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There have been a number of media reports on Russia’s claims that the occupied Zaporizhzhya nuclear power plant in Ukraine could spread dangerous radiation across eastern Europe.
Professor Paul Norman, Professor of Nuclear Physics & Nuclear Energy, University of Birmingham, said:
“Most nuclear reactors, such as the ones at Zaporizhzhia, have a number of strong protective barriers to prevent radioactive release. These are a concrete containment (metres thick of concrete) and a steel pressure vessel (just under a foot thick of steel) as well as the fuel’s casing. They are designed to withstand aircraft impact, earthquakes, explosions, and similar. However, nothing is indestructible, and sufficiently powerful and sustained targeted attacks would eventually break through.
“In a nuclear incident much depends on the “source term” and prevailing conditions (the latter being mostly the weather). The source term means the actual amount and nature of the radioactive release, which would be highly dependent on the scale and specifics of the damage caused (for example at Chernobyl the explosion, caused by it being a bad/unstable design, blasted a plume into the air – whereas at Fukushima there wasn’t the same power to send things over a wide range).
“Whilst it’s very uncertain what might happen in such an event (you could have a small release or large release, and winds could preferentially blow things one way or another), clearly the places closest by would likely be the most affected. So for example following Chernobyl most of the radioactive material went to Ukraine itself, Belarus, and Russia.
“Danger from a missile hitting a reactor is the potential for release of the radioactive inventory (inside of the reactor) itself. It’s important to note that this would not trigger a nuclear explosion from the nuclear material itself (so it doesn’t further detonate, like a chemical explosive might do – nuclear fission works in a different way to that).
“However, a nuclear incident might be caused by other things besides a strike on the reactor itself. Hitting the fuel cooling ponds (whilst fuel is in them) could cause a radioactive dispersion. Similarly with any radioactive waste stores on site. Damaging certain cooling systems could also prevent the reactor from properly cooling itself and lead to overheating – a “meltdown”.
“The need for cooling persists even after the reactor has been shut down (i.e. after the chain reaction has been ceased). This is due to radioactive products built up in the fuel due to its earlier operation, and is called “decay heat” (this can be likened a bit to the dying embers of a fire, after a fire has been put out). Although it varies over time, this equivalent of “dying embers” emits of order 1% of the reactor’s full power over a longish timescale. 1% may not sound much, but in normal operation a 1 GW electrical output reactor is generating about 3 GW of thermal (heat) energy, so this is about 30 MW – the equivalent of about 30,000 or so 1 kilo Watt little electric heaters/radiators!!”
Professor Malcolm Sperrin, Director of the Department of Medical Physics and Clinical Engineering, Oxford University Hospitals NHS Trust, said:
“This is not Chernobyl. The type of reactor is different and the potential failure modes are also different. It also needs to be pointed out that there is a fundamental difference between the causes of the Chernobyl and Fukushima reactor releases and any potential breaching of containment using munitions. The various levels of containment are very strong and not easily penetrated. However, radioactive material does exist outside of the reactor confinement such as in areas put aside for storage pools, laboratories etc which would be more susceptible to release to the environment either to the atmosphere or ground water and this does create the potential for risk to surrounding countries but not on the scale of Chernobyl. It also needs to be bourne in mind that the prevailing wind may lead to compromise of Russian held areas. It is important to consider the future; the clearing of radioactive compromised areas such as damaged power plant is clearly of concern. The deliberate targeting of critical infrastructure is against the Rules of Combat which Russia and the Ukraine are signatories of.”
Professor Gerry Thomas, former Professor of Molecular Pathology at Imperial College London, said:
“In the extremely unlikely event of hostile activity resulting in a radioactive release as a result of a meltdown and breach of the containment surrounding the reactors, the only concern for those not in the immediate vicinity of the plant would be exposure to volatile isotopes that have been ejected into the atmosphere – primarily 131-I and 137-Cs. Heavier isotopes would not be dispersed widely – as was the case during the Chernobyl accident. 131-I has a short physical half life of 8 days, and therefore significant amounts of this isotope would be unlikely to reach neighbouring countries. Cs-137, because of its longer half life of 30 years, is more likely to reach beyond Ukraine. We know that the only radiological consequence of the Chernobyl accident was thyroid cancer in those who were very young at the time of the accident, and the increase in this was only observed in the areas closest to the accident site (areas of Northern Ukraine, Southern Belarus and a very small area of Russia that borders Ukraine and Russia). No effects have been seen from exposure to Cs-137, either in those areas where thyroid cancer has increased nor at greater distances from Chernobyl. Health effects are related to dose to the individual – the further away from the release site, the lower the dose, due to the dilution effect in the atmosphere, and the time taken for the radioisotopes to be deposited in places further away. The only health concern, in the unlikely event of a release from Zaporizhizhia NP, would be to those within the power plant itself, and to a lesser extent those still living in the towns and villages in the immediate area.”
Declared interests
Prof Malcolm Sperrin: “No conflicts of interest.”
Prof Gerry Thomas: “I don’t have any competing interests to declare.”
For all other experts, no reply to our request for DOIs was received.