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Decontamination plan compiled

The Japanese Environment Ministry has come up with a revised plan to clear away radioactive substances from the crippled Fukushima Daiichi nuclear plant.

It announced details on Monday at a meeting of a panel of experts.

Ministry officials say decontamination will be carried out in areas where radiation levels are higher than 1 millisievert per year.

The ministry revised an earlier plan to only decontaminate places with more than 5 millisieverts per year. Municipalities in Fukushima Prefecture that have areas with less than 5 millisieverts argued they should be included in the cleanup.

The government will be responsible for the decontamination of no-entry zones and government-designated evacuation zones. Local governments will clean up the rest of the affected areas.

Areas with radiation levels higher than 20 millisieverts per year will be reduced stage by stage as soon as possible.

In areas with less than 20 millisieverts per year, radiation levels recorded at the end of August will be cut up to 60 per cent in the next 2 years.

Environment Ministry officials say the government will help prefectures that have a massive amount of radioactive waste.

The ministry's decontamination plan will be further discussed within the government before being adopted by the Cabinet as the basic national plan.

Monday, October 10, 2011 22:04 +0900 (JST)
www3.nhk.or.jp

Radiation dose, the task force estimated 40 percent reduction after two years without decontamination

Nuclear emergency response headquarters in 24 countries, together in the future method to predict the radiation dose by TEPCO Fukushima Daiichi nuclear power plant accident, the Nuclear Safety Commission. Without decontamination, the impact of wind and rain after two years they expect to reduce 40% of the dose estimates. The safety committee also note that a reference for determining the decontamination strategy for the future.

Currently, affecting the amount of radiation in the disaster area, but about 30 years and cesium 137 cesium 134 half-life of about two years from the nuclear scattering. Iodine-131 is a half-life of eight days, now reduced to below the detection limit. Also that strontium-90 is detected, the impact on a small dose.

Cesium 134 and 137 present in a ratio of almost 1:1, impact energy is higher dose of 134. In addition, the cesium-137 was accumulated in the nuclear fields in the past have shown that half-year results of 18.4 and the effects of wind and rain. translate.googleusercontent.com

@elainekirk I wonder if this is part of the slow admission of what a mess it really is.

Radiation detectors: Cheap and accurate never go together

BY RYOMA KOMIYAMA STAFF WRITER

2011/10/09

The accident at the Fukushima No. 1 nuclear power plant has prompted a surge in sales of radiation detectors--and also an increase in inaccurate measurements.

The characteristics of such devices for ordinary citizens vary considerably in terms of accuracy, method of measuring and price.

The best-known radiation detector is the Geiger counter. But a Geiger counter cannot distinguish between different types of radiation nor can it accurately evaluate the toxic effects on human health. It can only count how many times it has detected radiation.

It would be like owning a device that counts the number of animals but does not differentiate the species, whether they are elephants, rabbits or mice.

The least penetrative type of radiation is the alpha ray, which can be stopped by even a sheet of paper. Alpha rays, emitted by plutonium and other substances, are clusters of two neutrons and two protons.

The beta ray can penetrate paper but can be blocked by thin aluminum or other metal plates. Beta rays, ejected by strontium, cesium and other radioactive substances, are in fact electrons.

The gamma ray can only be stopped by lead or thick iron plates. Emitted by cesium and other substances, gamma rays are not particles but are electromagnetic waves of extremely high energy.

Neutron beams are emitted during nuclear fission of uranium and other matter. Water or concrete can be used to block them.

Radiation crashing against a human body generates electrons that disrupt DNA, but the amount of electrons generated by the collision differs according to the type of radiation. The levels of toxicity, which are also different, are measured in units of sieverts across all radiation types.

The Geiger counter is a simple mechanism that is sensitive to low radiation levels. Its central component is a container called the Geiger-Mueller tube. When radiation hits gas particles contained within the tube, electrons are ejected, generating electric currents in a circuit that the device can detect.

Since only a very small number of electrons are ejected, a voltage is applied to the GM tube so that the electrons accelerate and hit other gas particles, creating a cascade of electron flows. This contraption makes it possible to detect very small doses of radiation.

