SOME MATXS LIBRARIES

MATXS libraries are produced from evaluated nuclear data in the ENDF/B format using the NJOY nuclear data processing system (see Codes and Publications). As of version 2.0, the preferred libraries for TRANSX are based on ENDF/B-VI. However, several older libraries based on ENDF/B-V have been converted to the current version of the MATXS format also.

MATXS10

This is a library with 30 neutron groups and 12 photon groups (30 x 12) that includes 117 materials from ENDF/B-VI. Photon production and photon interaction are included, but self-shielding isn't. The Legendre order for the scattering matrices is P4. The materials are given at a temperature of 300 K. A complete list of materials and reactions included can be obtained from an INDEX of the library (a partial listing of this index will be found here).

MATXS10 was prepared with a fusion + fission + 1/E + thermal Maxwellian weight function. It is useful for many high-energy calculations, including criticals such as GODIVA. It works surprisingly well for many shielding problems for which resonance self-shielding is not too important. The library is compact, and TRANSX runs usually require only a few seconds on a fast computer.

MATXS5

This library is similar to MATXS10, except that it was generated from ENDF/B-V. It includes neutron data for 100 materials (including 13 Dosimetry isotopes), photon production for 65 materials, and photon interaction cross sections for 87 elements. Several special Los Alamos evaluations and a lumped fission product from the Westinghouse Hanford Engineering Development Laboratory (HEDL) are also included. See the INDEX for more details.

MATXS11

This is an 80 x 24 library from ENDF/B-VI intended for fast-reactor analysis. However, the group structure and weight function used also make MATXS11 a reasonable choice for fusion studies and shielding calculations.

This library features extensive self-shielded cross sections for the temperatures 300, 400, 600, 800, 1200, 1600, 2000, 3000, and 4000 K. Background cross sections vary from infinity down to a lower limit that depends on the normal applications of the materials. The Legendre order is P5 for both neutrons and photons. See the INDEX for a complete list.

The 24-group photon structure is much better than the 12-group structure for low photon energies and for energies around the annihilation peak at 0.5 MeV. It also does a better job of describing the high-energy ''shoulder'' of capture gammas in some systems. This can be important for heating calculations.

MATXS is more expensive to use than the 30 x 12 libraries, but it is capable of giving good results for a wider range of problems.

MATXS6

This 80 x 24 library is similar to MATXS11, except that it was prepared from ENDF/B-V. There are 148 materials, including 72 with photon production.

MATXS12

This is a 69 x 24 library from ENDF/B-VI for light-water-reactor problems. It includes self-shielded cross sections for the important actinides. Thermal scattering data are given for all the materials, with bound scattering for the important moderators. The group structure has 42 thermal groups extending up to 4.00 eV.

MATXS7

This is also a 69 x 24 library, but it is based on ENDF/B-V. There are 118 materials, including the most important fission products. Photon production is included for 42 materials.

MATXS13

The MATXS13 library has 187 neutron groups and 24 photon groups for a limited number of materials useful for shielding problems. It includes neutron data, photon data, thermal data, and self-shielding data in one unified package.

The photon data are the same as in MATXS11, but the increased neutron accuracy leads to better calculations of capture, hence better photon spectra.

The thermal structure includes 55 groups below 4.45 eV, thereby providing better resolution around the 1-eV Pu-240 resonance and more accuracy at energies below 0.0253 eV. The fine epithermal group structure tracks the slowing down of neutrons better than the coarse groups of MATXS12. As more materials are added to this library, it will become an accurate general purpose tool for thermal problems.

Finally, for high-energy problems, the thermal groups can be collapsed out. The result will still have a finer group structure than MATXS10 or MATXS11, and it can be used to attack difficult problems that do not seem to converge with the simpler libraries.

MATXS8

This library is similar to MATXS13, except that it was processed from \newline ENDF/B-V. It is an 80-group library for fast-reactor and fusion-reactor problems.

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