From: Sebastien WURTH (wurth@ipno.in2p3.fr)
Date: Wed May 17 2006 - 10:55:43 CEST
Alfredo Ferrari a écrit :
> Dear Sebastien
>
> the results should be indeed in pSv/s, if everything is setup correctly.
> I would suggest to add also a pure fluence scoring (not weighted with
> deq99c) which will be in particles/cm^2/s and apply some "back of the
> envelope" average conversion factor, just to check everything is
> consistent.
>
> Obviously the results are already including the beam intensity if you
> specified its values in the irrprofi card. Sorry for the dumb
> question, did you input in irrprofi the beam intensities in particle/s?
> Did you checked in the output that the FLUKA "interpretation" of your
> cards (particularly those defining the irradiation profile) is the
> one you expect?
>
> What does it mean dose rates are much higher than expected? A factor ten
> or 10^6? I mean, could it be a somewhat surprising result still
> compatible with common sense, or is it nonsense?
>
> Ciao!
> Alfredo
>
> On Tue, 16 May 2006, Sebastien WURTH wrote:
>
>> Hello dear fluka users and developpers,
>>
>> I'm trying to score dose rate after several decay times with USRBIN
>> and the
>> cards to simulate radioactive decay and scoring : RADDECAY, IRRPROFILE,
>> DCYSCORE and DCYTIMES.
>>
>> I use the fluence calculation of all particles (code 201) using fluka
>> executable linked with deq99c.f routine
>> in order to convert fluence to dose.
>>
>> According to the manual, DCYSCORE section, note 1. [...]all quantities
>> are expressed per unit time [...].
>>
>> I assumed that my results are expressed in pSv/s beacuse :
>>
>> - USRBIN when fluence is scored expresses its results in
>> part/cm²/primary particle
>> - With FLUSCW + deq99c.f, results are expressed in pSv/primary particle
>> - With IRRPROFILE, and DCYSCORE, results are expressed in pSv/s ==> IS
>> THAT TRUE, AFTER ALL ?
>>
>> I'm asking because the results are not as I expected, the dose rates are
>> far to important.
>> (They actually become lower when the decay times increase but...).
>>
>> Thank you kindly in advance for all your answers and advices.
>>
>> Sebastien.
>>
Dear Alfredo,
Thank you for your answer.
About the questions you asked :
I did the pure fluence scoring with no USERWEIGH card and the default
fluka executable --> flukahp.
When I use a "hand-made" approximated conversion factor, it seems to be
consistent with the run
in which direct conversion is applied. There may be a factor 10 or so,
but not enough to explain the problem.
I gave the right irradiation profile I guess : 50 MeV electron, with 10
µA intensity during three weeks.
This leads to 6.25E+13 part/s during 1814400 seconds.
These values are properly interpreted by fluka according to the *.out
file, as well as my six cooling times and the direct conversion from
fluence to dose
(according to the message which is printed just before the first
particle is followed in *.out).
In the SDUMs of my USRBIN cards I put EWT74, and never had to complain
about it untill now.
The results are to high by a factor 1000 at least, and it's quite
senseless in my opinion.
Something concrete :
The experiment consists in the irradiation of a UC2 target by an
electron beam.
I try to predict the dose rates of the removable part of the target. The
unloading operation (by a man) is scheduled
one week after the end of the irradiation.
The estimated dose rate (calculations after similar experiments) gives
~50 µSv/h after a decay time of one week.
My simulation with fluka gives (lower value) ~72000 µSv/h after the same
decay time. In this case, it is absolutely out of question to
unload the all thing.
When I score dose rate during irradiation (no radioactive decay
applied), results are high (of course) ~ several Sv/h
but more or less what I expected.
Of course, here, USRBIN results are expressed in pSv/electron and
converted in Sv/h using the beam intensity in bpawlev routine.
I'm quite sure fluka has nothing to do with it,
it's only a matter of multiplicative factors (and units I believed).
I'm still looking for some mistakes I could have done in the input file...
Best Regards.
Sebastien.
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