Regulator approves resumption of construction at Paks II nuclear power plant after January incident

Hungary’s nuclear regulator (HAEA) has issued a permit to resume construction activities across the entire excavation site for the planned first unit of the Paks II nuclear power plant. Work was suspended following an incident on 30 January 2025, when two unstable corners of the retaining walls gave way in the southern part of the excavation.

Immediately after the incident, HAEA prohibited Paks II from continuing work on the affected southern wall and ordered a thorough review of the stability of all the excavation walls. The authority also required the company to describe in detail the methods and measures intended to prevent similar situations that could endanger workers’ safety.

Review of the excavation site

According to HAEA, Paks II inspected the condition of all the excavation walls, which have a perimeter of more than 700 metres, and identified potentially hazardous areas. Damaged and unstable sections where blocks could become detached and subsequently collapse were removed.

Based on the submitted documentation and an on-site inspection, HAEA lifted the ban on construction work, on condition that protective netting is installed on the affected sections of the excavation’s internal walls. During further work, the movement of the groundwater level, the excavation walls and nearby structures must be monitored continuously.

The regulator also required the intervention and warning thresholds of the monitoring system to be revised, so that any future movements can be predicted more accurately and preventive measures taken in time. Further activities, such as starting concrete pouring, may proceed only after all conditions and hold points set out in subsequent HAEA permits have been met. The authority is also separately assessing whether the measures taken to stabilise the soil in the excavation are adequate.

Concrete pouring to be delayed

Concrete pouring was originally scheduled to begin this year. However, in a recent statement to Russian news agency RIA Novosti, Hungary’s Minister of Foreign Affairs and Trade Péter Szijjártó said that, given the “unhealthy political circumstances in the world”, next year now appears more likely.

The Paks nuclear power plant, located approximately 100 kilometres south of Budapest, currently operates four VVER-440 pressurised water reactors commissioned between 1982 and 1987. Under an intergovernmental agreement signed in 2014, the plant is to be expanded with two new units equipped with VVER-1200 reactors. Up to 80% of the project’s financing is covered by a Russian state loan of up to 10 billion euros (approximately CZK 248 billion).

The application for a construction permit was submitted in July 2020, and the permit itself was issued in August 2022. Paks received the permit for concrete pouring in November 2024. The new units are scheduled to be connected to the grid in the early 2030s.