UK Joins Global Nuclear Liability Convention, Boosting Safety and Climate Goals

The United Kingdom has formally joined the Convention on Supplementary Compensation for Nuclear Damage (CSC), marking a major milestone in international efforts to strengthen the global nuclear liability regime. The UK deposited its instrument of accession on 3 October 2025, becoming the 12th Contracting Party to the CSC. The convention will officially enter into force for the UK on 1 January 2026.

This landmark step enhances the international framework governing nuclear safety, compensation, and accountability—reinforcing the role of nuclear power as a reliable contributor to clean energy, economic growth, and climate change mitigation.

Strengthening Global Nuclear Cooperation

The CSC, adopted under the auspices of the International Atomic Energy Agency (IAEA) on 12 September 1997 and entering into force in April 2015, provides a uniform legal structure to ensure prompt and adequate compensation for damage caused by nuclear incidents. It covers harm to people, property, and the environment, ensuring fair and non-discriminatory treatment across borders.

By joining the CSC, the UK not only aligns with international standards of nuclear liability but also bridges existing regional frameworks, particularly between the Paris and Vienna Conventions. This development is seen as a breakthrough toward creating a single, global system that ensures financial protection in the event of nuclear accidents.

IAEA Director General Rafael Mariano Grossi hailed the decision as a historic moment:

“As the first Party to the Paris Convention to join the CSC, the UK’s accession establishes—for the first time—treaty relations across both the Paris and Vienna regimes and States belonging to neither. This is an important step towards achieving a truly global nuclear liability regime.”

The CSC: An ‘Umbrella’ Framework for Nuclear Accountability

The CSC operates as an “umbrella” instrument that can be joined by States adhering to existing conventions—such as the 1963 and 1997 Vienna Conventions on Civil Liability for Nuclear Damage or the Paris Convention on Third Party Liability in the Field of Nuclear Energy—as well as States that are not part of any of these agreements but whose national laws comply with CSC provisions.

One of the CSC’s key features is the establishment of a supplementary international fund. In the event of a nuclear incident, this fund provides additional compensation beyond national levels, supported by contributions from all Contracting Parties. This system ensures broader coverage and international solidarity in the aftermath of nuclear accidents.

Expanding Coverage of Global Nuclear Reactors

When the UK’s membership takes effect in 2026, the CSC will cover approximately 190 nuclear power reactors, or about 45% of all operational reactors worldwide. This expansion significantly enhances the treaty’s global reach and reinforces nuclear safety as a shared international responsibility.

Currently, the CSC has 11 Parties — Argentina, Benin, Canada, Ghana, India, Japan, Montenegro, Morocco, Romania, the United Arab Emirates, and the United States — and 11 Signatories, including Australia, Italy, Czech Republic, and Indonesia. The UK’s entry marks the first accession by a state already party to the Paris Convention, setting an important precedent for other European countries to follow.

The IAEA’s online CSC Calculator allows countries to model potential contributions to the fund, reflecting transparency and predictability in how the financial burden would be shared internationally.

A Decade-Long Global Effort

For more than ten years, the IAEA’s General Conference has called on Member States to join international nuclear liability agreements to establish a truly global system of legal and financial protection. The UK’s accession fulfills one of the IAEA’s long-standing objectives—to unite different legal regimes under a shared framework ensuring compensation for nuclear damage worldwide.

The CSC Parties and Signatories continue to coordinate through annual meetings, with the Fifth Meeting of the CSC Parties held in Vienna from 23–26 June 2025, where discussions focused on harmonizing liability practices and strengthening the operational aspects of the CSC fund.

Supporting Climate and Energy Security Goals

The UK’s participation also underscores the growing recognition of nuclear power’s role in achieving net-zero emissions and enhancing energy security. As the world faces escalating energy demand and climate challenges, nuclear power is increasingly viewed as a low-carbon, stable, and scalable energy source.

By bolstering legal certainty around nuclear liability and compensation, the UK’s move aims to build public trust and attract investment in the next generation of nuclear technologies, including Small Modular Reactors (SMRs) and advanced fusion research.

A Step Toward a Safer Nuclear Future

The UK’s accession to the CSC represents a major advancement in global nuclear governance. It aligns national and international legal frameworks to ensure that, in the unlikely event of a nuclear accident, affected communities and ecosystems receive swift and fair compensation.

As Director General Grossi emphasized, this step brings the world closer to a universal standard for nuclear responsibility — one that safeguards people, the planet, and the promise of clean, sustainable energy for future generations.