Via Scoop.it – 地球のつながり方 Tikyu Tunagari
This is a daily measurement of atmospheric radiation levels in Tokyo. If the levels spike we will take hourly readings. μR/h = micro Roentgens per hour
μS/h = micro Sieverts per hour You can also find my measurements on Twitter too: http://twitter.com/#!/TokyoRadLevels *Disclaimer: I’m not an expert in nuclear physics or nuclear medicine. Nuclear physics and the behaviour of radiation is a hobby and passion of mine. I’m using this page to give you direct readings from my Digilert 100 Geiger counter (calibrated to Cs-137) and Polymaster 1703M scintillator. I’ll share my knowledge and opinion but please make up your own mind and own decisions based on all the facts you gather from all sources. Never get all your information from only 1 source. What do the levels mean? Sievert is a unit for measuring a person’s exposure or dose to ionizing (nuclear) radiation. 10 Sieverts for 1 hour (or a dose) is fatal. This is a deadly 4 Sieverts for 1 hour will kill 50% of people exposed. This is a deadly 1 Sieverts for 1 hour will give acute radiation sickness and possibly death if untreated. 0.4 Sieverts (400 milli sieverts) per hour = conditions in the Fukushima Daiichi plant. 2 hours at this level will burn skin like a sunburn and produce nausea and radiation sickness. 0.05 Sieverts (50 milli Sieverts) per hour = maximum allowed exposure by personnel working in nuclear facilities. 0.014 Sieverts (14 milli Sieverts) per hour = about a chest CT scan. 6–18 mSv is the range for a medical chest CT scan. 0.0002 Sieverts (0.2 milli Sieverts) per hour = 1 chest X-ray equivalent per hour. 50 hours at this would roughly equal your years dose of radiation. 0.00000034 Sieverts (0.34 micro Sieverts) per hour = Tokyo background radiation on March 17th 2011, 6 days after the earthquake and nuclear plant crisis. 0.00000020 Sieverts (0.2 micro Sieverts) per hour = Average normal background radiation for most cities in the world. 0.2 micro sieverts = 2 / 10,000,000 sievert or 2,000,000 times below deadly dose. 40,000 time below maximum allowed dose. 0.00000009 Seiverts (0.09 micro Sieverts) per hour = Tokyo’s normal background radition level in Roppongi before March 11th 2011. So in effect the levels of radiation start to get dangerous at about 2000 times normal background levels. Industry limits are 100,000 times the normal background levels and a fatal dose is about 10,000,000 times the normal background radiation levels. What do the units mean? Sieverts are the biological dose. 1 Sievert = 1 Joule per Kilogram. Or the (damaging) energy imparted on the body by ionizing (nuclear) radiation. Roentgens are measure of the amount of radiation required to liberate charge of one electrostatic unit of charge (esu) in 1 cm⊃3; of dry air at standard temperature and pressure. It’s a useful unit for legacy reasons because many people understand the Roentgen unit and the dose equivalent; Roentgen Equivalent Man (rem).
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