**1. NAME AND TITLE OF DATA LIBRARY**

DDXLIB: 125-Neutron Group Double Differential Cross Section Library.

**2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS **

BCD To Binary Computer Code for Converting Data to Binary Form.

Binary to BCD Computer Code for Converting Binary To BCD.

**3. CONTRIBUTOR**

Japan Atomic Energy Research Institute, Ibaraki-ken, Japan.

**4. HISTORICAL BACKGROUND AND INFORMATION**

Anisotropy of neutron scattering plays an important role in the energy and spatial distributions of high energy neutrons encountered in fusion reactor shielding and blanket neutronics calculations. The conventional multigroup method using the Pn expansion for anisotropic scattering sometimes fails to predict the neutron transport in materials with highly anisotropic cross sections. The use of lower order Pn expansion of the angular distribution leads to negative elements of energy transfer matrices, hence negative flux. Moreover, the conventional multigroup method cannot accurately take account of the energy-angle correlated kinematics for neutron scattering. In order to overcome these problems, the use of double-differential form scattering cross sections was proposed for the accurate treatment of the energy-angle correlated kinematics.

**5. APPLICATION OF THE DATA**

The multigroup neutron library can be used in discrete ordinates codes such as ANISN-DD (CCC-583/DDXCODES) and DOT-DD (available at JAERI) and the Monte Carlo code MORSE-DD (CCC-583/DDXCODES).

**6. SOURCE AND SCOPE OF DATA**

The DDXLIB data were produced from the ENDF/B-IV data with the use of the PROF-DD Computer code (CCC-583/DDXCODES). The number of energy groups is 125, and 20 equi-cosine bins are used for the angular mesh. In the production of the library, a 1/E spectrum above 0.32 eV and the Maxwellian below this energy are used for the weighting function. The library contains production, fission, capture, total cross sections and the energy-angle distributions of secondary neutrons for each nuclide.

**7. DISCUSSION OF THE DATA RETRIEVAL PROGRAMS**

A program is provided in the package to convert the data from BCD to binary form and vice versa.

**8. DATA FORMAT AND COMPUTER**

Card images; FACOM M-780 (D00123FM38001).

**9. TYPICAL RUNNING TIME**

None noted.

**10. REFERENCE**

T. Mori, M. Nakagawa, and M. Sasaki, "One-, Two-, Three-Dimensional Transport Codes Using Multi-Group Double-Differential Form Cross Sections," JAERI-1314, Ibaraki-ken, Japan, November 1988.

**11. CONTENTS OF PACKAGE**

The package contains the reference document and the data libraries. The data library is transmitted on one DC6150 cartridge tape in TAR format.

**12. DATE OF ABSTRACT**

February 1991.

**KEYWORDS:** CTR NEUTRONICS CROSS SECTIONS; NEUTRON CROSS SECTIONS;
MULTIGROUP CROSS SECTIONS BASED ON ENDF/B