WeeklyWorker

14.04.2022
Nuclear power is no panacea: mimicking the sun with fusion is still a long way off

No quick fix

Mimicking the sun and producing power using nuclear fusion has long been a dream and it appears that will be the case for a long time to come. Yassamine Mather explains

As the price of fuel continues to spiral in the aftermath of Russia’s February 24 invasion of Ukraine, Boris Johnson’s government has presented its 38‑page energy strategy, specifying targets for wind and solar power, along with a U-turn regarding greater exploitation of North Sea oil and gas reserves and the proposal to build eight new nuclear power stations.

There is a threefold aim: (1) getting to 95% clean electrical generation by 2030; (2) achieving net-zero by 2050, as pledged at Cop26; (3) especially in light of Ukraine, ensuring UK energy security.

Commenting on the proposed £400 billion annual budget target (about 0.6% of gross domestic product), Dieter Helm, a professor of energy policy at the University of Oxford and until recently a government advisor, says this is nowhere near enough and renders its goal of reaching net zero by 2050 “hopelessly unrealistic”.1 Helm tells us that the transition to clean energy can never be achieved at “very low cost”. The government’s whole strategy assumes “not only that the costs of renewables and low-carbon technologies will keep falling, but also that government policy will be perfect”. This is “nonsense”, he added, because “the unfortunate reality is that the costs do not go away by assumption”.

Anyone following the disastrous consequences of underestimating the costs and time scales for the nuclear industry will certainly agree with Helm. The whole nuclear sector has been plagued by accidents, soaring costs and massive delays ... and, eventually, when a nuclear station is up and running, it produces very expensive electricity.

Mycle Schneider, lead author of the annual World Nuclear Industry Status Report (WNISR), has highlighted these problems. He estimates that since 2009 the average construction time for reactors worldwide was just under 10 years - well above the estimate given by the World Nuclear Association of between five and nine years.

Those researching and proposing the next generation of nuclear power stations keep telling us they have learned lessons from the mistakes and problems of the past. Despite that, nothing can hide the exorbitant sums involved: estimates are in the range of $5,500-$8,100 per kilowatt or between $6 billion and $9 billion for each 1,100-megawatt plant.

In fact, while other energy sources have declined in cost, nuclear has become more expensive:

Over the past decade, the WNISR estimates levelised costs (which compare the total lifetime cost of building and running a plant to lifetime output) for utility-scale solar have dropped by 88% and for wind by 69%. For nuclear, they have increased by 23% [my emphasis].2

What about nuclear power as a panacea for global warming? Schneider damningly writes: “Stabilising the climate is urgent, [but] nuclear power is slow.”3

Then there are the inherent dangers. Leave aside the problem of disposing of spent fuel rods and other such waste material and keeping it away from humans - for example, stored deep underground for many thousands of years. There have been well over 100 serious accidents in nuclear power plants, the worst being Three Mile Island (1979), Chernobyl (1986) and Fukushima (2011). While the new designs have much better fail-safe mechanisms built into them, there is still the horrid prospect of terrorist or military attack.

A Boeing 747 or a ballistic missile slamming into a nuclear power plant would send a ploom of deadly radioactive dust high into the atmosphere and then to wherever the prevailing wind takes it, potentially killing hundreds directly and sentencing tens of thousands more to an agonising early grave.

That is why various environmentalists, physicists, journalists and politicians hold out the prospect of going for nuclear fusion, as opposed to nuclear fission. Indeed, the Johnson government is considering a Scottish site for a new nuclear fusion energy station - despite the Scottish government’s opposition. The Tories are also intending to nominate four potential sites south of the border.

According to the Scottish paper, The National:

A total of £222 million in preparatory funding has been allocated to select a site and develop a concept design, with a “considerably higher quantum of money” than required to build the working power plan by 2050, according to Leon Flexman of the [UK Atomic Energy Authority].4

So what are these two processes? How do they differ from each other? Fission and fusion are both physical processes that produce massive amounts of energy from atoms through nuclear reaction - as opposed to carbon-based coal and gas or obtaining power from windfarms, solar radiation or water.

Fission is based on splitting the nucleus of a larger atom into two or more smaller nuclei, a process which releases energy. The nuclear power reactors, where the process takes place, use uranium and plutonium. Both products are highly dangerous with a half-life of up to 24,100 years. But in theory both are easy to control. Energy is released in these reactors, heating water and producing steam, which is used to spin a turbine in order to produce carbon-free electricity.

Fusion is almost the opposite: two light atomic nuclei combine to form a single heavier one, while also releasing energy. This is something learnt from studying similar processes that power the sun and stars. A common example is the fusion of two hydrogen atoms, which fuse in order to form a helium atom. The process requires exceedingly high temperatures to overcome their mutual electrical repulsion.

Fusion creates more energy than fission - in some cases up to four times as much. The illustration shows how the process works in the sun: Tritium and Deuterium (isotopes of hydrogen, Hydrogen-3 and Hydrogen-2 respectively) unite under extreme pressure and temperature to produce a neutron and a helium isotope.

Fission requires a nuclear power plant with all its technical complexity. Such plants must satisfy strict safety regulations and that in part explains the time delays and cost overruns.

