[ RadSafe ] Dose conversion in beta exposure readings at Fukushima Daiichi ?

Sun Sep 1 08:59:27 CDT 2013

Jaro,

See latest article:
http://www.cnn.com/2013/09/01/world/asia/japan-fukushima-radiation-spike/in
dex.html?hpt=hp_t2

Quote from above article:"But TEPCO also took issue with reporting by some
news outlets that the new radiation levels
were high enough to cause death after several hours of exposure.
It said the highest

levels measured were so-called beta radiation, which quickly dissipates
over short distances and is easily shielded through the use of thin
sheets of metal and foil.

"Since beta radiation is weak and can be blocked by a thin metal sheet
such as aluminum, we
think that we can control radiation exposure by using proper equipments
and cloths," the company added."

Regards,

Sandy

-----------------------------------
Sander C. Perle 
President
Mirion Technologies
Dosimetry Services Division
2652 McGaw Avenue
Irvine, CA 92614

+1 (949) 296-2306 (Office)
+1 (949) 296-1130 (Fax)

Mirion Technologies: http://www.mirion.com/

On 8/27/13 11:54 AM, "Jaro Franta" <jaro_10kbq at videotron.ca> wrote:

>The latest TEPCO handouts include the first I have seen that reports
>analysis results on tritium.
>
>The data is NOT for the recent water leak around the H-area storage
>tanks, but nevertheless provides a useful indication of a typical ratio
>of tritium versus other nuclide activity.
>In this case the ratio is about 39.2 relative to Cs137 (using 2000/51 for
>“North side of Unit 1-4 water intake channel”).
>
>Taking the tank water results published earlier – 100 Bq/cc of Cs137 –
>and including the 15.8 depletion factor from the Cs stripping process --
>the tritium activity should be about 39.2 x 15.8 x 100 = 61,960 Bq/cc.
>
>As noted earlier, total fission product beta based on Sb125 ratio should
>be 242 x 71 Bq/cc = 17,202 Bq/cc.
>
>Adding 61,960 Bq/cc tritium and 17,202 Bq/cc fission product beta yields
>79,163 Bq/cc total beta – virtually identical to the “All ß” figure of
>80,000 Bq/cc originally reported for the tank water.
>
>Is it just coincidence that the numbers match ? …seems unlikely.
>
>http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/2013/images/2tb-east_1308
>2601-e.pdf
>
>
> Jaro
>^^^^^^^^^^^^^^^^^^^^^^^^^
>
>
>
>
>
>
>-----Original Message-----
>From: radsafe-bounces at health.phys.iit.edu
>[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jaro Franta
>Sent: August-26-13 10:34 AM
>To: 'The International Radiation Protection (Health Physics) Mailing List'
>Subject: Re: [ RadSafe ] Dose conversion in beta exposure readings at
>Fukushima Daiichi ?
>
>Thanks Jim,
>
>I am not familiar with conversion factors for deriving skin dose
>expressed as dose equivalent.
>
>Is there a decent on-line reference somewhere, please ? (PS. I’m not an
>HP, but judging by the number of responses to my question, that doesn’t
>seem to make much difference…)
>
>Also, is it normal practice to leave people guessing about what sort of
>interpretation is the correct one, rather than simply spelling out what
>it is that’s being published ?
>
>
>Jaro
>
>^^^^^^^^^^^^^^^^^^^^^^^^^
>
>
> 
>
>From: Jim Hardeman [mailto:jim.hardeman at gmail.com]
>Sent: August-26-13 10:13 AM
>To: jaro_10kbq at videotron.ca
>Subject: Re: [ RadSafe ] Dose conversion in beta exposure readings at
>Fukushima Daiichi ?
>
> 
>
>Jaro --
>
> 
>
>Yeah, I was thinking that Sr-90 and Pu-241 might make a significant
>contribution.
>
> 
>
>Looks as if the Japanese were PERHAPS a bit more rigorous in performing
>their dose estimates than I originally thought. I'm interpreting TEPCO's
>latest as being (shallow) skin dose expressed as dose equivalent as
>opposed to organ dose to the skin. Is that your interpretation as well?
>
> 
>
>Jim
>
> 
>
