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PostPosted: Sun, 20-03-11, 22:17 GMT 
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Just my attempt to make some calcolus with the unities of measure. I'm unable to find the direct conversion amongst microSv and Bequerel.

From the converter found here: http://online.unitconverterpro.com/unit-conversion/convert-alpha/convert.php?cat=radiation---radioactivity

I've take up the microSv in Tokyo between the 15 - 16 March, that is 0.5 microSv and converted in Rontgen.
0.5 microSv = 0.00000419 Rontgen.
Then I've converted Rontgen to milliCurie:
0.00000419 Rontgen = 5e-7 millicurie.
From milliCurie I've got the Bequerel:
5e-7 milliCurie = 18.5 Bequerel.

The question is: how the atomkraft physicist accounts for the hours and the kilograms into the relevants contest? Are 18.5 Bequerel the disintegrations of 18.5 radioactive nucleii (either Iodine 131 or Cesium 137) per kilogram of water? If yes, why such water's radioactivity has been found just now and not before?

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PostPosted: Mon, 21-03-11, 15:26 GMT 
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Massimo,

while I am NOT a nuclear physicist, I still remember these somewhat tricky issues about units in radioactivity from my University lectures a long time ago.

The main point is that one has to be very careful not to mix up units that serve different puposes in radioactivity. Otherwise you try to convert "apples" into "pears"...

Also, one should focus on the modern SI (international) units throughout.

Let's only consider ionizing radiation and the 3 groups of units describing
1) the radioactive activity of substances and 2),3) for quantifying the amount of radiation striking other objects, particularly people.


1) Activity of a substance
===================
Here one frequently uses decays per minute[dpm] or Becquerel [Bq] with

1 Bq = 1 / 60 dpm = 1 dps

since 1 Bq = 1 decay per second [dps]. Curie[Ci] is the old unit rarely used today.

Next in 2) and 3) I turn to radiation units that focus on the absorbed dosage e.g. by people

2) Absorbed radiation dose
=====================

Here we need units that denote basically absorbed [radiation energy/weight]. The standard SI unit is

1Gray [Gy] = 1 joule of absorbed radiation energy / Kg = 100 rad

X-ray and gamma-ray exposure is often expressed in units of roentgen [R]. The roentgen [R] unit refers to the amount of ionization present in the air.

3) Dose equivalent
===============
The dose equivalent is a measure of the biological effect of the irradiation on the whole body.

The dose equivalent is equal to the product of the absorbed dose (Gray) and the "penalty" Weight factor W. For X-rays, Gamma rays, or beta radiation: W = 1. However, for the harmful alpha rays, W = 20!!

The modern SI unit here is sievert [Sv]. The older one is rem.

1 Sv = 1Gy * W = 100 rem

Hence again a conversion factor depending on the type of radiation particle...

++++++++++++++++++++++

To illustrate the typical conversion problematics, let us consider a Geiger-Müller counter (e.g. GM-10) that is a standard instrument for measuring ionizing radiation activity.

The crucial hardware part is a tube filled with inert gas that becomes briefly conducting when a ionizing particle of radiation from some source passes through it. These conductivity 'blips' are expressed in counts per minute [cpm] (see my posts above). But the entrance window of a Geiger counter has a certain limited geometry and thus will not catch ALL decays. So there is an unknown efficiency factor < 1 if you want to convert

cpm <-> dpm or Bq

That efficiency factor will depend strongly on the type and energy of the radiation ( particle), the window geometry etc. Hence there is NO single conversion factor e.g. from cpm to μSv/h. In addition, not all Geiger counters can sense the (dangerous) alpha particles (He^2+) besides beta radiation (e^-, e^+) and gamma rays (photons).

Many radiation meters are calibrated to Cs137 or Co60. Here is a table for GM-10 showing the empirical conversion factors from cpm <-> μSv/h in case of Cs137 and Co60:

...........................Cs137.......................Co60..............
.................mR/h........ μSv/h..........mR/h........... μSv/h
GM-10....0.000833....0.00833....0.000926......0.00926
GM-45....0.000333....0.00333.....0.000277.....0.00277

http://www.blackcatsystems.com/GM/conve ... _mRhr.html

The GM-45 is a more sensitive model than the GM-10, illustrating the completely different model-dependent conversion factor...

http://www.blackcatsystems.com/GM/geiger_counter.html

Unfortunately, most relevant radiation in Japan for now is I-131, where I didn't find the GM-10 conversion factor yet.

I hope this was somewhat useful,

Fridger


Last edited by t00fri on Mon, 21-03-11, 16:48 GMT, edited 5 times in total.

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PostPosted: Mon, 21-03-11, 15:46 GMT 
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Please have a look to the online Geiger--Müller counter (GM-10 in Tokyo) that I linked in above.

