Current status of epidemiological studies of the late effects of internal radium in humans, and mechanistic investigations of those effects.

Quarterly report on activities of Argonne National Laboratory's Nuclear Technical Programs, including results of studies to measure the degradation of backfill materials after their exposure to temperature and humidity expected in high-level nuclear waste repositories.

A data bank of field experiences with heat exchanger tube vibration reveals numerous cases of tube failures at, or near, the baffle. The objective of this study is to provide qualitative impact/fretting wear information for heat exchanger tubes through the performance of a series of tests involving the pertinent parameters: impact force level, between the tube and its support; tube to support plate hole clearance; tube support plate thickness; and tube vibration frequency. The characteristics of impact/fretting wear relative to tube motion pattern, material combination and surrounding fluid were also investigated. The test apparatus consists of a cantilevered tube with a simulated tube support plate at the ''free end''. Tube vibration is induced by an electromagnetic exciter to simulate the flow-induced tube motion occurring in a real heat exchanger at the tube/tube support plate interface. Tests are conducted in air, water, and oil, all at room temperature. Wear rate increases significantly with the magnitude of the impact force between the tube and its support plate; the degree and trend of the wear rates are highly dependent on the mechanical and metallurgical properties of the tube/support material combination; the rate of impact/fretting wear decreases with increasing frequency. An empirical formula is …