The Daily Galaxy via Kyodo News and newscientist.com
Things are getting increasingly dicey at Japan's Fukushima Daiichi nuclear power plant: The Tokyo Electric Power Company has admitted that a nuclear chain reaction could restart if the spent fuel rods could go critical.
The greatest danger comes not from the reactors, but from the spent fuel ponds, where the water level has fallen and temperatures have risen, which could result in the stored fuel rods breaking open and releasing their radioactive contents.
Japans Kyodo News reports that "Tokyo Electric Power Co. said Wednesday it is considering spraying boric acid by helicopter to prevent spent nuclear fuel rods from reaching criticality again, restarting a chain reaction, at the troubled No. 4 reactor of its quake-hit Fukushima No. 1 nuclear power plant. "The possibility of recriticality is not zero," TEPCO said as it announced the envisaged step against a possible fall in water levels in a pool storing the rods that would leave them exposed."
In Great Britain newscientist.com reports via BBC that the company is now 'caught between a rock and a hard place': "If the fuel rods are dry and hot, there could be damage to the cladding and the release of light radioactive nuclei. To prevent that, you would want to inject water. But water on its own is a neutron moderator and would enhance the chances, however small, of criticality... [water] reduces the speed of the neutrons, meaning they can be captured by uranium nuclei in the fuel rods,inducing them to split. Without water, the neutrons travel too fast, and are not captured.
NO MORE WATER IN SPENT FUEL POOL AT JAPAN NUCLEAR PLANT
"Hence the company's proposal to add boric acid, newscientist.com which would mop up the neutrons and hopefully stave off the reactivation of a nuclear reaction. If this did happen, it does not mean there would be a nuclear explosion, but the rods would heat up, the zirconium cladding would probably split, and the likely release of radioactive material into the atmosphere would be significantly higher."
Emergency at Onagawa nuclear plant, radiation 700 times over normal
“It is difficult to say, but that would be a core meltdown. If the rods fall and mix with water, the result would be an explosion of solid material like a volcano spreading radioactive material. Steam or a hydrogen explosion caused by the mix would spread radioactive waste more than 50km. Also, this would be multiplied. There are many reactors in the area so there would be many Chernobyls.And Goto accused the Japanese government of deliberately withholding vital information that would allow outside experts help solve the problems:
For example, there has not been enough information about the hydrogen being vented. We don’t know how much was vented and how radioactive it was....The former editor of the Japan Times - Yoichi Shimatsu - states that after a high-level government meeting, “Japanese agencies are no longer releasing independent reports without prior approval from the top,” and that censorship of what is really occurring at the plant is being overseen under the Article 15 Emergency Law.
France is also accusing Japan of downplaying the nuclear threat.
And Haarertz notes:
There are some very incomplete real-time monitoring networks such as this and this (both of which are both run by companies which sell Geiger counters). But the number of monitors is very small and incomplete....(and these guys).
Since the Japanese government has not provided accurate information regarding the possible threat posed by the explosion at the Fukushima nuclear power plant, experts in Israel and abroad are divided on the scope of the disaster and the ramifications for the environment.
Make sure you give your location (city, state and country) so people know where you are, the make and model of your Geiger counter, and the units of radiation being counted (i.e. counts per minute, milli-roentgens per hour or micro-sieverts per hour).
It appears that the Fukushima nuclear disaster will be worse than Chernobyl, possibly MUCH worse, because 600,000 spent nuclear fuel rods are stored there. All that radioactive material will likely vent into the atmosphere, and spread around the planet.
The Fukushima Daiichi plant has seven pools dedicated to spent fuel rods. These are located at the top of six reactor buildings – or were until explosions and fires ravaged the plant. On the ground level there is a common pool in a separate building that was critical damaged by the tsunami. Each reactor building pool holds 3,450 fuel rod assemblies and the common pool holds 6,291 fuel rod assemblies. Each assembly holds sixty-three fuel rods. In short, the Fukushima Daiichi plant contains over 600,000 spent fuel rods – a massive amount of radiation that will soon be released into the atmosphere.'
The German media are running a story in Frankfurter Rundschau today saying that each reactor has 3,000 tons of spent fuel rods stored on top plus whatever active rods are used for reactor operation and there are 25 to 30 such reactors with this quantity in Japan.
I suspect everything is in full meltdown and they lost control of the situation and it is beyond going in and securing anything due to radiation and temperatures.
170 microSv/h = 0.17 mSv/h = approx. 1, 490 mSv/yr
If sustained for a year, this level would therefore be past the level of 350 mSv/lifetime which, according to the WNA table, was the “criterion for relocating people after the Chernobyl accident”. Of course, the 170 miscroSv/h radiation dose is unlikely to be sustained for a year and it may go down quickly.
BUT, from the measurements in the attached document, it seems like this high level is recurring: 167 microSv/h was recorded at 13:10, 170 microSv/h at 14:00, and 158 microSv/h at 15:00. So I think this means that these ‘high’ levels cannot be associated with one ‘blast’ as was explained when the 400 mSv recording occurred a couple of days ago....
These levels equivalent to 1, 490 mSv/yr are definitely past the naturally-occurring background radiation level typically from about 1.5 to 3.5 mSv/yr.