Nuclear physicist Pavel Povinec. (source: ESET Science Award/ Linda Kisková Bohušová )
Pavel Povinec says that his entire life is tied to radioactivity. A professor of nuclear physics at the Faculty of Mathematics, Physics, and Informatics at Comenius University in Bratislava, his research on radioactivity has taken him across the world, including nuclear disaster sites and where atomic bomb tests were carried out in the Arctic and Pacific oceans, and won him a team Nobel Prize for Peace.
This article is supported by the ESET Foundation, whose annual ESET Science Award recognises exceptional scientists.
His ocean research, he tells The Slovak Spectator, was unusual for someone like him. "I headed marine radioactivity research in Monaco, which was quite a rarity because I come from a landlocked country," he says.
Povinec was one of the first people to graduate in nuclear physics in Slovakia and has been involved in radioactivity research since the 1960s.
When he started in science, things were very different, he says. Obtaining or manufacturing instruments for research today is relatively easy - if financial support is available; when he first began, he and his colleagues had to build their own scientific instruments and simultaneously develop methods for measuring radioactivity and sample preparation.
He says that the experience and skills he gained in doing so are the foundation of his scientific success.
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Remembering Chernobyl
A substantial part of Povinec's work is in environmental physics. He was among the scientists who had to evaluate the radiological impact on the environment after the Chernobyl disaster on April 26, 1986.
He was on his way to work when a friend called and told him that a radio station in Vienna had reported that something had exploded in the Soviet Union. By that time, the radiation from the disaster had already reached Sweden. This had been picked up during checks on workers at Swedish nuclear power plants. Radiation contamination was found on people when they turned up for work, but checks showed the nuclear reactors in the country were working fine.
"When I arrived at work, I was supposed to give a lecture, but I started preparing with my students sampling equipment as I recognised that a radioactive plume from Chernobyl should reach Bratislava soon. That day we took the first samples from the air, but we didn't detect anything. It was only on the following day that we detected radioactive nuclei from Chernobyl. We were the first in Czechoslovakia and Central Europe to do so," Povinec recalls.
Most of the information was obtained from analyses conducted at the Department of Nuclear Physics which he was heading. They even checked food, e.g. salad, fruits, wild mushrooms, etc. An emergency commission was formed by the government, where they shared their results and discussed necessary measures. These, however, were not released to the public immediately.
"During the critical period, it did not rain in Slovakia when radioactive clouds passed over the country. Therefore, for example, contamination in Scotland was higher than in Slovakia. There were areas like Dunajská Streda and Slovenské Rudohorie where the concentration of radionuclides was elevated, but not to the extent that it would cause fatalities," he says.
Povinec saw the Chernobyl power plant himself two years later when he went there to investigate the transition of radionuclides in the environment, mainly from soil to trees. The sarcophagus that had been placed around the plant left a lasting impression on him. "That was an experience of a lifetime," he says, adding, though that it was not the only sight that left him in awe - he also saw a red coniferous forest, cats as big as large dogs, and metre-high tulips.
A land-lubber goes to sea
In 1993, Povinec became head of the laboratory for marine radioactivity research at the International Atomic Energy Agency (IAEA) in Monaco. He started work on January 1, 1993, on the same day Slovakia became independent. His tenure ended in 2005 when he retired from IAEA.
"I was the first and last Czechoslovak citizen to get a diplomatic post at IAEA. Naturally, also the first Slovak," he jokes.
During his tenure, he organised several oceanographic expeditions. He travelled to the Novaya Zemlya archipelago in the Arctic Ocean, the Mururoa and Bikini atolls in the Pacific Ocean, where the Soviet Union, France, and the United States, respectively, conducted atomic weapons tests. He was studying how radionuclides spread in the sea and whether they posed a threat to the environment and local people.
The first expedition was to Novaya Zemlya, the main base for tests on massive nuclear weapons conducted by the Soviet Union, such as two explosions in 1961 of the Tsar Bomba, the most powerful nuclear weapon ever created.
He also went to Mururoa island in French Polynesia in the south Pacific.
Povinec said that it was very interesting because, despite being a test site, the island appeared very beautiful (Mururoa in the Polynesian language has a mythological meaning: a mysterious island). There were even plans to open the island to tourists, but this idea was not realised, and the island remains closed today.
France stopped atmospheric nuclear tests in the 1970s and shifted to underground testing when it began drilling shafts into the lagoon up to a depth of about one kilometre, where the nuclear bomb tests occurred.
"It must be said that not all tests were successfully carried out and some charges did not explode, so the entire shaft was concreted to prevent environmental impact. France conducted its last nuclear test at Mururoa in 1995 as part of a series of underground tests that led to a complete cessation of nuclear testing in January 1996. At that time, Jacques Chirac was president, and the French government invited the IAEA to conduct radioecological studies on the impact of nuclear bomb testing on the marine environment; therefore, we participated in several scientific expeditions," he says.
"We even swam in the lagoon - the concentration of radionuclides was not very high. We were more afraid of sharks," he says.
Povinec also visited the Bikini atoll, where the U.S.A. tested nuclear weapons, and investigated transport of Bikini radionuclides in the north-west Pacific Ocean. Native inhabitants were relocated at the time, although some have already returned under certain restrictions. However, the soil is still contaminated with caesium-137, which means that land use for food production is limited.
