First estimates of thermal-hydraulic conditions in DC 1-1r diagnostic rod cluster during step by step reduction of flow rate, calculation/experiment comparison

During the 17-th reactor campaign at Rheinsberg NPP DC 1-1r diagnostic rod cluster had been installed in WWER-2 reactor. Extensive computations with CHANNEL code have been carried out for a steady state boiling experiment conducted on 10.22.83. During this experiment the coolant flow rate through the diagnostic rod cluster was throttled step by step from 21.1 kg/s down to 5.4 kg/s. In each step temperature, pressure and neutron flux have been measured. CHANNEL code is used in DDR at nuclear power plants to calculate both steady state and nonstationary regimes of PWR core. It is based on an adiabatic channel model with zero flow rate loss. Calculations for subcooled boiling can be done with LEVY model. The objectives of neutronic and thermal-physical studies with the diagnostic rod clusters were the experimental verification of low-dimensional computer codes employed at NPPs and establishing their applicability scopes. The completed calculation studies and comparison with experiment confirm that CHANNEL code is suitable for describing the thermal-hydraulic state of PWR