Professor Tim McGloughlin writes that small modular reactor nuclear technology – suitably designed and commissioned and underpinned by appropriate regulation and legislation – can enable Ireland to become energy independent.

Almost 20 years ago during a meeting of engineering faculty at the University of Limerick the conversation turned to renewable energy. The discussion revolved around wind, wave, solar and non-fossil fuel energy sources.

'Princely' status in energy mix

An eminent scholar from Queen's University Belfast, while positive about these energy sources, expressed doubt as to whether they would successfully dislodge oil and gas from their 'princely' status in the energy mix. I remember his remarks very clearly: “The big challenge is the energy density of the source fuel”. This remains the case.

In the intervening years, Ireland has witnessed an explosion of demand for power to fuel its booming economy. The addition of perhaps as many as one million electric vehicles and further large increases in the number of power-hungry data centres is expected to push annual demand up by 10-15%.

There has been a great deal of public commentary about the power needs of data centres, with some commentators suggesting that they will consume as much as 25% of the national output by 2030.

Indeed, already EirGrid and the energy regulator are recommending that new data centres provide their own standby generation. One current strategy being proposed involves the construction of gas-fired standby power facilities.    

The market for power has also been liberalised and this has given rise to a very welcome increase in the use of renewable energy in the supply chain with wind power now supplying almost 40% of the total in 2020 and 30% in 2021 due to lower wind levels.

The chart in Figure 1 shows the changing profile of the Irish energy mix, reflecting the growth of wind and the steady decline in the use of coal, oil and peat-fired generation.

The pace of elimination of fossil fuel sources will further accelerate in the next few years with 'dirty coal' being the first to be retired. However, peak demand continues to rise dramatically, and meeting this surging power requirement is likely to pose a major challenge for renewables.

While the data shown in Figure 1 dates from 2014, peak power demand in the Republic of Ireland for 2020 was 5.48GW and in 2021 it was 5.65 GW (increases of more than 20% on the 2014 values). This demand has placed significant pressure on generation capacity as highlighted in the national press throughout 2021.

Figure 1: Total installed generation capacity and annual peak demand in Ireland(1)

The national grid has been very successfully managed by EirGrid and linked via interconnectors to the north (1996), UK (2012). Further expansion of the interconnector network to the European power grid is already under way.

It is worth noting that these interconnectors link to nuclear generation in the UK (currently at 20% of the total and with a further 3.2G being added at Hinkley Point C by 2026) and France (70%, and with no planned power station closures).

There has been justifiable concern about the environmental impact, long lead times and economic benefit of the large-scale nuclear power plants such as Hinkley Point C and Barakah (5.4GWe) in the UAE.

'Can’t power the world without nuclear energy'

Despite the misgivings relating to the environmental impact of large nuclear plants, there are many positive developments relating to smaller scale units. Indeed, many experts believe that, to achieve the global greenhouse gas emissions targets and reduce the rate of global warming, nuclear energy needs to be in the mix. This is highlighted by the recent letter to COP21 by leading climatologists.

“We’ve done the math and we can’t power the world without nuclear energy.” – Open letter to COP 21: Ken Caldeira, Carnegie Institute of Science, Kerry Emanuel, MIT, James Hansen, Columbia University, Tom Wigley, University of Adelaide(2).

Thus, the recent paradigm shift in the nuclear story in energy supply with the development of small modular reactors (SMRs) by several companies with deep knowledge of the benefits and challenges of nuclear power, seems to offer considerable promise.

This drive towards SMRs is being led by NuScale (backed by Fluor Corporation and US Department of Energy), Rolls-Royce (UK, with major backing from Qatar Sovereign Wealth Fund), GE Hitachi and Terrestrial Energy (partnered by Siemens), all companies with a wealth of expertise in nuclear technology and power engineering. Russia and China are also actively developing SMR capability.

The fundamental benefit of the SMR approach lies in the utilisation of the energy density of the uranium fuel. The unmatched advantage of nuclear power is the incredible energy density of zero-carbon uranium fuel. Uranium fuel pellets are inserted into rods which are used in the fuel assemblies of the SMRs. One pellet which is the size of a thimble, contains the same amount of energy as five barrels of oil as shown in Figure 2(3).

