A Mechanistic Interpretation of Activity Pick-up Data

A series of long-term activity pick-up tests was conducted to assess the tendency of various materials to pick up radioactivity upon exposure to coolant of a pressurized water reactor (PWR).  Testing was conducted at the Advanced Test Reactor (ATR).  Several materials with a variety of surface treatments were included in the tests.  A review of the gamma-ray spectroscopy data has identified three different mechanisms by which radioactivity is picked up: incorporation of radionuclides into a growing corrosion film, direct activation of elements within an alloy and non-specific adsorption of radionuclide particulates.  This paper provides the data analysis which identifies these distinct mechanisms by which radioactivity is picked up.  This methodology may prove useful in assessing or predicting activity pick-up in other materials or in other systems.