WP4: Chemistry of volatile radionuclides

Participants: SCK•CEN, PSI, UGent

Objectives

The first aim of this work package is an in depth study of the low temperature evaporation (< 500 °C) of polonium from LBE which has turned out to be very complex as discovered during the SEARCH project. Secondly, the evaporation of fission products, will be studied under MYRRHA-relevant conditions, as specifically requested by the licensing authority. Evaporation will be studied in conditions relevant for both normal operation and accidents. Finally, adsorption of the most volatile species on various materials will be studied in order to assess surface deposition and identify filtering solutions. More specifically, the objectives are the following:

  • development of sensor/pump for in situ measurement and control of dissolved oxygen concentration during evaporation experiments
  • study of polonium evaporation from LBE at temperatures below 500 °C, without and with control of dissolved oxygen content, in ultra-pure inert atmosphere as well as in atmospheres containing up to percentage levels of hydrogen, moisture and oxygen. Depending on the physicochemical process involved, quantities such as Henry constants or release rates will be determined, which will be used in safety assessments for MYRRHA but of course also apply to similar nuclear systems
  • study of fission product (e.g. I, Te, Ru, Cs) evaporation from their solutions in LBE over a wide concentration range, also with control of dissolved oxygen and carrier gas composition. As for polonium, Henry constants and release rates will be determined.
  • characterization of evaporated polonium molecules from carrier free and carrier added sources by thermochromatography under different conditions of starting temperature and carrier gas composition
  • characterization of evaporated fission product molecules by both thermochromatography and mass spectrometry
  • theoretical study of small Po-containing gas molecules with parallel study of the Te containing homologues to establish a link with themochromatography (for Po) and mass spectrometry (for Te) results.

Adsorption of volatile molecules containing polonium and fission products on various materials in order to assess surface deposition and identify filtering solutions.

Resources will be allocated in detail as a function of the importance for solving the questions asked by the Belgian Safety Authorities in the MYRRHA pre-licensing phase.

Deliverables

D4.1 Evaporation, speciation and capture of volatile polonium and fission products (SCK•CEN)(M48)
D4.2 Ab initio predicted binding energies of small and medium-sized Po-containing molecules (UGENT)(M15)
D4.3 Report on volatilization and deposition studies (PSI)(M48)