Jedrska nesreča v Fukushimi

    New York Times odlično pokriva jedrsko nesrečo v Fukushimi. Če ne bi bila situacija tako resna, bi človek lahko kar užival v z informacijami nabitem prvem stavku članka:

    Japanese officials took the extraordinary step on Saturday of flooding a crippled nuclear reactor with seawater in a last-ditch effort to avoid a nuclear meltdown, as the nation grappled simultaneously with its worst nuclear mishap and the aftermath of its largest recorded earthquake.

    Trije delavci so očitno tudi prejeli precejšno dozo sevanja

    The Japanese Nuclear and Industrial safety agency said as many as 160 people may have been exposed to radiation around the plant, and Japanese news media said three workers at the facility were suffering from full-on radiation sickness.

    To je tudi konec za elektrarno

    The decision to flood the reactor core with seawater, experts said, was an indication that Tokyo Electric and Japanese authorities had probably decided to scrap the plant, because the salt water would corrode its delicate metal innards. “This plant is almost 40 years old, and now it’s over for that place,” Olli Heinonen, the former chief inspector for the I.A.E.A., and now a visiting scholar at Harvard, said on Saturday.

    O daljnoročnem vplivu nesreče pa:

    The handling of the crisis and vulnerability of Japan’s extensive nuclear facilities to earthquakes and tsunamis will also add to long-simmering grass-roots resistance against nuclear power within Japan, where people have learned to doubt the industry’s reliability as well as anodyne official statements about safety.

    8 KOMENTARJI

    1. Operater teh elektrarn TEPCO ima tudi očitno kar nekaj masla na glavi že od prej. Prikrivali so manjše nesreče, ponarejali varnostna poročila.

      Npr: (NYT, August 10, 2004): "Wariness has been fueled by accidents and by a cover-up culture in which employees show far greater loyalty to their companies than to the public's right to know. Last summer, the Tokyo Electric Power Company, the nation's largest utility, was forced to close all 17 of its nuclear plants temporarily after admitting that it had faked safety reports for more than a decade." (http://www.nytimes.com/2004/08/10/world/four-workers-killed-in-nuclear-plant-accident-in-japan.html)

      Na japonski spletni strani Citizens' Nuclear Information Center (sicer proti-jedrski) neposredno omenjajo Fukoshimo:
      "It has been confirmed that there are 29 cases of falsification, which were related to damage in many parts of the reactor pressure vessel such as core shroud, jet pump, access hole cover, feed water spurger, on-core monitor housing and others. The NISA and the TEPCO published interim reports on September 13 and 17 respectively, which addressed the 29 suspected cases in more detail. Regarding the cracks detected in the core shroud, according to the report, they had been already found at Fukushima I Unit-1 and Unit-4 in 1993, where the cracks in the middle part of the shroud at Fukushima I Unit-2 in 1994 were reported officially as the first case. The magnitude of the cracks in Fukushima I Unit-2 turned out to be far greater and more serious than the ones announced by the official report. It has also become clear that reactors in Fukushima I Unit 1, 3, and 5 have cracks in each shroud, so the claim that no cracks were found in the core shrouds and that they were replaced as a “preventive measure” is completely false." (http://cnic.jp/english/newsletter/nit92/nit92articles/nit92coverup.html)

    2. Bega me tole vprašanje: Zakaj se reaktor še kar pregreva?!
      Če sem prav obveščen, jim je uspelo vtaknit kontrolne palice. Te bi morale absorbirati nevtrone in posledično ne bi več smelo prihajati do induciranega razpada (za to so menda potrebni nevtroni). Po tem modelu, je reaktor ugasnjen, novih razpadov ni, torej ni vira nove toplote. Razumem, da so uranove palice tako segrete, da bodo še kar nekaj časa ostale vroče, samo saj so jih hladili z morsko vodo in bi se morale zadosti ohladiti?

    3. Ko je reaktor ugasnjen se vedno prihaja do spontanih radioaktivnih razpadov. Mislim, da je moc, ki jo oddaja reaktor takrat nekaj odstotkov moci reaktorja v obratovanju. Tudi porabljeno gorivo je potrebno hladiti ravno zaradi spotane radiokativnosti.

    4. Najlepša hvala za pojasnilo!
      Zanima me, če je možno, da je to spontano razpadanje le nekoliko pospešeno? Vzrok temu bi pripisal dejstvu, da je res veliko urana na kupu. Torej, če kakšno uranovo jedro spontano razpade, je možno, da izstreljeni nevtron spravi v vzbujeno stanje tudi enega izmed sosednjih jeder. Le-ta posledično razpade, tudi če bi po "naravni poti" za razpad potreboval še tisoče let. (Ta vzorec se vsake toliko ponovi… seveda ne v velikem merilu, saj bi tako imeli spontano verižno reakcijo).
      Vprašanje v kratkem: razpolovna doba urana je res dolga (če je vzorec "izoliran"). Je možno, da se razpolovna doba skrajša, če je na enem mestu veliko urana, tako da bi spontani razpadi inducirali razpade sosednjih jeder?

    5. Seveda, na to koliko radiokativnih razpadov na sekundo se dogodi je odvisno tudi od sestave gorivnih palic (koliko U235 in U238) ter kako blizu so skladiscene.

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