With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: The Chernobyl disaster was a cataclysmic nuclear incident.
text_B: The Chernobyl disaster , also referred to as the Chernobyl accident , was a catastrophic nuclear accident .. catastrophic. Catastrophic failure. nuclear accident. Nuclear and radiation accidents and incidents. It occurred on 26 April 1986 in the No. 4 light water graphite moderated reactor at the Chernobyl Nuclear Power Plant near Pripyat , in what was then part of the Ukrainian Soviet Socialist Republic of the Soviet Union -LRB- USSR -RRB- .. Pripyat. Pripyat. Soviet Union. Soviet Union. light water graphite moderated reactor. light water graphite moderated reactor. Chernobyl Nuclear Power Plant. Chernobyl Nuclear Power Plant. Ukrainian Soviet Socialist Republic. Ukrainian Soviet Socialist Republic. graphite. nuclear graphite. During a late night safety test which simulated a station blackout power-failure and in which safety systems were deliberately turned off , a combination of inherent reactor design flaws , together with the reactor operators arranging the core in a manner contrary to the checklist for the test , eventually resulted in uncontrolled reaction conditions that flashed water into steam generating a destructive steam explosion and a subsequent open-air graphite fire.Although most reports on the Chernobyl accident refer to a number of graphite fires , it is highly unlikely that the graphite itself burned .. station blackout. power blackout. safety systems. control rod. reactor design flaws. RBMK. arranging the core. Iodine pit. checklist. checklist. uncontrolled reaction conditions. prompt critical. steam explosion. steam explosion. graphite. nuclear graphite. According to the General Atomics website < http : /  / gt-mhr.ga.com / safety.php >  : `` It is often incorrectly assumed that the combustion behavior of graphite is similar to that of charcoal and coal .. graphite. nuclear graphite. General Atomics. General Atomics. charcoal. charcoal. Numerous tests and calculations have shown that it is virtually impossible to burn high-purity , nuclear-grade graphites . ''. On Chernobyl , the same source states  : `` Graphite played little or no role in the progression or consequences of the accident .. The red glow observed during the Chernobyl accident was the expected color of luminescence for graphite at 700 ° C and not a large-scale graphite fire , as some have incorrectly assumed . ''. graphite. nuclear graphite. luminescence. black-body radiation. Similarly , nuclear physicist Yevgeny Velikhov , < http : /  / news.bbc.co.uk / 2 / hi / europe / 4918742.stm > noted some 2 weeks after the accident that `` Until now the possibility of a catastrophe really did exist  : A great quantity of fuel and graphite of the reactor was in an incandescent state '' That is , all the nuclear-decay heat that was generated inside the uranium fuel -LRB- heat which would normally be extracted by back-up coolant pumps , in an undamaged reactor -RRB- was instead responsible for making the fuel itself and any graphite in contact with it , to glow red-hot .. graphite. nuclear graphite. 2 weeks. decay heat. incandescent. incandescent. decay heat. decay heat. red-hot. incandescent. This is contrary to the oft cited interpretation , which is that the graphite was red-hot chiefly because it was chemically oxidizing with the air .. graphite. nuclear graphite. red-hot. incandescent. oxidizing. oxidizing. This fire produced considerable updrafts for about 9 days , that lofted plumes of fission products into the atmosphere , with the estimated radioactive inventory that was released during this very hot fire phase , approximately equal in magnitude to the airborne fission products released in the initial destructive explosion .. fission products. fission products. Practically all of this radioactive material would then go on to fall-out / precipitate onto much of the surface of the western USSR and Europe .. fall-out. nuclear fallout. The Chernobyl accident dominates the Energy accidents sub-category , of most disastrous nuclear power plant accident in history , both in terms of cost and casualties .. Energy accidents. Energy accidents. nuclear power plant accident. International Nuclear Event Scale. It is one of only two nuclear energy accidents classified as a level 7 event -LRB- the maximum classification -RRB- on the International Nuclear Event Scale , the other being the Fukushima Daiichi nuclear disaster in Japan in 2011 .. International Nuclear Event Scale. International Nuclear Event Scale. Fukushima Daiichi nuclear disaster. Fukushima Daiichi nuclear disaster. The struggle to safeguard against scenarios which were , at many times falsely , perceived as having the potential for greater catastrophe and the later decontamination efforts of the surroundings , ultimately involved over 500,000 workers and cost an estimated 18 billion rubles .. decontamination. decontamination. over 500,000 workers. Liquidator ( Chernobyl ). During the accident , blast effects caused 2 deaths within the facility and later 29 firemen and employees died in the days-to-months afterward from acute radiation syndrome , with the potential for long-term cancers still being investigated .. 2 deaths. Deaths due to the Chernobyl disaster. 29 firemen and employees died. Deaths due to the Chernobyl disaster. acute radiation syndrome. acute radiation syndrome. The remains of the No. 4 reactor building were enclosed in a large sarcophagus -LRB- radiation shield -RRB- by December 1986 , at a time when what was left of the reactor was entering the cold shut-down phase ; the enclosure was built quickly as occupational safety for the crews of the other undamaged reactors at the power station , with No. 3 continuing to produce electricity into 2000 .. sarcophagus. Chernobyl Nuclear Power Plant sarcophagus. radiation shield. radiation shield. cold shut-down. Shutdown ( nuclear reactor ). occupational safety. occupational safety. The accident motivated safety upgrades on all remaining Soviet-designed reactors in the RBMK -LRB- Chernobyl No. 4 -RRB- family , of which eleven continued to power electric grids as of 2013 .. safety upgrades on all remaining Soviet-designed reactors. RBMK#Improvements since the Chernobyl accident. RBMK. RBMK
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