Thermal-hydraulics, Hydrogen, Aerosols and Iodine (THAI) Project
Joint project

The experimental investigations carried out in the frame of the THAI (2007-2009) and THAI-2 (2011-2014) projects contributed significantly to improve the understanding of hydrogen and fission-product-related issues in a water-cooled reactor containment in design basis and severe accident conditions. The tests were conducted by Becker Technologies (Germany) in the 60 m³ stainless-steel THAI vessel. For THAI-3 (2016-2019) the facility had been enhanced to a linked, two-vessel apparatus named THAI+ with a total enclosed volume of 80 m3.

THAI phases

First phase (2007-2009)

THAI provided an experimental database devoted to the spatial distribution of hydrogen in containment, its removal by passive autocatalytic recombiners (PARs) and slow hydrogen combustion processes in accident conditions. Concerning fission products (FPs), the programme focused on iodine and aerosol interaction with PARs and a scoping test on a wash-down of soluble aerosol from walls by condensate film.

Second phase (2011-2014)

THAI-2 addressed additional experimental and analytical needs regarding hydrogen-related issues: PARs performance under different thermal-hydraulic conditions including the effect of reduced oxygen content in the air on PARs onset and ignition behaviour; one test series focused on investigating hydrogen deflagration during water-spray operation. Experimental investigations related to FPs focused on the interaction of gaseous iodine with tin oxide and silver aerosols and the release of gaseous iodine from a flashing jet.

Third phase (2016-2019)

Open issues related to hydrogen and FPs were investigated in THAI-3 and benefited from the enhanced capabilities of the THAI+ facility where the following experiment series were performed:

  • PARs performance in the adverse conditions of counter-current flow
  • hydrogen combustion and flame propagation in a two-compartment system and looking in particular at the impact of higher flow velocities of the unburned gas on flame acceleration
  • FP re-entrainment from water pools at elevated temperature
  • resuspension of FP deposits (aerosol and molecular iodine) due to a highly-energetic event, e.g. hydrogen deflagration.

Experimental investigations in the THAI+ facility addressing remaining containment hydrogen and source term issues are being conducted in the THEMIS project (2020-2024).

THAI-2 seminar  THAI-2 members' area  THAI-3 members' area (password protected | reminder)


THAI: Canada, Finland, France, Germany, Hungary, Korea, the Netherlands and Switzerland

THAI-2: Canada, Czech Republic, Finland, France, Germany, Hungary, Japan, Korea, the Netherlands, Sweden and the United Kingdom

THAI-3: Belgium, Canada, China, Czech Republic, Finland, France, Germany, Hungary, India, Japan, Korea, Luxembourg, Slovak Republic, Sweden, Switzerland and the United Kingdom.

Project period

THAI: Jan 2007 to Dec 2009
THAI-2: Aug 2011 to July 2014
THAI-3: Feb 2016 to July 2019


THAI: EUR 2.8 million
THAI-2: EUR 3.6 million
THAI-3: EUR 4.75 million