Figure 2: The energy density of nuclear pellets

As a result of this very high energy density, the design teams at Rolls-Royce, NuScale and others have developed some remarkable possibilities for SMRs  

Figure 3: Artists impression of an SMR facility. Image: Rolls Royce UK

Rolls-Royce SMR design

In the Rolls-Royce case it believes that their SMR design will:

  • Provide 220MW to 470MW of power, depending on the configuration, equivalent of up to 150 onshore wind turbines;
  • Supply power to the grid in a timely manner at lower cost to the taxpayer and consumer, generating electricity as cheap (per MW) as power generated by today’s large-scale reactors – and perhaps cheaper as SMRs go into volume production;
  • Sit within a power station that would be roughly three times the size of the pitch at Croke Park, about four hectares (see Figure 3), about a tenth of the area of a large nuclear power plant;
  • Take just five years from the start of construction to the generation of the first electricity;
  • Be up and running by 2030;
  • Minimise operating costs such as refuelling and the burden of decommissioning;
  • Last for 60 years.

NuScale’s flagship power plant design can house up to 12 modules for a total gross output of 924 MWe. The scalable, multimodule features of the NuScale plant make it an ideal option to match to different coal power plant energy outputs, many of which are between 300 MWe and 600 MWe.

NuScale power plants can fit within the confines of an existing coal-fired power plant property and the company is actively seeking to substitute old coal-fired plants with NuScale SMRs.

The 12-module, 924 MWe NuScale plant has a small protected (EPZ) area of 34 acres (14 hectares). By comparison, wind generation requires 94 square miles (24,400 hectares) to generate the 924 MWe that a 12-module NuScale plant generates and solar photovoltaic (PV) requires at least 17 square miles (4,400 hectares)(4).

The SMR technologies currently being developed have major advantages in terms of constant availability of power, size, speed of construction, repeatability, and quality as a result of factory assembly.

Very attractive for smaller countries

Additionally, SMRs can provide affordable, and reliable process heat for chemical processing or production of clean fuels such as hydrogen or for low pressure applications such as district heating(4)

Their modular nature makes them very attractive for smaller countries like Ireland and SMRs can facilitate high quality grid management. The important issue of waste handling is expected to be more manageable with SMRs due to the smaller unit size and greatly reduced volumes of radioactive materials on site.

One supplier suggests that safe on-site storage for 15 years is possible. This would, in my opinion, be a very valuable complementary approach to the highly successful drive towards renewable sources of energy already adopted by Ireland.

Indeed, if properly managed, it is possible that SMRs could eliminate the need for the fossil fuel back-up units being considered for the next generation of data centres.

Furthermore, there is evidence that SMRs can reduce the cost of power significantly. They could also help minimise power price surges as have recently been experienced in Europe because of supply challenges with natural gas.

A major policy issue needs to be addressed before SMRs can be considered as part of the Irish energy mix. The issue is a political one and requires a change of national legislation.

Remarkably, when I was researching this article, I discovered that Australia (the world’s third largest exporter of uranium) has similar legislation to Ireland. Thus, nuclear fission may not be used for the generation of power in either Ireland or Australia.

This situation is already being examined in Australia especially in the light of its planned purchase of nuclear submarines. Indeed, Australia, conscious of recent European energy supply chain challenges, may well decide that nuclear power could make the nation energy self-sufficient as coal-fired and other fossil fuel power stations are phased out

The topic has already been raised in Ireland by a number of groups, most notably 18for0 (, a voluntary groupwhich is a strong supporter of the need for the inclusion of nuclear power in the Irish (and indeed European) energy mix to achieve the climate change targets set by COP26.


I believe that small modular reactor nuclear technology – suitably designed and commissioned and underpinned by appropriate regulation and legislation – can enable Ireland to become energy independent.  

In line with stated policy of the environment minister Eamon Ryan, such an approach could enable Ireland to become a leading exporter of green power produced without greenhouse gases and with fossil fuel use approaching zero.  

I suggest that we need to add the consideration of SMRs to the national debate on our response to climate change and the mix of sources of renewable power. 

Author: Professor Tim McGloughlin FIEI, emeritus professor of biomedical engineering, University of Limerick


1.) F Gaffney et al  A 100-year review of electricity policy in Ireland (1916-2015), Energy Policy 105 (2017)


3.) SMRs Small modular reactors in the Australian context, Minerals Council of Australia (2021)  Dr Ben Heard

4.) Nuscale-smr-technology-an-ideal solution.pdf (2021)

5.) Corrected Overnight Capital Costs