Six structural materials (aluminum 2S, aluminum 72S, copper, iron, steel, lead and bismuth) were irradiated for about 100 kilowatt hours in the center of the Argonne pile. The alpha and gamma decays were then followed for 130 days on Geiger counters and are presented here graphically as number of rays per minute per gram per kilowatt hour vs. time of decay. A quantitative interpretation of the gamma-ray decay curves gave fair agreement with the chemical analysis of impurities found in the materials.

The temperature coefficient of eta has been measured with the thermal column of the Argonne pile using uranium foils of different isotopic ratios. The temperature change was effected by filtering neutrons through silver. The measured fractional change per degree centigrade is [formula].

The present report is concerned with the electronic relay which, upon the reaching of a pre-determined value of ionization current in the associated chamber, actuates the safety rod release mechanism. The are here proposed two independent suggestions: (1) An improved trip circuit of such sensitivity and stability as to allow it to be actuated by a signal directly from the chamber without the necessity of interposing intermediate amplifier stages. The value of chamber current at which tripping occurs is stable to +- 0.4%. (2) A triple-wound relay to prevent shut-downs of the pile which would otherwise be caused by development of defects in the safety circuits.

The resonance absorption of a lump is described in terms of three components. Calculations of resonance absorption are carried out using the model for the resonance spectrum of uranium recently derived; calculations are also made with variations of this model which involve local fluctuations in level strengths. For metal and oxide lumps the agreement with observation is satisfactory. For dilute mixtures, whose resonance activation was measured by Mitchell, computed values fall 20% to 30% above measured ones.

It is usual to determine the density of neutrons by using foils of metals which become radioactive as a result of bombardment in the region under investigation. From the rate of disintegration of the newly formed radioactive element the number of neutrons absorbed can be calculated. By use of the capture cross section of the element of which the foil is composed the density of the neutrons can then be computed. By counting the alpha particles from a bismuth foil of known weight after exposure to neutrons the density of the neutrons which produced this activity can be calculated. The least accurately known value which enters into this evaluation is the capture cross-section of bismuth for pile neutrons. This value may be improved by future measurements. It is of importance only for absolute measurements of neutron density so that relative values can be measured with considerable accuracy on the basis of known data.

A good determination of the resonance absorption of uranium when admixed with various substances is necessary so that calculations can be made on the efficiency of homogeneous piles. The original experiments along these lines were undertaken by Creutz, Jupnik, and Snyder (C-116) and consisted of experiments on the resonance capture in pure U, UO2, U3O8, and one experiment on capture in a mixture of U3O8 and graphite. These experiments were done at the cyclotron in Princeton and consisted of determining the ratio of the twenty-three minute activity of uranium to an iodine monitor placed in some position with respect to the sample. By using spheres of different radii both the volume and the surface absorptions were measured. It was considered very desirable to extend these measurements to mixtures containing large amounts of graphite to uranium and also to investigate other substances containing hydrogen and deuterium. In addition it was decided to use both iodine and gallium monitors in the experiments. While the experiments were in progress, an absorption curve for uranium metal was made by Marshall using iodine and gallium detectors, which showed that there was a certain amount of overlapping of resonance levels of uranium and iodine.

Technical report with short reports from the (1) Experimental Nuclear Physics Group; (2) Theoretical Physics Group ; (3) Lattice Design Group; (4) Pile Design Group; (5) Exponential Experimental Group; (6) Radiation Group; and (7) Shielding Group.

It was desired to determine a method of evaporating boron to form a rather pure uniform tenacious coat of specified thickness. These coats are needed as monitoring films for neutron intensities, particularly in steel ionization cylinders. The most satisfactory method of evaporating boron employed a graphite filament. A mixture of amorphous boron and Carbenoid A was painted onto the filament which was then heated by electrical resistance method to 2300 degree C at which temperature the boron evaporated. Opaque films with purities up to 98% boron or better could be deposited by this method. Much heat was liberated by the filament, and it was found necessary to cool the steel cylinders during evaporation to prevent alloying of boron with the steel. Cathodic deposition also proved satisfactory for producing high purity films; this method has the advantage that little or no heat is produced during the process, but requires much time. Other less efficacious methods of depositing lighter films of born were developed; these are included in the following discussion.

Fermi, Anderson, and Nagle's experimental distribution of Indium resonance neutrons around a point source of fission neutrons in water has been fitted by analytic expressions which are source functions in the two-group, three-group, Fermi and Christy-Wheeler pile theory. The Christy-Wheeler function (exponential followed by a Gaussian) is the best fit; the two-group function (exponential) is slightly better than the Fermi Gaussian.

The change in the simple [formula] distribution of neutrons in a spherical lump of uranium caused by the distribution in velocities of thermal neutrons is calculated. If the calculated curve is fitted as well as possible by a simple [formula] curve, it is shown that the value of [formula] obtained in this way is a function of [formula], the radius of the sphere. For small radii the [formula] obtained in this manner will be as much as 25% greater than the [formula] corresponding to average velocity neutrons. The change in the thermal utilization caused by the distribution in velocities is discussed. The flux of neutrons into a sphere is calculated taking into account the velocity distribution and this is compared with the usual theory.

Aluminum oxide occupies a larger volume than the aluminum it contains would fill as metal, consequently, the assumption has been made that holes in metallic aluminum would close by a sufficient amount of oxidation. Therefore, we were asked to investigate the rate of plug formation under conditions to be expected in the pile. For the latter we were requested to approach the pile conditions as nearly as we could by employing the Chicago cyclotron. It seems to us that the problem divides itself into two separate questions: (1) under what conditions may holes be expected to close? (2) if holes do close how much corrosion of uranium may be expected before the closure becomes impervious to water vapor? In this report only the first question is considered. The experiments and theory coupled with the data collected by other workers on the project definitely define the limits within which pores in the aluminum cans may be expected to close by an oxidation process. Under the most favorable conditions only small holes may be sealed in this manner. In the large majority of the cases the holes not only fail to close but become larger.

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).

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.

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.

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.

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.

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. 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.

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.

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. 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.

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.