JSC Atomenergoproekt (Moscow) has presented to Turkish specialists an improved melt confinement device (corium catcher) for the Akkuyu NPP (JSC Atomenergoproekt is the General Designer for this NPP project). The modernized catcher for the conditions of Turkey features increased seismic resistance, increased impact and dynamic strength, simplified technology of installation, and a number of other advantages.
‘The improved corium catcher retains succession and does not differ from its predecessors in physical processes and chemical reactions. At the same time, a number of modifications improving the catcher’s operational properties and enhancing the plant safety level have been incorporated in the design,’ Alexandr Sidorov, Head of a Sector of Atomenergoproekt’s Bureau for Schematics and Operating Conditions, who is one of the developers of the Russian know-how, said.
As Sidorov explained, the corium catcher design has been modernized taking into account a higher level of loads caused by the ultimate design earthquake the power unit can withstand and also in connection with increasing the power unit independence time to 72 h in the new NPP projects.
The modernized catcher has a more efficient design of cooling its own load-bearing elements, due to which a smaller specific expenditure of materials is achieved for the catcher equipment essential for operability of its main component, i.e., the vessel with the filler.
On the whole, in comparison with the version installed at the Novovoronezh-2 NPP (JSC Atomenergoproekt is the General Designer and General Contractor for this NPP), the weight of the modernized catcher has become by almost 15% smaller. In addition, the developers have improved the device installation technology.
‘From design to design, we improved the catcher assembly and installation methods, modifying and enlarging individual elements of its design as scientific results and new technological approaches to manufacture became available. As a result, a simpler and more convenient catcher installation scheme has been developed, which will make it possible the catcher installation works to be accomplished within at least by a month shorter period of time,’ Alexandr Sidorov explained.
The corium catcher is a know-how of Russian nuclear power engineers. The device is a reservoir placed beneath the bottom of the reactor pressure vessel. In case of a hypothetical accident, the catcher retains liquid and solid fragments of the reactor core, as well as fragments of the reactor structural materials, thereby excluding damage to the sealed containment and preventing the release of radioactive substances into the environment. The catcher is filled with sacrificial materials during interaction with which the molten core loses part of its accumulated heat; in addition, a number of chemical processes take place, the totality of which make it possible to set up conditions for confining the melt and for cooling it for a long period of time.
Corium catchers were installed for the first time in the world at the Tianwan NPP in China and at the Kudankulam NPP in India. The Novovoronezh-2 NPP and the Leningrad-2 NPP became Russia’s first NPPs equipped with corium catchers.
The Akkuyu NPP (JSC Atomenergoproekt is its General Designer) is being constructed in the Republic of Turkey on the Mediterranean Sea coast in the Mersin Province. This NPP is constructed according to the Generation 3+ AES-2006 project developed by JSC Atomenergoproekt, which incorporates the latest solutions in the field of NPP safety.