Nuclear Energy is Reliable

In December 2021, regular maintenance checks in a French nuclear power plant reveal signs of corrosion on pipes of a safety system responsible for the insertion of a neutron absorber into the coolant in case of emergency. The presence of such a neutron absorber would drastically reduce the multiplication factor, hence shutting down the reactor. This safety system is one of the many safety barriers implemented in modern nuclear reactors. Modern nuclear energy is built upon the defence-in-depth philosophy, which “builds in layers of defence against hazards so that no one layer by itself, no matter how good, is completely relied upon.” [84] The equipment could thus theoretically be repaired while keeping the reactor online. Nonetheless, the French operator EDF decided to shut down the plant and replace the affected parts immediately.

Further investigations revealed that the predominant factor causing the issue was likely to be the geometrical configuration of the piping. More reactors were thus likely affected. A race around the clock began to repair all the concerned nuclear power plants in time for the next winter, when the energy demand peaks. The year 2022 would be a record low for the french nuclear electricity production : only 279 TWh, while it had been around 380 TWh in previous years—that is respectively 54% and 73% of the theoretical maximum. By January 2023, two thirds of the french nuclear power fleet was once again available. By March, the french nuclear electricity production was comfortably in line with past average.

What are the lessons to be learnt here? First, security prevailed over convenience or performance. Even with the defence-in-depth safety net, the affected reactors were shut down, and the repairs performed immediately. Second, that nuclear energy can be relied upon even in severely adverse conditions. In this instance, the French nuclear sector was organised and responsive enough to identify and repair a fault that impacted most of its fleet in a record amount of time.

Figure extracted from the WNA “World Nuclear Performance Report 2023” report, published in July 2023. The global capacity factor of nuclear power plants has remained above 80% since 2000, an exceptionnal performance.

While this corrosion issue in the French fleet was handled with astounding professionalism, it remains a truly exceptional situation. The average capacity factor of nuclear power plants at the global level has remained above 80% since 2000. [85] This metric represents the amount of energy that was actually produced versus the amount of energy that could have been produced if all facilities were running full-time. The downtime of nuclear power plants can largely be attributed to maintenance and refuelling operations.

A certain fraction of the downtime, however, also stems from load following—a little known ability of nuclear power plants. The marginal production cost of nuclear energy being very low, it makes the most sense to keep nuclear power plants running at full power as much as possible. In the energy mix, this is referred to as baseload. For instance, the German fleet had the highest rate of change in load combined with the most power per unit of all the country’s electric power production portfolio. Nuclear power plants in Germany could adjust their output down to 50% at a rate of 5% per minute, and from 80% at a rate of 10% per minute. That is a staggering 140 MW per minute. The fastest non-nuclear units are a small number of new fossil-fired power plants, capable of only around 40 MW/min. [86]

External factors such as topology, climate, weather or the day and night cycle have no influence over nuclear energy. The Palo Verde Nuclear Generating Station, in the USA, is located in the Arizona desert and reclaims uses wastewater from local cities for condenser cooling water. The Bilibino Nuclear Power Plant, in Russia, operates in a subarctic climate with average temperatures going down to -30°C, with peaks at -40°C. The robust design of nuclear power plants enables them to go through extreme natural events, such as earthquakes, tornados, volcanic activity, ice storms and flooding. An estimated 20% of all reactors are located in areas of significant seismic activity—we already covered the Fukushima incident in another section. [87]

Even fuel supply is a relatively secondary issue, given the energy density of uranium and the ease with which it can be stockpiled for many years. This also means that nuclear energy is less susceptible to price volatility in energy markets, contributing to its reliability in delivering a stable and predictable source of electricity.

Through thick and through thin, nuclear energy can be relied upon.

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