Obtaining the concentration multiplier

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mahulenak
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Joined: June 17th, 2020, 2:58 am
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Obtaining the concentration multiplier

Post by mahulenak »

I have trouble understanding the deposition multiplier and concentration mulitplier. I tried to calculate the factors shown in 15.1 but to no avail. The USEPA table states a conversion factor of

469.5 [mREM/y]/[mCi/cm^3] = 469.5 [10(-3) REM / 8760 hr] / [3.7 * 10(7) Bq / 10(-6) m^3], which according to my calculations translates to 1.45 * 10(-18) [REM/y]/[Bq/m^3] and the tutorial says it' s 3.4E-11 [REM/y]/[Bq/m^3]. Also how did we get 1.1E-12 (REM/hr) / (Bq/m2) ? What am I missing?
Tianfeng.Chai
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Re: Obtaining the concentration multiplier

Post by Tianfeng.Chai »

Can you provide the detailed source for "469.5 [mREM/y]/[mCi/cm^3] ?
There are many different exposure to dose conversion factors, e.g. due to submersion and inhalation.
The dose conversion factor for deposited radionuclides are related to groundshine where some assumption have to be made for surface characteristics and many other things as well.
mahulenak
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Re: Obtaining the concentration multiplier

Post by mahulenak »

As I mentioned, there is a link in the tutorial to http://www.iem-inc.com/information/tool ... on-factors and I used the "External in soil" factors.
Tianfeng.Chai
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Re: Obtaining the concentration multiplier

Post by Tianfeng.Chai »

I believe the inhalation pathway that affects lungs is more important for radionuclide in the air.
Inhalation conversion factor for Cs-137 used at NOAA is 4.60E-09 Sv/Bq.
As 1 rem = 0.01 sievert (Sv), this Cs137 factor is 4.60E-11Rem/Bq

The dose to human lungs due to breathing in Cs-137 in the air will be
4.60E-11 Rem/Bq * Breath rate (m3/hr) * Cs137 concentration (Bq/m3)

If the assumed 3.4E-11 (REM/hr) / (Bq/m3) conversion factor in the tutorial is solely due to inhalation,
then the Breath rate is 3.4/4.6 m3/hr
Assuming 20 breaths per minute (1200/hr), the volume of each breath (tidal volume) is 0.616 E-3 m3 =0.616 liter.
This is pretty reasonable compared to the average tidal volume of 0.5 litres given by Google.

But, please refer to a health physicist for dose conversion details, especially if applying it for incidents.
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