Nuclear Power: Keeping The Lights On??

People in the UK are currently (September 2021) expecting steep rises in the cost of fuel and electricity1, with some fearing the stability of supply2. There have been many explanations for this including lack of wind, increase in gas prices worldwide and problems with importing electricity from France.

Not surprising, the nuclear power industry has used this to argue for the need for more nuclear3.

However, the early closing of two nuclear plants (Dungeness B and Hunterston B) have led to a much greater drop in the UK’s electricity supply than the loss of the interconnection with France (although the data is now outdated, my analysis in a previous post showed that we mainly import electricity from France when demand is lowest).

The long lead times, delays in construction and unreliability of nuclear have, in fact, added to the UK’s electricity supply problems.

Dungeness B

Dungeness Units B-21 and B-22 are both 535MWe advanced gas-cooled reactors (AGRs).

In 2015 EDF announce a £150m investment in Dungeness B to keep it going until 20284. However, in September 2018 the Office of Nuclear Regulation issued “a direction for Dungeness B nuclear power station to carry out a review and reassessment of safety addressing the corrosion of concealed systems that fulfil a safety function” which was reported to the Internation Atomic Energy Authority with an INES rating of 25.

In March 2019 EDF announced6 that they would have to extend the outage to complete the required safety work.

Eventually, in June 2021, EDF announced that the reactors would be shut down with immediate effect and moved into defuelling phase7.

So after two and a half years of wavering, the UK electricity supply was cut by over 1,000MWe. Despite the fact that historically Dungeness has been less than reliable (see load factor below) this is still a major blow to UK electricity supply.

Dungeness Load Factor

Hunterston B

Like Dungeness, Hunterston B consists of two 530MWe AGR reactors. In 2006 concerns were raised about the graphite moderators8. In 2007 the output was restricted to 70% of full power. I have written about these problems in a previous post.

Despite these problems, EDF said that it could operate until 20239. However, in 2016 the  Office for Nuclear Regulation (ONR) had raised concerns about the cracks10.

Both reactors were taken offline in 2018 to work on issues related to their graphite cores. Following the approval of a safety case with the ONR but returned to service in late 2019. However, EDF announced that both reactors who enter decommissioning no later than January 2022.

So the UK is about to lose 1,000MWe of electrical supply one year early.

The Failed Nuclear Plan

In 2008 issued the White Paper on Nuclear Power – Meeting The Energy Challenge11. There they outlined the plan to start building a fleet of nuclear power plants to meet our energy needs.

The government plan was to licence and build nuclear plants are various sites, with the first being online in 2018.

If the timescales now seem overoptimistic, this is nothing compared to their estimates of cost:

This gives a total cost of £2.8 bn to build a first of a kind plant with a capacity of 1.6 GW.11

However, in 2019 The Engineer reported:

The UK’s landmark next-generation nuclear plant at Hinkley Point C has had a revised cost estimate, with £1.9bn-£2.9bn of additional spending predicted. This will bring the overall cost of the project to between £21.5bn and £22.5bn.12

New Nuclear

The problems, delays and increasing costs of EPR projects (similar to that being built at Hinkley and proposed at Sizewell) at Flamanville and Olkiluoto are well known and the final costs and start dates are still unclear.

However, more worrying is the EPR reactors in Taishan in China. After two years of operation, problems at the plants would have led them to be shut down by EDF if they were in France13.

1 UK energy bills to rise after record wholesale electricity prices, The Guardian, September 2021 (

2 U.K. Faces Winter Blackouts Risk After Fire Knocks Out Cable, Bloomberg, 15 September 2021 (

3 New nuclear only long-term solution for UK energy stability, Nuclear Industry Association, 19 September 2021 (

4 EDF Energy announces 10 more years for Dungeness B, EDF, 20 January 2015 (

5 External corrosion affecting multiple systems on a power reactor, International Atomic Energy Authority, January 2018 (

6 Outage extensions for UK’s Dungeness and Hunterston, Nuclear Engineering International, March 2019 (

7 EDF decides to move Dungeness B into defuelling phase, EDF, June 2021 (

8 Brief Review Of The Documents Relating To The Graphite Moderator Cores At Hinkley Point B And Other Advanced Gas-Cooled Reactors, Large & Associates, 2006 (

9 Hunterston B nuclear power plant will run until 2023, BBC, 2012 (

10 Nuclear reactor cracks ‘challenge safety case’, BBC, 2016 (

11 Meeting The Energy Challenge: A White Paper on Nuclear Power, BERR, 2008 (

12 Hinkley Point C cost estimate rises again, The Engineer, 2019 (

13 EDF says it would shut Taishan reactor if it were in France, Financial Times, July 2021 (


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