The cut has revived the status of nuclear installations, including the cooling capacity of the radioactive fuel on the site.
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The International Atomic Energy Agency (IAEA) announced, Wednesday, March 9, that the nuclear site of Chernobyl, Ukraine, had been Completely disconnected from the power grid due to Russian military actions, reviving fears related to the state of the facilities. The Director General of the IAEA, Rafael Mariano Grosse, has denounced a “violation” of one of the fundamental pillars of nuclear safety but said that this break had not, at this stage, “major impact” . According to the Ukrainian authorities, the site, now in the hands of the Russians, has emergency generators and enough diesel to operate for forty-eight hours.
Currently, 20,000 worn fuel assemblies are stored in the site storage pool. After being used in a reactor, the spent fuel is still radioactive and exudes heat: it is then stored in a “pool” – a basin filled with water – to be cooled. Once its radioactivity and thermal power have sufficiently decreased, after a few years, it can be transported to be, in general, transferred to dry storage sites.
The power supply is necessary for the pool water, which may contain small amounts of radioactive isotopes, which is pumped and cleaned, and to reintroduce cold water. Failure, the water will warm up and could, in theory, begin to evaporate, as well as some radioactive isotopes present in the water.
Remote Tracking impossible
In Chernobyl, however, worn fuels, which were being transferred to dry storage, had decades to cool. Due to the time that has elapsed since the 1986 nuclear accident in Chernobyl, “the thermal load of the pool and the volume of cooling water are sufficient to ensure efficient heat evacuation without electricity”, assured IAEA. The evaluation of the UN-nuclear-based “volerogram” is “understandable considering the age of the nuclear fuel”, and this “considerably reduces the risk of contamination inside the building,” reacted on Twitter Claire Corkhill, professor, at the University of Sheffield (United Kingdom), a specialist in the degradation of nuclear materials
In A note on the situation in Ukraine Posted on 25 February, the Institute for Radiation Protection and Nuclear Safety (IRSN) also explains that the studies carried out after the accident of the central Fukushima, Japan, on the consequences of a total loss of pool cooling, show a slow water temperature rise (up to a temperature of the order of 60 ° C) but no Displaying assemblies – that is, fuels would always be kept under water.
If the risk of radioactive leakage therefore appears in the limited state, the situation of the plant is not less worrying. Remote transmission of radioactivity level control systems is also interrupted and it is impossible to follow what is happening on site. The IAEA has also reaffirmed, Tuesday, its concern about the “stressful and particularly difficult” situation of some 200 people who work on the site, and who have not been able to leave the places since the control of the zone by the Russian armed forces on February 24th.