11/20/2023 0 Comments Nuclear fission chernobyl![]() ![]() Just about 37 years ago, on April 26, 1986, in the then Soviet Union, one of the four 1000 MW nuclear fission reactors in the Chernobyl nuclear power station started to go out of control, becoming possibly the worst industrial disaster in human history, in terms of its toll on human lives and health. Particularly when we are standing close to 11th March 2023, when one of the worst disasters took place in the Fukushima prefecture, in Japan 12 years ago. We in the West tend to forget that the shadow of Chernobyl falls primarily on the Ukraine, Belarus and Russia the countries that have most suffered, and continue to suffer, from the disaster.In this period of ever-increasing Climate Crisis, when many voices pushing nuclear fission power as a supposedly zero-carbon safe’ energy are being heard, it is fitting to remember some of the catastrophic disasters of the nuclear power industry. The average Western European dose, by comparison, was between 0.05 and 0.5 mSv a dose that pales into insignificance when one remembers that natural radioactivity exposes us to around 2.4m Sv a year. This fission product beeing shortlived, it was an extinct isotope never found in the fallout from atomic bombs.įor the 273,000 people living in close proximity to the power plant, the average dose of radiation absorbed over the following three years was 35 millisievert or mSv, with some having absorbed as much as 200mSv. The presence of caesium 134 was one of the most important signatures of the Chernobyl accident. At the moment of the disaster, 46% of the radiation emitted by the cloud was due to iodine 131, 36% was caused by tellurium 132, 7% by barium 140, 4% by caesium 137 and 2% by caesium 134. The resulting radioactive cloud rose to some 10,000 metres above sea level and was spread westward by the winds over several million square kilometres, most severely affecting the northern Ukraine. Approximately 4% of the radioactive substances contained in the reactor were released into the atmosphere including almost 50% of the caesium and iodine content and 100% of the xenon. The absence of a security system made the situation far worse. From the core of the disembowelled reactor, left bare, escaped large amounts of radioactive material. It took several days to tackle the fire in extreme conditions, a deadly radioactivity adding to the hell of fire. Then the large amount of graphite which served to moderate the neutrons caught fire. It took six major human errors for the disaster to occur.Ī violent explosion lifted the heavy slab covering the reactor. ![]() The reactor was then operated at levels forbidden by the safety guidelines, with the security systems temporarily disabled. In order to do this, they tried to conduct the test with the reactor turned off. The team in charge of the reactor had hoped to test what would happen if the security system were to fail, and the nuclear fuel to cool down. On the 26th of April 1986, after several errors of judgement were made during an attempt to improve security, a reactor at the Chernobyl power plant exploded. The radioactive releases due to the explosion and the fire are at the origin of the Chernobyl cloud. Then, steam continyd to escape from the still smoking ruins. Extinguishing the fire, lasted several days. The violent explosion that lifted the heavy slab covering the reactor was followed by an intense fire fed by the large amount of graphite present in the reactor core. Therefore, Chernobyl remains the only accident where control of nuclear fission was lost. Operators inadvertently deactivated safety systems during a low power test while the reactor was unstable. These weaknesses were nevertheless not the primary cause of the disaster. The RBMK reactors suffered from an additional weakness – it took too long to insert the control rods into the reactor (28s as opposed to 1s for Western-style reactors), thus making the instabilities harder to overcome. In particular, they may be become unstable at low power. ![]() RBMKs burned slightly enriched uranium, have graphite moderators and used water as a coolant. The Chernobyl nuclear reactor belonged to the RBMK class, a common type of reactor developped in the USSR and the Eastern Europe countries after the war. The urgency imposed dramatic conditions, but the habit of secrecy, the habit also to not be held accountable, made these authorities to hid 36 hours the nature of the accident. Ukraine, 1986: the world’s most devastating nuclear accidentĪp: The scale of the Chernobyl disaster that occurred in Ukraine, took the Soviet authorities by surprise. ![]()
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