Under the Nuclear Safety Directive, a topical peer review (TPR) is an EU-wide review conducted by experts from Member States on a selected nuclear safety topic. Its purpose is to share experience, identify best practices and common challenges, and recommend follow-up actions to address any weaknesses.
TPRs enable EU and other participating countries to collaboratively examine a technically significant aspect of nuclear safety that is currently relevant. These reviews, held at least every six years, promote continuous improvement in nuclear safety through cooperation among regulatory authorities and licensees across different countries. The process draws on the approach used for the nuclear stress tests conducted after the Fukushima accident in Japan in 2011. It is designed to be transparent and structured in three phases: national assessments, peer review, and follow-up implementation.
The first TPR (2016-2018) focused on ‘ageing management of nuclear reactors’, while the second TPR (2021-2025) addressed ‘fire-protection at nuclear installations’. Discussions on the topic of the third TPR (2027-2031) are now underway.
A key feature of TPRs is their transparency and openness towards stakeholders at both European and international levels. Stakeholder meetings are held, and participants have the opportunity to comment on process documents and submit written questions to countries regarding the information in their national reports.
ENSREG has a subgroup dedicated to the Topical Peer Reviews. Find more information on the group here.
Topical peer reviews I and II
TPR I: Ageing Management of Nuclear Power Plants and Research Reactors (2016-2018)
The first topical peer review (TPR I), conducted between 2016 and 2018, focused on ageing management in nuclear power plants and research reactors. This review was the most significant safety-related exercise after the post-Fukushima stress tests in Europe. It involved 19 participating countries (16 EU member states, plus Norway, Ukraine, and Switzerland).
Why Ageing Management?
The topic was selected due to the ageing profile of European nuclear power plants and the potential for long-term operation. ENSREG led the review, with technical support from the Western European Nuclear Regulators’ Association (WENRA).
TPR I Review process
The structured assessment included:
- National assessment reports – Drafted by nuclear safety regulators based on licensees’ self-assessments.
- Desktop peer review – Conducted by nominated experts from participating countries.
- Stakeholder engagement – Over 2 300 questions submitted by peer reviewers, experts and civil society.
- One-week workshop (May 2018) – Attended by ~140 experts, to discuss findings, questions and responses.
Outcomes and Follow-Up
In October 2018, ENSREG approved the final report on the review and country specific findings (Press release). National action plans were then developed to address the results. The entire review process was conducted with full transparency, ensuring open access to documentation and active stakeholder engagement throughout.
Key Challenges Identified
The review highlighted four major challenges where European-level action could enhance ageing management:
- Overall ageing management programmes
- Concealed pipework
- Reactor pressure vessels
- Concrete containment structures
National Action Plan Measures
Participating countries committed to measures such as:
- Formalising ageing management definitions for research reactors.
- Updating in-service inspections of civil structures in line with international standards.
- Enhancing monitoring, testing, and inspections for concealed pipework.
- Ensuring cable performance under extreme accident conditions.
- Defining performance indicators for ageing management.
- Applying ageing management practices to new constructions.
TPR II: Fire Protection at Nuclear Installations (2021-2025)
The second Topical Peer Review (TPR II), again led by ENSREG with WENRA’s technical support, focused on fire protection. 22 countries participated (18 EU member states, plus Switzerland, Türkiye, Ukraine and the UK).
TPR II Review Process
The review followed a structured approach:
- National Assessment Reports – Based on licensees’ self-assessments.
- Desktop peer review and site visits – Conducted by experts, including inspections of selected research reactors.
- Stakeholder engagement – Questions and comments phase.
- Two workshops –To discuss thematic findings, responses, and country reviews.
Why Fire Protection?
Fire was chosen as a priority topic because:
• It poses a significant risk to nuclear installations.
• There is extensive experience with fire-related incidents.
• Practical improvements are feasible.
• It is a technologically neutral field.
• It had not been covered in previous post-Fukushima assessments.
Key Challenges Identified
The review identified:
- Three EU-level challenges and four good practices,
- 54 areas for improvement and 38 examples of good performance at the national level.
Participating countries are actively addressing these challenges and areas for improvement.
Main findings
The primary focus areas include:
• Use of operational experience feedback,
• Management of fire loads and ignition sources,
• Methodologies for fire safety analysis,
• Strategies for fire detector installation and failure management.
For further details, see the Final report and country reviews.