SCALE Software Coordinator
This topic has been migrated from the SCALE 5 ORIGEN notebook.
Date: Fri Mar 14 12:14:49 2008
Dear Dr. Bowman
Looking at the personal publication list of Dr. O.W. Hermann, in his site, I saw your name in one of the references referred to the code Origen-S. I couldn´t contact Dr. Hermann and it seems that is not more at ORNL. So I decided to sent to you a couple of questions hoping you con help me. Please, let me tell you what is the problem I have. I´m trying to estimate the heat deposition in a cold source due to the Delayed Fission Product Gamma Rays (DFPG). I´m using the code Origen-2 to calculate the spectrum, the total number of gamma rays and the total energy released per fission by the DFPG. In the report from Robert E. Williams, Michael Rowe (both from NIST) and Mordechai Blau (Negev, Israel), "Benchmark of the Heat Deposition in the NIST Liquid Hydrogen Cold Source", I´ve read that they used the ORIGIN code to calculate the equilibrium distribution of fission products in the HFIR at ORNL. They reported that the DFPG´s resulted in 13.1 photons per fission, with 5.5 MeV per fission (compared with the 12.1 photons per fission, with 6.7 MeV per fission, in case of prompt fission photons).
Even when my fuel element is different (U3Si2, 20% enrichment, MTR type fuel plates) I expected to get around the same values. But...
a) The spectrum is much softer than the spectra reported in a some bibliography (Engineering Compendium on Radiation Shielding. Jaeger New York 1968, for example). The calculated average energy is only the 45% of the average energy reported in this compendium.
b) The total number of gamma per fission is lower than some values reported by Williams et al. (between 7.8 and 8.1 photons/fission, depending on burnup)
c) The total energy released by the DFPG´s per fission is very low: around 3.4 MeV/fission.
I have a couple of questions regarding this values.
a) Are the libraries for this version of the Origen-2 not adequate enough for this kind of evaluations?
b) Are they old libraries and should I get new versions of them? How can I do that?
c) What do you suggest to solve these differences?
d) Is there any relation between the codes Origen-2 and ORIGIN? Is it available for all the nuclear community?
I don´t know if you are the right person to ask for this problem. I´ll very much appreciate if you can contact for me the right person.
Thank you very much in advance. Looking forward to hearing from you soon, yours truly,
Carlos A. Lecot
SCALE Software Coordinator
Carlos,
If you are using a relatively up-to-date version of ORIGEN2, the photon data in ORIGEN2 and ORIGEN-S will be the same. The data are based primarily on work of Croff, Haese, and Gove (ORNL/TM-6055).
You need to be very careful when using ORIGEN codes for equilibrium fission calculations, since the codes are designed for calculating delayed radiation source terms and spent fuel properties. The libraries do not contain any prompt data. The ORIGEN codes have been used to calculate equilibrium fission product gamma ray spectra from delayed fission product decay (i.e., for Sn transport libraries). The total decay gamma energy (based on recoverable energy per decay Q values) has been validated down to about 1 sec after fission (see for example Report RC 1429 on the SCALE web site). However, when the photon spectra are calculated for these very short cooling times the total photon energy associated with the spectra can be significantly less than the value calculated using the Q values. This is because the photon library is missing many short-lived nuclides (these can be very hard to measure). The ORIGEN-S code attempts to correct for the missing photon data by normalizing the spectra to give the correct total MeV/s as calculated using the Q values. However, it must be recognized that as the decay times approach zero, the correction becomes more approximate since the very-short-lived nuclides tend to have higher energy photons. In addition to the delayed photon component the prompt gamma ray component needs to be added.
I can't comment on how ORIGEN2 handles this, or the specific photon library it uses. The ORIGEN2 code is no longer supported at ORNL and is not being developed. The ORIGEN-S code is supported as the depletion module of SCALE. A subset of SCALE that called the ORIGEN-ARP package will be released through RSICC this summer. It will include ORIGEN-S and the data libraries, a new easy to use Windows interface called OrigenArp, and a Windows plotting program for ORIGEN-S results called PlotOPUS. For more information, see the January 2001 issue of the SCALE Newsletter.
The photon data are currently more than 25 years old, and have been identified as needing an upgrade. I suspect that with a newer and more comprehensive data base including many more short-lived fission products that the difference between the photon spectrum energy and Q-value energy at short times will be significantly reduced.
Regards,
Ian Gauld