On May 18, 2019, Leningrad NPP II Unit 2 under construction has started one of the key operations of the year, i.e. flooding of process systems with the unsealed reactor.

The first (passive) stage was carried out using pressurizer and four accumulators of the emergency core cooling system (ECCS) which had been previously filled with chemically desalinated water by auxiliary system pumps. After compressed air was pumped into ECCS accumulators and valves were opened at drain loop, water under pressure started being supplied to the reactor pressure vessel while cleaning the affected pipelines. All by-passes were made at the local shutdown panel (LSP).

“The flooding with the unsealed reactor is the important stage of the commissioning, Chief Engineer of Leningrad Phase II Aleksander Belyaev said. “Its main task is to check for flow all pipelines connecting equipment of the primary circuit and their post-mounting cleaning from possible mechanical admixtures. High quality of pipeline mounting has been confirmed. In near time, the second stage (active) will start: 12 emergency pumps and two pumps of the make-up and boron control system will be trialed, loops of the main circulation pipeline (MCP) and their by-passes with emergency systems will be cleaned and the systems will be checked”, he said. He also added that the flooding is carried out in accordance with approved programs and schedules; it is related to the stage of individual tests and trials of equipment of the power unit under construction.