Fuel unloading completed for Unit 3 of Dukovany Nuclear Power Plant

On July 30, Unit 3 of the Dukovany Nuclear Power Plant completed the unloading of reactor fuel assemblies, and the planned refueling outage has now entered its next phase. During this outage, the plant will replace part of the nuclear fuel and carry out hundreds of inspections, tests, and maintenance activities to enhance nuclear safety levels and ensure the long-term stable operation of the unit.

In this outage, although the actual number of fuel assemblies to be replaced accounts for about one-fifth of the total, operators must first remove all fuel assemblies from the entire core and transfer them to the spent fuel pool. Subsequently, the reactor water level will be lowered to create conditions for maintenance of core cooling system components and inspection of some primary circuit equipment.

Roman Havlín, Plant Manager of Dukovany Nuclear Power Plant, stated that completing fuel unloading is an important milestone in the refueling outage, enabling staff to carry out a series of demanding maintenance and modification tasks on equipment that is inaccessible during normal unit operation. These tasks aim to ensure that Unit 3 continues to generate power safely and reliably for years to come.

According to the plan, after the relevant inspections and repair interventions are completed, the operator will reload most of the original fuel assemblies back into the reactor, while also adding new fuel assemblies, in preparation for the unit to enter its next operating cycle.

This outage for Unit 3 is one of the technically more challenging refueling outages in recent years. In addition to the routine partial refueling and comprehensive inspections, the outage scope also includes an update of the residual heat cooling system, cleaning of another steam generator, modernization of electrical protection devices in safety-related switchgear, replacement of aging cables, modification of the long-term residual heat removal system, and the decennial major overhaul of the diesel generators.

The scale of this outage is also somewhat unique. In August, the neighboring Unit 4 will also be shut down for about one month to allow for maintenance on systems shared by both units. According to current arrangements, the next similar-scale synchronized refueling outage for both units at Dukovany Nuclear Power Plant is not expected until 2032.

Bohdan Zronek, Member of the Board of Directors of ČEZ Group and Head of the Nuclear Energy Division, stated that this year's outage for Unit 3 not only involves a large workload but also requires coordination with the synchronized shutdown arrangement of Unit 4. Planned maintenance, inspections, and equipment modernization are part of Dukovany Nuclear Power Plant's efforts to promote safe and reliable unit operation for up to 80 years.

In recent years, nuclear power plants under the ČEZ Group have gradually extended their refueling cycles. Since 2024, Dukovany Nuclear Power Plant has extended its refueling cycle to 16 months, meaning the unit operates for about 14 months before a refueling outage that lasts over a month. The Temelín Nuclear Power Plant will also complete its refueling cycle extension this year, with the adjusted cycle being 18 months, i.e., operating for about 16 months and shutting down for about two months. Currently, Unit 2 of the Temelín Nuclear Power Plant is operating under this model, and Unit 1 is scheduled to enter the final phase of implementing the longer refueling cycle this autumn. These adjustments aim to increase total electricity generation, utilize nuclear fuel more efficiently, and reduce the technical load on equipment through stable operating parameters.