Pressure drops are reported for forced circulation flow of steam-water mixtures in a 23.5 foot long, 1.43 inch ID, 0.1 inch thick, horizontal annulus. The inner surface of the annulus was uniformly heated over a range from 97,000 to 233,000 Btu/hr-ft², exit pressures extended from 100 to 500 psig, and exit steam qualities varied from 0 to 60% by weight. Liquid water entered the annulus and boiling lengths up to 15 feet were investigated. Moreover, the Woods and the Martinelli and Nelson methods of calculating two-phase pressure drop were applied to the experimental conditions, and the deviations between the analytical and the test results are presented.

The conservative design criteria applied to process tubing may seriously hinder the advancement of high temperature reactor development. Factors of safety of 3 to 4 applied to an arbitrarily defined yield strength are used to calculate allowable internal working pressures. The effect of biaxial stressing on the tubes has been shown (2) to cause yielding at a lower internal pressure. However, tests conducted on biaxially stressed short lengths of tubing indicated that the ultimate tensile strength of the material was not affected.

It was suggested to the writer by K.A. Eschbach that liquid magnesium might offer certain advantages as a reactor coolant. As a result of this suggestion, a preliminary investigation of the possibilities of this material was made. Definite advantages for a restricted class of applications were found, but a detailed evaluation would seem to require further basic experimental research on the heat transfer, corrosion and flux-mechanical properties of the substance.

A knowledge of the mechanical and physical properties of uranium is important in understanding and explaining its pile behavior. The effects of irradiation on the properties of uranium will be dealt with in another chapter. However, it is important to know and understand the pre-irradiation properties of uranium prior to investigating the effects of irradiation.

A study was performed to determine the economic incentives associated with in-pile boiling, with the explicit assumption that this method of operation was technically feasible. A non-boiling reactor plant was used as a comparison, and the net electric generation was held constant at 400 Mw. The economic effect of variations in specific power from 47 to 32 kw/ft., and steam qualities of 10 to 60% were studied. The results showed that, under the conditions used, the unit power cost during single purpose operation would be in the range 5.9 to 6.1 mils/kw-hr at the generator bus-bar, compared to an estimated 6.6 mils/ kw-hr. for the non-boiling plant. These gains are realized under conditions of relatively high specific powers, greater than 32 kw/ft., relatively modest bulk outlet steam quality (greater than 20%), and high-pressure steam (1000 psia or higher) used directly in the turbines. During the dual market period, the power rate is about the same. An increase of 0.2 mils/kw-hr. is indicated when the specific power is lowered- Capital investment savings of perhaps four to five million dollars may be possible, but savings of this magnitude have little effect on the over-all power cost. The power cost savings stated above …

A nuclear safety indicator has been described. This is an instrument which will make it possible to determine the safety of performing contact maintenance work on certain long columns used in the continuous flow processing of plutonium.

This twenty-second quarterly report of the research and development activities of the Radiological Sciences Department, Hanford Atomic Products Operations, as before, includes some items charged to control but included for general interest. Such are identified as "not charged to research." The previous report of this series was numbered: HW-34408 January 10, 1955