MYRRHA is an innovative fast spectrum research reactor under design at the SCK-CEN. It is an accelerator driven system (ADS) consisting of a proton accelerator and a pool type reactor vessel containing a subcritical core. Lead bismuth eutectic (LBE) is used as primary coolant.
Preventing the release of radioactive products into the environment evidently is a primary objective in the design of MYRRHA. Fission products such as iodine may leak out of defective fuel pins and come in contact with the LBE coolant. It is frequently suggested that the LBE forms an excellent barrier to prevent further release of fission products to the environment and therefore has a significant mitigating effect on the source term. However, currently available data are insufficient to accurately predict the release of fission products from LBE under the various expected normal operating and accidental conditions in MYRRHA.
In this PhD, the release of selected fission products (iodine, cesium, tellurium) from LBE will be characterized and quantified. LBE samples doped with fission products and representative compounds will be prepared and characterized. Using these samples, release experiments under a wide range of conditions relevant to MYRRHA will be carried out. In particular the influence of other impurities on the release of fission products needs to be evaluated. These include dissolved as well as gaseous oxygen in contact with the doped LBE sample and water vapor. The work also includes measurement of fundamental thermochemical properties of dilute solutions of the selected fission products in LBE and the characterization of the gas phase in equilibrium with such solutions.
The instrumentation will consist of evaporation setups developed at SCK-CEN. Specially designed sample cells will allow in situ measurement and control of the oxygen potential in the LBE. The analysis of the released amount of fission products will be done by post-test chemical methods (such as NAA and ICP-MS) or, for volatile compounds, in situ by a dedicated mass spectrometer coupled to the evaporation setup. Knudsen effusion mass spectrometry will be used to characterize the gas phase molecules and to determine specific thermochemical properties. The experimental work will be supported by thermochemical computations.
The student is expected to undertake regular travels to JRC in Karlsruhe to work in the laboratory of Prof. Rudy Konings.