Dr Victor Luca, Nuclear Chemist, 6-Mar-22
Figure 1. (a) Fermi’s Chicago Pile-1 and (b) the Zaporizhzhia nuclear plant showing the six reactors.
It was war time and the race between America and Nazi Germany to develop the atomic bomb led to a frenetic research effort in America code-named the ‘Manhattan Project’. The project had small beginnings involving just a handful of Chicago scientists including Enrico Fermi, Leo Szilard, Walter Zinn and Herbert Anderson. Eventually, 150,000 personnel were recruited to work on the project including scientists, engineers and others. At one point it was as though every scientist in America had some involvement. No one questioned, where the money would come from!
The first demonstration by the Fermi team that an atomic chain-reaction could be self-sustaining occurred in 1942 and took place in a squash court underneath the football stadium at the University of Chicago.
The experimental pile that was completed 1-Dec-1942 and was known as Chicago Pile-1. It consisted of 349,720 Kg of graphite arranged in 57 layers, and containing in its core 36,555 Kg of uranium oxide and 5,624 Kg of uranium metal. The pile was surrounded by lead bricks in order to contain the radiation. Its worth at the time was approximately $1 million dollars. It was a lot of money to spend on a physics experiment in those days.
As the last control rod preventing the nuclear reaction from occurring was removed from the pile, neutron detectors positioned in and around the pile measured an increase in neutron count coming from the sustained chain reaction. No explosion, no great production of heat and no flash of light had occurred within the pile of lead bricks. Just the irrefutable increase in neutrons that prior calculations had indicated would be measured if a self-sustaining nuclear reaction was taking place in a controlled manner.
This is physics at its best where the practice incontrovertibly confirmed the theory.
These original scientists knew that what they had done had serious military implications but they hoped that perhaps the building of power plants, and the production of radioactive elements for science and medicine would become the paramount objectives.
Today there are a total of about 440 nuclear fission reactors in the world. Many of the existing reactors have safely produced somewhere between about 12 and 17% of world electricity over almost half a century. Fifteen Russian-designed VVER reactors are currently operating in the Ukraine and six of these reactors alone are located at the Zaporizhzhia nuclear power plant. One of the ancillary plant buildings was recently hit by a stray Russian projectile and caused minor damage and a fire, but no radiation leak.
The war that Putin is prosecuting in the Ukraine for reasons that are complex involve one heavily nuclear armed state and one with extensive nuclear power facilities. NATO nuclear weapons states are thankfully not involved yet in the fighting, although they are involved in the provision of conventional weapons and the application of sanctions and financial measures. The NATO member countries I am referring to are the United States, United Kingdom and France and they have not just civilian nuclear power programs but are also armed to the teeth with nuclear weapons.
The VVER reactors operating in the Ukraine are water-cooled and moderated. Deprived of coolant a nuclear reactor of this type will get very hot and can potentially melt-down and even explode just like a car engine that runs out of water.
As we know from the Chernobyl event in 1986 an exploding RBMK-model nuclear reactor could, depending on atmospheric conditions, disperse radioactive material for thousands of kilometers. The fallout from the Chernobyl reactor located in the Ukraine, which was Soviet Union territory at the time, reached Sweden in the west. In fact the only reason anyone outside of the Soviet Union knew that an accident had taken place at all was because the radiation was detected in Sweden and the alarm raised. A reasonably accurate depiction of what caused this accident was presented in the HBO miniseries ‘Chernobyl’ released in 2019.
What is fallout? Basically, fallout is debris from the reactor explosion that can consist of building material, reactor components and nuclear fuel of different size from large fragments that travel small distances to aerosols that travel great distances in the atmosphere. Because the uranium (in the form of UO2) within the reactor core is being transmuted through the fission reaction into a wide range of isotopes, reactor fuel that is undergoing fission will contain isotopes of many elements. Some of these will decay quickly (seconds, hours, days) and others will decay very slowly (hundreds of thousands of years).