Pavel Povinec. (source: ESET Science Award/ Linda Kisková Bohušová )
Understanding marine radioactivity
Povinec has also worked on the research of seawater contamination due to dumping of radioactive wastes. Initially, there was no ban on disposing of radioactive waste into the oceans, for example, low-level radioactive waste from hospitals. Later, when a ban was put in place, the practice was supposed to stop, but the Soviet Union, especially around Vladivostok, released liquid waste into the Japan Sea. The Japanese and Korean authorities subsequently approached the IAEA to determine the impact of what the Soviets had done.
"Fortunately, the amount of material that entered the environment was not significant. The Pacific Ocean and its surrounding seas have very strong currents that quickly disperse water to the open Pacific. We conducted marine radioactivity research in the Pacific for more than 20 years, and when the Fukushima disaster occurred in 2011, our previous work and radionuclide data on seawater, sediment, and biota, which have been stored in the IAEA’s Marine Radioactivity Database (MARIS), allowed us to identify how the Fukushima accident changed the distribution of radionuclides in the Pacific Ocean and its surrounding seas," explains Povinec, who, together with his Japanese colleagues, published two scientific monographs, one immediately after the disaster and another 10 years later, as well as more than 30 scientific papers. His worldwide marine radioactivity studies have been covered in more than 200 scientific papers in several monographs.
According to Povinec, the main problem in Fukushima was that the tsunami was 14 metres high. Water flooded the diesel generators, which stopped producing electricity, and the reactors ceased to cool. When the power plant was built, a height of seven metres was considered sufficient based on the historical experience of tsunamis.
A disaster
Because Povinec has seen the impact of radioactivity on the environment first-hand, he has serious concerns about the situation at the Zaporizhzhia nuclear power plant in Ukraine.
"I feel that there is a lot of risks are involved in this nuclear power plant, the largest in Europe. It's as if no one realises that the reactors are very close to each other; if an accident were to happen to one, it could affect the others. From the reports we receive, we don't know much about what's going on there," he says.
He says that the best thing to do would be to place the plant under UN administration, supported by major powers, and a demilitarised zone would be set up around it.
He describes the possible use of nuclear weapons in the Ukraine war as “tactical posturing”.
"Everyone is aware that it would be a disaster. If small tactical weapons were used, the impact would not be catastrophic, but if there were large explosions, Europe would be on the brink of an apocalypse. It is impossible to predict how things would develop. History shows that military authorities often overestimate their control possibilities, and there have been cases in the past where things have gotten out of hand."
Making a unique laboratory
In 2005, Povinec, as a member of the IAEA team, won the Nobel Peace Prize for research on marine and ocean radioactivity.
This work was the last he did for the agency, and a year later, he returned to the Comenius University, where he continues to work to this day.
At the IAEA, he had been among the first to use accelerator mass spectrometry - an ultrasensitive and quick method for analysing radioactive isotopes, even those with very long half-lives spanning tens to billions of years. Using traditional techniques, it would require waiting for a long time when a sufficient amount of decay events would accumulate, not to mention the need for very large samples.
There are two types of nuclei: stable, which do not change, and radioactive, which decay over time to other nuclei. Scientists like Povinec look for the products of this decay. For example, caesium-137 has a half-life of 30 years, and when it decays to another radionuclide, it emits gamma-radiation. By placing a detector such as a gamma-spectrometer in the path of this radiation, it's possible to determine the energy and number of emitted photons, and thus the activity of the source.
The introduction of accelerators into spectrometry marked a significant advancement because it is not necessary to wait for accumulation of the signal from decaying radionuclides (from days to weeks), but we can analyse them as they would be stable by measuring their masses. This will increase the sensitivity by several orders of magnitude to the extent that rare radionuclides could be separated from the background and the analysis of even very small samples in a short time (tens of minutes). This means the method can be used in many areas, such as rare nuclear processes, radiopurity of materials, climate change, astrophysics, solar activity cycles, cosmic weather, meteorites, in environmental research, forensic, groundwater protection, dating in archaeology, even determining whether a painting is genuine or a forgery, and more.
Povinec and his colleagues built an accelerator mass spectrometry (AMS) laboratory within the Centre for Nuclear and Accelerator Technologies (CENTA) at Comenius University and have been using it in national and international projects.
For example, in the framework of an international consortium several charcoal samples from the St. George Church in the village of Nitrianska Blatnica and the St. Margaret of Antioch Church in Kopčany were dated, showing that they are the oldest preserved sacral buildings in Slovakia.
"We found mall pieces of charcoal and can tell when the churches were built. We found - with an 80 percent probability - that the churches in Kopčany and Nitrianska Blatnica were possibly built before the arrival of Saints Cyril and Methodius to Great Moravia," Povinec says.
He adds that the CENTA facility can also be used for elemental analysis of samples, also called ion beam analysis (IBA). It can determine what elements are present in a meteorite, in food, tree rings, or living organs. For example, rabbits exposed to the same radiation as people receive from mobile phones were found to have an increased concentration of certain heavy elements in their brains.
The CENTA facility equipped with AMS and IBA beam lines, together with the Low-background gamma-spectrometry laboratory which Povinec and his colleagues have set up, represents the state-of-the-art facility, he says.
"Our laboratory is unique in the world; there are only a few where everything that we do can be done do as well. When you have such equipment, you are world-class. No one will take you into collaboration just like that, but when you are good, they want you. We are participating in several top-level collaborations searching for rare nuclear decays and dark matter (LEGEND, CRESST, SuperNEMO), and recently a French group has now approached us with a new collaboration project", he says.