How about fusion? Obviously, given fission’s evident shortcomings, this option is getting a lot of attention and funding. However, is it the answer? Not if the intention is to deal with the impending climate disaster! The US strategic report relating to a fusion pilot plant gives the following timeline: design - 2020s; construction - 2030s; operation - 2040s.

All this will depend on the following:

  1. throwing the power of computation and machine learning into the fusion process;
  2. relying on the assumption that the latest models have reliable predictive power;
  3. assuming that turbulence can be optimised in stellarators (ie, plasma devices that rely primarily on external magnets - scientists researching magnetic confinement fusion aim to use stellarator devices as a vessel for nuclear fusion reactions).

When we study the sun and stars, we find that high temperatures and powerful gravitational forces naturally prepare a fusion environment. But on earth we face the challenge of creating the same conditions, so that we can achieve self-sustaining ignition. This is not a minor problem, as it requires maintaining the plasma (a mixture of gaseous deuterium, tritium ions and atoms, and the helium fusion product) at millions of degrees Celsius. But it soon became clear that scientists could not find any materials capable of withstanding such high temperatures. That is why they came up with the solution of keeping the plasma in a magnetic field, using superconducting magnets surrounding a fusion vessel or chamber.

When it comes to radioactive waste, fusion has an advantage over fission, in that nuclear fuel chain reaction does produce radioactive waste, while in a nuclear fission reactor the radiation consists of beta particles, alpha particles and gamma rays. In a nuclear fusion reactor, the vessel wall is the only part that the high-energy neutrons can bombard.

In a worst-case scenario, if the enclosure of the main fusion vessel layers breaks, the neutron radiation will end as soon as the fusion reaction stops. But in a fission reactor the radiation continues to exist in the waste materials. For nuclear fusion, the activated materials (eg, the containers and vessel walls that neutrons have bombarded) must be stored safely for centuries. However, in fusion the radiation level is so small that it can be reused in the reactors.

In February 2022 a team of scientists from the Joint European Torus - a magnetically confined plasma physics experiment based in Oxfordshire - produced 59 megajoules from a sustained reaction lasting five seconds. This was heralded as a major achievement - it was more than double what was achieved in similar tests back in 1997, producing enough power to boil about 60 kettles. One of the main achievements of the experiment was proof that new materials used to construct the inner walls of the fusion reactor worked as intended.

However, it should be remembered that the current estimate for actually using this type of energy is the 2040s. In the words of BBC science correspondent Jonathan Amos: “Fusion is not a solution to get us to 2050 net zero. This is a solution to power society in the second half of this century”.

The two types of nuclear power summed-up

 

Fission

Fusion

Type of reaction

Not a natural process.

Similar to the process occurring in stars, such as the sun.

Radioactive by‑products of the reaction

Fission produces many highly radioactive particles.

Few radioactive particles are produced by fusion reaction, but, if a fission ‘trigger’ is used, radioactive particles will result from that.

Conditions     

Critical mass of the substance and high-speed neutrons are required.

A high-density, high-temperature environment is required.

Energy requirement

Takes little energy to split two atoms in a fission reaction.

Fusion requires temperatures of 100 million Kelvin - six times hotter than the core of the sun

Energy released

The energy released by fission is a million times greater than that released in chemical reactions, but lower than the energy released by nuclear fusion.

The energy released by fusion is three to four times greater than the energy released by fission

Nuclear weapons

One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.

One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to ‘trigger’ a fusion reaction.
To date, no nuclear weapon makes use of nuclear fusion alone, though governmental defence programmes have put considerable research into such a possibility.

Energy production

Fission is used in nuclear power plants.

Fusion is an experimental technology for producing power.

Fuel used

Uranium is the primary fuel used in power plants.

Hydrogen isotopes (Deuterium and Tritium) are the primary fuels used in experimental fusion power plants.

Nuclear waste

The by-product of fission is radioactive waste that takes thousands of years to lose its dangerous levels of radiation. This means that nuclear fission reactors must also have safeguards for this waste and its transport to uninhabited storage or dump sites.

Fusion does not emit harmful toxins like carbon dioxide or other greenhouse gases into the atmosphere. Its major by-product is helium - an inert, non-toxic gas. There is no long-lived radioactive waste.

Mathematics

Nuclear fission is the splitting of a massive nucleus into photons in the form of gamma rays, free neutrons and other subatomic particles. In a typical nuclear reaction involving 235U and a neutron:
23592U + n = 23692U, followed by 23692U = 14456Ba + 89 36Kr + 3n
+ 177 MeV

The energy released in fusion is related to E = mc2 (Einstein’s famous energy-mass equation). On earth, the most likely fusion reaction is Deuterium-Tritium. Deuterium and Tritium are both isotopes of hydrogen. 2 1Deuterium + 3 1Tritium = 42He + 10n + 17.6 MeV.
Fusion of deuterium with tritium, creating helium-4, freeing a neutron and releasing 17.59 MeV of energy.

 


  1. worldnewsera.com/news/finance/energy-expert-slams-uks-net-zero-strategy-as-hopelessly-unrealistic.↩︎

  2. Ibid.↩︎

  3. www.reuters.com/article/us-energy-nuclearpower-idUSKBN1W909J.↩︎

  4. www.thenational.scot/news/19867784.uk-government-consider-ayrshire-coast-nuclear-plant-despite-scottish-government-opposition.↩︎