XII — 1. Introduction

The design of WWER-1000/392 (V-392) was developed by FSUE ‘Atomenergoproject’ (Moscow, Russian Federation), FSUE EDO ‘Gidropress’ (Podolsk, Russian Federation) and the Russian National Research Centre ‘Kurchatov Institute’ (Moscow).

The primary purpose of the V-392 is to ensure the safety of the personnel, the public, and the environment against radiation effects exceeding the specified (prescribed) radiation doses. This principle also addresses the standards for releases of radioactive substances and their content in the environment under normal operation conditions, anticipated operational occurrences, design, and beyond-design-basis accidents during the plants life. The objective of the reactor plant design and nuclear plant process systems is to achieve estimated probability of severe core damage not above 1.0E-5 per reactor-year and the probability of accidental radioactive releases not above 1.0E-7 per reactor-year. These values are specified in Russian safety standards.

The design of NPP with WWER-1000/392 improves technical and economic parameters. Wide application of passive safety means, using natural physical processes, along with the traditional active systems is a specific feature of this design. Each plant designer must solve problems caused by implementing passive safety systems. The passive systems have their own advantages and drawbacks in comparison with the active systems both in the area of plant safety and economics. Therefore, a reasonable balance of active systems and new passive means is adopted in V-392 design to improve safety and public acceptability of nuclear energy.

The passive systems of WWER-1000/392 [1,2] are:

• Passive quick boron supply system,

• Passive subsystem for reactor flooding HA-1 (hydroaccumulators of first stage),

• Passive subsystem for reactor flooding HA-2 (hydroaccumulators of second stage),

• Passive system to maintain low inter-containment gap (annulus) atmosphere pressure,

• Passive residual heat removal system via steam generator (PHRS),

• Passive core catcher.

The reactor main coolant pump flywheel inertia provides the initial boron injection to the primary
system. Nitrogen gas at high pressure injects borated water from the hyrdoaccumulators in two stages

to the core. Gravity provides the driving force in some of the passive safety systems. The last three systems operate in a natural circulation loop providing decay heat removal from the core.

The overall configuration of the safety systems based on passive principles mentoned above is shown in Figure XTTT-1.

The overall functions of the safety systems based on passive principles mentioned above in comparison with active safety systems are shown in Figure XTTT-2.