Here are the exact data of the counter from the original site:
http://park30.wakwak.com/~weather/geiger_index.html

+++++++++++++++++++++++++++++++++
Nuclear radiation detector:Black Cat Systems GM-10 Geiger-Müller Counter
Radiation detected: Alpha - Above 3 MeV , Beta - Above 50 keV , Gamma / X-Ray - Above 7 keV
Location: Latitude: N 35 ° 39 ' 28 '', Longitude: E 139 ° 24 ' 5 ''  
Altitude: 101m Hitoshi Minami 2-chome, Hino, Tokyo,
two-story wooden house, location near the window.

120CPM = about 1 μSv/h
Reload every 10 minutes.
+++++++++++++++++++++++++++++++++

First, note the wind direction displayed above the GM-10 output.

Wind direction, wind speed & weather (Tokyo):
-------------------------------------------------------------------
ImageImage Image


In agreement with weather forecasts (for Mon, March 21 and Tue, March 22) the wind direction now ranges between NW .... E directions, implying that the chances for an influx of radiation from the Fukushima region into Tokyo will increase. Fortunally the wind speed is still low.

Indeed, one can see a clearcut rise in the radiation rate [cpm] for today, March 21!...
Until yesterday the average radiation level was quoted as

<cpm> = (16.52 +- 3.8 )

Today the average rose to

<cpm> = (23.61 +- 5.38 )

as is printed on the online GM-10 output below.

For your convenience, here is a redisplay of the online output. A clear rise on the right is obvious:

Image

Fridger


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PostPosted: Mon, 21-03-11, 21:13 GMT 
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For comparison with the previous evidence of increased radiation in Tokyo, here is again the official plot from http://eq.wide.ad.jp/index_en.html . Units are again μSv/h with x-axis being date/time.

Image

You can clearly see the rise of the radiation on the right hand side of the plot.

An analogous, but much more dramatic effect you see in today's official plot of the radiation in the town of Mito (Ibaraki prefecture) North of Tokyo. According to Google maps, from Mito to Tokyo it's about 2 hours South and from Mito to the Fukushima plant it's about 3 hours North...

Image

Presumably is is all due to the changed wind direction as of today, Monday March 21?

Fridger


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PostPosted: Tue, 22-03-11, 11:38 GMT 
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The contamination of the tap water has further increased (cf my previous display)! Here is the latest comparison with official measurements taken on March 21. Units are again Bq/Kg. The first value in the table refers to I-131, while the second one refers to Cs-137.

Image

The I-131 contamination in the more northern prefecture Ibaraki is more then 10 times that of Tokyo! The contamination in Tokyo has almost doubled (2.9 -> 5.3 Bq/Kg) since March 19.

As noted before, the limits are:

According to the Nuclear Safety Commission of Japan", upper limits for intake are: I-131:More than 300Bq/kg, Cs-137:More than 200Bq/kg


++++++++++++++++++++++
The water in the sea has been found to be strongly contaminated (fish!): e.g. the value of I-131 has been found to be 127 times the legal uper limit! Nevertheless, TEPCO continues to argue that this high value is not harmful to human health...
++++++++++++++++++++++


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PostPosted: Tue, 22-03-11, 13:38 GMT 
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Thank you Fridger, for dedicating yourself in these matters. I rely on you about the smashing of "softened" data eventually argued by TEPCO.

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PostPosted: Tue, 22-03-11, 20:45 GMT 
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fenerit wrote:
Thank you Fridger, for dedicating yourself in these matters. I rely on you about the smashing of "softened" data eventually argued by TEPCO.


You're welcome.

F.


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PostPosted: Tue, 22-03-11, 20:50 GMT 
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Hi all,

I now located an online radiation monitor in Tokyo that directly displays readings in units of μSv/h. The values displayed look pretty much consistent with the latest official, governmental readings.

+++++++++++++++++++++++++++++++
Online Geiger-Müller counter (Radex)

http://www.ustream.tv/channel/7578296
+++++++++++++++++++++++++++++++

Here are the official readings from http://eq.wide.ad.jp/index_en.html
in [μSv/h]
for comparison

Time starting 17-18h, hourly intervals for 24 hours

Yesterday, March 21, starting 17-18h
===========================
0.131 0.129 0.128 0.127 0.127 0.128 0.128 0.130 0.137 0.139 0.138

Today, March 22, starting 0-1h
=======================
0.134 0.135 0.134 0.137 0.137 0.141 0.141 0.142 0.137 0.134 0.134
0.133 0.133

Normal values (before Fukushima accident)
=================================
0.028~0.079

Fridger


Last edited by t00fri on Tue, 22-03-11, 20:55 GMT, edited 1 time in total.

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PostPosted: Wed, 23-03-11, 0:04 GMT 
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ERRATA CORRIGE:

The plots doesn't matches around 15 - 16 March, since their microSievert values are opposites; nonetheless I make a vectorial calcolus upon the radiation exposure, setting apart the scalar questions onto decays.

