**1. NAME AND TITLE**

LEAP-ADDELT: Multigroup Thermal Neutron Scattering Data Generator for Hydrogen in
Light Water and Deuterium in Heavy Water.

**AUXILIARY ROUTINES**

TIMER

CALPIN

**2. CONTRIBUTOR**

United Kingdom Atomic Energy Authority, Winfrith, Dorchester, Dorset, England through the OECD Nuclear Energy Agency Data Bank, Issy-les-Moulineaux, France.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV, Assembler Language; IBM 360/370.

**4. NATURE OF PROBLEM SOLVED**

LEAP calculates the scattering law from a phonon frequency function which may contain solid or
both solid and diffusive modes, but it will deal only with continuous or piece-wise continuous spectra.
ADDELT receives a scattering law as input and adds to it the effect of delta functions in the phonon
frequency spectrum. LEAP and ADDELT may be used in tandem when the phonon frequency
spectrum contains solid, or both solid and diffusive modes, and delta functions.

**5. METHOD OF SOLUTION**

LEAP treats a phonon frequency spectrum by using either the "phonon series" expansion to calculate the scattering law, S(alpha,beta), or the saddle point method. A set of criteria is provided to determine which technique is applicable for particular values of alpha and beta. The calculation completed by LEAP is provided as input for ADDELT.

ADDELT calculates the scattering law, S(alpha,beta), from a series of up to 50 delta functions.
It requires a scattering law defined over an (alpha,beta) mesh as input (which is provided by LEAP)
and adds to it the effect of delta functions in phonon frequency spectra.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for LEAP-ADDELT.

**8. COMPUTER HARDWARE REQUIREMENTS**

LEAP-ADDELT is operable on the IBM 360/370 computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

Fortran IV and Assembler Language compilers are required.

**10. REFERENCES**

A. T. D. Butland and S. M. Oliver, "The Preparation of WIMS Light and Heavy Water Thermal Scattering Data," AEEW-R 950 (June 1974).

A. T. D. Butland, "LEAP and ADDELT, A Users Guide to Two Complementary Codes on the ICL-470 for Calculating the Scattering Law from a Phonon Frequency Function," AEEW-M 1200 (June 1973).

A. T. D. Butland, "Comparison of LEAP, TOR and SLAB, Programmes for Computing the
Scattering Law S(alpha,beta) from a Phonon Frequency Function," AEEW-M 1136 (October 1972).

**11. CONTENTS OF CODE PACKAGE**

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

**12. DATE OF ABSTRACT**

March 1984.

**KEYWORDS: ** DATA PROCESSING, SPECTRA; MULTIGROUP CROSS SECTION PROCESSING; NEUTRON CROSS SECTION PROCESSING