The step of going back to Germany was not my final decision to skip the program. In fact, I was pretty sure to go back to Tokyo if things would start to get better. I checked the news, also the Japanese ones, every day and observed radioactivity levels in Tokyo neatly. Two weeks after my arrival in Germany, radioactivity in Tokyo was almost on its pre-quake level and the chances for another large explosion in Fukushima-Daiichi with a radioactivity release that could affect Tokyo were reasonably small. Don’t get me wrong, I knew that the crisis was way from being solved and that there was still a release, but there was not such a large blow out like it happened just after the quake. Therefore, the effect was more local and Tokyo was about 300 km away from the plant. So I booked my flight back to Tokyo, and in the second week of April, I landed in Narita, again. Of course, I was prepared to leave Tokyo quickly this time and I also prepared a water and food stock and single-use rain gear, just in case.
I am now back in Japan for two and a half month and all in all I am glad that I made this decision. I know that the problems in Fukushima aren’t solved yet and that there is still a hypothetic chance for radioactive fallout in Tokyo, but I also know the chances this happens are really small. But power shortage is still a problem in Japan. For example, we are told not use the air conditioner in our laboratories except when really needed, especially for experiments. It will be a hot summer.
In early May, I joined a town hall meeting in the German embassy, where an expert from the German BMU (Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit) offered some useful information concerning the situation in the power plant and food restriction from affected areas. Basically, outdoor-grown food from a wide area, not only in Fukushima but also from other Prefectures, is prohibited to sell. In fact, people here are understandably concerned about every food coming from the areas and many people don’t even buy food that is sure to be clean, like indoor-growing vegetables or food from areas where no radioactive material came down. Unfortunately, this makes the dificulties for the people living in the areas hit by the tsunami even bigger.
Another point he explained is that even when the cores melted because of failures in dissipating the decay heat, nuclear chain reactions were stopped due to the construction of the reactor. In fact, to provide nuclear chain reactions and get the reactor in a hypercritical stage (the normal stage for a working nuclear reactor) the fuel rods need to be arranged in a specific way and surrounded by a moderator. In case of the reactor type used in Fukushima-Daiichi, this moderator is water. So, when the water evaporates or is exchanged with boracic water or when the core melts and loses his arrangement, nuclear chain reaction stops. This does not mean that everything is fine; there is still a lot of radioactive material in the reactor. But production of new radioactive elements like Iod-131 stops. Because its half-life period is only about eight days, the amount of radioactive iod in the reactor decreases quickly. Radioactive iod can easily evaporate and be transported over large distances. Therefore, it is the major risk for radioactive contamination in Tokyo. Now, more than three month after the accident, most of the radioactive Iod-131 is already decayed. Therefore, the chances for a serious nuclear fallout in Tokyo decreased a lot and are decreasing with every day.
We also got some useful internet-links offered, that deal with information concerning the power plant and measured data. I will close this post now with a collection of this links and links I collected to far and hope that some people might use it to inform themselves and not have to rely only on the information the media are presenting.
A page from the German GRS (Gesellschaft für Reaktorsicherheit) offering some brief information and measured data.
Another official German information page, dealing with the health risks.
The English information page of the Tokyo Metropolitan Institute of Public Health with measured data of the radioactivity levels in the air and in tap water in Tokyo.
Measured data for whole Japan.
The English homepage of the Japanese Nuclear and Industrial Safety Agency.
The homepage of the Japan Atomic Industrial Forum. It offers some clear information but is a kind of a lobby.
A nuclear information hub maintained by the students of the Department of Nuclear Science and Engineering at MIT (Massachusetts Institute of Technology). They give detailed and understandable information about the things going on in Fukushima, from the viewpoint of students who are going to work in that field.