3. DESCRIPTION OF PROGRAM OR FUNCTION
Within the International Evaluation Cooperation, four energy group structures for multigroup cross section libraries were defined and adopted. The main purpose is to facilitate the inter-laboratory benchmarking of the evaluated files: ENDF/B-VI, JEF-2, JENDL-3. These group structures are:
1. VITAMIN-J, a 175 neutron and 42 photon group structure aimed at fission and fusion reactor shielding and for fusion blanket shielding (based on VITAMIN-J and -D group structures).
2. XMAS, a 172 neutron group structure, based on group structures formerly used with APOLLO and WIMS. This group structure is aimed at thermal and intermediate spectra cell calculations.
3. ECCO-33, a 33 neutron group structure forming a subset of the VITAMIN-J structure. It is aimed at benchmarking fast reactor criticality calculations.
4. ECCO-2000, a 1968 neutron fine group structure based on a
lethargy grid of 1/120. It contains all the energy boundaries of the group structures VITAMIN-J, XMAS, and ECCO-33.
A computer program is provided for producing a weighting spectrum for group averaging purposes. This spectrum is the one adopted for the VITAMIN-J group cross section libraries and consists of
- temperature dependent thermal Maxwellian
- 1/E slowing down spectrum
- fission spectrum
- fusion spectrum.
The computer produces a table which is linearly interpolable to a specified tolerance.