Abstract. The probability of exceeding assigned values of displacements or forces in simple rod models assembled from slugs picked at random is discussed, and some estimate for the statistical gain resulting from use of shorter slugs is obtained. The probability that a rod with self-warping will touch the top of the tube appears great enough to justify a recommendation of the use of top ribs.

Abstract. The thermal conductivity of uranium as a function of temperature is measured by comparing its conductivity with that of a sample of brass. An absolute measurement is then made of the conductivity of the brass sample. The thermal conductivities as a function of temperature of two samples of extruded uranium rod are given.

Abstract. The effect of the neutron flux on the relative importance of different fission product poisons is discussed. The general expression for the poising of a fission product is given with the various equations for special cases of interest. The formulae are applied to the problem of finding the poisoning due to fission products at the end of one day in a pile operating with a flux of 4 x 10(14) neutrons/cm(2)/soc. These results are summarized in the table on page 12. Appendix I contains a revised list of cross sections x yields for all stable isotopes. Such a list was first given by Wheeler in CP-889. Appendix II contains a list of radioactive fission products with half lives greater than one day with data about yields, parents, gaseous ancestors, and numbers of neutrons.

Abstract. An apparatus for measuring the thermal conductivities materials which are moderately good conductors of heat is described. Results obtained with a sample of pure Th are given on p. 10, 12, and 13.

Abstract. Successive approximations ae obtained from transport theory for the neutron distribution around a black sphere surrounded by a spherical gap and a non-absorbing medium extending to infinity. Six cases are calculated numerically to show the difference between this treatment and simple diffusion theory. The extrapolation distance and a quantity that is essentially the thermal utilization are calculated in different approximations. It is found that the neutron density in the gap, instead of being a constant as predicted by the simple theory, may vary by a factor of one-third in cases of practical interest.

Abstract. A particle ionization chamber of sensitivity sufficient to detect a source of one neutron per second has been used to measure the neutron yield from a thick target of sulfur upon bombardment with polonium alpha particles. The high-geometry boron trifluoride chamber used had an efficiency of 1.9 percent for fission neutrons. The neutron yield from a thick target of sulfur was measured by this instrument and found to be .0035 +- .0013 neutrons per million incident polonium alpha particles.

Experiments wee performed to evaluate the feasibility of detecting swelled slug elements in Hanford reactors by measuring the force necessary to push the slug column in its tube. These experiments are described. The results indicate the method presents no unsolvable problems.

Abstract. Steady-state temperatures were measured in an electrically heated brass cylinder which was water cooled in a four-ribbed Al tube. Thermal transfer coefficients h were calculated from the measured temperatures. Curves of h values are presented for the regions of high and low ribs. the h curve is found to show a much sharper break in the region of high rib than in a low rib region. There is some evidence that h decreases linearly with annular thickness in the range considered. The low rib is found to exert a much greater effect than the high rib in decreasing the h value at points distant from the rib.

ABSTRACT. When solutions of high specific alpha activity are to be assayed for product, it is often difficult to obtain reproducible results by diluting the solution sufficiently to remove a small volume from which a sample can be prepared and counted at 52% geometry. In order to assay such a solution, most reproducible results have been obtained with minimum effort in sample preparation by making use of low geometry chambers. Two types of low geometry chambers are described: 1) The air-screen type which reduces the geometry simply by placing screens of various transparencies above the sample; and 2) The vacuum low geometry chamber which accomplishes geometry reduction by increasing the distance between sample and collecting electrode thus decreasing the solid angle subtended by the sample and aperture through which the particles pass into the ionization chamber. This type chamber was developed concurrently by this group and the instrument group of Chemistry Section C-I at the Metallurgical Laboratory. Because the geometry of the air-screen type chamber is quite critical to sample spreading and be- cause 12 mm sample plates are required, it has found very little use. On the other hand, the vacuum chamber, because it is noncritical to sample spreading …

Abstract. A method for calculating jacket temperatures in a region of varying heat transfer coefficients is given Some applications are made for temperatures above a supporting rib.

