**1. NAME AND TITLE**

REDIFFUSION: One-Dimensional Neutron Removal-Diffusion and Gamma-Ray Kernel Integration or Diffusion Theory Calculator.

REDIFFUSION supersedes and extends the capabilities of the COMPRASH code.

**2. CONTRIBUTOR**

Reactor Physics Division, UKAEA Atomic Energy Establishment Winfrith, Dorchester, Dorset, England through the OECD NEA Data Bank, Gif-sur-Yvette, France.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV, Assembler language; IBM 360/370.

**4. NATURE OF PROBLEM SOLVED**

REDIFFUSION calculates one-dimensional neutron and gamma-ray shield penetrations. Neutron reaction-rates and gamma-ray dose and heating rates may be printed out.

The code is intended for use by shield designers in situations where a rapid solution is required and limited accuracy is acceptable. It contains a number of input and output features which simplify the preparation of input data and the processing of the results.

**5. METHOD OF SOLUTION**

For neutrons, the removal-diffusion method is used. For gamma-rays, the user has the option of using either kernel integration with buildup factors or diffusion theory with a first flight correction. Linked calculations are possible in which the gamma-ray sources are calculated from the neutron fluxes.

The removal or uncollided fluxes from slab sources are fitted by sums of exponentials. For the gamma-ray first flight calculation, these exponentials are evaluated by solving the diffusion equation with appropriate parameters. The diffusion equation is solved by a finite difference method.

**6. RESTRICTIONS OR LIMITATIONS**

There are no restrictions on individual magnitudes. Dynamic storage allocation is used, and the total storage available is easily changed to accommodate different problem sizes. The housekeeping routines of the WRS Modular Programming System must be loaded with the code.

**7. TYPICAL RUNNING TIME**

Running time is made up of the following:

Calculation of neutron diffusion parameters approximately 1 sec per material;

Neutron removal-diffusion calculation for 400 meshes and 16 groups approximately 5 secs;

Either Gamma-ray kernel method for 5 groups ½ sec per output point

Or

Gamma-ray diffusion method for 400 meshes and 32 groups approximately 5 secs (must be repeated if contributions from different sources required separately).

Therefore, a total of about 1 minute is required for a typical practical problem.

**8. COMPUTER HARDWARE REQUIREMENTS**

REDIFFUSION is operable on the IBM 360/370 computers. Approximately 500 K bytes of core are required for a typical problem.

**9. COMPUTER SOFTWARE REQUIREMENTS**

Fortran IV and Assembler compilers are required.

**10. REFERENCES**

M. J. Grimstone, "User's Manual for the REDIFFUSION Programme," AEEW-R836 (June 1978).

M. J. Grimstone, "REMOVAL WRS System Module Number 42869 for Calculating the Removal Flux in a Slab Shield," AEEW-R827 (June 1978).

J. Emmett and M. J. Grimstone, "SCRIM WRS System Module Number 22947 for Small Core Removal Calculations," AEEW-R1158 (June 1978).

M. J. Grimstone, "SREM WRS System Module Number 3348 for Calculating the Removal Flux due to Point, Line or Disc Sources," AEEW-R849 (February 1978).

M. J. Grimstone, "PARAMETERS WRS System Module Number 35836 for Calculating Age-Diffusion Parameters," AEEW-R819 (June 1978).

M. J. Grimstone, "DIFFUSION WRS System Module Number 7539 for Solving a Set of Multigroup Diffusion Equations in One Dimension," AEEW-R818 (February 1978).

M. J. Grimstone, "GRAB WRS System Module Number 60221 for Calculating Gamma-Ray Penetration in Slab Shields by the Method of Kernel Integration with Build-up Factors," AEEW-R834 (June 1978).

M. J. Grimstone, "REGROUP WRS System Module Number 13774 for Energy Group Conversion of Flux Spectra," AEEW-R1160 (June 1978).

M. J. Grimstone, "DOCTOR WRS System Module Number 1827 for Calculating Reaction Rates from a Set of Fluxes," AEEW-R825 (February 1978).

M. J. Grimstone, "MIXGAM WRS System Module Number 1300 for Mixing Gamma-Ray Cross Sections for Removal Diffusion Calculations," AEEW-R1157 (June 1978).

M. J. Grimstone, "MINNIE WRS System Module Number 17133 for Converting Material Composition Data to a Standard Form," AEEW-R826 (June 1978).

M. J. Grimstone, "GAMSOURCE WRS System Number 38474 for Calculating Gamma-Ray Source Produced by Neutron Capture," AEEW-R828 (June 1978).

M. J. Grimstone, "REMTWO WRS System Module Number 299 for Calculating the Removal Flux in a Slab Shield," AEEW-R848 (June 1978).

M. J. Grimstone, "NADCON WRS System Module Number 23016 for Mixing ADC Method A Data for Neutrons," AEEW-R1159 (June 1978).

**11. CONTENTS OF CODE PACKAGE**

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

**12. DATE OF ABSTRACT**

January 1982.

**KEYWORDS:** ONE-DIMENSION; NEUTRON; GAMMA-RAY; REMOVAL-DIFFUSION;
KERNEL; DIFFUSION THEORY; SPINNEY METHOD