Computer Programs

NAME OR DESIGNATION OF PROGRAM, COMPUTER, NATURE OF PHYSICAL PROBLEM SOLVED, METHOD OF SOLUTION, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, UNUSUAL FEATURES OF THE PROGRAM, RELATED AND AUXILIARY PROGRAMS, STATUS, REFERENCES, REQUIREMENTS, LANGUAGE, OPERATING SYSTEM OR MONITOR UNDER WHICH PROGRAM IS EXECUTED, OTHER RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHOR, MATERIAL, CATEGORIES

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Program name | Package id | Status | Status date |
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NEARREX | NESC0171/02 | Tested | 01-APR-1966 |

Machines used:

Package ID | Orig. computer | Test computer |
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NESC0171/02 | IBM 360 series | IBM 360 series |

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3. NATURE OF PHYSICAL PROBLEM SOLVED

NEARREX computes neutron- induced, average fluctuation (or compound nucleus) cross sections. Provision is made for the computation of compound elastic and inelastic neutron cross sections, radiative capture and fission cross sections, as well as other processes, such as proton emission. It can also be used to compute proton-induced average cross sections.

NEARREX computes neutron- induced, average fluctuation (or compound nucleus) cross sections. Provision is made for the computation of compound elastic and inelastic neutron cross sections, radiative capture and fission cross sections, as well as other processes, such as proton emission. It can also be used to compute proton-induced average cross sections.

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4. METHOD OF SOLUTION

At each incident neutron energy E, a neutron partial wave channel is specified by its orbital angular-momentum quantum number, L, by the total neutron angular momentum, jay= L+(or-)1/2, by the total angular momentum, J, and by the residual state of the target nucleus. These residual states can be any one of the ground or excited states of the target nucleus, for which excitation energies, spins, and parities (Pi) must be specified. The average resonance parameters for each of these neutron channels are computed as a function of the compound transmission coefficients, specified as input. The latter will usually be obtained from an optical model calculation. The average resonance parameters for radiation channels are computed using various approximations. The parameter sigma can be given the values 2, 4, 6, 8, or 10. Setting sigma equals 0 or 12 results in F identically equal to 1, or F identically equal to 2J+1, respectively. The lumped resonance parameters for each J,Pi are assumed to be independent of the resonance indices.

At each incident neutron energy E, a neutron partial wave channel is specified by its orbital angular-momentum quantum number, L, by the total neutron angular momentum, jay= L+(or-)1/2, by the total angular momentum, J, and by the residual state of the target nucleus. These residual states can be any one of the ground or excited states of the target nucleus, for which excitation energies, spins, and parities (Pi) must be specified. The average resonance parameters for each of these neutron channels are computed as a function of the compound transmission coefficients, specified as input. The latter will usually be obtained from an optical model calculation. The average resonance parameters for radiation channels are computed using various approximations. The parameter sigma can be given the values 2, 4, 6, 8, or 10. Setting sigma equals 0 or 12 results in F identically equal to 1, or F identically equal to 2J+1, respectively. The lumped resonance parameters for each J,Pi are assumed to be independent of the resonance indices.

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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The statistical parameter, Q(alpha), must be specified to have the same value for all channels in this program. For This reason, it is in general only safe to specify q values between 0 and 1. Each neutron partial wave is assumed to be distributed according to the chi-square distribution with one degree of freedom (Porter-Thomas).

The statistical parameter, Q(alpha), must be specified to have the same value for all channels in this program. For This reason, it is in general only safe to specify q values between 0 and 1. Each neutron partial wave is assumed to be distributed according to the chi-square distribution with one degree of freedom (Porter-Thomas).

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7. UNUSUAL FEATURES OF THE PROGRAM

The input format for the elastic and inelastic T(alpha,comp) is the same as the format of the transmission coefficients that can be punched from the ABACUS2 optical mode code. However, the number of transmission coefficients punched by ABACUS 2 will usually not coincide with the number required in the input of NEARREX.

The input format for the elastic and inelastic T(alpha,comp) is the same as the format of the transmission coefficients that can be punched from the ABACUS2 optical mode code. However, the number of transmission coefficients punched by ABACUS 2 will usually not coincide with the number required in the input of NEARREX.

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NESC0171/02, included references:

- P. A. Moldauer, C. A. Engelbrecht, and G. J. Duffy,NEARREX, A Computer Code for Nuclear Reaction Calculations,

ANL-6978, December 1964.

- A. Prince, G. Reffo, E. Sartori:

"Report on the International Nuclear Model Code Intercomparison,

Spherical Optical and Statistical Model Study", October 1983

NEANDC/INDC(NEA)4

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NESC0171/02

File name | File description | Records |
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NESC0171_02.001 | SOURCE & DATA 360/65 | 1201 |

NESC0171_02.002 | OUTPUT | 83 |

Keywords: capture, compound nuclei, cross sections, elastic scattering, fission, inelastic scattering.