NEA-0658 THRUSH.

1. NAME OR DESIGNATION OF PROGRAM:  THRUSH.

3. DESCRIPTION OF PROBLEM OR FUNCTION

THRUSH computes the thermal neutron scattering kernel by the phonon expansion method for both coherent and incoherent scattering processes. The calculation of the coherent part is suitable in particular for calculating the scattering kernel for heavy water.

4. METHOD OF SOLUTION

To evaluate the scattering kernel from the double differential scattering cross section, it is necessary to perform angular integration over scattering angle. This integra- tion is performed analytically in the THRUSH code. A "generalised" spectral density is used from which the coherent as well as the incoherent scattering effect can be calculated. The Sjoelander expansion or short time expansion is used to overcome the poor convergence at high incident neutron energy or high temperature.

The generally difficult to calculate inter-molecular elastic scattering from the atom pair of a different molecule is evaluated using Butler's model.

The present version of THRUSH accepts only isotropic "generalised" spectral density. Further improvements will be to accept delta- function and anisotropic spectral densities.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maximum number of frequency mesh points for spectral density is 400  (IMAX).
Maximum number of convolution integrals for Phi n (omega) is 8000/ IMAX.
Maximum number of energy meshes for the scattering kernel is 101.

6. TYPICAL RUNNING TIME:

NEA-DB executed the test case included in this package  on a CDC CYBER 740 computer in 102 seconds of CPU time.

7. UNUSUAL FEATURES OF THE PROGRAM

An analytic treatment of the angular integration over the scattering angle.

8. RELATED AND AUXILIARY PROGRAMS

THRUSH employs the same method of Sjoelander expansion as is used in the code SUMMIT.

10. REFERENCES

- H. Kadotani:
  "THRUSH A Code for Calculating Thermal Neutron Scattering Kernel"
  JAERI-M 8927 (1980).
- A. Sjoelander:
  Ark. Fis., 14, 315 (1958).
- J. Bell:
  (SUMMIT)
  GA-2492 (1962).

11. MACHINE REQUIREMENTS

THRUSH uses only the standard input and output logical units (tape 5 for input, 6 for output and 7 for card  punch).

To run the test case on a CDC CYBER 740 computer, 163,000 (octal) words of main storage are required.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:

NOS 1.4-531 (CDC CYBER 740).

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

          Hiroyuki Kadotani
          Century Research Center Corporation, 2, 3-Chome, Hon-Cho
          Nihonbashi, Chuo-ku
          Tokyo, Japan.

File name	File description	Records
NEA0658_01.001	Information file	47
NEA0658_01.002	JCL	8
NEA0658_01.003	THRUSH source program (FORTRAN IV)	1332
NEA0658_01.004	THRUSH sample input	28
NEA0658_01.005	THRUSH sample output	1188