SEVASTOPOL, April 24. /TASS/. Scientists from Sevastopol State University (SevSU) have discovered that in just a few decades time, the main hazard from the Chernobyl nuclear accident will not be plutonium as many would assume, but another radioactive substance - americium, which more easily seeps into water and plants, emits more dangerous alpha radiation, and could remain active for over 4,300 years, the study’s authors told TASS.

"This study focuses on plutonium-241, which accounted for approximately 98% of the plutonium isotope prevalence after the release. On the one hand, it has low beta emission energy. However, its decay produces a daughter product - americium-241 - which poses a serious hazard as it is a long-lived alpha emitter and will remain active for over 4,300 years," said Lidia Lukina, PhD in Chemistry and Associate Professor at SevSU.

Scientists from various fields contributed to the study: Lukina, a specialist in radioecology; Dmitry Moiseyev, Dean of the Faculty of Information Technology at SevSU; and Nikolay Kovalev, a radiation accident liquidator and head of the Nuclear Chemical Technologies Research Laboratory who holds a PhD in Engineering. "We calculated the activity dynamics of the remaining plutonium-241 due to its natural decay and the resulting americium-241 from the accident over a period of 70 years, until 2056. By 2056, only 3.3% of the amount released into the environment will remain plutonium-241, and its prevalence will decrease. However, americium-241 will only increase in abundance, and, as a result, its contribution to the total prevalence will increase over time," Kovalev explained.

Americium-241 hazard

"The resulting americium-241 poses the primary radioecological hazard in plutonium-contaminated areas. This is confirmed by data on the physicochemical and toxicological properties of the elements plutonium and americium, as well as the radiation properties of the isotopes of plutonium-241 and americium-241," Moiseyev emphasized, drawing on the study’s data. He said that americium is a more refractory and lighter metal than plutonium. Its compounds are water-soluble, making it mobile in soil and capable of seeping into plants through their root systems.

Consequently, this substance spreads more easily through ecosystems and, along with plant food, can enter the bodies of animals and humans. This is extremely dangerous, given that americium-241 emits alpha radiation, which causes the greatest damage when ingested. "Compared to short-lived plutonium-241, this radionuclide has a long half-life—it will remain active for more than 4,300 years. It’s worth noting that in soils in areas where contamination was highest, the americium-241 content already equaled the total plutonium isotopes by 2000-2001, and by 2060, it will be double their prevalence. Given all of the above, areas affected by this contamination will be unsuitable for agricultural activity for millennia," Moiseyev specified.

He added that americium-241 has now effectively become the primary dose-forming radionuclide among the isotopes of transuranic elements. "However, I would like to draw attention to one more detail. The data we presented on the activity of plutonium and americium isotopes are purely mathematical. Under natural conditions, there remains a chance that these processes will be influenced by natural factors, and that humans will find ways to rehabilitate ecosystems in contaminated areas," the scientist noted.

About seminar

The research results will be presented on Friday at the seminar "40 Years after the Chernobyl Accident: Current Research and Forecasts" at the Institute of Southern Sea Biology of the Russian Academy of Sciences. Specialists at this institution began researching its impact on the ecosystem of the Black Sea and several other regions of the world almost immediately after the disaster, and this remains an important area for the Department of Radiation and Chemical Biology of the Institute of Southern Sea Biology. At the seminar, scientists from across the Russian Federation will discuss how the Chernobyl accident affected marine, freshwater, and terrestrial ecosystems in various regions.

The accident at the Chernobyl Nuclear Power Plant, located in the Kiev region, occurred on April 26, 1986. During testing of a turbogenerator at the plant’s fourth power unit, an explosion and fire occurred, leading to the worst disaster in the history of nuclear power. More than 200,000 square kilometers were contaminated with radioactive substances. The northern regions of the Kiev and Zhitomir regions of the Ukrainian SSR, the Gomel region of the Byelorussian SSR, and the Bryansk region of the RSFSR were the most contaminated.