The third tier of the internal containment shell has been installed at unit 1 of the Akkuyu NPP under construction in Turkey, project company Akkuyu Nuclear said on 7 June. The installation of the cylindrical structure, weighing 322 tons, took a whole day.

The third tier of the internal containment shell is a welded metal structure consisting of 24 sections, each 11.5 metres high, 5.8 metres wide and weighing 13.4 tons. The sections were assembled into a single block 138 metres long in a circle. The structure was assembled near the reactor building, after which the quality of all welded joints was confirmed by ultrasonic testing. The installation was carried out by one a powerful crawler cranes a using a specially developed technology to ensure accuracy – the acceptable deviation from the intended diameter value is within the range of 5 mm.

Following installation, the height of the reactor building was increased by 11.6 metres to more than 28.55 metres. Specialists must now join the second and third tiers, and reinforce and concrete the shell. The walls will be 1.2 metres thick. In total, the internal containment shell will consist of four tiers and a dome. Once all elements are in place, the shell will be tested for tightness.

“Just a week ago, we installed the reactor vessel at the first power unit, and now we have passed another key stage of construction: installing the third tier of the inner containment,” said Sergey Butskikh, First Deputy General Director and Director of the NPP under construction at Akkuyu Nuclear. We have achieved a good pace in implementation of the main stages of construction. The next key operations we have to perform this summer are at the second power unit – to install the armoured block of the reactor shaft, the second tier of the inner containment and the support truss. At unit 3 we have completed the concreting of the turbine building foundation and the foundation slab of the reactor building will be ready in the near future.”

The reactor buildings of the Akkuyu NPP project have a double containment shell. The outer containment shell is formed from reinforced concrete and is designed to withstand any extreme external influences. The inner containment consists of a steel lining, which ensures the tightness of the reactor compartment and special concrete. The inner containment is a localising safety system that ensures the stability of the reactor compartment, serves as a support for pipeline penetration and a polar crane, with the help of which, at the stage of NPP operation, operations are carried out to maintain the nuclear reactor.

The Akkuyu NPP construction project is being implemented by Akkuyu Nuclear following an intergovernmental agreement signed between Russian and Turkey in 2010. The Akkuyu NPP, with four VVER-1200 units, is being constructed on a build-own-operate basis by Rosatom, with commissioning of the first unit planned for 2023.