| (Not Updated since 2011/3/26)
Q1. How can I see the values of radioactive ray on the graph?
Every minute I can see the CPM value of radioactive ray on the
radiation detectors type GM-10 that I am using and I put red colored
points on the graph. The red colored points
are connected by blue lines. And then the graph is showing Gaussian
distribution as the CPM values are different every minute. The gray line
is showing the average value of CPM calculated by using standard
deviation, maximum value, and minimum value.
Q2. How accurate are the values on the graph?
A2. The radiation detectors type GM-10 that I am using should have been
inspected carefully when they were dispatched from the factory, However,
my own GM-10 has not been checked by any official authority. Therefore,
I also can not guarantee its accuracy at 100% and I would like to ask you
to keep in mind the values are rough figures. Still you can see the change
and tendency of the CPM values by comparing with the past values
Q3. Can I compare CPM values after the damage at the Fukushima nuclear power plant with the values before?
I have started showing the graph of the CPM values that was measured in
December, 2010 below the graph of the present CPM values.
Q4. Does the radiation detector measure the radioactive ray inside building?
As the radiation detector is not waterproof, it is placed facing to
window glass inside my house. I have checked that there is not so big
difference between the
CPM values measured inside my house and outside due to the house mainly
made of wood. I think that the CPM values measured inside my house is
20% lower than the CPM values measured outside because the radioactive
ray is not the one floated in the natural world but the one diffused
from the nuclear power plants (I checked it by myself this time).
Q5. Do you know the other web sites which show the similar information to yours?
A5. Son of my friend, Mr. Hideki Kuroda, has just started measuring the CPM values by using the same radiation detectors (GM-10) in Bunkyo-ku, Tokyo and showing the similar information on his web site.
Japan quake radioactive material monitoring post MAP
Q6. At which level of CPM value is it risky for human body?
A6. As I am basically a communication engineer, I am not familiar with such kinds of field. I advise you to ask the specialists.
Q7. Can I use your graph data for my own analysis or research?
A7. Yes, you can. I hope that my graph data will be used by any people who think that it is important and useful for the earth
Q8. I noticed on your graph that maximum vertical scale is 100CPM . Is it possible for you to show your graph with bigger scale?
A8. Yes, it is possible. When the CPM value become more than 100, I will change the scale.
Q9. Sometimes the size of horizontal scale of
your graph is changed. At that time it is not clear and can not be
A8. I have to stop measuring the radioactive ray when the software should be up-to-dated or due to the failure
of power supply. When I re-start measuring, the indication of my graph
is reset and that effects the size of the horizontal (time) scale. After
15 hours since the time of the reset the size of the scale become
normal. I will try my best possible efforts to avoid this kind of stop
Q10. Conversion from CPM to μSv/h
A10.The value of CPM can be converted to μSv/h easily by using the factor.
The radiation detectors type GM-10 that I am using can measure only the
values of radioactive ray from Cobalt 60 and Cesium 137 even there exist
some other radioactive materials such as Americium 241 and Gamma 45, The
values of radioactive ray from these other radioactive materials can be
obtained from the special graphs (not be shown here). As there does not
exist Cobalt 60 in the air and Cobalt 60 is not produced inside nuclear
power plant, I am using the value of CPM for Cesium 137 produced at nuclear
fission. The value of μSv/h can be calculated by multiplying the value
of CPM with the figure of 0.00833, that is 120CPM=1μSv/h.
Q11.The value in the graph would be 0.17 microsieverts(μSv)/hour based on the conversion of 120 CPM = 1.00 μSv/h , which becomes rather greater than the ones officially announced as the results in Metropolitan area by Environmental Radiometry, information related to Fukushima Nuclear Plants, and/or the ones in Yokohama reported by Yokohama Environmental Advancement Agency (Yokohama Kankyo Sohzoh Kyoku). I am wondering how I should interpret these discrepancies? (2011.3.21)
A11. Likewise, I am unsure of an exact cause. What I understand is that
those would come from differences between: 1) the original values in normal
state, and 2) the amounts of natural radioactivity. To my limited knowledge,
it is said that the radioactivity in nature greatly vary in different areas/regions.
The different methods in radiometry could result in those discrepancies.
As I mentioned earlier, this site is just to show, in situ, show what the
GM-10 counter has been detecting in order for readers to read changes by
comparing to the past data (cf. The second graph located below the current
one). Hope you understand this site is not intended for guaranteeing accuracy
in absolute value.