Different numbers of electrons are generated by different types of radiation. The radiation type could be identified if the initial amount of electrons was known, but this is impossible after the electrons have been multiplied in the GM tube.

Therefore, the dose in sieverts indicated on the Geiger counter is a mere estimate. It's like estimating the total weight of all the animals counted under the assumption they were all rabbits.

"Geiger counters can be used to check if food or other products are contaminated or not, but they do not tell you how harmful they are," said Keiji Kusama, head of the radiation safety section of the Japan Radioisotope Association.

He said the public should not rely on products available for tens of thousands of yen (hundreds of dollars).

Using the animal-counting comparison, some products cannot even reliably count the number of creatures.

The performance of a Geiger counter depends on the size of the GM tube. A larger tube can hold more gas for electrons to be generated, resulting in a higher measurement capability.

Geiger counters sold at tens of thousands of yen, however, have GM tubes the size of a fingertip. Their measurements, spanning only several seconds, can produce estimates ranging from half to double the real values, Kusama said.

"Cheap products can detect radiation only several times a minute," said Kouichi Yamada, director of the measuring systems sales division at Hitachi Aloka Medical Ltd. "Errors are large because the calculations are based on scanty data."

Other types of detectors, including the ionization chamber, can distinguish between radiation types.

The ionization chamber takes measurements from electrons generated by radiation crashing into air particles. The ionization chamber resembles the Geiger counter in this sense, but the electrons are not multiplied to be counted.

It would be like summing up the weights of elephants, rabbits and mice measured individually and carefully. This enables a precise evaluation of the total weight of all animals, or the total level of toxicity of all types of radiation.

But to measure low radiation levels in a short time, the device must be so big that is no longer portable. And the prices for the larger ionization chambers can cost millions of yen. These devices are used at monitoring posts or fixed measurement stations.

Portable types of ionization chambers are available for hundreds of thousands of yen, but their sensitivity is so low that they cannot even measure radiation levels at a distance of 50 kilometers from the Fukushima No. 1 nuclear plant.

Municipal governments across Japan are introducing detectors of yet another type--scintillation survey meters--to locate radiation hot spots. These devices, which use crystals that emit light when they are irradiated, are not as accurate as ionization chambers, but they can still produce sievert estimates by distinguishing between different types of radiation. They have about a 15-percent margin of error and cost hundreds of thousands of yen.

Some detectors use semiconductors that generate electricity when they are irradiated. These devices also distinguish different radiation types, but products available for tens of thousands of yen have semiconductor chips only several millimeters in size.

A semiconductor detector can be used to measure total exposure to radiation if it is carried over an extended period of time. But it is not suited for measurements in short intervals.

Experts agree that there are no radiation detectors that are both cheap and accurate. The figures these products produce should be taken as rough estimates, they say.
www.asahi.com

i cannot believe my eyes !!! no-go-zone ?

partying on the edge of hell.

@Edano these photo's may be meant to look jolly but they are just sad

@Edano it's the fact they don't know what is waiting round the corner just innocent families believing the government want to make them all be happy when in reality it is an attempt to fool foriegners that all is well and they should come gawp at these colourful people and spent lots of money

@Edano oh so they seek to decieve too!
audi found this Japan \\times article that gives hope search.japantimes.co.jp
First, the tragic events of March 11 and the concomitant radiation contamination have catalyzed many young people. I sense it in the students at Tokyo Institute of Technology, where I teach, and at other tertiary institutions. Call it a renewed awareness in themselves and a belief that they should be doing something to redress the pain and ills their country is experiencing.

Second, I believe that many people in Japan today, by no means only young ones, feel sick of the lies fed to them by the captains of industry and their servants in the upper echelons of the government bureaucracy.

but lots of references for 2010.

@Edano rockhopper says The second worker,seems so upset about corruption surrounding the on-site management.

@Ian I am going to put together something on the two videos of unit 3 by the pool gate. You mentioned the first video was actually Aug not Sept. Did you have any other notes on the two vids I should add? I have a pile of photo stills I took over the weekend.