TITAN-2, said in a February 11 statement that it was preparing for the main phase of work to begin at the site.
The news comes after the Russian nuclear regulator, Rostekhnadzor, gave the go-ahead for the project on 22 January.
Work, which involves restoration of the extension route joints, will require the replacement of up to 350 process channels. The success of the project at Leningrad 1, Russia's oldest RBMK reactor, will play a role in whether or not to extend the lifetime of the remaining RBMK fleet.
A decision on whether to restart or permanently close Leningrad 1 is expected by November.