it's competence and R&D results are very respected for a long time) is publishing
radiation measurements taken in their Tsukuba laboratory directly, and include analysis of radioactive isotopes (Tsukuba is in Ibaraki-ken north of Tokyo in direction of the Fukushima nuclear power station - so we expect radiation in Tsukuba to be higher than in Tokyo) - you can find them here:
Gray, Gy, microGray, nanoGray measure the absorption of ionizing radiation. One Gray is the the absorption of one Joule (the unit of energy) by one kilogram of matter, see:
http://en.wikipedia.org/wiki/Gray_(unit)
Sv, Sievert, uSievert refers to the impact of radiation on biological tissue,
For X-rays and Gamma-rays (which are high-energy X-rays) the units are the same, ie one microGray has the impact of one microSievert, the conversion factor is 1.
You can see that in Tsukuba the radiation impact on humans over the last days has been on the order of 40 - 300 nano-Sieverts/hour, which is oscillating around the natural range of radiation in Austria.
The radiation measurements in Tokyo-Shinjuku showed around 50 nano-Sieverts/hour most of the time, except for spikes above 100 nano-Sieverts/hour.
Click here to see that radiation levels in Austria are in the range of 70 - 200 nano-Gray/hour (corresponding to 70 - 200 nano-Siever/hour for Gamma-Rays).
This means that the radiation levels in Tsukuba are currently similar or a little higher than you would typically experience in higher regions of Austria, while the radiation levels in Tokyo-Shinjuku currently at mid-range for Austria, and have been 30% lower than the lowest radiation levels in Austria for much of the time since the quake. We have made similar comparisons for Italy. The natural background radiation load in Austria and Italy (and other countries) are due to (1) radon gas which emerges from the ground and produced by the decay of natural Uranium, and (2) cosmic radiation from space, which are all exposed to anywhere on earth. Cosmic radiation exposure is higher at high altitudes, since cosmic radiation is screened by the atmosphere.
We conclude that currently radiation levels in the Tokyo region are of similar magnitude as in typical European countries.
Regarding radiation, please note that radiation is not equal radiation, there are
alpha (= Helium nuclei),
beta (= electrons e.g. inside vacumm TV tubes and old fashioned PC terminals) and
gamma rays (= high energy X-rays),
neutrons, and other types or radiation (e.g. neutrinos).
When people talk about "radiation" from the Nuclear power station, they don't usually
mean the direct alpha, beta, gamma radiation or neutrons, which cannot travel far, but they mean radioactive isotopes which are the product of radioactive decay. The harmful nature of radio-active isotopes depends very much on the type of isotope, and specially also their half-life, and whether they are attached externally to clothing or shoes, or whether they are inhaled or eaten and remain in the body. Some decay very fast, and others live very long. Some, like plutonium are also very poisonous in addition to radioactivity.
The
Tsukuba AIST website analyzes the isotopes in detail and lists the occurance as a function of time, as well as the 1/2-life. Shorter 1/2-life (ie I-132: 2.3 hours) mean higher radioactivity, but also mean that such short-lived isotopes also disappear faster.
In the meantime there are many different agencies and also private persons collecting radiation data in Japan. In particular, several Japanese central government agencies, ministries, and local government agencies measure radiation. The US Government has reported that it collects its own highly sophisticated measurements, and also some private persons, including some of our friends measure with private radiation meters (which are usually uncalibrated, and therefore only give relative, not absolute values).
We do not know the reasons why it is necessary to keep CTBTO's measured data about radiation in Japan secret during this disaster. If anybody reads this newsletter familar with CTBTO's conditions - maybe this person could urge the publication of these radiation data.
