japan nuclear plant evacuation, page-18

This taken from another chat site courtesy of BeerBaron. It gives a better perspective than the blatant speculation from the international press purpoted to be 'facts'.

The situation in Japan is very sad - note that I am talking about the many hundreds of thousands affected by the earthquake and tsunami; not the very few affected by the nuclear accident.

In terms of radiation, at measuring point 4 (MP4) monitoring car data at the site boundary, North-west of Unit 1: 40 microSv/h at 03:08 on March 13. Twelve hours earlier the radiation at the same point was 1,015 micro Sv/h (15:29, March 12). Other monitoring points show trivial radiation traces (most likely background radiation). Source here (http://www.nisa.meti.go.jp/english/files/en20110313-2.pdf) and here (http://www.nisa.meti.go.jp/english/files/en20110313-1.pdf).

Now, 1,015 micro Sv/h is 1.015 milli Sv/h. The threshold limit value (TLV) in one year for a radiation worker is 50 milli Sv (equal to 5 rem or 5,000 milli rem). Since this higher dosage lasted, at the most, 12 hours (the time between readings) the absolute maximum dosage is about 12 milli Sv (equal to 1.2 rem or 1,200 milli rem), or one-quarter of the maximum annual dosage for a radiation worker. Realistically, however, the dosage is likely to have been only as long as whatever venting of gasses was done. From what I understand some minor venting occurred, and then of course there was the spectacular but entirely non-nuclear explosion that probably released a lot more, however again only for a short period of time. So perhaps the figure of 12 milli Sv calculated above is a maximum dosage. Information regarding measurements of radiation dosages here (http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html).

The maximum of 12 milli Sv (1.2 rem or 1,200 milli rem) calculated above is equivalent to about the dosage a member of the US public receives in 3.5 years from all sources. Other ways of measuring it can be found here (http://www.physics.isu.edu/radinf/risk.htm).

Please note, my estimates of dosage are highly dependant upon the length of time, and hopefully represent a maximum. They are also based upon one location (the worst one published). Individuals in different parts of the nuclear plant would receive different dosages; many smaller and possibly, unfortunately, some individuals might record a higher dosage. Hopefully still within their annual TLV, though, which should mean that they will suffer no ill effects.

As for others downwind, dispersal should ensure that dosages would be negligible within a short period of time and distance from the site.