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[en] The methods of void determination with neutrons can be grouped into thermalization of fast neutrons by hydrogenous materials in small samples, into attenuation of thermal neutrons by hydrogenous materials, and into moderation and attenuation of fast neutrons in hydrogenous materials which contain strong thermal neutron absorbers. A small probe was developed consisting of a californium source and a detector in a cadmium hull which allowed the traverse of a water tank to determine local void fractions. Some boundary effects were observed. Neutrons from the californium were thermalized in a nylon sleeve and collimated for void fraction determination. Calculations using exponential absorption with a polynomial build-up factor were used to determine void fractions. A neutron beam passing through a water test section containing a high amount of dissolved boron was directly related to the amount of local thermalization and thus the fast neutron flux. The fast flux was related to the average void fraction along the beam. Collimation was only needed for the detector. (U.S.)

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[en] Separate abstracts were prepared for the 21 papers in the proceedings of the Health Physics Society 1981 Summer School on Reactor Health Physics

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[en] A two component laser doppler velocimeter with polarized beams and frequency shift was used to measure the turbulent flow field for axial flow between the rods of a nine rod, square pitch rod bundle. Parameters measured include mean axial and lateral velocities, turbulence intensities and the friction factor. The axial velocities for 10 000 to 40 000 Reynolds number are slightly higher than those reported by Rowe. The maximum lateral velocities measured are about 1% of the bulk velocity; somewhat larger than suggested by earlier authors. Axial and lateral turbulence intensities are larger than those in pipe flows. (orig.)

[en] This paper describes the results of an experimental investigation of the transient behavior of a liquid metal heat pipe. A 0.457 m (18 inch) long, screen wick, sodium heat pipe with 0.0127 m (0.5 inch) outer diameter was tested in the sodium loop facility at the University of Kentucky. The major finding was that the heat pipe did reverse under a pulse heat load applied at the condenser. The time at which the heat pipe reversed was approximately 15 to 25 seconds. When only the end section of the condenser was heated, the heat pipe may not reverse. It can function in two directions with the condenser in between two evaporator providing that the middle unheated section can removed all the input heat. The start-up and the operational shut-down by forced cooling of the condenser were also studied. During the start-up process, at least part of the heat pipe was active. The active region extended gradually down to the end of the condenser until all working fluid in the heat pipe was molten. With forced cooling at the condenser, the heat pipe approached its heat transport limit before section of the condenser became frozen