NEA-0547 HASSAN.

1. NAME OR DESIGNATION OF PROGRAM:  HASSAN.

3. NATURE OF PHYSICAL PROBLEM SOLVED

The programme calculates simultaneously, stepwise in time, the temperature, stress and strain distributions in high temperature reactor (HTR) fuel pins of tubular and hollow rod types. Any sequence of ramp and step changes of power may be followed. At each time step, the programme computes the operating stresses, also the residual stresses which develop if, at  that point in time, the reactor is shut down and the fuel pin cools  to a uniform temperature. Variations of material properties with temperature and neutron dose may be taken into account. In the structural analysis, axial symmetry and plane strain conditions are  assumed. The programme cannot therefore give the stresses with sufficient accuracy in the region of pin ends or in regions of cross-pin flux or temperature tilt. In the thermal analysis, the fuel is assumed to be distributed uniformly along the fuelled length of the channel. The calculated temperature distributions are therefore not accurate for the pin end regions.

4. METHOD OF SOLUTION

At each time step, the energy equation is integrated numerically along the channel to obtain the coolant axial temperature distribution(s). In the case of a tubular fuel pin, the  radius of the adiabatic surface, which determines the heat fluxes to the inner and outer channels, is found by iteration. Radiation and convection heat transfer mechanisms are assumed, using appropriate empirical convective heat transfer correlations. The one-dimensional Fourier equation is used to determine the fuel pin internal temperature distribution. Heat transfer across internal (helium filled) gaps is assumed to be by conduction and radiation. The neutron-irradiation-induced dimensional changes (Wigner strains) are determined from sets of polynominals fitted to experimental data.
Incremental creep strains are calculated iteratively assuming a Maxwell model with dose and temperature dependent parameters. Total  creep strains are obtained by summation of the incremental creep strains and the stresses are calculated using closed-form expressions. Radial displacements are calculated and checked for interaction between components. In the case of interaction, the interface pressure is found by iteration.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The present version of HASSAN is restricted to the following maximum dimensions:
number of axial positions for stress/strain analysis = 10
number of axial positions for temperature calculation = 21
number of radial mesh points in each component (tube) = 20

6. TYPICAL RUNNING TIME

The programme running time, on a CDC 6600 computer, for a typical case requiring thirty time steps, is about 15 min.

7. UNUSUAL FEATURES: UNUSUAL FEATURES OF THE PROGRAM

8. RELATED AND AUXILIARY PROGRAMS

Stress analysis code HASSAN. Channel heat transfer code COCO2.

10. REFERENCES

- A. Jezernik, J.L.Head:
  "Stresses in the Graphite Fuel Tubes of a High Temperature Gas Cooled Reactor"
  D.P. Report 662 (January 1970).
- U. Weicht, W. Mueller:
  "TAPIR-COCO-DELTAP, Three Computer Programmes for the Thermal Analysis of a Reactor Core Containing Internally and/or Externally    Gas Cooled Prismatic Fuel Elements"
  D.P. Report 748 (March 1971).

- A. Alujevic, J.L. Head and J.C. Uhry:
  HASSAN - A Computer Programme for Thermal and Structural Analysis
  of Prismatic HTR Fuel Elements
  DP report 826 (June 1974).

11. MACHINE REQUIREMENTS:  About 45k of central memory on CDC 6600.

13. OPERATING SYSTEM OR MONITOR UNDER WHICH PROGRAM IS EXECUTED:  SCOPE on CDC 6600.

14. ANY OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Input = tape 5 Output = tape 6. Tape 2 is used for intermediate results in case of a continuation run.

15. NAME AND ESTABLISHMENT OF AUTHOR

   Principle author: A. Alujevic
   Mechanical Engineering Dept
   Imperial College
   London, S.W.7 U.K.

File name	File description	Records
NEA0547_02.001	INFORMATION	2
NEA0547_02.002	SOURCE PROGRAM F4-EBCDIC	2384
NEA0547_02.003	SAMPLE PROBLEM DATA	88
NEA0547_02.004	SAMPLE PROBLEM PRINTED OUTPUT	3921