A prevailing narrative that nuclear plants can’t operate flexibly and are unsuitable for low-carbon hydrogen production is leading to nuclear being excluded from a big part of the envisioned future energy mix. It’s a narrative that needs to change.

The seasoned energy analyst reads a table of nuclear plant capacity factors in much the same way as sports pundit reads through a list of team stats. Any score under 85% and the verdict is that the plant must be underperforming – taking too long on outages or tripping for presumably no good reason at all. Capacity factors have long served as the benchmark of nuclear excellence, and the universal aim of plant operators is to maximise the number of kilowatt-hours sold in order to earn as much revenue as possible.

Or is it?

It is no secret that most nuclear plants are technically capable of varying their output to support the needs of the grid. French plants have done so routinely for decades, flexing in tune with the daily cadence of electricity demand.

Until recently so did several German plants. Increasingly across Europe and even in North America we see plants adopting flexible operation to help balance the volatility created by the rising share of intermittent renewable generation.

Nuclear plants can provide a range of flexibility services to help ensure grid stability. They can provide frequency regulation automatically or through minor adjustments on the turbine, and thus help the grid operator deal with small daily fluctuations. They can also provide a tertiary response wherever plants are adapted to operate in load-following mode and increase or decrease their output substantially in order to help balance any significant deviation in grid voltage or frequency.

This fact alone suggests that industry analysts should start putting nuclear plant availability as the primary metric of plant performance, rather than capacity factor. So far, even this minor adjustment in thinking has been hard to win acceptance for.

It seems that many in the nuclear industry still resist the idea of flexible operations. Yes, they grant, existing nuclear plants can load follow, but why should they? Some operators clearly don’t want to mess with the finely- honed operation and maintenance regimes which have allowed them to achieve high performance levels, and certainly don’t want to involve the regulator in a modified safety case. Plant owners don’t want to have the difficult conversations with market operators or come up with the arrangements that will adequately compensate the income from lost generation.

Beyond this is a sense of fairness, the belief that as nuclear plants were on the grid first, newcomer generators should take on the additional costs and challenges of flexibility. While perhaps reasonable in some ways, the underlying mindset is that the rest of the energy system should flex around the nuclear plants, rather than the other way around! This must be why in document after document industry continues to refer to nuclear technologies as ‘baseload’ with the firm conviction that this is a selling point.

Given this, it is perhaps understandable that energy modellers often do not allow for nuclear flexibility at all. You will find this baked in as a hard constraint in many zero-carbon scenarios. The impact is that as (according to another assumption) intermittent renewable energy sources continue to get cheaper and the need for flexibility grows, nuclear plants are outcompeted in favour of batteries, storage and other flexibility options. By contrast, when nuclear load following is allowed, the amount of nuclear energy output shoots up, and the technology plays a very sizeable role in a low-carbon future.

One could have a field day analysing these models and judging the scalability of low-carbon flexibility solutions, such as demand-side management, batteries & energy storage, and CCS on fossil plants. Given practical and technical constraints, it is unlikely that they can cover seasonal variations in energy demand and renewable supply. The recent cold snap in Alberta highlights the difficulty in kicking unabated fossil fuels off the grid. Energy scenarios are consistently weak on this front.

However, the point is to highlight how industry’s own language is hurting its prospects. That old and outdated trope – base load – is effectively being used to squeeze nuclear energy out of the predestined future low-carbon energy mix.

Put another way, this myth – that nuclear is inflexible – is arguably as persistent and harmful to the industry as those relating to safety and waste. But unlike the latter, industry does little to address the former. It is in fact deeply ironic that nuclear technology, which is responsive enough to meet manoeuvrability needs of submarines, is seen by many clean energy dilettantes as fundamentally inflexible and incompatible with a green/renewable future. Nuclear energy is already plenty flexible. The reality is that we need it to become more flexible still if we are to enjoy the same level of energy and societal resilience in the future as we have under today’s fossil-backed energy system.

As extreme climate events and other energy disruptions become more frequent, nuclear plants will need to take on more of the role currently provided by gas plants. It’s a tall order, but one the industry must meet, because if it doesn’t it is genuinely unclear what will. Certainly, advanced nuclear technologies offer a lot of promise in this regard.

If ‘base load’ is out as a descriptor, but ‘flexible’ is considered a bridge too far by some, then what word should we use? MIT researcher Jesse Jenkins coined the term ‘flexible base’ and postulated this as one of three essential components of a balanced low-carbon energy system. That seems to be a good match.

Some may see all this as a purely academic concern, but energy scenarios such as the IEA’s Net Zero Energy (NZE) are increasingly being used to inform government policy and influence the lending practises of major financial institutions. For these institutions, nuclear flexibility and complementarity with renewables really does matter.

The question of flexibility, and whether nuclear plants can be anything other than gigawatt-scale electricity generators, extends beyond differences of opinions over load following. There is a related energy policy development which will have a very real financial impact on what gets built. In recent years Western governments have become obsessed with low carbon hydrogen as the missing ingredient for accomplishing the low-carbon energy transition.

While electrification is expected to do much of the heavy work, low-carbon hydrogen is expected by many to play a role in transport, heating and of course electricity storage. Low-carbon hydrogen technologies now enjoy the level of direct subsidies and support that once-expensive renewable projects used to benefit from.

Make no mistake, nuclear is one of the most promising technologies for the production of low-carbon hydrogen. Nuclear plants offer superior hydrogen production capabilities compared to intermittent renewables because of their high availability factors. This allows much greater volumes of hydrogen production and quicker amortisation of electrolysers. Nuclear heat can also be used directly to open up more efficient high temperature conversion processes. Crucially, nuclear plants are not locationally constrained, and can be located near to hydrogen demand centres, thereby lowering the costs of transport and storage – both of which are major cost factors in the hydrogen economy. Japan has even successfully demonstrated high temperature nuclear hydrogen production, showing this can be done.

Yet somehow the nuclear industry has to date found itself essentially excluded from hydrogen financial support in both the EU and the USA. Rather than focus on commercialising a set of promising low-carbon hydrogen production technologies, these policies have been co-opted to become the latest renewable subsidy schemes.

In the EU this was blatant and transparent with renewable hydrogen having its own distinct prioritised policy package. In the USA this is being threatened via a proposed regulation that will restrict credits to generators that come online within three years of opening hydrogen facilities.

Unsurprisingly, many hydrogen modellers also do not include hydrogen production from nuclear plants in their energy scenarios. As with nuclear load following, it appears that the flexibility potential of nuclear technologies is being deliberately ignored and sidelined.

The idea that nuclear plants are nothing more than bulk electricity producing machines is a difficult one to dislodge. Overcoming this requires industry to embrace flexibility of thinking as well as the flexibility of its own technologies.

Author: David Hess is a policy expert specialising in nuclear energy, he is currently Senior Vice President of Strategy and Sustainability at DeepGEO