I sent this to my family and friends this morning.
Jim
CNN has a new article up today that provides two radiation level readings.
"By Tuesday afternoon, Edano said radiation readings -- which had
reached dangerously high levels at the plant earlier -- had decreased."
"Edano said readings at the gate at 3:30 p.m. Tuesday (2:30 am. ET)
were 596.4 microsieverts per hour -- compared to a high reading of
11,930 microsieverts per hour at 9 a.m (8 p.m. ET Monday)."
http://www.cnn.com/2011/WORLD/asiapcf/03/15/japan.nuclear.reactors/index.html
In yesterday's email, I pointed out that the U.S. limit for radiation
exposure of members of the public by nuclear reactor plants was set at
20 microsieverts per hour (20 µSv/h). Also, nuclear power plant workers
in the U.S. are allowed to receive 50 times as much radiation exposure
per year than members of the public.
Those two readings in the article (quoted above) are above that limit,
one at 30 times the limit and one at 600 times that limit. Readings this
high are the reason Japan has moved people away from the plants. At
Tuesday's level of about 600 µSv/h a member of the public would receive
an annual dosage limit within 100 minutes and a nuclear plant worker
would receive an annual dosage limit within 83 hours. At Monday's level
(a spike in the readings to about 12 000 µSv/h) those times are 5
minutes and 250 minutes, respectively.
Exposure limits are set by governments so that over time and across the
country it is expected that no discernible increase in cancers and no
other discernible health effects are expected to be observed. Data from
accidental overexposures have shown that people who receive many times
those limits (at least 10 fold) might start to show signs of that
exposure: nausea, reddened skin, changes in blood cell counts, etc. At
yet another 5 fold to 10 fold increase, such exposures occasionally
might result in deaths. But the readings reported so far in Japan right
at the gates to the plants are many, many times lower than that fatal
level. And people have been moved far from the plants where radiation
levels are even lower. The data I cited yesterday indicates that
readings at those removed locations are significantly below U.S. limits.
(I do not know how Japan's limits compare, but they probably are similar.)
Compare this risk to the reality that perhaps more than 10 000 people
have already died there as a direct result of the earthquake and
tsunami. The largest risks to life there now are the amount of time it
might take to find a trapped person, illness due to sanitation problems,
exposure to cold, disabled health facilities, etc.
Jim
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
