1. NAME AND TITLE

JN-METD: Neutron Transport Code System with Isotropic Scattering, Bare Slabs and Homogeneous Slabs (JN Method 1), Multilayer Slabs (JN Method 2).

2. CONTRIBUTOR

Nuclear Studies Division, CCR EURATOM, Ispra (Varese), Italy, through the OECD NEA Data Bank, Gif-sur-Yvette, France.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370, IBM 360/65/91.

4. NATURE OF PROBLEM SOLVED

JN-METD solves stationary neutron transport problems in bare spherical reactors to obtain the asymptotic time constant, the effective multiplication factor or the critical radius, and the flux distribution as a function of space and energy. It also solves stationary problems in homogeneous slabs to obtain the space, angle, and energy-dependent flux due to a plane isotropic, point isotropic, or monodirectional boundary source. The first and second time moments are calculated for the time-dependent flux in the slab with a point isotropic or monodirectional delta function source on one boundary. JN-METD solves time-dependent problems in a non-multiplying bare sphere without up-scattering of neutrons to evaluate the space, energy, and time-dependent flux resulting from the incidence of an external source at the center; and solves time-dependent problems in a non-multiplying homogeneous slab without upscattering of neutrons to evaluate the space, angle, energy, and time-dependent flux in the slab without upscattering of neutrons to evaluate the space, angle, energy, and time-dependent flux in the slab with a point isotropic or monodirectional source on one boundary.

5. METHOD OF SOLUTION

The JN method, an analytical approach to neutron transport in a finite system is used within the context of the multigroup and (up to) J7 approximation by assuming that the scattering of neutrons is spherically symmetric in the laboratory system. This method uses the expansion into spherical Bessel functions of the Laplace-Fourier transformed emission density of neutrons and the kernel of the integral equation (resulting from the Laplace and Fourier transformation of an integral transport equation with respect to time and space, respectively).

6. RESTRICTIONS OR LIMITATIONS

The present size of the floating common for all subscript variables is set to be 72,000 bytes. The core storage requirement is less than 305 K bytes in the FORTRAN IV, version G on the IBM 360/65.

7. TYPICAL RUNNING TIME

Typical running time on the IBM 360/65 is nearly 4 minutes to obtain the time-dependent lowest group angular and total flux in a slab with a delta function source on one boundary (in a 7-group J7 approximation with 2 space, 3 angle, and 56 time points), including the time required for obtaining the stationary flux as well as the time-dependent flux due to a Gaussian pulse source. The calculation of the stationary angular, total and leakage flux in a slab takes 1 to 2 minutes in a 7-group J7 approximation with 11 space and angle points.

8. COMPUTER HARDWARE REQUIREMENTS

JN-METD was designed for the IBM 370 computer. Test runs were made on the IBM 360/91.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required.

10. REFERENCES

T. Asaoka, "JN-METD1, A FORTRAN-IV Programme for Solving Neutron Transport Problems with Isotropic Scattering in Bare Spheres and Homogeneous Slabs by the J_N Method," EUR 4601e (1971).

T. Asaoka and E. Caglioti Bonanni, "JN-METD2A FORTRAN-IV Programme for Solving Neutron Transport Problems with Isotropic Scattering in Multilayer Slabs by the J_N Method," EUR 4839e (1972).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

December 1972; updated May 1975.