The Influence of Wall Materials on the Deposition of Cs in HTR Cooling Circuits

[Automatically extracted and translated] For the planning and operation of high-temperature reactors, the distribution of fission products in the primary circuit is of great importance. Not only the amount of deposited activity plays a role, but also the type of deposition. For example, it can be of great practical interest whether a simple decontamination procedure is applicable. Within the framework of the HHT project, the accessibility of the turbine is a crucial condition. For this reason, we investigate the deposition mechanisms of the most important fission products Cs, I, Sr, and Ag on high-temperature materials suitable for this application. The program underlying this report began in 1973 at the Institute for Technical Physics of the Kernforschungsanlage Jülich and is now being continued at the Institute for Interface Research and Vacuum Physics, which emerged from the first-mentioned institute at the beginning of 1974. Our specific topic is the influence of surface properties on deposition. Unlike other activities at the Institute for Reactor Components at HRB and AVR, we consider the problem detached from the issue of helium flow. Helium only plays the role of a solvent and carrier of certain impurities for us. The main topic of this lecture is the deposition of Cs on relevant materials, with a special focus on TZM (99.4% Mo, 0.5% Ti, 0.08% Zr). In the following sections, 1. Model concepts, 2. Adsorption and desorption, 3. Solubility and diffusion, and 4. Surface investigations are discussed.