**1. NAME AND TITLE**

GROUPXS: Processing of Double-Differential Cross Sections in the New ENDF-VI Format

**2. CONTRIBUTOR**

Netherlands Energy Research Foundation (ECN), Petten, The Netherlands, through the OECD
NEA Data Bank, Issy-les-Moulineaux, France.

**3. CODING LANGUAGE AND COMPUTER**

Fortran; CDC 7600 and CYBER 740.

**4. NATURE OF PROBLEM SOLVED**

GROUPXS does file handling and processing of the double-differential continuum-emission cross sections stored in the new MF6 format of ENDF/VI. It treats the energy-angle data that are supposed to be represented by a Legendre-polynomial expansion in the center-of-mass system and can do the following: (1) Conversion of MF6 data from center-of-mass system to the laboratory system, with the possibility to continue the calculation with the options (2), (3), and (4).

(2) Conversion of Legendre-polynomial representation into point-wise angular data, in MF6 format.

(3) Conversion of data from MF6 into MF4 + MF5 (ENDF-V).

(4) Calculation of group constants, scattering matrices and transfer matrices for arbitrary group structures with a fusion micro-flux weighting spectrum (PN-approximation).

The code treats only continuum reaction types that are stored in the MF6 format with the
restrictions as specified for the European Fusion File (EFF1). These restrictions are not inconvenient
for the purpose of fusion neutronics calculations and they facilitate relatively simple processing .

**5. METHOD OF SOLUTION**

Numerical integration methods are used (DCADRE routine from the IMSL library).

**6. RESTRICTIONS OR LIMITATIONS**

Incident energies on the ENDF input file for MF=3 and for MF=6 are supposed to be exactly the
same, and in increasing order. The code has been tested for outgoing neutrons only (other particles
are treated as well).

**7. TYPICAL RUNNING TIME**

The sample problem takes 82 CP-seconds on Cyber 170/855, under NOS/BE.

**8. COMPUTER HARDWARE REQUIREMENTS**

70 K central memory on the Cyber 170/855 under NOS/BE.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran V (Fortran 77 under the CDC operating system NOS/BE) is required. Double-precision
may be needed for the c.m. to lab. conversion on IBM computers.

**10. REFERENCES**

** Included with document:**

H. Gruppelaar, J. M. Akkermans, and D. Nierop, "Processing of Double-Differential Cross
Sections in the New ENDF-VI Format, GROUPXS Code Description and User's Manual," ECN-182
(April 1986).

**b. Background information**

"DCADRE, Numerical Integration of a Function Using Cautious Adaptive Romberg Extrapolation," IMSL Library, reference manual, Vol. 1.

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code plus sample problem input and output.

**12. DATE OF ABSTRACT**

August 1987.

**KEYWORDS:** MULTIGROUP CROSS SECTION PROCESSING; ENDF FORMAT