The CHIP experimental test bench is designed to reproduce the thermal-hydraulic and chemical conditions existing in the primary cooling system during a loss-of-coolant accident. The aim is to represent the homogeneous and heterogeneous chemical reactions occurring during the transport of iodine from the damaged reactor core to the reactor containment.
The CHIP bench was created during the CHIP program (Chemistry of Iodine in the Primary Circuit; 2005-2018), whose objective was to study the transport of iodine in the primary circuit in order to evaluate the fractions in the form of gases and aerosols likely to arrive in the containment.
Experimental device and test conditions
The device is composed of:
Several generators to produce chemical species in vapour or gas form (I2, H2/H2O, Cs, B, Mo, Ag, In, Cd...);
A line designed to heat the different reagents to temperatures between 1,500 °C and 1,600 °C. This temperature level corresponds to those encountered in the upper part of a core undergoing melting;
A transport line made from the same material as that used for the primary cooling system, and including two types of sampling devices designed and developed by the VTT Research Institute:
High-temperature sampling between 500 °C and 900 °C to study hot-leg break conditions;
Low-temperature sampling at around 150 °C to study cold-leg break conditions.
The parameters studied are the temperature at the sampling points, the concentration ratios of the chemical reagents, and the hold time in the system. They are representative of the different ranges encountered under accident conditions in the primary cooling system of a pressurised water reactor. The pressure in the CHIP facility is that existing in a primary system with a large break, equivalent to an absolute pressure of about 2 bar.