NEA-1344 ZZ-GROUPSTRUCTURES.

1. NAME OR DESIGNATION OF PROGRAM:  ZZ-GROUPSTRUCTURES.

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.

4. METHOD OF SOLUTION

The program replaces the analytical form of the weighting spectrum by a table of energy versus weight in which the interpolation law is linear-linear. It uses a multipoint fractional  error thinning algorithm to minimize the size of the table.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM:

6. TYPICAL RUNNING TIME:

The test problem required about 4 seconds of CPU on a VAX 8810 computer.

7. UNUSUAL FEATURES OF THE PROGRAM

The function WFUN describing the weighting function can be replaced by one specified by the user.

8. RELATED AND AUXILIARY PROGRAMS:  NJOY. ZZ-VITAMIN-C/B, WIMS/D.

10. REFERENCES:

- E. Sartori, OECD/NEA Data Bank:
  Standard Energy Group Structures of Cross Section Libraries for
  Reactor Shielding, Reactor Cell and Fusion Neutronics
  Applications: VITAMIN-J, ECCO-33, ECCO-2000 and XMAS
  JEF/DOC-315 Revision 3 - DRAFT (December 11, 1990).

11. MACHINE REQUIREMENTS:

Main storage requirements are 350 Kbytes on a VAX 8810  computer.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:

VMS (VAX 8810).

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHORS

      Enrico Sartori
      NEA Data Bank
      Bat. 445
      91191 GIF-SUR-YVETTE CEDEX
      France
and
      G.C. Panini
      TIB-CALC-DATINV
      ENEA-CRE E. Clementel
      Viale Ercolani 8
      40138 BOLOGNA
      Italy

File name	File description	Records
NEA1344_01.001	Information File	83
NEA1344_01.002	VITAMIN-J (175) Neutron Group Boundaries	31
NEA1344_01.003	VITAMIN-J (42) Gamma Group Boundaries	9
NEA1344_01.004	XMAS (172) Neutron Group Boundaries	30
NEA1344_01.005	ECCO-33 (33) Neutron Group Boundaries	7
NEA1344_01.006	ECCO-2000 (1968) Neutron Group Boundaries	330
NEA1344_01.007	VITAMIN-J Spectrum Generation Program	459
NEA1344_01.008	Dummy plotting routines	22
NEA1344_01.009	JCL for running spectrum generation program	23
NEA1344_01.010	Sample Problem output spectra	1013
NEA1344_01.011	Sample Problem printed output	10
NEA1344_01.012	Group Structures Comparison	1976