Czech utility ČEZ is to invest CZK3.8bn ($181m) billion this year to upgrade the Temelín NPP and CZK 4bn for modernisation work at the Dukovany NPP. Two VVER-1000 units are in operation at Temelín, which began operation in 2000 and 2002. Four VVER-440 units are currently in operation at the Dukovany site, which began operating between 1985 and 1987.
At Temelín, where ČEZ has already invested almost CZK38bn, work planned for this year includes completing the transition to a longer fuel cycle, continuing to modernise the control system and expanding the use of artificial intelligence and modern control methods.
Energy engineers have been gradually switching Temelín to a longer fuel cycle since 2023. In the spring, unit 2 will switch to 16-month operation between shutdowns, and in autumn unit 1 will also switch. “This is a very important step in terms of the efficiency of the power plant’s operation. Of course, the transition was preceded by a rigorous security assessment,” said Bohdan Zronek, ČEZ Board member and Director of the nuclear energy division.
“Thanks to the extension of the fuel cycle, we will reduce the pumping life of the unit because of fewer shutdowns, and therefore reduce cooling and heating of the units. We will also get increased production of almost 2 TWh a year for both NPPs. The year before last, we completed the transition to a longer fuel campaign in Dukovany,” Zronek noted. According to ČEZ management, a longer fuel campaign will further increase safety and efficiency and will create the conditions for the long-term operation of all Czech nuclear units.
Temelín will continue to transition to a new control system supplied by Westinghouse. Since last year, part of the new control system has been introduced at unit 1. In the first months of this year, the same adjustment will also take place at unit 2. The modernisation, which began three years ago, will end in 2029. “The transition is gradual, it takes place during shutdowns. Since last year, operators have been working with the new system, which also controls approximately a third of the equipment at unit 1. Art unit 2, the transition will take place essentially in the same way,” said Temelín NPP Director Petr Měšťan.
In the autumn, workers will transfer another part of the unit 1 equipment to the control of a new system. In addition to controlling circulation cooling water pumps or cooling used fuel pools, the new system will also control most technological systems in the nuclear part of the power plant, such as main circulation pumps, primary circuit replenishment and discharge systems and a number of air handling systems.
This modernisation has been underway since 2022 during which time technicians installed dozens of new servers, laid 80 kilometres of mostly optical cables, made modifications to the control room and replaced the process units of the control boxes. The deployment was preceded by several months of testing. In total, the system controls thousands of devices and it can deal with tens of thousands of pieces of information in one second.
The use of artificial intelligence (AI) and introduction of modern control methods is also underway. For two years, the plant has been using AI to reduce its own consumption. Thanks to AI, units save a thousand MWh of electricity every year. In 2026, the plant will further strengthen the role of AI. It is now deploying advanced AI models for working with documentation. This includes thousands of projects, security or operational documents. “Data represents corporate gold. There is a huge amount in the environment of a nuclear power plant,” said Měšťan. “At both power plants there is a total of 12 kilometres of archive shelves. AI can make working with this data a lot more efficient for us. We already use it to work with documentation texts, we gradually want to extend it to images, drawings and diagrams.”
At both nuclear power plants, ČEZ continues to use drones for inspections of difficult-to-access technology and the introduction of the most modern repair methods, such as laser cleaning and welding, advanced methods of applying metal material (coldspray) and modern pipe route renewal technologies. These procedures reduce intervention time and reduce the need for downtime.
This year, Temelín is facing two shutdowns. First, in mid-February, workers will shut down the unit 2 for two months. In mid-October, the unit 1 will also suspend operations for approximately the same period. These are standard shutdowns for fuel changes, inspections and various upgrades. Temelín will complete the transition to a longer fuel cycle during these outages. Experts will place 66 new fuel assemblies into the reactors at both units, and will place seven containers with 133 used assemblies in the warehouse.
ČEZ also plans to accept almost 100 new staff at Temelín – people with technical experience and education including mainly machinists, electricians and engineers, but non-technical graduates will also find employment. Temelín currently employs 1,552 people.
At Dukovany, ČEZ wants to start a large-scale project to modernise engine rooms this year. A number of investment actions related to turbines, pumps and other key equipment aim to ensure the long-term operation of the power plant and potentially to further slightly increase its performance.
ČEZ said the investment is needed as some low-pressure parts of the turbogenerator are reaching the end of their life as the NPP is preparing to supply a hot water pipeline to Brno as part of a district heating project. In addition to steam turbine upgrades, the focus will be on generators, steam separators, low- and high-pressure regeneration systems, as well as condensers and equipment used to transfer electrical power.
The upgrades will be carried out gradually during planned maintenance outages and are expected to result in a small increase in output due to increased efficiency.
“The project involves a series of investment actions that we must coordinate so that the renovation of the facility not only makes sense technically, but also brings an additional effect in the form of savings or increased production,” said Zronek. He added that the plant was also investing in modern maintenance, diagnostic and control methods and technologies to help optimise costs and limit downtime.
In addition to the renewal of classic technology, Dukovany also continues to introduce modern maintenance, diagnostic and control methods and technologies. These ensure higher quality and make it possible to shorten the time of work, optimising costs. “We want to make full use of, for example, new welding methods, anti-corrosion protection of equipment, but also drones and elements of artificial intelligence. At the same time, we will continue to systematically digitise those activities where it makes sense,” Zronek noted.
“Calculations and analyses of individual devices and circuits are currently underway,” said Dukovany Director Roman Havlin. “We expect the final technical and economic evaluation of the entire project at the end of this year. Although some preliminary results look promising, it is essential to assess everything in a broader context and as a whole. According to assumptions, the modernisation of the engine room equipment could bring an increase in the unit’s electrical output by up to several megawatts.”
Dukovany has experienced an almost complete “generational change” according to ČEZ, with the majority of those who worked at the plant when it was launched in 1985 now retired. This had brought down the average age at the plant to 42 years.
