A heat exchanger of the BN-800 sodium-cooled fast reactor at Russia’s Beloyarsk NPP has been replaced for the first time – an operation the plant described as a rare and large-scale procedure. A similar procedure was carried out in 2005 for the 600 MWe BN-600 fast reactor at Beloyarsk unit 3.

At the BN-800 heat transfer from the 1st to the 2nd sodium circuits is provided by six such heat exchangers. And each of them carries about 1.4 tonnes of liquid sodium a second at a temperature of 547 degrees. Therefore, the replacement of such equipment is a time-consuming task. The intermediate heat exchanger (PТО – Promezhutochnii TeploObmennik) weighs 58 tonnes, with a height of about 14 metres and a diameter of 2 metres.

The replacement was carried out by personnel of the repair sites for the reactors and steam generators of units 3&4, crane operators, welders from the central repair shop, scaffolders and thermal insulation and heating personnel of Uralatomenergoremont – about 100 people.

First, the supply and outlet pipelines from the heat exchanger to the reactor, with a diameter of 600 millimetres were dismantled. Protective covers were removed, and pipes were sawn off. Work was performed on scaffolding at an altitude of about 10 metres. They cut off the antennal weld, and with the help of a set of special devices the PTO was removed from the reactor and moved to the shaft for washing large-sized equipment. The new heat exchanger was taken from storage, warmed up and installed in the reactor using a complex of special structures. The outlet and supply pipelines were then replaced.

Beloyarsk NPP Director Ivan Sidorov said: “Ensuring the safe operation of power units gives us confidence. Among the work remaining to be done is the repair of the turbogenerator, the modernisation and repair of equipment of various auxiliary systems, and operational control of metal structures.”

The Beloyarsk NPP at Zarechny, in the Sverdlovsk region, comprises four units. Units 1&2, both light water graphite reactors, are permanently shut down. Units 3&4 are fast neutron reactors with gross electrical capacity of 600 MWe and 885 MWe respectively.

Image courtesy of Beloyarsk NPP