ENERGY SAFETY GROUP DISCUSSES KEY SAFETY CHALLENGES AT AN INTERNATIONAL CONFERENCE IN KHARKIV

On April 15–17, 2026, the 3rd The V.M. Voevodin International Scientific and Technical Conference «Problems of modern nuclear energy» was held in Kharkiv. The event brought together the scientific community, energy company representatives, and relevant institutions to discuss key challenges facing the industry’s development. The event took place at the «YermilovCentre» Center for Contemporary Art of V. N. Karazin Kharkiv National University, as well as in online sessions.

The conference was organised by the Ukrainian Nuclear Society, the National Science Center «Kharkiv Institute of Physics and Technology», and V.N. Karazin Kharkiv National University, with the support of JSC «NNEGC «Energoatom» and the Kharkiv Regional Military Administration. Over the course of three days, the conference program addressed issues related to the development of Ukraine’s nuclear energy sector, improving the safety and operational efficiency of nuclear power plants, managing radioactive waste and spent nuclear fuel, and the latest scientific research in the field.

Energy Safety Group, which also served as a partner for the event and is an active member of the UkrNS NGO participated in the conference as an active contributor to the professional discussion, presenting its own research in the fields of probabilistic safety analysis, the implementation of hydrogen technologies, and the analysis of severe accidents at nuclear power plants. The company’s young specialists presented research results that could potentially be applied at operating nuclear power plants.

In particular, Vladyslav Moroziuk, an engineer in the thermal-hydraulic analysis group, presented a study on the impact of modifications to core melt propagation models on the containment system’s behaviour during a severe accident. The presentation showcased the results of an updated model for the MELCOR code, which accounts for the transfer of molten core chemical composition between rooms, changes in melting temperatures due to interactions with concrete, and scenarios involving jamming of the reactor shaft containment doors during the off-vessel phase of a severe accident.

The results of calculations for scenarios involving a complete power loss with operator intervention confirmed that the pressure relief system is sufficient to maintain parameters within design limits; however, they also revealed a critical dependence of the accident progression on the conditions of molten core cooling in the reactor shaft. Separately, it was demonstrated that the condition of the sealed doors significantly affects the spread of the molten core: if they become jammed, localized melting of the concrete occurs, followed by the spread of the molten core. Based on the study results, the need for additional analysis of the molten material layer thickness and consideration of engineering solutions, in particular the use of sacrificial or refractory materials, was emphasized.

Denys Havlichuk, a senior engineer in the probabilistic analysis group, focused his presentation on approaches to modelling the initiating event «transverse rupture of the reactor vessel» within the framework of probabilistic safety analysis for VVER-1000 power units. He pointed out that the traditional approach to assessing this event remains overly conservative: by default, calculations assume that such a scenario immediately leads to severe damage to the core, without a detailed analysis of possible outcomes.

At the same time, according to Denis, as risks under other scenarios decrease following the implementation of safety enhancement measures, a reactor vessel rupture takes on significantly greater weight in the overall risk profile and may become one of the dominant factors. It was also emphasised that the use of outdated approaches and data when assessing this event could lead to a formal exceeding of current safety criteria for new power units. In this context, the need to review approaches, conduct an in-depth analysis of international experience and reduce excessive conservatism was highlighted in order to improve the quality and objectivity of probabilistic safety analysis.

Anna Topal, an engineer in the R&D group, presented the results of a study on the impact of a potential hydrogen station’s operation on the probabilistic safety indicators of Power Unit No. 2 at the Khmelnitsky NPP. The study identified key impact scenarios for the power unit; in particular, using the HAZID methodology, the most critical scenario was identified—an explosion in the buffer tank of the hydrogen station, which could lead to damage to the outdoor switchgear and a loss of power supply, effectively triggering the initial accident event.

To assess the consequences, this scenario was integrated into a probabilistic model of the power unit, taking into account the specific nature of the impact, particularly the absence of damage to the spray pools, which distinguishes it from other external events. The results showed that even under conservative assumptions, the impact on the overall safety level is minimal and does not lead to exceeding regulatory criteria. At the same time, it was emphasized that further refinement of the models is necessary to reduce conservatism and transition to a more realistic risk assessment.

In addition to participating in the scientific program, the Energy Safety Group also contributed to shaping the content of the professional discussions held during the conference. The company’s CTO, Oleksandr Mazurok, moderated two key thematic panels: «Development of Ukraine’s Nuclear Energy Sector» and «Improving the Safety and Operational Efficiency of NPP`s». It is precisely these areas that today define both the strategic role of nuclear energy in restoring the power system and practical approaches to ensuring its resilience in the face of new risks.

During these sessions, participants discussed the development of new technologies, the modernization of existing power units, the implementation of modern safety standards, and the integration of the Ukrainian sector into the European energy space. Speakers included representatives from research institutions, JSC «NNEGC «Energoatom», specialized enterprises, and international cooperation programs, ensuring a combination of applied and scientific approaches to addressing industry challenges.

«Today, safety in the nuclear energy sector is not just about compliance with regulatory requirements, but about the ability to systematically manage risks, uncertainties, and scenarios that go beyond design conditions. Conferences like this create an environment where this expertise comes together and transforms into practical solutions», noted Oleksandr Mazurok, CTO of Energy Safety Group.

Energy Safety Group continues to actively engage with professional platforms that shape the nuclear energy development agenda, combining engineering practice, analytical expertise, and participation in international dialogue on the safety and resilience of energy systems.