JEK2: cooling with natural convection, favorite, 274 kilometers of logistical challenge and electricity price from 65 to 103 EUR/MWh

As part of preparing extensive documentation and analyses preceding the announced referendum on the new nuclear block in Slovenia (JEK2), the GEN energija company has published new feasibility studies. The documents provide the most detailed insight so far into cooling options, the complex transport logistics, and the financial structure of the project whose investment decision is expected between 2028 and 2029.

A 200-meter cooling tower: The answer to climate change

The feasibility study, prepared by the engineering firm John Cockerill Hamon, analyzed four cooling options. As the optimal solution, a natural convection tower was selected, with a height between 193 and 198 meters (depending on the chosen reactor type).

The key advantages of natural convection are reliability, minimal consumption of its own electrical power (since there are no fans to generate airflow) and lower maintenance requirements. As the only acceptable alternative, a combined system with two smaller towers (75–80 meters) was identified, but with significantly higher operating costs.

The design company emphasizes that the impacts of climate change are directly accounted for in these studies, and that the final choice will undergo further technical verification and spatial planning to ensure that the solution is socially acceptable.

Transport venture: 274 kilometers and 112 route modifications

The preliminary transport study analyzed eight potential routes from sea and river ports to Krško for transporting heavy and bulky components. The most favorable option chosen was a road route 274 kilometers long, which runs from the Port of Koper, via Ljubljana and Celje, to Krško.

To enable heavy equipment to pass along this route, construction and infrastructural interventions will be necessary at as many as 112 locations (widening of road shoulders, raising vertical profiles, and strengthening bridges). The final transport study is planned to be completed by the end of 2028.

Financial frameworks: From 9.8 to 15.4 billion euros

Estimated construction costs (overnight costs, at 2024 prices) amount to:

• €9.8 billion for a 1,000-megawatt power block (reactor candidates Westinghouse AP1000 or EDF EPR1200).
• €15.4 billion for a stronger 1,650-megawatt block (EDF’s standard EPR).

When financing costs are included, the estimated average price of electricity that guarantees a return on investment is 65 euros per megawatt-hour (€/MWh) with a real weighted average cost of capital (WACC) of 2%, or 103 euros per MWh if the WACC is 4%.

Analytical commentary by Nuclear Perspective: data decisive for the entire region

The JEK2 project represents one of the central strategic cases that Nuclear Perspective continually follows, because the preparation process in Slovenia serves as a model example of political-economic and technical transparency for all countries in the region considering nuclear energy.

The decision to prioritize cooling towers with natural convection directly confirms the theses we have written about on our portal throughout the summer. Extreme heat waves and reduced river flows — as we observed on the Danube and Sava — have shown that the concept of direct through-flow cooling with river water has become a bottleneck for grid stability under climate change conditions. The transition to closed cooling systems with taller towers is no longer an aesthetic or peripheral issue, but a fundamental condition for the plant's operational availability and energy sovereignty during its 60 to 80-year operating life.

Equally important is transparency regarding the price of electricity: the range from 65 to 103 euros per megawatt-hour clearly shows how much the cost of capital (WACC) matters more than the price of equipment itself. For regional decision-makers, this is a lesson that nuclear projects should not be contracted through closed memoranda, but through precise modeling of financial risks and public technical verification as Slovenia is currently demonstrating.

S.A.