The operation principle of a Pressurized Water

Reactor (PWR) A PWR plant has two circuits for heat transmission. Water is kept under high pressure by the pressurizer (1) and circulated by the main reactor coolant pumps (2) in the reactor circuit (3) and transfers the reactor heat (4) to turbines (5) in the heat exchanger. Reactor efficiency is adjusted by control rods (6). The pressure in the turbine circuit is much lower than in the reactor circuit, which makes the water boil in the heat exchanger i.e. in the steam generator (7). The steam from the steam generator makes the turbine (8) rotate. The turbine rotates the generator (9) on the same axel shaft generating electricity to the national grid. The steam from the turbine is cooled to water in the condenser (10) with seawater (11). Condensation water is fed back to the steam generator with feed water pumps (12) and the warm sea water is pumped back to the sea.

OL3, Building responsibilities

Framatome ANP´s scope of supplies and services comprises the entire nuclear island which includes design procurement and supply of the mechanical and electrical components, plant instrumentation and control (I&C) equipment, fuel for the first core, a simulator and building construction as well as erection and initial startup.

Siemens Power Generation´s scope of supplies and services comprises the entire turbine island with the turbine generator set. This includes design, procurement and supply of the electrical and mechanical components, the turbine I&C equipment and building construction as well as erection and initial startup.

TVO as owner is responsible for the licensing process with the Radiation and Nuclear Safety Authority, Finland (STUK) and is responsible for site infrastructure and excavation grid connection and some auxiliary buildings.

The safety system consists of four redundant trains, each capable of performing the required safeguard function on its own.

In a very improbable serious accident at OL3 the core melt is transferred to the corium spreading area where is it cooled and solidified.

In the event of a core melt accident the core melt escaping from the reactor vessel is collected in the core catcher and passively transferred to a special spreading area in the base of the reactor building, which is equipped with a cooling system.