Report discussing progress in research and development by the Health Instrument Divisions, Hanford Works, for the term from January through March, 1951.

A metallurgical examination of several resistance thermometers for 105-KW were examined before startup (1). This examination revealed that the silver brazes joining the type 305 stainless steel blades to the type 416 stainless steel nuts were defective. The braze metal did not penetrate into the joint; the brazes were porous and appeared to be inadequately bonded to the type 416 nuts. After startup of KW, many of the thermometers became inoperative, and several were visually examined to determine the integrity of the units. The presence of corrosion products at the junction of the braze and the nut led to further metallurgical examination of the brazed joints. Twenty units from 105-KW, 12 prototype units from 105-H, and two "new model" units were included in this examination. The examination was conducted to determine the cause and nature of the failures observed on units under service conditions.

The majority of two-phase flow problems involving equations of state are solved by use of point-wise utilization steam table values. In this manner, problems involving the use of the various flow equations of continuity, momentum and energy are generally forced into iterative solutions. Considerable effort towards the development of an analytical expression for the state equation seems indicated so as to simplify the analysis of two-phase problems, particularly the transient cases. The question of instability of state and mixture condition is particularly apparent in the analysis of systems undergoing phase transformation as demonstrated by the significant difference between simple theory and experimental critical flow determinations. The assumption of homogeneous, equilibrium mixtures is indicated as a first attack upon the problem.