Nuclear Reactions Flare Up Deep Inside Chernobyl's Ruins


Tom Hale

Senior Journalist

clockMay 11 2021, 17:01 UTC

The abandoned Chernobyl nuclear power station, Ukraine. Image credit: JoRanky/

Deep in the ruinous pits of the Chernobyl Nuclear Power Plant, 35 years after the worst nuclear accident in history, nuclear fission reactions have started to flare up again in an inaccessible basement room. 

Ukrainian scientists from the Institute for Safety Problems of Nuclear Power Plants (ISPNPP) recently detected an unusually high number of neutrons emanating from an inaccessible room in the Chernobyl Nuclear Power Plant, suggesting that a fission reaction has started reoccurring, Science Magazine reports.


“It’s like the embers in a barbecue pit,” Neil Hyatt, professor of nuclear materials chemistry at the University of Sheffield and member of the UK's Committee on Radioactive Waste Management, told Science. When the nuclear disaster occurred on April 26, 1986, much of the contents of the Unit Four reactor’s core melted down in a searing intense heat, causing some 170 tons of irradiated uranium to flood into the reactor hall’s basement rooms where it eventually cooled and hardened like congealed lava. 

Levels of radiation remained relatively stable over the years, but it was noted that a spike of neutrons (evidence of a nuclear fission reactor) would occur after a downfall of rain. Despite the initial shelter installed over the reactor hall shortly after the disaster, rainwater still seeped into the problematic area. The presence of water increased levels of fission because it slows neutrons and ups their chances of hitting and splitting uranium nuclei, thereby releasing more neutrons and so on. A new sarcophagus was installed over the power plant's ruins in 2016, designed to help further stop the leak of radiation. This has largely been successful until the ISPNPP noted unusual spots of radioactivity around room 305/2 where much of the fuel was dumped.

The cause of the reaction is not completely understood, but it does raise some rather worrying possibilities. According to Science, the ISPNPP data suggests the drying of the fuel is somehow making the neutrons more likely to hit and split any uranium nucleus, rather than less. Independent scientists, such as Professor Hyatt, have also confirmed this is a possibility, although not certain. 

Now comes the issue of how to address this problem. One plan is to use a robot to drill holes into the hardened radioactive slop and insert boron rods, which effectively act as a control rod in a reactor and reduce the number of neutrons flinging around.


Fear not, however. While this recent discovery is a problem that authorities and scientists are undoubtedly going to have to keep a close eye on, it's highly unlikely to spark another disaster anywhere near the scale of the original, as some tabloids have suggested. Nevertheless, the issue does highlight how the legacy of the 1986 disaster is going to linger for many years to come. The Ukrainian government has applied for UNESCO World Heritage Status to ensure people don't forget.

Amended 12/05/2021: Due to a spelling mistake, the third paragraph of this article originally said "spike of neurons." It has since been amended to say "spike of neutrons." 


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