Originally posted by Ashyr
reply to post by elevenaugust
how to read this? the blue lines and blobs are readings of higher concentrations of radioactive particles in the air?
or the ground? is this from satellite is this from topographical, on site analysis?
sorry im not sure how to read this graph.
Well, firstly, one needs to know the natural proportion of Ce137 radioactivity in the atmosphere, which is around 0.001 to 0.01Bq/m2.
The medium blueish area have an average Cs137 radiation dose between 0.01 and 0.1Bq/m2
The light-blue area have an average Cs137 radiation dose between 0.1 and 1Bq/m2
The yellowish area have an average Cs137 radiation dose between 1 and 10Bq/m2
The orange area have an average Cs137 radiation dose between 10 and 100Bq/m2
The red area have an average Cs137 radiation dose more than 100Bq/m2
Deposition: The dry (and wet) deposition display the total accumulated deposition along the path of the plume, to the ground then.
These maps are created by weather National services, and they used radionucleide ground sensor all around the world as well as weather balloons and
rain water falls collectors.
In addition to the GIF animation of the worlwide Cs137 isotope dry deposition accumulation, I'll now add the everyday update of
]UC Berkeley Nuclear Engineering Air Monitoring Station[/url], from the Department of the Nuclear
Engeneering, University of California, Berkeley.
Here are the preliminary statements:
The UC Berkeley Department of Nuclear Engineering is currently performing measurements to detect a potential increase in radiation here in Berkeley
that could be associated with the release of radioactive materials in Japan. We perform this measurement by sampling air flowing through a particle
filter mounted at the top of Etcheverry Hall. We first calibrated the monitor to account for normal background radiation levels.
After a period of 8-12 hours of particle collection, we take the filter down to our counting station in our laboratory and, using highly sensitive
detection instruments, can determine the concentration of target radioactive elements within the air sample collected by counting gamma-ray photons
emitted. This is to determine if any radiation signatures are present above normal background radiation levels.
The detection instruments we are using are not only able to measure the amount of radiation in the sample, but also its energy. More specifically, we
measure gamma rays and their energies in our detector, which provides a unique fingerprint of a specific radioisotope.
By measuring the energy of the gamma rays with high precision, we can not only determine the amount of radiation due to a specific radioisotope, but
we can distinguish it from the natural background radiation we measure as well.
For example, we can measure gamma rays from isotopes of Cesium (Cs) such as Cs-134 or Cs-137, Iodine (e.g. I-131), or Tellurium (e.g. Te-132), which
we would expect to see from the release due to the fission products in Japan. It is important to realize that all because we can detect radiation
does not mean it is harmful. Our instruments are so sensitive that we can measure radiation far below the levels of the natural background radiation
we live in day to day.
For example, even if we are able to observe a tens of counts per hour of I-131 or Cs-137, we have to compare that to a natural background radiation
level of > 300000 counts per hour when expressed in these terms. Therefore, even if we were able to observe these small amounts of radiation, it will
only lead to a very small increase in the radiation we are exposed to due to the natural radiation and will have no measurable health effect.
We express the biological effect of radiation in terms of doses and dose rates expressed for example in terms of millirem (mrem) or milli-Sievert
(mSv) per hour, day, or year. One millisievert is equivalent to 100 millirems. The average dose of a person living in the U.S. is about 620 mrem (6.2
mSv) per year. This can be broken down into about 300 mrem per year due to natural background, such as radon and ultraviolet rays from the sun, and
320 mrem per year due to artificial exposures, such as X-rays or Computed Tomography (CT) scans. One Chest-CT scan produces about a 1,000 mrem dose of
radiation exposure, or about three times the level due to just the natural exposure. The radiation levels we expect to measure due to the events in
Japan will be 1,000 times smaller than the natural levels of background radiation.
The maximum measured dose rate at the Fukushima plant has been reported at 11.4 mSv/hr which puts the dose in one hour to be near a full-body CT
scan and one-fifth the annual US dose limit for US radiation workers. No health effects have been proven below the 50mSv per year level.
3/29 (11:35am): Our air results and rain water results have both been updated. The isotope amounts in both have leveled out, which means that we might
not be observing a downward trend at this point. We are continuing these tests so that we can observe the eventual expected decline in activities.
3/28 (2:24pm): Latest Air and Water Results data/spectra is now posted. We note decreased levels from previous peaks. This could be due to a number of
reasons to include the lack of rain in the past 48 hours to an actual lower amount of particles in the air. Note, this is not a trend unless we see a
sustained reduction. We are heading into a period of high pressure in the Bay Area and the jet stream will shift away from our area and this may cause
even lower readings. We continue to test run-off creek water, tap water, and milk.
3/27 (2:00pm): Strawberry Creek run off results posted. We do observe all signatures in the run off creek water, but the dilution is from ~2% for
I-131 to 15% for Cs137. However, Cs137 and Te132 are just below minimum detectability for our system and the real dilution is most likely closer to
2-5%. Reservoir and tap water sampling begins next week. These activities are factors of 10 to 50 below rain water results.
The dry deposition displaying the total accumulated deposition along the path of the plume
edit on 30-3-2011 by elevenaugust because: (no reason given)