**RSIC COMPUTER CODE PSR-026**

**1. NAME AND TITLE**

NEVEMOR: Multigroup-Multiregion Calculation of Flux Spectra and Energy Deposition for
Fast Neutrons.

**2. CONTRIBUTOR**

AECL Whiteshell Nuclear Research Establishment, Pinawa, Manitoba, Canada.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; IBM 360/75/91.

**4. NATURE OF PROBLEM SOLVED**

NEVEMOR was developed to compute various quantities related to fast neutron dosimetry in a
heterogeneous nuclear reactor. It considers a cylindrical lattice cell (a unit cell which repeats itself
periodically in space) and divides it into homogenized annular regions. The fast neutron spectrum is
then calculated for each region. From this, the kinetic energy transferred from fast neutrons to each
material in each region is calculated. Radioactivity induced in various fast neutron activation detectors
can also be estimated. The dose rate and the induced radioactivity can be measured experimentally,
thus providing a check on the calculations.

**5. METHOD OF SOLUTION**

NEVEMOR utilizes a multigroup-multiregion method for calculating fast neutron flux spectra, neutron energy deposition, and foil activations due to fast neutrons in an heterogeneous lattice cell.

Estimates are made of the effects of using group cross sections and of homogenization. Non-isotropic elastic scattering of neutrons off light nuclei (in the laboratory coordinate system) is
considered by applying transport corrections in such cases. Inelastic scattering is handled by assuming
that there is only one state to which the target nucleus could be excited, except for ^{238}U where detailed
group-to-group cross sections are used.

**6. RESTRICTIONS AND LIMITATIONS**

A maximum of 20 materials can be handled by NEVEMOR. The full complement of 20 materials
can only be used if the option of correcting for forward scattering by light nuclei is not used. This
correction introduces 4 new materials which occupy the reference numbers 17-20, corresponding to
the materials occupying the reference numbers 8-11, respectively. Therefore, no data can be assigned
to reference numbers 17-20, since these will be occupied by the new materials.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for NEVEMOR.

**8. COMPUTER HARDWARE REQUIREMENTS**

NEVEMOR is operable on IBM 360/75/91 computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required.

**10. REFERENCE**

K. K. Mehta and P. R. Kry, "Calculations of Flux Spectra and Energy Deposition for Fast
Neutrons," AECL-3423 (September 1969).

**11. CONTENTS OF CODE PACKAGE**

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

**12. DATE OF ABSTRACT**

November 1983.

**KEYWORD: ** KERMA