HEAVY WATER LATTICE PROJECT ANNUAL REPORT

Technical Report · Sun Sep 30 00:00:00 EDT 1962

OSTI ID:4720152

Kaplan, I; Profio, A E; Thompson, T.J. eds.

: < 9 G ; 7 ; 7 9 5 6 6 8 9 uranium involved developing configurations to provide an incoming flux appropriate for macroscopic and microscopic measurements. Analytical and experimental methods giving accurate results were devised; computer codes for deriving buckling from measured flux traverses were arranged. The macroscopic flux distribution was found to have a simple form throughout most of the system. Buckling values for triangular lattices of 1.0 inch diameter natural U rods in 4.5, 5.0, and 5.75 in. lattice spacing were determined and compared favorably with other results. Measurements of axial and radial traverses were made for a triangular lattice of 0.25 in. diameter rods containing 1.03% U/sup 235/ with 1.25 in. lattice spacing. A new method was developed for measuring the ratio of the fission rate in U/sup 238/ to the fission rate in U/sup 235/, and the effects of varying experimental conditions on the ratio were examined. Measurements of the ratio for a single 1.0 in. diameter natural U rod in heavy water and for triangular lattices of such rods with 4.5, 5.0, and 5.75 in. spacings showed the ratio for the tightest lattice to be only about 6% greater than for the single rod. A ratio of 0.0126 plus or minus 0.0004 was obtained for a single U rod 0.25 in. in diameter with a U/sup 235/ concentration of 1.143% in heavy water. Measurements of the ratio of the epicadmium to subcadmium fission rates in U/sup 235/ were made for a single rod and three lattices; the results were compared with ratios calculated from gold-cadmium ratios. Similar research was done on lattices of enriched uranium rods. Study of resonance capture in U/sup 238/ involved measurement of the average U/sup 238/ cadmium ratio of the fuel rods, of the average ratio c/sup */ of the U/sup 238/ capture rate to the U/sup 235/ fission rate in fuel rods, of the distribution of resonance neutrons in the moderator, and of quantities related to the effective resonance integral of the rods. Results of the c/sup */ and cadmium ratio measurements are presented. Resonance integrals were measured by comparing the rod cadmium ratio with cadmium ratios of Na/sup 23/ and Mn/sup 55/ and Co/sup 59/. Initial studies of a similar nature were begun on enriched U rod lattices. Intracell thermal neutron distributions and associated quantities were measured for three lattices of natural U rods in heavy water and for one lattice of partially enriched U rods in heavy water. The measured values of neutron density distributions were compared with values calculated using the THERMOS code. Good agreement was achieved for the natural uranium rods but discrepancies were noted for the enriched lattice. Use of a two-dimensional code seems likely to alleviate the discrepancies. Intracell activity distributions were obtained with bare and cadmium-covered foils of europium and lutetium to investigate the gross spectral dependence of the intracell thermal neutron distributions. Once again the distributions for natural U agreed well with THERMOS predictions while discrepancies were noted for distributions of the enriched lattices. The THERMOS code does apparently give a good estimate of the degree of spectral hardening. For natural uranium lattices disadvantage factors measured agreed well with THERMOS computations and with those calculated by the Amouyal, Benoist, and Harowitz method. Thermal utilization values obtained by the three methods also agreed. For the enriched lattice, measured and THERMOS values disagreed. Theoretical small exponential assembly research included applying age-diffusion theory to the general case of cylindrical subcritical assembly with a thermal neutron source at one end, developing correction methods for measurements of lattice parameters, and preparing tables of characteristics for a range of possible subcritical assemblies. Experimental radial flux traverses agreed well with theoretical values for the nine lattices studied, and experimental axial thermal neutron flux traverses gave reasonable agreement. Measurements of the U/sup 238/ cadmium ratio and the calculated

• Research Organization: Massachusetts Inst. of Tech., Cambridge
• NSA Number: NSA-17-017419
• OSTI ID: 4720152
• Report Number(s): MITNE-26; NYO-10208
• Country of Publication: United States
• Language: English

Related Subjects

ABSORPTION
BUCKLING
CADMIUM
CADMIUM RATIO
COBALT 59
CONFIGURATION
CONTROL ELEMENTS
CRITICAL ASSEMBLIES
DIFFERENTIAL EQUATIONS
DIFFUSION
DISTRIBUTION
ENRICHMENT
EPITHERMAL NEUTRONS
ERRORS
EUROPIUM
EXPONENTIAL PILES
FERMI AGE
FISSION
FOILS
HEAVY WATER MODERATOR
LUTETIUM
MANGANESE 55
NATURAL URANIUM FUEL
NEUTRON DETECTION
NEUTRON FLUX
NEUTRONS
PROGRAMMING
PULSES
REACTIVITY
REACTOR CORE
REACTOR TECHNOLOGY
RESONANCE ESCAPE PROBABILITY
SLOWDOWN
SODIUM 23
SPECTRA
THERMAL NEUTRONS
THERMAL UTILIZATION
URANIUM 235
URANIUM 238