SCALE Software Coordinator
This topic has been migrated from the SCALE 5 ORIGEN notebook.
Date: Mon Mar 3 18:09:07 2008
Hi Bryan,
I compared the spontaneous fission spectra of Cm244 calculated by ORIGEN-S SCALE4.4A and ORIGEN-S SCALE5.1. The differences are here:
MeV Mev SCALE5.1 SCALE4.4A DIFF %
31 1,40E+01 - 2,00E+01 1,27E+03 0,00E+00 -
30 1,30E+01 - 1,40E+01 1,73E+03 0,00E+00 -
29 1,20E+01 - 1,30E+01 4,01E+03 5,40E+03 -25,78
28 1,15E+01 - 1,20E+01 3,66E+03 3,38E+03 8,39
27 1,10E+01 - 1,15E+01 5,52E+03 5,97E+03 -7,54
26 1,05E+01 - 1,10E+01 8,31E+03 9,87E+03 -15,79
25 1,00E+01 - 1,05E+01 1,25E+04 1,39E+04 -10,23
24 9,50E+00 - 1,00E+01 1,86E+04 1,48E+04 26,17
23 9,00E+00 - 9,50E+00 2,77E+04 1,42E+04 95,07
22 8,50E+00 - 9,00E+00 4,10E+04 3,48E+04 18,04
21 8,00E+00 - 8,50E+00 6,05E+04 4,85E+04 24,80
20 7,50E+00 - 8,00E+00 8,87E+04 9,07E+04 -2,15
19 7,00E+00 - 7,50E+00 1,30E+05 1,21E+05 6,94
18 6,50E+00 - 7,00E+00 1,88E+05 1,79E+05 4,68
17 6,00E+00 - 6,50E+00 2,70E+05 2,68E+05 0,90
16 5,50E+00 - 6,00E+00 3,86E+05 4,02E+05 -3,84
15 5,00E+00 - 5,50E+00 5,47E+05 5,40E+05 1,26
14 4,50E+00 - 5,00E+00 7,67E+05 7,48E+05 2,54
13 4,00E+00 - 4,50E+00 1,06E+06 9,69E+05 9,57
12 3,50E+00 - 4,00E+00 1,45E+06 1,55E+06 -6,45
11 3,00E+00 - 3,50E+00 1,95E+06 1,88E+06 3,51
10 2,50E+00 - 3,00E+00 2,56E+06 2,44E+06 5,17
9 2,00E+00 - 2,50E+00 3,28E+06 3,27E+06 0,34
8 1,75E+00 - 2,00E+00 1,93E+06 1,95E+06 -1,03
7 1,50E+00 - 1,75E+00 2,11E+06 2,21E+06 -4,39
6 1,25E+00 - 1,50E+00 2,28E+06 2,56E+06 -11,09
5 1,00E+00 - 1,25E+00 2,41E+06 2,73E+06 -11,84
4 7,50E-01 - 1,00E+00 2,46E+06 2,75E+06 -10,33
3 5,00E-01 - 7,50E-01 2,40E+06 3,05E+06 -21,29
2 2,50E-01 - 5,00E-01 2,13E+06 2,37E+06 -10,14
1 0,00E+00 - 2,50E-01 1,31E+06 0,00E+00 -
Is this reasult realistic? There are big changes, mainly in the 23th group. The Cm244 spectrum is the most significant in spent fuel neutron source problems.
What is the reason? I read in manual about the new method for neutron source calculation, adapted from SOURCE code, but the Watt spectrum is so different?
Best,
Sándor Patai-Szabó
SCALE Software Coordinator
Dear Sándor,
Bryan forwarded your question to me. Neutron source spectra for Cm isotopes 242 and 244 in SCALE 4.4a were calculated based directly on spectral measurements made by Stoddard in 1964 (USAEC report DP-939, Savannah River Laboratory). The same spectra were also published in Cm data sheets (ORNL-4357, 1969). These measurements are fairly old and included some large uncertainties. A summary of the new methods and validation studies is published in the RPSD Topical Meeting 2002 and is available from the SCALE website publications area (see I. C. Gauld, E. F. Shores, and R. T. Perry, New Neutron Source Algorithms in the ORIGEN-S Code,"</A> in Proc. of the ANS 12th Biennial RPSD Topical Meeting, April 14-18, 2002, Santa Fe, New Mexico.
The paper specifically looks at Cm-244 and compares spectra measured by Stoddard (1964), Herold (1965), and Firestone (1974) against the new source methods based on Watt spectral parameters for spontaneous fission. The figure illustrates the variation between experiments and shows that the Stoddard measurements are likely high for energies less than about 2 MeV. Based on the validation studies to date we feel that the new methods generate more accurate neutron spectra. As indicated in the paper, the effect of the spectrum change is less than 5% for the neutron dose rate outside a typical shielded spent fuel storage cask.
Let me know if you have any other questions about the methods or the paper.
All the best
Ian Gauld