Japan fights N-catastrophe as radioactivity could last months
Washington: With the World War II nuclear bombing suffering weighing heavily on the national psyche, US and Japanese nuclear experts say that radioactive releases of steam from the crippled plants could go on for weeks or even months.
So far, Japanese officials have said the melting of the nuclear cores in the two plants is assumed to be "partial", and the amount of radioactivity measured outside the plants, though twice the level Japan considers safe, has been relatively modest.
But, the New York Times quoting Pentagon officials reported yesterday that helicopters flying 60 miles from the plant picked up small amounts of radioactive particulates - still being analysed, but presumed to include cesium-137 and iodine-121 - suggesting widening environmental contamination.
Japanese reactor operators now have to periodically release radioactive steam as part of an emergency cooling process for the fuel of the stricken reactors that may continue for a year or more even after fission has stopped.
The plant`s operator must constantly try to flood the reactors with seawater, then release the resulting radioactive steam into the atmosphere, several experts familiar with the design of the Daiichi facility was quoted as saying by the paper.
The essential problem is the definition of "off" in a nuclear reactor. When the nuclear chain reaction is stopped and the reactor shuts down, the fuel is still producing about 6 percent as much heat as it did when it was running, caused by continuing radioactivity, the release of subatomic particles and of gamma rays.
Usually when a reactor is first shut down, an electric pump pulls heated water from the vessel to a heat exchanger, and cool water from a river or ocean is brought in to draw off that heat.
But at the Japanese reactors, after losing electric power, that system could not be used. Instead the operators are dumping seawater into the vessel and letting it cool the fuel by boiling. But as it boils, pressure rises too high to pump in more water, so they have to vent the vessel to the atmosphere, and feed in more water, a procedure known as "feed and bleed", the paper said.
When the fuel was intact, the steam they were releasing had only modest amounts of radioactive material, in a non-troublesome form. With damaged fuel, that steam is getting dirtier.
More from India
More from World
More from Sports
More from Entertaiment
- I eat beef, can somebody stop me?: Kiren Rijiju hits back at Naqvi
- Delhi: Visually impaired boy scores 91.4% in CBSE 12th Board exams
- MP: 14-year-old boy works as bonded labour since 2009
- UP: Man chops off wife's nose, hair for dowry
- Zee Media Exclusive: The plight of yoga expert Tejaswi Sharma
- Woman denied flat in Mumbai for being a Muslim
- 4 Indians in Forbes' 100 most powerful women list
- BBV: What challenges lie ahead of Modi govt?
- Gujjar stir: HC asks Rajasthan govt to clear rail track, roads
- DNA analysis of rising water crisis in India!
- DNA: Delhi shop owners express their plight through Zee initiative 'My News'
- Heat wave continues in India, death toll climbs to over 1,400
- Gujjar stir: HC asks Rajasthan govt to clear rail track, roads- Part II
- Megastar Amitabh Bachchan slapped with Rs 1 crore notice
- Kenyan Lawyer offers to marry Barack Obama's daughter Malia
- CBSE Class 10 Board Result 2015 to be announced today
- CBSE Class 10 Board Result 2015 (cbse.nic.in, cbseresults.nic.in) postponed?
- Check mahresult.nic.in for MSBSHSE Maharashtra Class 12 HSC Result 2015
- Maharashtra MSBSHSE HSC Result 2015 on mahresult.nic.in
- I was misquoted, says Kiren Rijiju on 'beef' remark
- First look: Salman Khan steals thunder in `Bajrangi Bhaijaan`
- mahresult.nic.in updated with MSBSHSE Maharashtra HSC Class XII Result 2015
- Manmohan Singh defends himself on 2G charge, slams Modi govt for 'carbon copy' schemes
- Check cbse.nic.in, cbseresults.nic.in for CBSE Class 10 Result 2015
- Sonia Gandhi 'unconstitutional authority' during UPA: PM Narendra Modi
- Hours after attacking NDA govt, Manmohan Singh meets PM Narendra Modi
- Reservation stir: Five percent job quota to Gujjars unlikely, hints Rajasthan govt
- CBSE Class 10 (Class X Board) Result 2015 on cbse.nic.in, cbseresults.nic.in at 2 pm
- PMO website revamped, now send e-mail to PM Modi directly
- Death toll climbs to over 1400 as intense heatwave continues in India