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Spanish: History
#1
Chernobyl - O Desastre Nuclear http://professoralucianekawa.blogspot.co...l?spref=tw

via google translate, sample section:

"Causes:
  • Saturday, April 26, 1986, at 1:23:58 am local time, the fourth reactor of the Chernobyl power plant - known as Chernobyl-4 - suffered a catastrophic steam explosion that resulted in a fire, a number of additional explosions, and a nuclear meltdown.
But the most important factor was that Anatoly Dyatlov, chief engineer responsible for testing the reactors, even though the reactor was dangerous in some conditions and against the security parameters arranged in the operating manual, has carried out intentionally performing a power reduction test resulting in disaster.
  • The installation manager was composed largely of unqualified personnel in RBMK: the director, VP Bryukhanov, had experience and training in coal-fired power plant. His chief engineer, Nikolai Fomin, also came from a conventional power plant. Anatoli Dyatlov himself, former chief engineer of Reactors 3 and 4, only had "some experience with small nuclear reactors".
In particular:
  • The reactor had a void fraction dangerously high positive. Simply put, this means that vapor bubbles are formed in the cooling water, the nuclear reaction is accelerated, leading to over speed if no intervention.
Worse, at low load, this coefficient to be empty was not offset by other factors, which made the reactor unstable and dangerous. Operators were not aware of this danger and this was not intuitive for an operator not trained.
  • A more significant defect was the design of reactor control rods. In a nuclear reactor, control rods are inserted into the reactor to lower the reaction. However, in the RBMK reactor design, the tips of the control rods were made of graphite and the extenders (the end areas of the control rods above the tips, measuring one meter in length) were hollow and filled with water, while the rest of rod - the truly functional part that absorbs the neutrons and thus stops the reaction - was made of carbon-boron.
With this design, when the rods were inserted into the reactor, the graphite tips commuted an amount of cooler (water). This increases the rate of nuclear fission, since graphite is a more powerful neutron moderator. So the first few seconds after activation of the control rods, the reactor power increases, rather than decreases, as desired. This behavior of the equipment is not intuitive (on the contrary, would be expected that the power start downloading immediately), and, especially, was not aware of the operators.
  • Operators violated procedures, possibly because they were ignorant of the reactor design defects. Also many procedural irregularities contributed to causing the accident. One was the inefficient communication between the security office (in the capital, Kiev) and the operators in charge of the experiment conducted that night
It is important to note that the operators switched off many of the reactor protection systems, which was banned by the published technical guidelines, unless there was a malfunction.
  • According to the report of the Government Commission, published in August 1986, operators removed at least 204 reactor core control rods (a total of 211 this reactor model). The same guide (quoted above) prohibited the RBMK-1000 operation with less than 15 rods inside the core zone."
Pia
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