Written evidence submitted by the Office for Nuclear Regulation


  1. Please provide a brief summary of the requirements placed on dutyholders to identify, plan for and mitigate the effects of climate change, including extreme weather events, and the reporting requirements placed on them

1.1.       The Office for Nuclear Regulation (ONR) is the UK’s independent nuclear regulator for safety, security, and safeguards, as defined in the Energy Act 2013.

1.2.       We typically operate a non-prescriptive, goal-setting regulatory regime. Dutyholders are responsible for demonstrating that they have met their legal duty of reducing the risks associated with their activities so far as is reasonably practicable. We assess dutyholders’ safety submissions against Safety Assessment Principles (SAPs) together with supporting Technical Assessment Guides (TAGs). The SAPs and TAGs provide our regulatory expectations for safety of activities undertaken on nuclear licensed sites and a framework for inspectors to make consistent regulatory judgements.

1.3.       We require facilities to withstand severe weather conditions, including the reasonably foreseeable effects of climate change over the lifetime of the facility. Similarly, facilities are required to withstand flooding hazards, which include combined storm events which could be affected by climate change.

1.4.       Our expectations are that meteorological and flooding hazards should be defined as an event with a one in 10 000 chance of being exceeded per year. In addition, dutyholders are required to consider events that are even more severe to demonstrate that adequate margins exist beyond this and that there is an absence of ‘cliff edge’ effects[1].

1.5.       Section 4 of the Nuclear Installations Act 1965 enables us to attach conditions to a nuclear site licence in the interests of safety. We attach 36 standard licence conditions to each nuclear site licence [[1]]. The following licence conditions are relevant to this query:

a)        Licence condition 7 requires dutyholders to make and implement adequate arrangements for the notification, recording, investigation and reporting of incidents occurring on the site. This would include incidents initiated by weather conditions that posed an actual threat to the safety of the nuclear installation or that significantly affected site personnel in the performance of duties necessary for safe operation [[2]].

b)        Licence condition 15 requires dutyholders to make and implement adequate arrangements for the periodic and systematic review and reassessment of safety cases. Reviews are usually undertaken every ten years. Dutyholder reviews are expected to consider and apply lessons learned from events, and new knowledge and experience. This would include recent scientific knowledge of climate change effects and implications for relevant natural hazards. We consider the latest UK Climate Projections, published in 2018 (UKCP18) to be relevant good practice [[3]].

  1. How far in advance do you require dutyholders to plan for the effects of climate change, and how regularly are they required to report on this work?

2.1.       We expect dutyholders to consider the reasonably foreseeable effects of climate change over the lifetime of the facility. Some nuclear licensed sites and sites for storing or disposing of radioactive waste will have lifetimes that will extend well beyond 2100.

2.2.       To account for the uncertainty in climate change, we advise dutyholders to adopt a managed adaptive approach [[4]]. The managed adaptive approach aims to build flexibility into options and decisions today, so that they can be adjusted depending on what happens in future. This is considered reasonable given the timescales over which climate change effects are expected to occur. There are two elements to the managed adaptive approach:

a)        to build in the ability to adjust an option should it be required (e.g., flexibility to increase the height of a sea wall);

b)        for dutyholders to develop plans that build flexibility into the decision process itself through observing and learning as scientific understanding of climate-related risks increases.

2.3.       Not all of the options to manage future climate change will be suitable for a managed adaptive approach of observing and learning. Consequently, a combination of a design containing precautionary elements and the managed adaptive approach is likely to be the most suitable approach for UK nuclear sites, particularly those in coastal locations.

2.4.       During the operational phase of a facility, as noted in the previous section, dutyholders are required to undertake a systematic review and reassessment of safety cases, usually every ten years. In addition, our inspectors undertake targeted interventions to provide additional confidence in the adequacy of dutyholders arrangements, such as flood protection measures or climate change planning assumptions.

  1. Have you established something akin to resilience standards against extreme weather and the effects of climate change, against which you assess dutyholders in the short, medium and longer term?

3.1.       Our regulatory expectations in relation to external hazards including for climate change are set out in guidance documents available on our website, so that dutyholders understand the principles against which their safety submissions will be assessed. This guidance is applied by our inspectors in a consistent, and proportionate manner based on risk.

3.2.       As stated above, licenced facilities are required to remain safe during severe weather and flooding conditions, including the reasonably foreseeable effects of climate change over the lifetime of the facility.

3.3.       Compliance against these expectations for existing facilities is typically assessed during the systematic review, usually every ten years. For new build projects arrangements to ensure the facility will remain safe until nuclear material is removed from the site are considered prior to start of nuclear operations.

  1. What is your assessment of the current state of climate resilience in your sector, and what obstacles are preventing achievement of the agreed/desired standards of resilience?

4.1.       Through our assessments, inspections, and routine regulatory engagements we have high confidence that the UK nuclear industry is resilient against the effects of climate change from a safety perspective.

4.2.       Our expectations for an event that can be safely withstood and the need to consider the reasonably foreseeable effects of climate change over the lifetime of a facility provide resilience based on current climate change projections. Our expectations for the demonstration of being able to withstand even more unlikely events and an absence of cliff edge effects provides further confidence that nuclear facilities will remain safe subject to the effects of climate change. This is supplemented over the lifetime of a facility through the adoption of a managed adaptive approach and the periodic review process, whereby dutyholders implement reasonably practicable enhancements to increase resilience. This is possible because the timescales that climate change effects are expected to occur over enables measures to be implemented.

4.3.       Ultimately, we have the power to direct a facility to shut down in the interests of safety if the managed adaptive approach is not appropriately applied in a timely way.

4.4.       We consider that there may be climate change effects that may have an impact on the nuclear industry that is beyond our legal vires. For example, instability in the electricity grid due to extreme conditions (high temperature or storms) may require nuclear facilities to shut down in order to remain safe. In such a scenario the contribution of nuclear power to the grid during extreme weather events may be limited.

21 February 2022



[1]               A cliff edge is where a small change in hazard severity results in a significant increase in risk to the facility. Dutyholders are expected to demonstrate no disproportionate increase in risk with hazard magnitude.

[1]               ONR, Licence Condition Handbook, February 2017.

[2]               ONR, Notifying and Reporting Incidents and Events to ONR, ONR-OPEX-GD-001 Revision 7, January 2021.

[3]               ONR, Use of UK Climate Projections 2018 (UKCP18) by GB Nuclear Industry. Position Statement.

[4]               ONR and Environment Agency, Principles for Flood and Coastal Erosion Risk Management, Joint Advice Note, Version 1, July 2017.