Evaluation of Materials-Compatibility Problems in the EBR-II Reactor

Abstract

Three cases of slow, direct interaction of a material of construction with the high-temperature sodium coolant are discussed:

• 1. Copper was dissolved from an exposed bus bar and transferred to other reactor parts. An ex-reactor investigation indicated that neither the deposited copper nor the copper in solution in the sodium reacted further with stainless steel surfaces.

• 2. Beryllium copper (Berylco 25) wear bushings eroded and corroded in the high-temperature sodium. An aluminum bronze (Ampco 18–13) bushing proved to be a satisfactory replacement.

• 3. Tantalum was slightly attacked by the sodium. The resultant fine, highly radioactive corrosion product increased handling difficulties during disposal.

In addition, three instances of failure of thin sections of materials that are usually resistant to sodium are analyzed. In two instances the investigation indicated contamination of the component by a carbonaceous material prior to insertion in the reactor. In the third instance (valve bellows) exposure of the component to sodium containing oxygen prior to insertion in the reactor system is postulated as the cause of failure.

This work was performed under the auspices of the U. S. Atomic Energy Commission.