The effect of composition on volatility from a copper alloy

AbstractDuring a loss of coolant accident activated structural material can be mobilized through oxidation. Information on how much material is mobilized in an accident is necessary for performing safety assessments of fusion reactor designs. The Fusion Safety Program at the Idaho National Engineering Laboratory has an experimental program to measure mobilized mass as a function of temperature for various oxidizing environments. Materials studied have included beryllium (important because of its toxicity), copper alloys, a niobium alloy, austenitic and ferritic steels, tungsten (pure and an alloy), and a vanadium alloy.Some materials undergo a significant change in composition during irradiation. An example of this is copper (a candidate for the ITER first wall, divertor substrate, and various instrumentation probes and antennas), which can have as much as 1 wt.% zinc because of transmutation. Additionally, as the design for ITER evolves, a slightly different copper alloy may be selected. Compositional changes may affect the extent that various elements are mobilized because of such mechanisms as diffusion through the alloy, and penetration and release from oxide layers formed on the material. To calculate accurately offsite doses for various irradiation scenarios, we must understand the effect of composition on mobilization.We have carried out a series of experiments in our volatilization of activation products oxides reactor apparatus with a copper alloy containing non-radioactive elements added to represent transmutation products. We prepared samples containing copper, nickel, cobalt, zinc, magnesium, iron, manganese, zirconium and aluminum. We prepared three different sample compositions with varying amounts of cobalt, nickel, and zinc. We tested the samples in the temperature range 600–1200 °C in both air and steam. The species mobilized by volatilization and oxide spalling are carried downstream and collected in a filter or deposited on the system surfaces. The system components and the filter, consisting of quartz, are chemically cleaned with hydrofluoric acid and processed into solutions that are analyzed. These tests provide a mass flux (grams per square meter per hour) as a function of temperature for each element.We used the information from the these tests to calculate offsite early doses (for 1 h at temperature) as a function of temperature resulting from mobilization of the first wall. We present results for both air and steam exposure. We discuss the effect of copper alloy composition on these doses.