COMMENTARY: Zaporizhzhia Nuclear — The 750 kV Line Repaired but Unusable, the Danger Persists

COMMENTARY: Zaporizhzhia Nuclear — The 750 kV Line Repaired but Unusable, the Danger Persists

Introduction: A nuclear power plant on a single power thread

A permanent risk scenario since March 2026

Since March 24, 2026, the largest nuclear power plant in Europe — the Zaporizhzhia Nuclear Power Plant (ZNPP), occupied by Russia since March 2022 — has been receiving its external electricity supply from a single backup line: the 330 kV Ferosplavna-1 line. The main line that should power it — the 750 kV Dniprovska line — has recently been technically repaired but still cannot be returned to service. The reason: a substation located more than 100 kilometres to the northwest of the plant sustained damage so severe during military operations in May 2026 that experts from the International Atomic Energy Agency (IAEA), who visited the site, observed near-total destruction of its essential equipment.

This situation — a 6-reactor nuclear power plant, the most important on the continent, powered by a single backup line in an active war zone — is one of the most alarming nuclear risk situations in modern history. It unfolds in silence, far from the headlines covering the latest drone strikes or diplomatic negotiations. Yet if that backup line were severed, the ZNPP would be forced to switch to its emergency diesel generators — a situation already experienced seven times since the invasion began. A single accident, a single failure, and we are talking about a major nuclear incident in the heart of Europe.

The local ceasefire and IAEA repairs

The extraordinary logistical complexity of what the IAEA managed to organize must be acknowledged. Repairs to the 750 kV Dniprovska line required a local ceasefire negotiated by the UN agency along the front line — a front line running precisely through the infrastructure zone to be repaired. Demining teams had to secure corridors to allow technicians access to damaged pylons and cables. All of this, in a zone where every night brings its share of drone strikes and artillery shells. IAEA Director General Rafael Mariano Grossi confirmed the state of the work and the substation's condition in official communications.

The geography of risk: why the substation is critical

A broken power chain over 100 km away

To understand why the repaired 750 kV line cannot be returned to service, you need to understand the geography of the power grid. A 750-kilovolt line does not operate in isolation: it must be connected to transformation substations at both ends, capable of handling voltage levels and distributing energy to the local grid. The damaged substation — located more than 100 kilometres to the northwest of the ZNPP — is precisely the missing link. Without it, even if the main line's cables are intact, electricity cannot flow. It is like having a perfectly repaired pipe with a broken tap at one end.

IAEA experts who visited the substation found severe damage to essential equipment — transformers, circuit breakers, control systems. This type of high-voltage equipment is extremely difficult to replace quickly: manufacturing and delivery lead times are measured in months, and parts available in Ukrainian stockpiles are virtually nonexistent after four years of war and hundreds of strikes on the national power grid.

The 330 kV line: a safety net, not a solution

The 330 kV Ferosplavna-1 backup line currently powering the ZNPP is designed as an emergency backup — not as a permanent main supply. It offers lower power transmission capacity than the main 750 kV line, and is therefore less robust against load fluctuations. More importantly, it represents a single point of failure: if this one line were to be damaged — by a strike, a technical fault, or extreme weather — the plant would have no external power supply at all.

The context of Russian occupation of the ZNPP

Four years of occupation unprecedented in nuclear history

The Zaporizhzhia Nuclear Power Plant has been occupied by Russian armed forces since early March 2022 — a situation without precedent in the history of nuclear energy worldwide. No civilian nuclear power plant had ever been militarily occupied before. The plant's 6 reactors have been shut down since autumn 2022, but reactors in cold shutdown still require external power supply to maintain the cooling of spent fuel — a failure of that cooling potentially leading to partial core meltdown and radioactive releases.

Since 2022, the ZNPP has lost its external power supply connection seven times, forcing the use of emergency diesel generators. Each of those episodes put the nerves of the global nuclear community on edge. An eighth episode — or a more prolonged one if diesel reserves ran out — would represent a catastrophic risk for Ukraine and for all of Europe.

Russia: legally and practically responsible for safety conditions

It is essential to state who is responsible for nuclear safety at the ZNPP under current conditions. Russian forces occupying the plant are legally responsible for its safety under international humanitarian law and nuclear safety conventions. Every time safety conditions at the ZNPP deteriorate — whether power outages, infrastructure destruction, or security incidents — primary responsibility rests with Russia, which illegally occupies this site.

