Most of the publications in the open literature available to us agree that sodium does not readily react with graphite, though potassium, rubidium, and cesium readily enter between the planes of the graphite lattice. In view of the conflicting evidence available, it seems inadvisable without very extensive further study to consider the use of graphite in direct contact with liquid sodium, except under very mild conditions of temperature and irradiation, and then only with very pure sodium and completely graphitized graphite.

Theory of operation and test results are given for a resistance type of liquid metal level instrument. The voltage across a steel rod in the tank is amplified by a magnetic amplifier and indicated by a milliammeter. Temperature compensation is provided for tank temperatures up to 1000 F.