Prior to operating a chain reacting, graphite moderated, water cooled uranium pile at Hanford, the corrosive action of water on uranium was studied. It was necessary to enclose the uranium cylinders in Al jackets. Preliminary data were available which indicated Al jacket corrosion might be influenced by the water temperature. Therefore, in order to specify safe operating conditions, it was desirable to know the temperature at any position on the Al jacket of a slug in the tube. Because of the experimental difficulties encountered in the measurement of the correct surface temperature, the problem has been attacked primarily from a mathematical standpoint. Mathematical formulae have been developed for most of the proposed Hanford designs. The purpose of this report was to evaluate and summarize the theoretical and experimental information for calculation of Al jackets surface temperatures for the design now installed at Hanford. Also, the summarized results were to be put into a form suitable for use in routine calculations. As a result of this survey, the Al surface temperature for the Hanford tube and slug design may be calculated with 15 degrees C by employing routine methods and certain simple factors and equations contained in this report. The factors …

Abstract. The diffusion length of thermal neutrons in water as a function of the water temperature has been measured. The results are expressed as a linear relation: L = 2.644 + 0.0061T where L is the diffusion length in centimeters and T is the temperature in degrees centigrade.

Abstract. Given the maximum intrinsic curvature of a rod, the maximum force required to confine it between parallel rigid walls is computed.

Maximum curvatures and forces set up in taking a rod in a tube are considered.

This technical report discusses a method proposed to measure neutron energies by accurately determining the momenta of recoil protons in a magnetic spectrometer specially designed for this purpose. The main consideration in the design of the spectrometer is the shielding of the detector from the high radiation background associated with intense neutron beams.

Abstract. Slow neutron transmission measurements as a function of the time of flight of the incident neutron have been made for three different thicknesses of Beryllium. The energy region from 0.004 eV to 50 eV was investigated using the Columbia neutron beam spectrometer system. Particular emphasis was placed on the very low energy region (from 0.004 eV tp 0/2 eV or from 0.6 to 5 [length]) where pronounced crystal interference effects were observed. The effective slow neutron cross section (in the unity of X 10(-24)ce(2)atom) for several different energy values were: 6.1 at 0.2 [length], 3.5 at 1.5 [length], 2.3 at 2.5 [length] and 0.6 at 4.6 [length]. The positions of the discontinuities in the cross section agree fairly well with the values obtained from the X-ray measurements.

The problem of lining a hollow aluminum sphere, 10 inches i.d., with lunes of heavy metal foil, was assigned to this group by Dr. E. Creutz. The work was carried out under the direct supervision of Dr. D.H. Gurinsky. the problem was divided naturally into tow parts: first, forming fitting the lunes, and second, cementing hem to the inside of the sphere.

Abstract. Temperatures are measured at two points in an internally heated jacketed slug which is cooled by water flowing in an off-center annulus around the slug. The variations of these temperatures with water velocity, water temperature, power, and the amount the annulus is off center are measured. The temperature near the slug surface which approaches and comes in contact with the water jacket does not increase as much as anticipated. The temperature near the slug surface on the side which is moved away from the water jacket increases nearly as much as on the side approaching the slug. An explanation for this unexpected increase of temperature as on side moving away from the jacket is given.

Bi-Pb eutectic and pure Bi penetration of graphites of various densities under 300 degrees C and pressures up to 20 psi was found be of the order of magnitude of 1.0 g/cm(2) and was uniform throughout the graphite. Bi was absorbed less than the eutectic but the oxidation rate of Bi would be prohibitive. There was heavy nitriding in N atmospheres with the Bi and the eutectic.

An approximate calculation is made of the variations of the flexibility of a long cartridge with the length of the slug used, assuming that the jacket slides without friction.

Effect of aquadag coating on noise reduction in polyethylene coaxial cable was tested. A satisfactory combination of coaxial cables and connectors interconnecting sources of small ion currents or ionizing impulses with the measuring device is described.

Abstract. If a pile rod gets bowed within its cooling tube it becomes warmer on the side which approaches the tube wall, and thermal expansion tends to warp it in the same direction as the original displacement. This was discussed roughly in N-601, and it was there concluded that the mechanism was not important for an isolated short slug. In connection with current development of continuous jacket (cartridge) assemblies, it seems desirable to look at this question again. In this case it is possible that the effect may be of some concern.

Abstract. Recently (CP-1989) it has been shown that the neutron density, and thus the heat production, at the end of a slug with an A1 cap may be appreciably higher than that at the middle of the slag. A re-examination of earlier temperature calculations is made in light of this effect.

The distribution of thermal neutrons in a W slug having a one centimeter aluminum end cap has been calculated on the basis of simple diffusion theory. It is found that the average neutron density, and therefore the power output, at the end of the slug is about 34% higher than the density far from the end cap. This result agrees well with the recent Argonne pile experiments (CP-1729).