The implications for regional security

A nuclear incident: consequences at European scale

In the event of a prolonged total loss of external power and depletion of diesel reserves, a nuclear incident at the ZNPP would have consequences reaching far beyond Ukrainian borders. Atmospheric dispersion models show that significant radioactive releases could reach Poland, Romania, Moldova, Hungary, and potentially more distant areas depending on weather conditions. All of Europe is therefore indirectly affected by ZNPP safety — which justifies the IAEA's engagement and the ongoing diplomatic pressure on Russia to guarantee minimum safety conditions.

The permanent IAEA delegation maintained on-site since September 2022 is a crucial element of monitoring and early warning. Its continued presence, despite war conditions and security incidents, represents a remarkable commitment by the agency and its Director General Grossi.

The local ceasefire: a fragile diplomatic innovation

The local ceasefire mediated by the IAEA around the ZNPP and along the repair line is a fragile diplomatic construction. It enabled repairs to the 750 kV line — but the damaged substation remains a major obstacle. The durability of this ceasefire in a context of active fighting is uncertain. If the parties resume strikes in the protected zone — intentionally or accidentally — the plant's safety conditions could deteriorate sharply.

The current situation: risk maintained but not immediate

The six reactors in cold shutdown

The current technical situation at the ZNPP must be described accurately to properly contextualize the risk. The plant's 6 reactors have been shut down since late 2022 — in what is called "cold shutdown." In this state, the reactors are not producing electricity and are not undergoing nuclear fission. However, they continue to generate residual heat from the decay of fission products accumulated in the spent fuel. This residual decay heat must be maintained indefinitely — for months, even years — to prevent fuel meltdown and radioactive releases.

It is precisely for this cooling that the external power supply is indispensable. Cooling pumps, control systems, safety lighting — all of this requires a stable, continuous power supply. The Ferosplavna-1 backup line currently provides this supply, but with a reduced safety margin.

Ongoing repairs and an uncertain timeline

Repairs to the damaged substation — a prerequisite for returning the 750 kV line to service — are not expected "in the near future," in the IAEA's words. This means the ZNPP will remain dependent on its single backup line for an indefinite period. The ongoing deterioration of the plant's safety conditions — in a context where the war shows no signs of abating — keeps the risk level at an unacceptably high level for a nuclear installation.

The IAEA between monitoring and powerlessness

Grossi's impossible mission

IAEA Director General Rafael Mariano Grossi is in an extraordinarily difficult position. His agency is responsible for monitoring global nuclear safety — but has no means of compelling Russia, a nuclear power and permanent member of the UN Security Council, to comply with safety standards. His repeated calls for a "nuclear safety perimeter" around the ZNPP, his risky field missions, and his alarm communiqués have received no coercive response from the international community.

What Grossi has achieved — maintaining a permanent on-site presence, negotiating local ceasefires, securing access for repairs — is considerable under the circumstances. But it is insufficient to guarantee real nuclear safety as long as Russia militarily occupies the plant.

Minimum requirements for real nuclear safety

International nuclear experts agree on the minimum conditions for genuine ZNPP safety: the withdrawal of armed forces from the plant, the restoration of Ukrainian or international civilian control, and the repair of the entire power supply grid. None of these conditions are currently met. Short of that, the two absolute minimum conditions are: maintaining external power supply on at least one functioning line, and keeping diesel reserves at a level sufficient to cover several weeks without external supply.

Historical precedents and nuclear doctrine in conflict zones

Situations without equivalent in nuclear history

The situation at the Zaporizhzhia Nuclear Power Plant is without precedent in the history of civilian nuclear power. Never before had an installation of this scale — six reactors, the largest plant in Europe — been militarily occupied by a foreign power in an active state of war. The international agreements governing the protection of nuclear sites — notably the Geneva Conventions and the 1977 Additional Protocols — simply had not anticipated this scenario.

The IAEA found itself in a paradoxical position: its inspection teams have maintained a permanent presence on-site since September 2022, but their capacity for action is limited to monitoring and reporting. They can neither order the Russian army to leave, nor physically guarantee the safety of operations. Their regular reports document a troubling situation — insufficient staff, degraded safety equipment, psychological pressure on Ukrainian engineers forced to work under occupation — but the mechanisms to remedy the situation are absent.

