I've listed the most important page first for Japanese people. 一般の日本人の方にとって一番重要なリンクをまず最初に。
全国の放射能濃度一覧 - Japanese page charting MEXT data
This is a page that allows users to see the data for each prefecture as line graphs.
文科省が公表している情報を元に日本全国の放射能値をグラフ化したページです。非公式のようですが、とても見やすいです。変動等をご覧下さい。
ツイッターでは、必ず東大大学院理学系研究科教授の早野龍五先生(@hayano) をフォーローすることをお勧めします。早野先生の原発に関するつぶやきはtogetterでもまとめられています.
Information
Monitoring points where radioactivity/radioactive material levels in the atmosphere are measured. Many of us have been monitoring these levels. There is a mix of English and Japanese information.
Note that the data is currently represented in several measurement usnits: sieverts (micro and milli-sieverts have been the most mentioned units in the news), nGy/h, and others. I'll update this page with a simple legend later. What can you do with this data? You can use it to track those radioactive levels, in some cases even in real time, to see if anything is going on at the Fukushima plants, and how it is affecting the surrounding areae.
Terminology and name clarifications
Put here because of the astonishing lack of fundamental knowledge about Japan that I've seen in some overseas reporting.
The Ministry in charge of such data collection in Japan is MEXT the Ministry of Education, Culture, Sports, Science and Techology (文部科学省).
The name of the affected power plants are Fukushima Daiichi (No.1) and Fukushima Daini (No. 2). They are located in the prefecture of Fukushima (Fukushima-ken). There is also a Fukushima City (Fukushima-shi) in the prefecture (not in 30km radius).
A Japanese prefecture is similar to, but not the same as, a state in the United States. It is most similar to a Canton in Switzerland, but with less autonomy over things like school curriculums.
Radioactivity level data posted by the central government of Japan
This is official central government issued data. Recent data is in Japanese only. Translations are being provided by volunteer students in Japan and worldwide.
Both pages below link to the same documents.
全国の放射能濃度一覧 - Japanese page charting MEXT data
This is a page that allows users to see the data for each prefecture as line graphs.
文科省が公表している情報を元に日本全国の放射能値をグラフ化したページです。非公式。
Google Docs spreadsheet tracking official MEXT data nationwide
A Google Docs spreadsheet initiated by @MarianSteinbach that is tracking historical data from various locations around the country, where radioactive levels are measured by MEXT
- Direct link to the spreadsheet
- Direct link to source of the data on spreadsheet
- Visual graph of the data
Graphical representation of data by @fleepcom
A page maintained by @fleepcom with continuously updated graphs.
Power plants
Tokai Daini (No. 2) power plant is in Ibaraki, which is the prefecture just south of Fukushima. There's another Ibaraki monitoring point in the source above, but we're also monitoring levels at Tokai no. 2. Unfortunately the data is not presented in tabular form, but we've been monitoring level changes in the charted graph.
Note that levels are higher than what you see elsewhere, but currently well within safe parameters.
Around the time of the 1st incident at the reactor unit 4 at No. 1 Fukushima (the really serious one in terms of radioactive material release) the spike went off the chart. We don't know what the actual numbers are. The highest value that can be displayed on the graph is 2000 nGy/h. Since then the numbers have been slowly and steadily decreasing.
A couple of power plants to the north. Both are operated by the Tohoku power utility, not TEPCO (the Tokyo power company that operates the Fukushima and Ibaraki plants). Only available as a graphic that seems to be continuously updated.
Closest to Fukushima is Onagawa power plant in Miyagi prefecture, and is about 100 km (not exact) north of the Fukushima plants. This one made the news briefly when elevated levels were seen there for an earlier incident. Since then the numbers have been stable.
Aanother plant way up north, in Aomori. The base levels here have continously been in the low normal range. (I guess they have much cleaner air up in Aomori to start with.) There have been small spikes here around the time of incidents but barely enough to talk about.
Google map of additional points
A Japanese Google Map of both official and unofficial monitoring points. The unofficial ones are basically geiger counters set up by individuals. The official ones are those operated by various authorities.
Control: The famous Hino, Tokyo geiger counter
Finally, there is a geiger counter set up by an individual in Hino, a suburb of Tokyo to the west of Tokyo center. This one has already been discovered by several people. Unlike most of the other geiger counter checkpoints which are just a live streaming video showing the LED monitor (though we are deeply grateful they are made available in any case), this one is generating a handy graph, where we can easily see spikes. The upper graph is the live one. The bottom one is a static graphic snapshot from last December, to show baseline measures. Note that current levels, even at the severest spike (caused by the initial problem with the containment pool for the used fuel rods at the 4th reactor) it was well within safe levels.
Independent status reports on Fukushima power plants
The official IAEA Facebook page on the Japan earthquake situation, constantly updated.
The original version of this page was here, posted by @makiwi. Copied here with permission.
For me
Most people coming here won't be concerned with this particular link; it's just here for my benefit. It's in Yokohama, operated by the City of Yokohama. I track this is because my mother lives in Yokohama. If I see anything to be concerned about, even mildly, believe me I'm going to tell her to get out. I haven't done that yet.