Photo: Reactor cover for Akkuyu 1 (Credit: AEM)The Volgodonsk branch of Russia’s AEM-Technologies (part of Rosatom's engineering division – Atomenergomash) has completed the manufacture of the reactor cover for unit 1 of the Akkuyu NPP under construction in Turkey.

The reactor cover is one of the main assemblies of the upper block and is designed to seal the main connector of the reactor and keep the reactor internals from floating.

The cover weighs 93 tons and has a diameter of 4.5 metres. The reactor cover has a plate-like shape and is a stamp-welded structure consisting of a truncated ellipsoid and a massive flange. On top of the cover there are nozzles that are used to fasten the drives of the protection control system (CPS).

Reactor lid manufacturing is a long process and takes up to one and a half years. The main stages include welding components, boring holes for main connector studs, and surfacing. The key operation is pressing and welding of branch pipes, where specialists need to accurately install 139 branch pipes weighing 35-50kg into the holes of the cover. These elements are pressed in with liquid nitrogen at a temperature of -196 degrees Celsius.

The specialists also carried out hydraulic tests, during which they confirmed the strength and density of the base metal and welded joints of the reactor head. To confirm the alignment of the elements, the reactor lid undergoes a control assembly as part of the upper section. The main stages of manufacture took place under the supervision of the Turkish Nuclear Regulatory Agency (NDK).

The top of the reactor is hermetically sealed with a lid with drives of mechanisms and controls and protection of reactors installed on it and nozzles for outputting cables of sensors for in-reactor control. The cover is attached to the body with studs. In the upper part of the body there are nozzles for supplying and removing the coolant, as well as nozzles for emergency supply of the coolant when the circuit is depressurised.

Photo: Reactor cover for Akkuyu 1 (Credit: AEM)