>On Mon, Aug 26, 2013 at 9:08 AM, Jaro Franta <jaro_10kbq at videotron.ca>
>wrote:
>
>Additional instrument info posted by Tepco today:
>
>"Measurement device: Shallow ionization chamber survey meter (AE-133B)"
>
>Also, the same four high dose rate numbers listed previously as "γ+β ray"
>are now listed as "Dose equivalent rate measured from 70μm (β ray)"
>
>http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_13
>08 
><http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_1
>30823_05-e.pdf> 
>23_05-e.pdf
>
>
>
> Jaro
>^^^^^^^^^^^^^^^^^^^^^^^^^
>
>
>
>
>-----Original Message-----
>From: radsafe-bounces at health.phys.iit.edu
>[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jaro Franta
>
>Sent: August-23-13 7:53 PM
>To: 'The International Radiation Protection (Health Physics) Mailing List'
>Subject: Re: [ RadSafe ] Dose conversion in beta exposure readings at
>Fukushima Daiichi ?
>
>Jim, I will save you the time:
>
>Here are the results of SNF decay after 2.49y, obtained using the
>SpentFuelExplorer java tool, by K. Sorensen.
>
>One is in pie chart form, the other a table:
>
>https://dl.dropboxusercontent.com/u/11686324/SNF_2%2C49y_old.JPG
>
>https://dl.dropboxusercontent.com/u/11686324/SNF_2%2C49y_old_table.JPG
>
>Cheers,
>
> Jaro
>^^^^^^^^^^^^^^^^^^^^^^^^^
>
>
>
>From: Jim Hardeman [mailto:jim.hardeman at gmail.com]
>Sent: August-23-13 9:02 AM
>To: jaro_10kbq at videotron.ca
>Subject: Re: [ RadSafe ] Dose conversion in beta exposure readings at
>Fukushima Daiichi ?
>
>Jaro --
> 
>It's unclear to me that what TEPCO calls "all Beta" is tritium -- I think
>it's more likely to be a gross beta measurement, which would include both
>Cs-134 and Cs-137 and any other non-volatile beta-emitters in the water.
>This long after the incident, I'd have to do some decay calculations to
>see
>what I would "expect" to be in the water, but the Cs isotopes, while
>certainly the most prominent, aren't the only ones.
> 
>Jim
>
>On Fri, Aug 23, 2013 at 8:07 AM, Jaro Franta <jaro_10kbq at videotron.ca>
>wrote:
>Tepco's latest analysis results:
>
>Aug 23, 2013 - Sampling Results Regarding the Water Leak at a Tank in the
>H4
>area in Fukushima Daiichi Nuclear Power Station
>
>http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/2013/images/south_dischar
>ge 
><http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/2013/images/south_discha
>rge_130823-1e.pdf>
>_130823-1e.pdf
>
>....where the "All beta" numbers are much closer to the Cs numbers -
>suggesting but not confirming that the 80kBq/cc in the leaked water from
>tank no.5 is largely tritium (these latest results sample nearby "drainage
>channel B", not the water from the tank..)
>
>
> Jaro
>^^^^^^^^^^^^^^^^^^^^^^^^^
>
>
>
>-----Original Message-----
>From: radsafe-bounces at health.phys.iit.edu
>[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jaro Franta
>Sent: August-22-13 9:41 AM
>To: 'The International Radiation Protection (Health Physics) Mailing List'
>Subject: Re: [ RadSafe ] Dose conversion in beta exposure readings at
>Fukushima Daiichi ?
>
>A search on Tepco's web site turned up this reference document:
>
>Radiation Monitoring at the site - measuring method  (November 19, 2011)
>http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111119_04-e.pdf
>
>Some of the more interesting slides:
>
>Slide 7:  Estimation of Sv/h from Bq/cm2
>
>Quote: "In the case of Cs-137 contamination radius (40cm), Distance (1m):
>13,000cpm = approx. 0.04 Sv/h"
>
>..presumably this conversion applies only to gamma ?
>(...yet in their table published this week, they report beta + gamma dose
>rates of ~100 mSv/h, with only a tiny fraction of that being gamma)
>
>
>Slide 9: Radiation Meter for contamination measurement (GM Survey Meter)
>Slide 11: External exposure evaluation measure Slide 15: Beta nuclide
