NEA Thermal-hydraulics, Hydrogen, Aerosols and Iodine Project Phase 2 (THAI-2)

The NEA THAI Project was conducted between January 2007 and December 2009. 70 experiments were performed in the THAI facility in Frankfurt, the name of which is an acronym for thermal-hydraulics, hydrogen, aerosols and iodine. Within the NEA THAI project, the following test series had been performed:

A concluding seminar on the main outcome of the THAI Project was organised on 6-7 October 2010.

The objective of the THAI-2 follow-up project was to address remaining questions and to provide specific water-cooled reactors, aerosol and iodine issues, and hydrogen mitigation under accidental conditions. The project addressed open questions concerning the behaviour of a) release of gaseous iodine from a flashing jet, iodine deposition on aerosol particles; b) hydrogen combustion during spray operation and passive autocatalytic recombiner operation in case of extremely low-oxygen content. The understanding of the respective processes is essential for evaluating the amount of airborne radioactivity during accidents with core damage (iodine and aerosols) and for containment integrity (hydrogen). The programme generated valuable data for these. Concerning fission products, the programme will focus on iodine release from a flashing jet and gaseous iodine deposition on aerosols. Regarding hydrogen mitigation, the programme will focus on its combustion during spray operation and on its effective removal by means of passive autocatalytic recombiners when approaching oxygen starvation. An analytical effort will accompany the experimental programme, mainly consisting of code calculations for pre-test assessments, result evaluations and extrapolation to reactor situations.
By means of experiments in the THAI facility, safety-relevant improvements on the issues referred to in the proposed experimental programme were achieved by the following:


Canada, Czech Republic, Finland, France, Germany, Hungary, Japan, Korea, the Netherlands, Sweden and the United Kingdom

Project Period

August 2011 to July 2014


EUR 3.6 million

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Last updated: 11 September 2015