4.02%-Enriched U0 2 Experiments) 3-16 3^10. Test Insert Assembled With Test Region and Void Can (4.02%-Enriched U0 2 Experiments) 3-17 4-1. Radial Flux Distribution (Unpoisoned Test and Buffer) ... 4-18 4-2. Axial Flux Distribution (Unpoisoned Test and Buffer) .... 4-19 4-3. Epithermal Flux Distribution (Unpoisoned Test and Buffer) _i • •_ .4-20 4-4. Sector Foils in fym/fyf Measurement 4-21 4-5. U-Al Foils in C 25 Measurement 4-22 4-6. Loading Arrangement for C 28 Measurement 4-23 4-7. Ap Vs Mass of Poison (Unpoisoned Buffer) 4-24 4-8.
The EMI 5311 photomultiplier tube differs from the usual tube in that the electrodes are of the Venetian blind type rather than sections of electron optical lenses. This type of tube has been used as a scintillation counter with trans -stilbene crystals. The shape of the scintillation pulse in charac-
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