>measurement (Tritium)
>
>
>Tepco report slide:
>http://db.tt/UfPU1FpJ
>
>
> Jaro
>^^^^^^^^^^^^^^^^^^^^^^^^^
>
>
>
>-----Original Message-----
>From: radsafe-bounces at health.phys.iit.edu
>[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jaro Franta
>Sent: August-21-13 2:57 PM
>To: 'The International Radiation Protection (Health Physics) Mailing List'
>Subject: Re: [ RadSafe ] Dose conversion in beta exposure readings at
>Fukushima Daiichi ?
>
>Thanks Jim,
>
>Its important to get to the bottom of this bizarre dose rate reporting.
>
>Here's why: According to Reuters,
>
>"Water in the latest leak is so contaminated that a person standing close
>to
>it for an hour would receive five times the annual recommended limit for
>nuclear workers."
>
>http://www.reuters.com/article/2013/08/21/us-japan-fukushima-severity-idUS
>BR 
><http://www.reuters.com/article/2013/08/21/us-japan-fukushima-severity-idU
>SBRE97K02B20130821>
>E97K02B20130821
>
>......how on earth does one get "five times the annual recommended limit
>for
>nuclear workers" from an external beta dose ?
>......and how does one even calculate a dose rate in mSv/h from an
>instrument reading of beta radiation in the environment ?
>
>Jaro in Wonderland
>
>
>
>
>
>From: Jim Hardeman [mailto:jim.hardeman at gmail.com]
>Sent: August-21-13 10:49 AM
>To: jaro_10kbq at videotron.ca
>Subject: Re: [ RadSafe ] Dose conversion in beta exposure readings at
>Fukushima Daiichi ?
>
>Jaro --
> 
>My GUESS is that what TEPCO is talking about isn't an actually dose rate
>MEASUREMENT, but a dose rate ESTIMATE performed with some sort of GM tube
>/
>counter with a removable beta shield -- something like the old HP-270 "hot
>dog probe". Seems to me that they're simply reporting open window readings
>as "beta + gamma" and closed window readings as "gamma". I doubt they're
>doing much in the way of making beta dose rate conversions.
> 
>My $0.02 (US -- don't know what that is these days in Canadian)
> 
>Jim Hardeman
>jim.hardeman at gmail.com
>
>
>
>
>
>On Wed, Aug 21, 2013 at 10:35 AM, Jaro Franta <jaro_10kbq at videotron.ca>
>wrote:
>Here's a question about exposure/dose rate numbers reported by Tepco at
>the
>FD contaminated water storage tank farm earlier this week.
>
>A picture from Tepco's pdf document is linked below.
>
>Of interest are the sample analysis results for "Leakage water" in the
>table
>at bottom left, reported in Bq/cm3:  Note especially the "All beta" figure
>of 8.0E+4 figure.
>
>The curious part is the table at right, which lists dose rates at various
>points around the site in mSv/h - for either "beta + gamma" or gamma
>alone:
>the highest number being ">100 mSv/h" for "beta + gamma" at point #1, and
>similar values for points 10, 11, and 12.
>
>My question is how does one apply dose conversion factors to instrument
>readings, to derive "beta + gamma" dose rates in mSv/h ? ..which look to
>be
>mostly beta, if one deducts the gamma-only number in the right column.
>
>This is clearly not a case of committed dose due to radionuclides absorbed
>in the body. So what is it ? ..if its simply a conversion of instrument
>beta
>particle count rate, what sort of conversion factor would one apply to
>betas
>from tritium, to get mSv/h ?
>
>And although its not explicitly stated, the activity numbers in the lower
>table suggest that much of the 8.0E+4 Bq/cm3 activity is tritium, with
>very
>low beta energy (this water was used for cooling the damaged reactors, and
>circulated in a closed loop through filters that remove much of the
>fission
>products, but not the tritium..)
>
>
>Tepco report slide:
>http://db.tt/UfPU1FpJ
>
>Thanks
>
>Jaro
>^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
>
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