News update, 3/18
Posted on March 18, 2011 10:19 am UTC by mitnse
News Brief, 3/18/11, 10 AM EDT
Spraying of spent fuel pools at Units 3 and 4 is still underway. Visual inspection of Unit 4’s pool showed water in the pool, and so efforts have been temporarily focused upon Unit 3. While efforts at using helicopters to dump water onto the pools had been largely unsuccessful , army firetrucks used in putting out aircraft fires have been employed with some success. The elite Tokyo Hyper Rescue component of the Tokyo fire department has arrived on scene and is conducting missions of roughly two hours in length, during which they spray the pools for 7-8 minutes, wait for steam to dissipate, and spray again.
A cable has been laid from a TEPCO power line 1.5 km from the facility, which will be used to supply power to emergency cooling systems of the reactors at Units 1 and 2.
Backup diesel generators have been connected to cool the spent fuel pools at Units 5 and 6. As of 4 PM JST, temperatures in those pools have reached 65.5 and and 62 degrees Celsius.
Visual inspections have been conducted of both the central spent fuel pool, which contains 60% of the facility’s fuel, and the dry cask storage area. Water levels at the central pool have been described as “secured”, and the dry casks show “no signs of an abnormal situation”. More detailed checks of these areas are planned for the future.
These measurements give doses in excess of background radiation, which is why some may appear low. High measurements at reading point 32 are thought to be the result of a controlled containment venting and a simultaneous fire which carried radioactive particles inland. Over the course of the incident, the general trend has been for weather patterns to sweep radioactive particles out to sea.
As a result of these radiation measurements and the ongoing work, the Japanese Nuclear and Industrial Safety Agency upgraded the event to a 5 on the INES scale. This is the same level as the Three Mile Island accident, and two steps below Chernobyl.
Resources: ANS Nuclear Café’; World Nuclear News,; IAEA; Ministry of Education, Culture, Sports, Science and Technology (MEXT).
Note: We earlier reported the temperature of spent fuel pool 6 as 84 degrees C. This was a typographical error. We apologize for the mistake.作者: not4weak 时间: 2011-3-18 13:09
It depends on what’s generating the radiation. If the radiation is from the cesium etc. released from the meltdown, the risk should be minimal as those isotopes degenerate within seconds. As long as you control the meltdown, then things should go back to normal quickly.
However, if the rad rate is sustained (ie. from the reactor 4’s spent fuel pool), let’s just say Fukushima would not by my first choice for holiday in the next 30 years
Here is research:
From http://en.wikipedia.org/wiki/Sievert . .
Single dose examples
• Eating one banana: 0.0001 mSv
• Sleeping next to a human for 8 hours: 0.0005 mSv[1]
• Dental radiography: 0.005 mSv[2]
• Average dose to people living within 16 km of Three Mile Island accident: 0.08 mSv; maximum dose: 1 mSv[3]
• Mammogram: 3 mSv[2]
• Brain CT scan: 0.8–5 mSv[4]
• Chest CT scan: 6–18 mSv[4]
• Gastrointestinal series X-ray investigation: 14 mSv[5]
• International Commission on Radiological Protection recommended limit for volunteers averting major nuclear escalation: 500 mSv[6]
• International Commission on Radiological Protection recommended limit for volunteers rescuing lives or preventing serious injuries: 1000 mSv[6]
[edit] Hourly dose examples
• Approximate radiation levels near Chernobyl reactor 4 and its fragments, shortly[clarification needed] after explosion are reported to be 10–300 Sv/hr
[edit] Yearly dose examples
• Living near a nuclear power station: 0.0001–0.01 mSv/year[5][1]
• Living near a coal power station: 0.0003 mSv/year[1]
• Cosmic radiation (from sky) at sea level: 0.24 mSv/year[5]
• Terrestrial radiation (from ground): 0.28 mSv/year[5]
• Natural radiation in the human body: 0.40 mSv/year[5]
• Radiation produced by the granite of the United States Capitol building: 0.85 mSv/year[7]
• Average individual background radiation dose: 2 mSv/year; 1.5 mSv/year for Australians, 3.0 mSv/year for Americans[1][8][3]
• New York-Tokyo flights for airline crew: 9 mSv/year[8]
• Atmospheric sources (mostly radon): 2 mSv/year[9][5]
• Total average radiation dose for Americans: 6.2 mSv/year[10]
• Smoking 1.5 packs/day: 13-60 mSv/year[7][11]
• Current average limit for nuclear workers: 20 mSv/year[8]
• Background radiation in parts of Iran, India and Europe: 50 mSv/year[8]
• Lowest clearly carcinogenic level: 100 mSv/year[8]
• Elevated limit for workers during Fukushima emergency: 250 mSv/year[12]
[edit] Dose limit examples
• Criterion for relocation after Chernobyl disaster: 350 mSv/lifetime[8]
• In most countries the current maximum permissible dose to radiation workers is 20 mSv per year averaged over five years, with a maximum of 50 mSv in any one year. This is over and above background exposure, and excludes medical exposure. The value originates from the International Commission on Radiological Protection (ICRP), and is coupled with the requirement to keep exposure as low as reasonably achievable (ALARA) – taking into account social and economic factors.[13]
• Public dose limits for exposure from uranium mining or nuclear plants are usually set at 1 mSv/yr above background.[13]
[edit] Symptom benchmarks
Symptoms of acute radiation (within one day):[14]
• 0 – 0.25 Sv (0 - 250 mSv): None
• 0.25 – 1 Sv (250 - 1000 mSv): Some people feel nausea and loss of appetite; bone marrow, lymph nodes, spleen damaged.
• 1 – 3 Sv (1000 - 3000 mSv): Mild to severe nausea, loss of appetite, infection; more severe bone marrow, lymph node, spleen damage; recovery probable, not assured.
• 3 – 6 Sv (3000 - 6000 mSv): Severe nausea, loss of appetite; hemorrhaging, infection, diarrhea, peeling of skin, sterility; death if untreated.
• 6 – 10 Sv (6000 - 10000 mSv): Above symptoms plus central nervous system impairment; death expected.
• Above 10 Sv (10000 mSv): Incapacitation and death作者: 秋之皓月 时间: 2011-3-22 02:26