Enhancing extreme hazard resilience

Above: Flooding events can present significant hazards for the nuclear sector

While nuclear power is not inherently unsafe, the consequences of any kind of event could be catastrophic. However, compared to other power sources, nuclear has had an enviable safety record for the past 50 years.

In many ways the nuclear sector has led the way in health and safety legislation – rigorously examining incidents when they occur and applying lessons learned to improve safety.

At every stage in the nuclear supply chain, operating companies should continue to work to promote this ingrained safety culture as they look to satisfy global nuclear power needs. It is also worth noting that the latest-generation facilities currently proposed as part of tomorrow’s clean energy mix have more advanced fail-safe systems built into their design than their predecessor technologies. The development of new technology is designed to be inherently safer, relying less on engineered systems and backup to be effective.

When nuclear facilities are designed and built they are subject to stringent international and national regulatory safety requirements, which are designed to account for the full spectrum of foreseeable events. A facility’s safety cases are created and designed to help it better withstand seismic hazards and prepare risk contingencies.

Multiple hazards and risks

While seismic hazards are an important consideration in the safe operation of nuclear power plants, they are not the only risk. Nuclear power plants are designed to withstand a wide range of hazards, including floods, fires, and human error. The safety systems and barriers at nuclear power plants are created to help address these various potential risks and better ensure safe operation under normal to extreme conditions.

Flooding, for example, is a significant weather risk for nuclear power stations almost everywhere reactors are operating or planned. By submerging critical equipment, disrupting power supply, and damaging infrastructure, flooding can severely impact the normal operation of a nuclear power station.

Extreme temperature events, such as the recent heatwaves seen across Europe and the USA, or prolonged cold spells, can also pose risks to nuclear power stations. High temperatures can impact the nuclear power station’s cooling systems, reducing their efficiency and consequently affecting safety margins. Conversely, prolonged cold spells can impact the performance of equipment, electrical systems, and other critical components – also potentially affecting the safe and reliable operation of a nuclear power station.

Each incident is unique and usually a result of issues at several points. Nonetheless, safer energy operations demand an environment where safety is a priority and improvement is constant. Many entities can play a role in this, from the regulators to the operators, to third-party organisations that can offer insights based on extensive experience in managing nuclear risk. It is key that a holistic approach to risk is adopted as it is vital to take account of the inter-dependencies between all parties involved.

Many third-party companies are recognised as elite operators precisely because they set best-practice guidelines and are committed to a process of continuous improvement. A key part of their role is distilling best practices and documenting them in a way that will be most useful to a company and its culture.

Ensuring a consistent approach to managing risk across legislative regimes, asset conditions, and work cultures is a very complex process. Owners and operators of high-risk assets should recognise the value of independent technical oversight in high-risk projects, from conceptual design and commissioning to construction, operation, maintenance, and decommissioning.

It is important that third-party companies work closely with clients to better understand not only their operations, but also their capability to respond to damaging natural hazard events. Engineers can evaluate existing equipment and buildings, help develop solutions, and offer training to help businesses better protect their people and to more quickly start the recovery process to resume normal operations when incidents do occur.

Improving safety by managing risk

The reality is that it’s impossible to deliver zero risk or zero instances of safety failures, but through technical expertise and lessons learned, you can always work to make power generation safer by managing and minimising risk.

A multi-hazard approach allows for an integrated risk assessment that accounts for the interactions and dependencies between hazards. This can help identify

potential vulnerabilities and failure modes that may not be evident when hazards are considered in isolation, while allowing for a more accurate assessment of the overall risk profile of a nuclear power station.

Last year, the International Atomic Energy Agency (IAEA) launched the External Events Notification System (EENS). This is a web-based tool that provides real time information on external events and hazards, such as earthquakes, tsunamis, volcanic eruptions, river and coastal flooding, and rotational winds. The tool also provides real time information on wildfires that have occurred or are expected to occur, including notifications on their severity and location, in addition to estimates of their potential effects on nuclear installations and major population centres. The system collects relevant data and sends it directly to the IAEA’s Incident and Emergency Centre (IEC) and External Event Safety Section (EESS) for assessment. It is an initiative that has been financially supported by France, Japan, and the United States.

The EENS helps to monitor the global natural hazard situation in the vicinity of all nuclear installations, not just nuclear power plants, including large cities where radioactive sources, such as those in hospitals, may be affected by a hazard. This system is an integral part of IAEA’s work, allowing it to evaluate the situation and help countries mitigate the associated risks.

One of the expectations outlined in the Safety Assessment Principles (SAPs) of the UK Office for Nuclear Regulation is that the reasonably foreseeable effects of climate change should be considered over the lifetime of a facility. Likewise, the UK National Security Risk Assessment (NSRA) and the National Risk Register (NRR) identify specific risk scenarios with the emphasis clearly on planning for and being able to respond to those risks.

Building resilience

Resilience encompasses society, infrastructure, buildings, the environment, culture, economics, and technology. Knowing how to build resilience helps manage risk and determine the decision-making criteria.

Technology is helping in this area. While there has been uncertainty around the disruptive potential of Small Modular Reactors (SMRs), modularisation technology could be the next big thing in power plant design. New ceramic fuels and silicon carbide reactors could dramatically extend the operational life span of nuclear facilities, and the next generation of reactor could change the way we think about nuclear waste and how to store and dispose of it. Importantly, technology, data, and statistical extrapolation is breaking new ground in helping to predict, plan, and protect for hazard scenarios that help to raise safety standards further and improve the framework of nuclear risk management and resilience capabilities.

The world faces major challenges from energy security, energy poverty, and global warming. There is no single answer for tackling these complex issues. Nuclear has had a role to play, and the question ahead is whether the associated safety implications and operational risks for each individual facility are acceptable. In the years to come, the severity of natural hazards is expected to increase because of climate change. When considering the big picture, the importance of managing risk is as much a socio- political question as a technical one.

Author: Andrew Buckley, Principal Engineer, ABS Group