The Supercritical Water Loop (SCWL) is an experimental device which serves for the simulation of technical and chemical parameters of the Supercritical-Water-Cooled Reactor (SCWR). SCWR is a water-cooled nuclear reactor from the Generation IV initiative, which uses water with parameters above critical point (374 °C; 22.1 MPa), both as the coolant and moderator. Recent nuclear power reactors are using much lower coolant parameters: temperatures are usually limited to 350 °C and pressure is kept below 16 MPa (approx. 160 atmospheres). Such a large increase in coolant parameters allow an increase in the efficiency of the thermal cycle used, however, it is also connected with the problematic selection of construction materials.


The SCWL heart is the active channel, where water reaches required parameters (pressure of 25 MPa; temperature of 600 °C; very clean demineralised water – i.e. water with minimum  chemical impurities -in water chemistry language, we can say the water is almost ‘clean H2O’). After successful out-of-pile (i.e. non active, without presence of radiation field) operation, the active channel is inserted into the LVR-15 research reactor core. The bottom part of the active channel is then submerged between the core’s fuel assemblies and will face a neutron flux of up to 1.5 × 1018 n/m2s (thermal neutrons) and 3 × 1018 n/m2s (fast neutrons).

Nominal paremeters

Loop temperature max. 390 °C
Temperature in active channel max. 600 °C
Pressure 25 MPa (max. 32 MPa)
Flow rate 200–500 kg/h
Loop volume ~ 42 dm3

Experimental possibilities

  • Corrosion processes of construction materials in supercritical water, with influence of radiation field
  • Supercritical water radiolysis and its influence on materials and water chemistry
  • Development and testing of sensors, mostly for measuring of electrochemical potential (ECP).
  • Testing and optimisation of supercritical water regimes


SCWL Chart

 SCWL chart

A Primary circuit
B Secondary circuit
C terrtiary circuit
D purification circuit
1 active channel
2 main heater
3 regenerative exchanger
4 ECP measurement
5 main cooler
6 sampling equipment
7 cooler
8 conductivity measurement
9  measurements of H2 a O2
10 dosing system