Figure 2. Source: Special Report: Counting the dead. Nature 440, 982–983 (2006).
Two isotopes with which I have been concerned with for a large part of my career are 137Cs and 90Sr. These isotopes emit gamma and beta radiation respectively and have half-lives of about 30 years. The radiation emitted from 137Cs decay can pass through lead bricks while that from 90Sr barely makes it through a sheet of paper. What makes these isotopes particularly problematic is that the elements are highly soluble in water and are highly mobile in the environment and can easily be incorporated into the human body. The 90Sr will concentrate in the bones while 137Cs will travel to all parts of the body. Another problematic isotope produced by the fission reaction is 131I, which concentrates in the Thyroid gland and causes cancer if sufficient accumulates there.
The map of Figure 2 shows the measured distribution 137Cs at 25 years after the Chernobyl accident in units of kBq/m2. These units essentially are a measure of concentration. Basically, the reader needs to appreciate that 137Cs from Chernobyl accident was distributed throughout Europe depending on atmospherics. In fact, we know that minute amounts of 137Cs from Chernobyl was even incorporated into tea leaves in Argentina.
Just as in the case of an aerosolized virus, dose makes the poison. So the greater the radiation dose or dose of any other poison that you incorporate into your body, the greater the chances of provoking harm. In the case of ionizing radiation, induces damage to DNA and this causes cancer. As it is, we know that about 4,000 people in the Chernobyl area got thyroid cancer probably as a result of the accident and that 15 of these died. Even now, we don’t really know how many future thyroid cancer deaths will eventually be clocked up to Chernobyl.
Now imagine what might happen if the six reactors at Zaporizhzhia were to be destroyed either by accident or on purpose.
The fallout would disperse throughout Europe and beyond. It would be inhaled directly by people and animals and be incorporated into the water, vegetation and livestock. It would contaminate the entire food chain for decades impairing the food production capacity of many countries.
Were accidental or deliberate bombardment of nuclear facilities occur, it could easily escalate into full-on nuclear weapons conflict. We in New Zealand, remote as we are, would not escape the holocaust that would ensue from a full-blown nuclear war between super powers. Even if those involved in the Ukraine-Russia conflict can negotiate a peaceful solution, the specter of US-China, and on-going US-Russia tensions pose an ever constant nuclear threat to all of humanity.
Personally, I do not think that Putin is stupid enough, or even suicidal enough, to deliberately hit a Ukrainian power plant because the blow-back on Russia might also be serious. Putin would have to answer to the Russian people as much as to the rest of the region. However, depending on atmospheric conditions the impact on neighboring countries and Europe in particular could be catastrophic. However, when missiles are flying around all over the place, the chances of an accident is increased.
Where the blame for the present conflict lies is a difficult question that deserves careful analysis of the history and the international relations landscape. Regardless, the consequences of a full-blown nuclear conflict is unthinkable and for the sake of humanity everything must be done to avoid it.
Mikhail Gorbachev (President of the USSR) in a BBC interview did not understate matters when he said, “As long as weapons of mass destruction exist, primarily nuclear weapons, the danger is colossal.”
References
Castelvecchi, D. Ukraine nuclear power plant attack: scientists assess the risks. Nature, 4-Mar-22. https://www.nature.com/articles/d41586-022-00660-z
De Cort, M. Atlas of Caesium 137 deposition on Europe after the Chernobyl accident. EUR 1673 EN/RU. January 1998 Publisher: Office for Official Publications of the European Communities. ISBN: 92-828-3140-X.
European Commission, Directorate-General for Research and Innovation, De Cort, M., Dubois, G., Fridman, S., et al., Атлас загрязнения Европы цезием после Чернобыльской аварии, Publications Office, 2009.
Special Report: Counting the dead. Nature 440, 982–983 (2006). https://doi.org/10.1038/440982a