Dukovany unit 4 offline since April, return expected in mid-June

The planned outage of unit 4 at the Dukovany Nuclear Power Plant is expected to end in mid-June, depending on the results of inspections. The unit has been offline since 17 April. Engineers are now inspecting key equipment as well as the reactor pressure vessel, from which the fuel has been removed. They will then replace approximately one-fifth of the fuel assemblies in the reactor. This was stated by ČEZ spokesperson Radek Doležal.

The condition of the massive pressure vessel is being verified inside the reactor by a modular inspection system. "Key work is related to the long-term operation of our nuclear units. For example, reactor vessels are among the components that we do not expect to replace, so we must be absolutely certain of their condition," said Bohdan Zronek, a member of the board and director of ČEZ's nuclear energy division.

At one of the plant's steam generators, experts are inspecting more than 50 kilometres of heat-exchanger tubing using the eddy-current method. "We are also focusing on the main circulation pumps and shut-off valves," said plant director Roman Havlín. A total of 18,000 work orders were prepared for the outage.

During every outage, specialists replace approximately one-fifth of the fuel assemblies in the reactor; this time, it is 78 out of 349. Both Czech nuclear power plants have gradually moved to extended fuel cycles. At Dukovany, a 16-month fuel cycle has been standard since 2024, with units operating for 14 months between outages followed by an outage lasting more than one month. Temelín will complete its transition to an 18-month fuel cycle this year. According to ČEZ, the aim is to increase electricity generation, make more efficient use of nuclear fuel and reduce the burden on equipment.

Czechia has six nuclear units at two power plants, which together generated 32.066 terawatt-hours (TWh) of electricity last year.

The four Dukovany units were commissioned between 1985 and 1987. According to ČEZ's current assumptions, they can operate for up to 80 years from their commissioning, i.e. until 2065 to 2067. South Korea's KHNP was awarded the contract to build two additional Dukovany units.