A high-density concrete shield is proposed for the biological shield. Adequate shielding of personnel and equipment can be obtained for about two-fifths the cost of a laminated shield of steel and masonite. The proposed shield is expected to behave satisfactorily during the life of the Reactor Unit and, in addition, the shield will possess considerable resistance to earthquake and blast loads. Details of design specification are given.

"As part of a program to determine the feasibility of using a fighter airplane as a parasite in combination with a Consolidated Vultee RB-36 for long-range reconnaissance missions (project FICON), an experimental investigation has been made in the Langley free-flight tunnel to determine the dynamic stability and control characteristics of a 1/17.5-scale model of a Chance Vought F7U-3 airplane in several tow configurations. The investigation consisted of flight tests in which the model was towed from a strut in the tunnel by a towline and by a direct coupling which provided complete angular freedom. The tests with the direct coupling also included a study of the effect of spring restraint in roll in order to simulate approximately the proposed full-scale arrangement in which the only freedom is that permitted by the flexibility of the launching and retrieving trapeze carried by the-bomber" (p. 1).

The question has arisen of how the beam in A-12 as a long resonant cavity might effect the frequency of operation and the field distribution. This study is published to make available the calculation of the direct beam effect as an illustration of general methods of attacking perturbing effects in resonant cavities.

The following report describes data on the provided phase equilibrium systems that show the general nature of the diagrams and the compounds and solid solutions which occur.

Report presenting an investigation at transonic speeds of the control balancing characteristics of three tabs on a full-span flap on an aspect-ratio-3, 45 degree sweptback wing. The results indicated that all the tabs tested, inset, attached, or detached, would balance the flap hinge moments throughout the speed range.

Abstract: "Preliminary data have been taken to evaluate X-ray absorption at the L III edge of uranium as a method of detection of uranium in solution. Uranium concentrations in water from 150 ppm to 30,000 ppm have been investigated. The effect of copper as a typical contaminant in the range of 737 ppm of copper to 36,850 ppm of copper has been investigated for a representative uranium solution. Instrumentation has been constantly improved and suggestions for further improvements in amplifying and counting equipment are included. Comparison of experimental data with theory indicates that the derived equations are adequate."

Since 1945 the routine production of plutonium (``A`` buttons) at Atomic Energy plants has been accomplished by heating mixtures of plutonium tetrafluoride, calcium and iodine in crucible-bomb assemblies. Yields above 97% and metal of adequate purity are consistently obtained by this process. Plutonium (``X`` button) production has also been carried out routinely by including plutonium turnings with the powder mixture given above. A majority (several thousand) of buttons produced in the 234-5 Building have been ``X`` buttons made by recycling up to 1.1 units of turnings/unit of plutonium in the plutonium tetrafluoride. Operating hazards exist in either process, however, and these are reviewed below.

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Summary of progress on various research projects conducted during January, 1952.

Report presenting free-fall testing of the airplane configuration described in the title to evaluate certain new testing techniques for near sonic speeds. Results regarding the drag measurements and pressure data are provided. The data obtained from this test is also compared to free-fall tests in the high-speed tunnel and for a rocket-powered free-flight model, and the results show generally satisfactory agreement.