Metsamor Unit 2 Reactor Undergoes Annealing Process

For the first time, unique work was carried out at the Metsamor Nuclear Power Plant on the recovery annealing of the plant's Unit 2 PWR-440 reactor vessel.
Metsamor NPPThe goal is to extend the service life of NPPs until 2026, Rosenergoatom said.
The annealing process took place in the reactor hall of the plant; the reactor was in its original place. An annealing plant with a height of a two-story building was delivered to the NPP disassembled, then it was assembled and installed in the reactor vessel. The metal was slowly heated to a temperature of 475 degrees Celsius, held for 150 hours and also gradually cooled. In total, the whole process took 10 days.
The reactor vessel is the main non-replaceable element of a nuclear power plant. Annealing will return the operational characteristics of the metal shell of the reactor to its original state by 80 percent to 85 percent.
Annealing is recognized as an effective way to ensure the safe and reliable operation of reactor facilities and for the first time, this technology was applied by Rosenergoatom in 1987 at the third power unit with a PWR-440 reactor at the Novovoronezh NPP. The technology for annealing the reactor vessel was developed by the specialists of CNIITMASH Rosatom.
The process was also "a guarantee of our security and the development of the Armenian economy," said Eduard Martirosyan, general director of the Metsamor plant, also referred to as the Armenian Nuclear Power Plant.
"The reliability and working capacity of the reactor vessel largely determines the safety of NPP operation as a whole. Thanks to the experience and high competencies of Russian specialists, the key works on the extension project went well,” said Martirosyan.
The annealing work was performed by specialists of Atomenergoremont, a subsidiary of Roenergoatom, together with plant personnel and specialists from Russian companies and organizations, including OKB GIDROPRESS, CNIITMASH, Kurchatov Institute Research Center and CNIIKM "Prometheus". The organization of work under the modernization contract is carried out by Rusatom Service, which is part of the electric power division of ROSATOM.
“Earlier, Atomenergoremont had already carried out annealing of the reactor vessel metal at nuclear power plants in Russia, Bulgaria and Ukraine. In order to carry out work at the Armenian NPP, the specialists of the repair company prepared all the necessary technical documentation, brought and assembled the annealing plant itself, tested it with the customer and installed it directly into the reactor. During the heating of the body metal, our operators monitored the temperature regime around the clock, which made it possible to quickly and efficiently make the necessary technical improvements,” said Alexey Chernikov, first deputy general director, chief engineer of Atomenergoremont.
 “At this stage, we have completed a very important procedure for the modernization of the station. And we hope that the result of our joint efforts will make it possible to further increase the safety of the NPP and extend it until 2026, and in the future for another 10 years,” said Yuri Sviridenko, the head of the project to extend the service life of the ANPP from the Russian side.
“The reactor vessel annealing technology is based on Russian technology. In 2018 Rosenergoatom, with the assistance of OKBM Gidropress and Kurchatov Institute Research Center for the first time in the world carried out work on annealing the vessel of a more powerful reactor – PWR-1000 of power unit No. 1 of Balakovo NPP. As a result, it received an additional 15 years of the authorized service life.
Recovery annealing was then carried out at PWR-440 reactors of such nuclear power plants as Kola NPP (Russia), Rovno NPP (Ukraine), Kozloduy NPP (Bulgaria) and Loviisa NPP (Finland).

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