SCALE Software Coordinator
This topic has been migrated from the SCALE 5 ORIGEN notebook.
Date: Tue Mar 27 12:01:55 2007
Dear Steve,
After having done quite simple calculation of a MOX and a UO2 fuel assembly, both with same specific power and burnup, I cannot explain the discrepancy between the ORIGEN-ARP output at discharge time, and the according OPUS output at discharge time.
Specifically, I am worried about Se-79 (knowing about the problems with the half-life).
If you take a look at the UO2 output file (BUBU48.out) you will find 7.020E+00 grams of Se79 within the fission product block at 48000 MWd/tHM and 1600 d Irradiation time (Se-79 as light element can be neglected due to its low mass, Se79m can also be neglected). For the MOX case (BMBU48.out) you will find 6.101E+00 grams for the same conditions. So far, so good, this differnce fits well into different fission yield of U and Pu.
But if you look up the activities in the OPUS output of the same files, of course both at 1600 d, discharge time, you will find 3.098E+09 Bq for the MOX, and ten times more, 3.565E+10 Bq, for the UO2 case?
Greetings from Switzerland,
René Sarrafian
SCALE Software Coordinator
Dear René,
The problem is in the old 14x14 library that you are using. Apparently it was generated before we corrected the Se-79 half-life about 10 years ago. The decay data predate the MOX libraries that were made later using a pre-release version of SCALE 5. The Se-79 half life was changed quite dramatically along the way. I ran your UO2 case with our new CE14x14 library in SCALE 5.1 and got the following results that agree well with the MOX results: 6.738 g and 3.830E+09 Bq for Se-79.
I recommend that you obtain SCALE 5.1. It is now available from the NEA Data Bank.
Please note that you should not use such a large NRANK value (i.e., 1200) for the OPUS case. This can lead to errors due to insufficient memory allocation in the program. The feature was not intended for more than a few hundred isotopes. We plan to correct this limitation in our next release.
Thanks,
Steve