SCALE Software Coordinator
This topic has been migrated from the SCALE 6 notebook.
Date: Wed Jan 19 19:01:46 2011
Ian,
I got your email from the OrigenArp Notebook and had a quick question..
As part of a recent analysis, I was using Origen-ARP to extract information on gamma spectra for a number of isotopes. To do so, I went directly to the library data file "origen.rev02.mpdkxgam.data" to get discrete energy and emission probability information. For almost all of the isotopes I was interested in, I got results that seemed to be reasonable when compared to other resources for this information.
However, I noticed that a number of energies and the total intensity of the spectra for Ir-192 did not meet my expectations. As an example, the high energy gamma emission at 884 KeV appears to be missing, and the total number of emissions per Curie of Ir-192 seems to be much lower then what I had calculated using information from the Table of Nuclides.
Actually running Origen-ARP and requesting this spectra in a decay case (with bremsstrahlung turned off) does in fact result in a significantly lower total gamma intensity then what I would expect based on information from a number of other resources. Is this a known issue?
Am I missing something?
Along the same lines as this inquiry, I noted that the data library "origen.rev02.mpdkxgam.data" did not contain information for Cs-137, yet when I run a decay case with Cs-137 in Origen-ARP gamma spectrum information for this isotope is presented. This leads me to believe I must be missing something in my understanding of how the system works.
It is quite possible that there are easy answers to these questions, as I am somewhat of a novice user with this software, but I thought they warranted an inquiry at the least.
Thank you for your time,
John Hannah
Engineer, Radiological Analysis
GE Hitachi Nuclear Energy
SCALE Software Coordinator
I checked the evaluations and confirm the discrepancy. The total gamma energy (listed in the mpdkxgam file) is about 32 keV. However, a cross check against the decay energy listed in the ENDF/B-VI based decay library (end6dec file) shows the total Q is 1.035 MeV with a gamma fraction of 79%, for a gamma energy of 818 keV. I confirmed the gamma energy against current data at the National Nuclear Data Center. This problem occurred only for nuclides that have multiple decay parents (e.g., formed by both EC and beta decay) and evaluations derived from ENSDF data (most are from ENDF/B-VI). The problem was introduced in a new gamma library mpdkxgam developed in 2002 and affects SCALE 5.0 and later.
Regarding Cs-137, I assume you are referring to the 662 keV line? This is actually emitted by the Ba-137m decay daughter and not Cs-137. Some evaluations merge the emissions of the daughter with the parent. In origen all gamma emissions are assigned to the actual isotope and simulated explicitly as the daughter product builds up during decay.
Let me know if you have further questions