Long-term dose estimation with con2rem

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jpj
Posts: 2
Joined: July 2nd, 2020, 4:07 am
Registered HYSPLIT User: No

Long-term dose estimation with con2rem

Post by jpj »

Hysplit version: April 2018 release (SVN 951)
OS: WIN10

I am running a 48 h simulation where I-131 (particulate form) is released hourly during the first 24 h. I am trying to estimate the doses related to this release with a one year integration time. If I have understood correctly con2rem does this with a switch -x8760. I did test simulations where the switch was on and off, inhalation dose was not taken into account in either of the cases. Results for ~5 km distance from the source in the direction of the main plume are presented below (taken from the file produced by con2asc):

-x8760 off:
I13100000 = 2.95E-03 mSv
I13100005 = 1.66E-04 mSv

-x8760 on:
I13100000 = 3.23E-03 mSv
I13100005 = 4.61E-02 mSv

Below are the con2rem calls from the batch scripts:

-x8760 off:
%PGM%\exec\con2rem -iCG_10%%D%%H -oDG_10%%D%%H -s1 -c0 -t0 -d1 -e0 -q1 -aC:\...\activity_unit_I-131.txt

-x8760 on:
%PGM%\exec\con2rem -iCG_10%%D%%H -oDG_10%%D%%H -s1 -c0 -t0 -d1 -e0 -q1 -aC:\...\activity_unit_I-131.txt -x8760

When the integration time of one year is applied the doses increase for both groundshine (I13100000) and cloudshine (I13100005) but the increase is more pronounced in case of cloudshine (~two decades!). In the hysplit manual it is mentioned that in case of longer integration times (-x switch on) only the deposited activity is taken into account in dose calculation. Thus there seems to be a contradiction between what the manual says and what the results are.

Could you elaborate on the functionality of con2rem -x switch? Does it remove the activity during the time period (in this case a year) or does it assume constant activity? Why in this case the prolonged integration time is having an effect to the cloudshine dose?

Best regards
Juha-Pekka
Tianfeng.Chai
Posts: 16
Joined: September 18th, 2017, 2:20 pm
Registered HYSPLIT User: No

Re: Long-term dose estimation with con2rem

Post by Tianfeng.Chai »

The explanation can be found in the user guide.

Additional decay time can be added using this field to estimate long-term doses. This calculation
applies to either -t option but only for deposition doses. This option permits longer-term doses to be
computed by adding additional decay to the existing output files.


As described above, the additional decay applies to deposition doses only.
The decay does not apply to concentrations. Thus, the constant concentrations contribute to
the cloudshine during the entire "prolonged integration time".

This utility is not recommended for cloudshine calculation with a long extended decay time.
If cloudshine calculation with a long extended decay time is needed, HYSPLIT simulation is recommended to
get the actual concentrations (or the dilution factors).
jpj
Posts: 2
Joined: July 2nd, 2020, 4:07 am
Registered HYSPLIT User: No

Re: Long-term dose estimation with con2rem

Post by jpj »

Thank you for your explanation.

I misinterpreted the description given in the manual and thought that long-term dose calculation is only applied to the deposition doses i.e. the cloudshine doses are left as they are after the original calculation even if long-term doses calculation is applied. I agree that it does not make a lot of sense to estimate long-term doses by assuming that the cloud stays put for a year and that the activity is constant during that time.

I guess that the easiest workaround for estimating only long-term deposition doses and leaving cloudshine doses as they are, would be to define deposition and air concentration grids separately and apply long-term doses calculation only to the deposition grid.

Best regards
Juha-Pekka
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