The bad science behind expensive nuclear
How an arcane model makes nuclear power expensive and why its time might be up
Today we released the first article from our next issue, Issue 19, of which the first section is reproduced here. Read the whole article on our website.
On 23 May 2025, President Trump signed four executive orders on nuclear power, intended to speed up approvals of and reduce regulatory burdens on new nuclear reactors in America. Buried in one of them was a requirement that the Nuclear Regulatory Commission reconsider its use of ‘Linear No Threshold’ (or LNT). LNT is the hypothesis that the relationship between radiation dose and cancer risk to humans is linear and that there is no truly ‘safe’ level of radiation. It underpins nuclear regulation worldwide and it may be one of the most important rules that almost no one’s ever heard of.
In 2013, GE Hitachi Nuclear Energy, a joint venture between General Electric and Hitachi, applied to build three advanced boiling water reactors in Wales. Fission reactions would boil water into steam, turning a turbine, powering a generator, and producing electricity. This specific design had been employed in four Japanese reactors, which had survived earthquakes of a greater magnitude than have ever hit the UK without posing any threat to workers or the public.
Even though the reactor had a flawless safety record, the UK’s Office for Nuclear Regulation was not satisfied. Over the course of a four and a half year process, it demanded a series of design changes. These included the installation of expensive, bulky filters on every heating, ventilation, and air conditioning duct in the reactor and turbine building, a new floorplan for the room in the plant’s facility that housed the filtration systems, and an entirely new layout for the facility’s ventilation ducts. This was justified on two grounds. First, it would optimise the ventilation system for accidents, despite the fact that the reactor design already had an entirely separate safety system, with redundancy built in, for this exact purpose. Second, it would cut radiation exposure during routine operation. As GE-Hitachi pointed out, this reduction amounted to 0.0001 millisieverts per year – the amount a human ingests when they consume a banana.
A CT scan hits a patient with ten millisieverts all in one go. Natural background radiation in the UK or US typically exposes people to two or three millisieverts during the course of a year, and exceeds seven millisieverts per year in Iowa and North Dakota and South Dakota. A single flight from New York to London exposes a passenger to 0.04–0.08 millisieverts; 0.0001 millisieverts is equivalent to 1/400 of the upper range of that, or about 72 seconds in the air per year worth of radiation.
The regulatory ratchet that makes nuclear unaffordable can be summarized in a single acronym: ALARA. This is the internationally accepted principle that exposure to ionizing radiation – the kinds of radiation produced by x-rays, CT scans, and the radioactive isotopes of elements used in nuclear power plants – should be kept ‘as low as reasonably achievable’. ALARA has been interpreted in major economies like the US, UK, and Germany as meaning that regulators can force nuclear operators to implement any safety improvement, no matter how infinitesimal the public health benefit, provided it meets an ambiguous proportionality standard.
ALARA stems from the Linear No Threshold hypothesis, the theory about how the body responds to radiation that May’s Executive Order took on. Critically, the hypothesis holds that any amount of ionizing radiation increases cancer risk, and that the harm is cumulative, meaning that multiple small doses over time carry the same risk as a single large dose of the same total magnitude.
In other areas of our lives, this assumption would seem obviously wrong. For example, the cumulative harm model applied to alcohol would say that drinking a glass of wine once a day for a hundred days is equivalent to drinking one hundred glasses of wine in a single day. Or that a jogger who ran a mile a day for a month was putting her body under greater strain than one who ran a marathon in a day. We recognise that the human body is capable of repairing damage and stress done to it over time.
But the Linear No Threshold assumption is the orthodoxy in international radiation protection, and its implications in ALARA regulations are among the most significant contributors to nuclear energy’s unaffordability in most of the developed world. But these assumptions are not just counterintuitive: they may be unscientific.
This is an excerpt from a new article on Works in Progress: read it here.
Great article - thanks.
The main threat to DNA is the occasional Reactive Oxidant Species (ROS). These are chemical radicals naturally produced by the oxidation of reductants (sugars etc.) in every animal cell. That oxidation provides energy, but ROS is occasionally released by accident. That's why we have anti-oxidants - to put out the 'fire-like mayhem' caused by ROS. At rest ROS is thought to cause about 10x the DNA damage of background radiation. Vigorous exercise increases the damage rate much more. It makes no difference how DNA gets damaged. The effect of DNA damage caused by ionizing radiation and ROS is the same.
Most damage happens to other cell proteins but as we know, DNA damage can cause long term problems. Fortunately, the double helix structure of DNA enables single strand breaks to get repaired quite quickly by the cell. Most double breaks take longer to repair by more complex cell processes. Where damaged DNA cannot be repaired the whole cell is sacrificed by apoptosis (immune response). Cancer cells develop in our bodies all the time and it is only as we age that our immune system weakens, raising the risk of developing cancer.
So yes, in an era where emissions from energy systems threaten mass extinction from Earth's climate, which is now warming at least 25x the warming rate that caused the worst mass extinction in geological history (End Permian or Great Dying), it would be laughable if it wasn't so sad that ALARA is used by misinformed ideologues to increase the cost of nuclear power.
Radioactive substances exist in all our food, our clothes, the ground, the structure of buildings, and the air - especially near coal plants, which emit uranium in their smoke. If you want to minimise the radiation you receive you should avoid go out on sunny days, and you should keep away from people and animals because they all have radioactive substances in their bodies. Carbon dating experts consider ideologues who declare themselves a radiation free zone 'in serious trouble': It means they must have dead at least 50,000 years.
> In other areas of our lives, this assumption would seem obviously wrong. For example, the cumulative harm model applied to alcohol would say that drinking a glass of wine once a day for a hundred days is equivalent to drinking one hundred glasses of wine in a single day. Or that a jogger who ran a mile a day for a month was putting her body under greater strain than one who ran a marathon in a day. We recognise that the human body is capable of repairing damage and stress done to it over time.
This is a false, harmful equivalence. None of the parallels you suggest involve *directly mutating your DNA*! There is *no* safe radiation level, and Linear No Threshold is accurate!
The problem, as you suggest elsewhere in your great piece, is ALARA, which chases marginal (but real!) improvements at massive cost.