XII — 1. Introduction

The design of WWER-640/407 (V-407) was developed by the FSUE SPAEP (St. Petersburg, Russian Federation), FSUE EDO ‘Gidropress’ (Podolsk, Russian Federation) and the Russian National Research Centre ‘Kurchatov Institute’ (Moscow).

The design basis of the V-407 is that the prescribed exposure dose limits and the standards for the release of radioactive substances into the environment should not be exceeded under normal operation, anticipated operational occurrences, and in design and beyond-design-basis accidents, for the life (50-60 years) of the plant.

For this purpose, the new WWER-concept V-407 makes wide use of passive systems and components. A number of relatively innovative passive safety systems are implemented in these designs to ensure the fundamental safety functions: reactivity control, fuel cooling, and the confinement of radioactivity.

One important problem related to the implementation of passive systems is the lack of sufficient operating experience using the passive systems/components under actual plant conditions. Besides, the existing computer codes for transient and accident analysis are not sufficiently validated for the conditions and phenomena which are relevant to the passive system functioning (low pressure, low driving pressure and temperature heads, increased effect of non-condensable, boron transport at low velocities, etc.).

The new design features are envisaged to be verified experimentally at a large-scale test facility (1:27 volume and power scale). The design is developed in accordance with the latest Russian safety regulations for nuclear power plants, which meet modern world requirements.

The passive systems of WWER-V-407 using natural circulation consist of:

• Containment passive heat removal system (C-PHRS)

• Emergency core cooling system with three subsystems

• Steam generator passive heat removal system (SG-PHRS).

The overall configuration of the WWER-640/407 reactor systems is shown in Figure XII-1.