Recently, the Belgian government gave the green light to the Belgian Nuclear Research Centre to start constructing MYRRHA, the first accelerator driven research reactor in the world. One of the primary objectives of MYRRHA is to demonstrate transmutation of spent nuclear fuel. Transmutation can help solve problems posed by the management of radioactive waste by strongly reducing its volume and the proportion of long-lived isotopes it contains.
A multidisplinary research team is currently supporting the MYRRHA safety analysis and engineering design. One outstanding research question is related to the consequences of a failure of the proton beam window. This window will form the barrier between the vacuum of the proton guide tube of the accelerator and the primary lead-bismuth coolant. It is a component that is under high stress (large temperature gradients, high radiation load, …) and therefore its failure is considered as a very likely event in the MYRRHA safety analysis.
If the beam window leaks or breaks, LBE can enter the beam tube and be heated to very high temperatures (>550 °C). At these temperatures, polonium from bismuth activation in the LBE can evaporate significantly into the beam tube. In such an event, the transport of polonium further in the beamtube, which may eventually lead to radioactive release, must be known and, if necessary, mitigated.
The objective of this project is to study the interactions of polonium with steel surfaces, which will influence its transport rate in the evacuated proton beam tube. Using a experimental setup equipped with dedicated heating stages, alpha detectors and a quartz crystal microbalance, these interaction properties will be determined at temperatures relevant for MYRRHA. The experiment design and data analysis will be supported by molecular flow calculations.