Interpretation of results from activation simulation

Thank you @adonadon and @amario for the guidance.

  1. I got the output of RESNUCLE , I have not used any volume, so is the unit of the output in Bq/cc ? The manual said that if I put mass in that ‘vol’ entry, the output will be in Bq/kg. That entry acts like a normalisation. Hence I am unable to properly understand what to put there if I want total activity produced in the target due to activation?

  2. Is it possible to get mass of activation products produced like we get activity in the output ?

  3. Is it possible to get information on activation product activity during irradiation stages? What I understood is we can get the information through RESNUCLE at each cooling period. Is it possible to get these values during irradiation stages also, say, at each 1 hr, 10 days of irradiation stages etc in a single run ? I can use a cooling period of 0 but then multiple simulation will be needed at each irradiation stage. Is there any alternative way to do so ?

  4. I am also interested in gamma emission rate from the gamma emitting radio-nuclides produced as a result of activation. I can place an air detector in front of the target and use USRTRACK to score the photons reaching there. Is it a proper approach or is there any other card available to directly get the photon emission rate from activated radionuclides ? Also in this case, do I have to keep both transport threshold for prompt part for decay part low ? (as opposed to the previous case where I have increased transport threshold for prompt part)

  5. Can we get this photon emission information radiouclide wise ? I mean, to identify which radionuclides are the major contributor of gamma dose at various cooling periods ?


Dear @riya,

Thanks for your questions.

  1. No, You will obtain just Bq. And as you said, if you add the mass, you can obtain Bq/kg. Considering that you want the total activity, it will be given to you when you do not add any normalization. (ref. * page 26)

  2. What you obtain from RESNUCLEi is the activity. If you are interested in the mass, you could obtain first the number of particles using the following formula:

Screenshot from 2022-07-27 14-28-53

A: Total activity
λ : Decay constant
N: Number of particles

and from there you an obtain the mass.
If this is not what you are looking for, please let me know what do you mean with the ‘mass’.

Look at this reference for more details: Radioactive decay - Wikipedia (rates seccion)

  1. Yes, it is possible. You have to use negative times. There you can obtain the information during those irradiation stages (ref * page 21)

4 & 5.

As you say, you could add a USRTRACK or USRBDX in the region of uranium. But, of course, your results will be ‘affected’ by the interaction of the gammas with the material.

Finally, regarding question 5 (and 4 as well), I’m still trying to find a better apporach, but I have two options for you, making use of userroutines:

Option 1:

For this case, you have to use the routines called USDRAW in mgdraw.f and USRRNC in usrrnc.f.

  • Subroutine USRRNC is called every time a residual nucleus is produced.
  • USDRAW is called after each particle interaction, but in particular, with the ICODE = 110, you can obtain just the products from the radiactive decay.

Then, you can dump the information of the residual nuclei when they are produced in USRRNC, and in USDRAW you can dump the products from the radiactive decay. You can even filter in USDRAW when there is a gamma generated using the variable JTRACK = 7.
Dumping this information, and a bit of processing of the data, you should be able to obtain the contribution of gammas from each radionuclides.

PROs: You are dumping all the necessary information to do the study
CONTRAs: The post-processing could be not so simple

Option 2:

Using the routine mentioned above (USRRNC) you can do the following. There is a parameter related to the weight of the particle ‘WEE’. What you can do is to modify the value setting WEE = 0 to all the isotopes except one (filtering by Z and A). In that case, your simulation will continue, but taking account only for the cases where WEE!=0. Then, all the gammas generated (if there is any) will be from that radionucleus in particular.

PROs: Easy to apply. Simple to do the scoring
CONTRAs: You will have to run a simulation for each case. This is particularly demanding considering that the material of your target is Uranium…

Regarding the thresholds, I would recommend you to use the option PROMPT in the EMFCUT card in order to just get rid of prompt ones, but not affecting the generated from the delay part.

If I find a better approach I let you know asap.
In case you need more clarification do not hesitate to ask.


Ref. *,

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Thank you @adonadon for the explanation.

Just to confirm my understanding is this what you meant to get information during activating stages ? Or the decay times are measured from the last time entry in the IRRPROFI card ? I mean for 30 year irradiation, I have to put decay time 0, for 20 year it will be -10 year ?? Is it so or is the way I mentioned in the attached figure correct ?


Dear @riya,

Remember that the Decay times are always with respect to the End of irradiation (EoI)


Then, in the cooling times you have, for example the -10 years case, It means that you are scoring at the end of the time lapse from the beginning of irradiation until the time that you are considering.

Time lapse [t0, t1]

t0: Beginning of irradiation
t1: 10 years before end of irradiation. This is equivalent to 0.5 day + 14 day + 1 year + 10 years + 20 years + 30 years - 10 years

Hope this helps to clarify.


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Hi @adonadon,

Regarding the following comment, I feel I misunderstood the irradiation time also. When I am using these (see the image) settings, does this then mean the irradiation time is 10 year, then 10+20 = 30 year, then 10+20+30 year = 60 year. Is it so ?? If yes, then my intention was to get irradiation at 10, 20 and 30 years. In such case, then do I have to put 10, 10 and 10 in delta t ??


Since there is no break in your irradiation profile (i.e. periods with 0 p/s in between, or a different beam intensity), it does not really make sense to split it into three intervals: it’s equivalent to a single 60 year irradiation period (10+20+30). Following your intention, you should define a single period of 30 years and then define in DCYTIMES decay times at 0 (i.e. after 30 years of irradiation), -10 years (i.e. after 20 years) and -20 years (i.e. after 10 years), with no need to split the irradiation profile.


Thank you @ceruttif, the topic is now clear to me.


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