Version II of the ENDF/B data file was released in August 1970. The description of the formats and procedures for the neutron data are documented in BNL-50274. The formats and procedures for photon production and interaction data are documented in LA-4549. The File 1 changes included the following. An index was added to MT = 451 (general information). Each record in the index contained a file number (MF), reaction type number (MT) and the number of card images required to specify the data for each section for the material. The format for specifying radioactive decay data (MT = 453) was extensively modified. The format for specifying fission product yield data (MT = 454) was modified to allow specification of yield data for meta-stable states. A new section was defined to contain data for delayed neutrons from fission (MT = 455).
The File 2 changes included the following. The test, LRF, which indicated the type of resolved resonance formula used, was expended to include, LRF = 1, single level Breit-Wigner parameters; LRF = 2, multi level Breit-Wigner parameters; LRF = 3, R-Matrix, Reich-Moore multi level parameters and LRF = 4, Adler-Adler multi level resonance parameters are given. All materials will contain a File 2. For those materials where resolved and/or unresolved resonance parameters are not given, File 2 will contain the effective scattering radius, AP. The previous test, LIS, has been removed, where LIS = 0 indicated the scattering cross section should be calculated from resonance parameters plus the smooth cross section from File 3. This meant that the elastic scattering cross section would always be calculated using the resolved and unresolved resonance parameters. The constant C (used to calculate the penetration factor) was replaced by a quantity AWRI. AWRI is defined as the ratio of the mass of a particular isotope to that of a neutron. An option, LRU=2, was added for specifying the unresolved resonance parameters, so that all average resonance parameters could be given as a function of incident neutron energy. Energy dependent parameters could be given for each l-J state.
The File 3 changes included the reaction Q-value was defined as the kinetic energy (in eV) released by a reaction (positive Q values) or required by a reaction (negative Q values). The threshold energy (negative Q only) is given by
Eth = |Q| (AWR+1) / AWRwhere AWR is the atomic weight ratio given on the HEAD record. The maximum number of allowed energy points per section was increased from 2,000 to 5,000. An initial state indicator was added to the HEAD record. This will allow the inclusion of cross section data for meta-stable states and more than one section may be given for the same reaction type (MT number).
No changes in File 4.
File 5 changes included the following. The definition of LF=3 (discrete energy loss law) was changed to read
F(E->E')=δ(E'-E((A2+1)/(A+1)2)+A/(A+1))θ,where A = AWR and θ is the level excitation energy (positive value). T and LT have been removed from the TAB1 records that contain p(E) for cases in which LF = 5, 7, or 9. A value, U, replaces T. U was introduced to define the proper upper limit for the secondary neutron energy distributions so that 0<=E'<=E-U,where E', E, U are given in the laboratory system. Further, the normalization constants for LF = 7 and LF = 9 have been redefined to account for the use of U. LF = 2, 4, 6, and 8 have been deleted.
| Old MT Number | New MT Number |
|---|---|
| 5 | 51 |
| 6 | 52 |
| 7 | 53 |
| 8 | 54 |
| 9 | 55 |
| 10 | 56 |
| 11 | 57 |
| 12 | 58 |
| 13 | 59 |
| 14 | 60 |
| 15 | 91 |
| 27 | No longer used |
| 29 | No longer used |
| 51 | 61 |
| 52 | 62 |
| 53 | 63 |
| -- | -- |
| -- | -- |
| 80 | 90 |
| 109 (Not assigned) | 109 (n,3) cross section |
| 455 (Not assigned) | 455 delayed neutron from fission |
| 700-799 (Not assigned) | 700-799 assigned |
For all files, certain reaction type (MT) numbers have been changed. The list is given in the table above.
The format for specifying temperature dependent data has been modified so that the data for the second (and higher) temperatures may be given at a lesser number of points than was given for the first temperature.
This version included evaluations for neutron reactions with fission product nuclei and data for various components of the energy release in fission.
-- Taken from the ENDF/B-VII format manual, Appendix I "Historic Perspective", By Norman Holden.