The aftershocks are continuing, the reactors at the Fukushima nuclear power plant are getting closer to collapse. Despite all the rescue continues, but the budget becomes black by the hour.
Report of the first explosion and growing alarm:
Fukushima, one of the safest plants in the world:
The Japanese Fukushima-1 nuclear power station, which at this time the world is holding its breath following the disastrous earthquake of 11 March, is one of the 25 more nuclear plants the way, designed by General Electric, and is (or was) considered one of the structures of its kind among the safest in existence. It 's a term now in its operational life, being now in operation for forty years: built in the late sixties, went into operation in 1971, and was to be decommissioned this year. Power stations of this kind, particularly those built in Giappone, territorio com'è noto fra quelli a maggiore rischio sismico, sono progettati per resistere a tutta una serie di catastrofi naturali o originate dall'uomo: dai terremoti alle bombe atomiche. Di fatto, nella centrale di Fukushima, la protezione principale dell'impianto, ovvero la grande gabbia di cemento armato che circonda il nucleo attivo, dove avviene la reazione nucleare che genera calore grazie alla radioattività delle barre di uranio, sembra abbia resistito. Ciò che è venuto meno sono le strutture accessorie, in particolare i circuiti di raffreddamento, formati da tubi in cui vengono fatte circolare sostanze (come il sodio) che assorbono il calore in eccesso. Questi impianti sono azionati da complessi sistemi di pompaggio that ensure the circulation and cooling fluid temperature controller. The earthquake, apparently blew the electrical power of the pumps, and coolant started to heat up over the allowed limit.
This type of incident widely expected, and there are safety procedures to prevent damage to the cooling system. In the case of Fukushima, apparently, the damage was so serious as to put out the systems of support. The Japanese authorities have made to flow on-site generators and batteries to ensure the autonomous power of the pumps, but this was not enough and it is determined an explosion in the cooling circuits, presumably caused by high pressure in the pipes caused by excess heat.
Nipponese authorities have also taken the measure, certainly extreme, to dispel the atmosphere of the superheated steam to cause a decrease in pressure. The condition has caused an increase in radioactivity in the environment within a radius of several kilometers around the reactor. The population was evicted from an area of \u200b\u200btwenty miles and instructions were issued to prevent damage from contamination (close to home, turn off air conditioners, breathe through a mask, etc.).. This, waiting for the winds dispersed the radioactive gas. The figures for alla contaminazione ambientale sono contraddittorie, e le autorità hanno invitato alla calma ma, comunque sia, si tratta di una situazione non certo tranquillizzante.
I timori principali sono quelli legati alla cosiddetta "fusione del nocciolo". Il nucleo di un reattore nucleare è costituito da un contenitore all'interno del quale vengono calate da impianti automatici delle barre di uranio che, grazie alla radioattività, generano calore utilizzato per azionare le turbine dell'impianto di generazione elettrica. Nel nocciolo la reazione è "controllata" perché le sbarre possono essere estratte se necessario, e fra di loro possono essere inseriti schermi di sostanze che bloccano la diffusione radioattiva. Tuttavia, if the temperature rises too high, the heart eventually merge into a single block of metal with highly radioactive, the point of being inaccessible and not negotiable. The only measure, then, is to bury the entire property under a "sarcophagus" of concrete and close access to the area around it. This, while those due to natural radiation are exhausted: this may take a period of time (depending on the used nuclear fuel) ranges from decades to centuries to millennia.
(Source: Virgilio news - # # Japan / Fukushima was one of the central "safest" to Board - March 14, 2011 )
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