class openmc.data.MadlandNix(efl, efh, tm)[source]

Energy-dependent fission neutron spectrum (Madland and Nix) given in ENDF MF=5, LF=12 represented as

$f(E \rightarrow E') = \frac{1}{2} [ g(E', E_F(L)) + g(E', E_F(H))]$

where

$g(E',E_F) = \frac{1}{3\sqrt{E_F T_M}} \left [ u_2^{3/2} E_1 (u_2) - u_1^{3/2} E_1 (u_1) + \gamma \left ( \frac{3}{2}, u_2 \right ) - \gamma \left ( \frac{3}{2}, u_1 \right ) \right ] \\ u_1 = \left ( \sqrt{E'} - \sqrt{E_F} \right )^2 / T_M \\ u_2 = \left ( \sqrt{E'} + \sqrt{E_F} \right )^2 / T_M.$
Parameters
• efl (float) – Constants which represent the average kinetic energy per nucleon of the fission fragment (efl = light, efh = heavy)

• efh (float) – Constants which represent the average kinetic energy per nucleon of the fission fragment (efl = light, efh = heavy)

• tm (openmc.data.Tabulated1D) – Parameter tabulated as a function of incident neutron energy

Variables
• efh (efl,) – Constants which represent the average kinetic energy per nucleon of the fission fragment (efl = light, efh = heavy)

• tm (openmc.data.Tabulated1D) – Parameter tabulated as a function of incident neutron energy

classmethod from_endf(file_obj, params)[source]

Generate Madland-Nix fission spectrum from an ENDF evaluation

Parameters
• file_obj (file-like object) – ENDF file positioned at the start of a section for an energy distribution.

• params (list) – List of parameters at the start of the energy distribution that includes the LF value indicating what type of energy distribution is present.

Returns

Return type

classmethod from_hdf5(group)[source]

Generate Madland-Nix fission spectrum from HDF5 data

Parameters

group (h5py.Group) – HDF5 group to read from

Returns