The Volgodonsk Branch of JSC "AEM-technology" (part of the machine-building division of Rosatom - Atomenergomash) has completed manufacturing of the reactor cover for the first unit of the Akkuyu NPP.
The reactor cover is one of the main components of the upper unit and is designed to seal the main reactor joint and keep the reactor internals from floating up. Product weight is 93 tons, its diameter is 4.5 meters. Like the reactor, the reactor cover belongs to equipment of the first category of seismic resistance. The service life of the reactor cover is 60 years, with the possibility of extending the service life by another 20 years.
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 control protection system (CPS).
Manufacturing of the reactor cover is a long process and takes up to 1.5 years. The main stages are welding of item components, boring of holes for main joint studs, overlay. The key operation is pressing and welding of nozzles, where specialists need to install 139 nozzles, weighing from 35 to 50 kg, into the holes of the cover with high precision. The components are pressed using liquid nitrogen at a temperature of -196 degrees Celsius.
Further, the specialists carried out hydraulic tests confirming the strength and tightness of the base metal and welded joints of the reactor cover. To confirm the alignment of the components, the reactor cover is subjected to check assembly as part of the upper unit. The main steps of the manufacturing have been completed under the supervision of Nuclear Regulatory Authority of Turkey.
A nuclear reactor is an item of the first safety class. It is a vertical cylindrical vessel with an elliptical bottom. The core and internals are located inside the vessel. The top of the reactor is hermetically sealed with a cover with drives of mechanisms and controls and protection of reactors installed on it and nozzles for outputting in-core monitoring cables. The cover is fixed to the vessel with studs. In the upper part of the vessel, there are nozzles for supplying and removing the coolant, as well as nozzles for emergency supply of the coolant when the circuit is depressurized.