Russia and nuclear risk as a pressure tool

Several experts and military analysts have advanced the hypothesis that Russia is deliberately using the implicit nuclear threat its presence at Zaporizhzhia represents as a geopolitical pressure tool. By maintaining permanent uncertainty around the plant, the Kremlin creates a zone of restraint — a space where Western allies and Ukraine itself hesitate to intensify certain types of military operations out of fear of a nuclear incident for which they could be held responsible.

This strategy of indirect nuclear blackmail is characteristic of Russia's approach throughout this conflict: using the fear of escalation to maintain a tactical asymmetry. The international community must recognize this manipulation for what it is and develop responses that do not reward this type of behaviour. The ultimate solution remains the same: a complete Russian withdrawal from all occupied Ukrainian territories, including the Zaporizhzhia plant.

Crisis-exit scenarios and security guarantees

Russian withdrawal: the only lasting solution

Nuclear safety specialists are unanimous: the only solution guaranteeing the long-term security of the ZNPP is the withdrawal of Russian military forces and the restoration of Ukrainian control over the installation. All other solutions — enhanced international observer presence, bilateral guarantees, buffer security zones — are stopgaps that do not resolve the fundamental problem of the military occupation of a civilian nuclear site.

In a ceasefire or negotiated settlement scenario, the question of the ZNPP will need to be addressed as an absolute top priority, before even the discussion of territorial borders. The plant's safety represents an interest that is not only Ukrainian but European and global — the fallout from a serious accident would respect no political border.

The international community facing its obligations

Signatories to the Nuclear Non-Proliferation Treaty (NPT), permanent members of the UN Security Council, member states of the IAEA — all have a moral and legal obligation to apply maximum pressure on Russia to restore normal safety conditions at Zaporizhzhia. Economic sanctions, exclusions from international bodies, bilateral diplomatic pressure — all these levers must be applied with intensity proportional to the risk this situation poses.

Inaction is not a neutral choice — it is a decision that implicitly validates Russia's strategy of taking civilian nuclear infrastructure hostage. If this precedent is left without adequate response, it opens the door to similar behaviour in future conflicts, with potentially catastrophic consequences for global nuclear security.

Conclusion: nuclear emergency in a distracted world

The normalization of risk is itself a danger

One of the most disturbing aspects of the ZNPP situation is the progressive normalization of the risk in public and media perception. Each incident — each loss of external power, each activation of diesel generators, each alarming IAEA report — generates less reaction than the previous one. This normalization of nuclear danger is itself a risk: it reduces political pressure on Russia to improve safety conditions, and it diminishes international vigilance at the precise moment when the technical situation is deteriorating.

The repaired 750 kV line, blocked: symbol of an impasse

The 750 kV line, repaired but unusable, waiting for impossible repairs on a substation damaged in an active war zone, is a perfect symbol of the impasse in ZNPP nuclear safety management. Technical solutions exist. Financial resources could be mobilized. But the constraint is neither technical nor financial — it is geopolitical and military. As long as Russia occupies the plant and the war continues, the ZNPP will remain the most dangerous nuclear time bomb in Europe.

By Maxime Marquette, columnist

Columnist's transparency note

My position and my sources

I cover the ZNPP situation from a pro-Ukraine perspective that recognizes the Russian occupation of the plant as both illegal and dangerous. Technical data and information on repairs come from official IAEA communications and Ukrainska Pravda. I am not a nuclear engineer, and my risk analysis is grounded in assessments published by recognized experts.

What I do not know

The actual state of the damaged substation's equipment — beyond the description "severely damaged" — is not directly accessible to me. The ongoing negotiations between the IAEA and the parties to organize the substation repairs are not public in their details. I base my analysis on information available in official reports and specialist media.

Sources

Primary sources

Ukrainska Pravda — Key power line at Zaporizhzhia Nuclear Power Plant repaired but cannot currently be put back into operation — June 26, 2026

The Guardian — Ukraine war briefing: Ballistic missile attack in Kyiv forces residents into shelters — June 28, 2026

Secondary sources

Euromaidan Press — Russia has hit Ukraine's energy system 6,000 times. Allies pledge €375 million in Gdańsk — June 25, 2026

Kyiv Independent — Ukraine faces possible daily 5-hour power cuts in July–August — June 25, 2026

The Guardian — Russian-occupied Crimea declares emergency as Zelenskyy's forces step up attacks — June 27, 2026

Euromaidan Press — Russo-Ukrainian war, day 1583: Russia bombs Ukraine's grain ports — June 26, 2026