From here: http://eq.wide.ad.jp/110315houshasen_en.html I get the microSievert/year and multiply to 365x24 = 8760 microSievert/hour. Therefore:

2012 (next year) = 0.15 (tonight) x 8760 = 1314 microSievert/h

between Regular public space (except medical area) and Natural Radiation per person/year (World Average)
Space 0.39
Food 0.29
Earth 0.48
Radon (in air) 1.26
; supposed be continuing thereafter, that is, just one day after.

2022 = (ten years after) = 0.15 x 87600 = 13140 microSievert/h
between Guarapari Beach, Brazil , and the Maximum permitted for Radiation workers and management workers (Policeman and Firemen).

2032 = 0.15 x 876000 = 131400 microSievert/h the "Maximum permitted for staff working in emergency cases (new guideline) "


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PostPosted: Wed, 23-03-11, 10:59 GMT 
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fenerit wrote:

The plots doesn't matches around 15 - 16 March, since their microSievert values are opposites; nonetheless I make a vectorial calcolus upon the radiation exposure, setting apart the scalar questions onto decays.


Sorry, Massimo,

I did not understand what you were doing, actually. Which plots don't match?? There are too many around, meanwhile. Did you refer to the new Radex Geiger counter? What did you mean with a "vectorial" calculation?? Where did you get vectorial data from?

What did you intend to show?

Fridger

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PostPosted: Wed, 23-03-11, 13:40 GMT 
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Ops! :cry: The different magnifications of the plots confused me amongst the day of the month and the hours of the days respectively; I apologize for this, of course the plots are identical.
While, for the data about μSv/year I did just a "conversion" to find the "equivalent" in μSv/h (365x24) and I've multiplied for the Tokio's value of yesterday's counter, which were 0.15 μSv/h in order to get, roughly, the value that one inhabitant would absorbed in a year whether such Tokio's value were to be summed up day by day for ten years. Of course it is not so; since such absorbed dose must be absorbed altogether, and 0.15 today + 0.15 tomorrow doesn't get 0.30 the day after tomorrow (I call this a "scalar" issue :o ). However, fur such concerns (the organic absorption in time) should be useful more explanation.


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PostPosted: Thu, 24-03-11, 15:16 GMT 
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Here you see the massive increase (a factor of 25) in radiative contamination of the tap water in Tokyo within a few days. Units are again [Bq/Kg]

collected date.....I-131......Cs-137
=========================
2011/04/06............1.63.........0.5
2011/04/05............2.6...........0.64
2011/04/04............3.82.........0.591
2011/04/03............2.93.........0.501
2011/04/02............2.0...........0.45
2011/04/01............2.1...........0.45
2011/03/31............3.4...........0.88
2011/03/30............5.1...........0.9
2011/03/29............5.6...........0.51
2011/03/28............9.8...........0.82
2011/03/27..........20..............1.2
2011/03/26..........37..............1.8
2011/03/25..........32..............2.1
2011/03/24..........25.6...........2.4
2011/03/23..........26..............1.5
2011/03/22..........19..............0.31
2011/03/21............5.3...........0.22
2011/03/20............2.85......Not detectable
2011/03/19............1.47......Not dettectable

Values were taken from the latest government sources
http://eq.wide.ad.jp/index_en.html

In the more northern Ibaraki prefecture (bordering Fukushima prefecture), the value of March 25 is 78 Bq/kg for comparison

Fridger

EDIT: updated to include March 25 data
EDIT: updated to include data until March 29
EDIT: updated to include data until April 3
EDIT: updated to include data until April 6
Note the decrease in contamination with time!


Last edited by t00fri on Thu, 07-04-11, 17:29 GMT, edited 7 times in total.

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PostPosted: Fri, 25-03-11, 15:38 GMT 
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Here is a survey, taken yesterday, March 24th, from a running car close to the 30km distance border around the Fukushima Daiichi plant (see plot). The units are again μSv/h

Image

As you see, the contamination ranges between 5.1 and 12.0 μSv/h, which is between 39 times and 92 times (!) the radiation measured in Tokyo (0.13 μSv/h)!

Fridger

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PostPosted: Fri, 25-03-11, 22:35 GMT 
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Underwater radiation monitoring, today, March 25th facing Fukushima nuclear plants at the shore. Units are Bq/liter ~ Bq/Kg

Fridger

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PostPosted: Sun, 27-03-11, 14:31 GMT 
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Sun, March 27
=============
Here is a detailed, official status report about all critical aspects of the 6 Fukushima I reactors:

http://www.jaif.or.jp/english/news_imag ... 26468P.pdf

The document has been prepared by the Japan Atomic Industrial Forum (JAIF)


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