>> you are referring to decay in the activation study mode (associated to a
>> cooling times list), not to the semi-analogue mode.
> Yes, correct. I am referring to the radioactive decays activated for
> requested cooling times (analogue mode).
That is not analogue at all! It's what in the manual is called activation
study mode, whereas 'analogue' and - more properly - 'semi-analogue' are
both used to mean the other mode in which "each single radioactive nucleus
is treated in a Monte Carlo way like all other unstable particles".
>> In that case, at the end of each primary history, the produced
>> radioisotopes are let decay (by default three times each, as in WHAT(3) of
>> RADDECAY) down to the end of their decay chain.
> But the manual says:
>
> WHAT(3) : number of "replicas" of the decay of each individual residual
> = 0.0: ignored
> < 0.0: reset to default
>
> Default = 1.0 for analogue decays, 3.0 otherwise
>
> Doesn't this mean by default, individual residuals are decayed only once in
> the analogue mode?
Indeed, but since we are talking about the other mode, the decay of each
individual residual is replicated three times.
>> All the so generated electromagnetic particles are transported (with
>> materials in the geometry
>> transformed into vacuum or blackhole on request), irrespective of the input
>> cooling times.
> Just to clarify... The generate e+,e-, gammas, as well as neutrons are
> transported through the decay material which by default are set to the same
> material during the irradiation time and only through vacuum or blackhole if
> requested by the user. Correct?
Decay particles (i.e. electromagnetic particles generated by beta and
gamma decays) are transported through the same materials as prompt
particles unless the user asked to change (some of) them to vacuum or
blackhole for decay particle transport purposes.
Which neutrons are you talking about? Decay radiation consists only of
positrons, electrons, and photons. Heavy radioisotopes give also alpha
decay, but, as recently reminded, decay alphas are not explicitly
generated in FLUKA so far.
> Also, as I understand, dose rates are calculated from the fluence of a given
> decay particle in a given volume (and not from the activities) at a given
> cooling time. How is this done?
A radioisotope is produced. It decays and generates (itself and/or its
daughters) electromagnetic particles. They are transported and their
fluence over a volume is calculated (fluence=tracklength/volume) and
converted to DOSE-EQ by the respective coefficients. DOSE-EQ scoring at a
given cooling time is done by putting together all the relevant
contributions each weighted according to the population (-> activity) of
the concerned radioisotope (the original one or one of its daughters) at
that cooling time.
Hope not to decay your understanding
Cheers
Francesco
Received on Sat Aug 04 2012 - 13:46:19 CEST
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