Integral reactors, developed in OKBM, being one of the varieties of PWR, are based on the common research and development work and on the experience in the creation, operation and development of such reactors.

But the novelty of the design decisions, connected with the integral lay-out of the reactor, the presence of a steam-gas pressurizer and guard vessel, the absence of circulation loops in the circuit and some others, demands special research work to be performed.

A lot of research work, connected with the experimental study of thermo-hydraulic processes in integral PWRs with a built-in steam-gas pressurizer have been performed in the existing experimental base.

The experimental investigations performed confirmed the main design decisions for equipment and systems and allowed substantion of the correctness of the chosen regime parameters, reliability and safety of the plant.

Together with the problems of the study of thermo-hydraulic processes, occuring in the plant in emergency conditions and of substantiation of the operability and efficiency of the provided safety systems, the most important problem for the experiments is to collect representative information for computer code verification.

The main investigations, which are being performed at present are the following:

— investigations of DNB in fuel assemblies and temperature state of fuel elements at partial and complete dry-out of the core;

— investigation of the conditions of steam condensation from steam-gas mixture in the heat exchangers-condensers of the emergency residual heat removal systems and in the built-in steam generators;

— investigations of steam-gas mixture distribution inside the pressurizer;

— investigations of water-gas and chemical conditions in the primary circuit, including gas transfer in the circuit;

— investigations at integral facilities, including a wide range of emergency conditions with primary circuit loss of tightness and heat removal disruption;

— investigations, verifying thermo-hydraulic and lifetime characteristics of steam generators.

Fig.4 shows the complex of facilities for thermo-physical investigations and safety of VPBER-600. *

To verify the results on the problem of corium confinement, it is necessary to perform additional investigations into thermo-physical, physico-chemical and thermo-mechanical processes, to improve calculation modes and computer programs. Besides, the conservativeness of assumptions made considerably compensates for the lack of information and gives every reason to obtain a positive solution of the problem of corium confinement in the reactor vessel or guard vessel.

Now testing facility for an integral PWR of 200 MW power is being made ready for putting into operation.