A new library for LWR is generated for the NECP-X code, including the multi-group
cross sections, which can be directly used for transport calculation, and
continuous energy cross sections for resonance calculation. The library
and its generation procedure will be introduced in the following subsections.
1.1. Library introduction
The library of NECP-X can be divided into 2 parts: the multi-group library named
NECL-MG, and the continuous energy library named NECL-CE which is used to generate
the RI table on-the-fly for resonance calculation. The nuclides considered in
the library and the multi-group structure is introduced as follows.
1.1.1. Nuclides in the library
There are 275 nuclides in the initial version of library, including 65 resonant
nuclides, and the follow figure shows the detailed information about the nuclides. It
contains 33 actinides, 173 fission productions, 69 activation nuclides. The NECL-MG
library contains multi-group cross sections for all the 256 nuclides and the
NECL-CE library contains continuous-energy cross sections for all the 75 resonant
nuclides. The current library is adequate for calculations of fresh assemblies
and cores. To consider the high burnup case more accurately, further development
of the libraries is undergoing for adding more nuclides and improve the fraction
of the resonant nuclides.
1.1.2. Group structure and selected temperatures
In NECL-MG, 6 temperatures are selected: 293.0 K, 600.0 K, 900.0 K, 1200.0 K,
1500.0 K, and 1800.0 K. The WIMS-69 energy group structure is adopted and
Table 1 shows the upper boundaries of the energy groups. The original resonance
energy range in WIMS-69 energy group structure is from 4 eV to 9118 eV which
doesn’t cover resonance peaks for Plutonium below 4 eV and cannot resolve resonance
peaks for 238U higher than 9118 eV. Therefore, the resonance energy range is brodened
from 0.625 eV to 24780 eV (energy groups from 13 to 45). As for the point
wise library NECL-CE, the continuous-energy cross sections are obtained from PENDF
generated from the module BROADR of NJOY, ranging from 293.0 K to 1800.0 K with
an interval of 50 K.
Table 1 Upper boundaries of energy groups used by NECP-X
| 1.000000E+07 |
6.065500E+06 |
3.679000E+06 |
2.231000E+06 |
| 1.353000E+06 |
8.210000E+05 |
5.000000E+05 |
3.025000E+05 |
| 1.830000E+05 |
1.110000E+05 |
6.734000E+04 |
4.085000E+04 |
| 2.478000E+04 |
1.503000E+04 |
9.118000E+03 |
5.530000E+03 |
| 3.519100E+03 |
2.239450E+03 |
1.425100E+03 |
9.068980E+02 |
| 3.672620E+02 |
1.487280E+02 |
7.550100E+01 |
4.805200E+01 |
| 2.770000E+01 |
1.596800E+01 |
9.877000E+00 |
4.000000E+00 |
| 3.300000E+00 |
2.600000E+00 |
2.100000E+00 |
1.500000E+00 |
| 1.300000E+00 |
1.150000E+00 |
1.123000E+00 |
1.097000E+00 |
| 1.071000E+00 |
1.045000E+00 |
1.020000E+00 |
9.960000E-01 |
| 9.720000E-01 |
9.500000E-01 |
9.100000E-01 |
8.500000E-01 |
| 7.800000E-01 |
6.250000E-01 |
5.000000E-01 |
4.000000E-01 |
| 3.500000E-01 |
3.200000E-01 |
3.000000E-01 |
2.800000E-01 |
| 2.500000E-01 |
2.200000E-01 |
1.800000E-01 |
1.400000E-01 |
| 1.000000E-01 |
8.000000E-02 |
6.700000E-02 |
5.800000E-02 |
| 5.000000E-02 |
4.200000E-02 |
3.500000E-02 |
3.000000E-02 |
| 2.500000E-02 |
2.000000E-02 |
1.500000E-02 |
1.000000E-02 |
| 5.000000E-03 |
|
|
|
1.2. Library generation procedure
The follow figure demonstrates the flowchart of the library generation system. Currently,
ENDF/B-VII.0 evaluated nuclear data library is utilized as the data source.
Several codes and scripts are used for the library generation, including NJOY and RMET21.
In the library generation system, the workflows for the generation of the
multi-group cross sections of the non-resonant nuclides, the multi-group cross
sections of the resonant nuclides and the continuous-energy cross sections of
the resonant nuclides are different.
For the multi-group cross sections of the non-resonant nuclides, several modules
of NJOY is used and the output of the WIMSR module is reformatted to the NECL-MG
format by scripts. The Goldstein-Cohen factors are generated by several Python
scripts and the theory described in NJOY manual is adopted.
For the resonant nuclides, the multi-group cross sections of the thermal and fast
energy groups is obtained by NJOY, with a similar process of non-resonant nuclides.
The multi-group cross sections in the resonance energy groups at typical
dilution cross section are also generated by NJOY modules. The resonance cross
section tables are generated by RMET21, where 21 dilution cross sections are used.
The Goldstein-Cohen factors are generated in the same way as the non-resonant nuclides.
For the continuous-energy cross sections of the resonant nuclides, the point-wise
cross sections of PENDF format from NJOY are reformatted according to the
requirement of NECL-CE library, which is a binary file that contains the
continuous-energy cross sections of all the resonant nuclides.
BROADR output and WIMSR output are obtained with the modules of NJOY as follow.