NESC0474 QX1

1. NAME OR DESIGNATION OF PROGRAM:  QX1

3. DESCRIPTION OF PROBLEM OR FUNCTION

QX1 solves the multigroup, one- dimensional, time-dependent diffusion equations. Problem geometry may be plane, cylindrical, or spherical. Steady-state initial conditions may be established either for a source-free system or for a system with an external neutron source. The reactor may be perturbed by changing material volume fractions and/or temperatures  or by changing the neutron source level. A first-collision pulsed source distribution may be specified. Resonance absorption feedback  is calculated by groupwise interpolation in a cross-section versus temperature table. A highly simplified fuel temperature model is included.

4. METHOD OF SOLUTION

The improved quasistatic method described in reference 1 is used to solve the time-dependent problem. The method  consists of factoring the total flux into the product of a space- energy-time dependent shape function and a purely time-dependent amplitude function, normalized so that the most rapidly varying part of the total flux is included in the amplitude function. The two coupled sets of equations which result are solved iteratively. The fuel temperature changes are calculated by a regionwise adiabatic model with the assumption that all power is produced in the fuel. The method was developed specifically for fast reactor safety analysis. The advantages of factorization are greatest for such systems, though the code has been shown to perform adequately on thermal reactor problems.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Maximum of
    30 energy groups
    15 downscatter groups
     6 delayed neutron families
    20 spatial regions
    16 material mixtures per region
   150 mesh points

6. TYPICAL RUNNING TIME

A 29-group, 15 downscatter, 51 mesh point rod-drop problem run to 30 reactor seconds executes in 10 minutes on the IBM360/75. A 10-group, 6 downscatter, 53 point pulsed reactor problem run to 1 msec. reactor time executes in 10 minutes on the IBM360/75. Running time estimates cannot be generalized because of the high degree of dependence on the required accuracy of solution,  type of perturbation, and the eigenvalue separation of the space-energy equation.

7. UNUSUAL FEATURES OF THE PROGRAM

The running time can be reduced greatly for problems requiring relatively low accuracy, and the code has been shown to reproduce the results of direct finite-difference  codes when convergence is tightened. An automatic time-step selector is provided to optimize the time distribution of shape function recalculations during the transient. A true point kinetics problem can be run using only the initial shape function. A compact problem  edit is given in terms of the familiar integral quantities of reactivity, effective delayed-neutron fraction, generation time, etc. Very general problem driving functions and time-step controls may by used. A group-collapsing system is built into the problem preparation module of the code.

8. RELATED AND AUXILIARY PROGRAMS:

10. REFERENCES

K.  O.  Ott  and  D.  A.  Meneley,  Accuracy  of  the
Quasistatic Treatment of Spatial Reactor Kinetics, Nuclear Science
and Engineering, Vol. 36, p. 402, 1969.
             D. A.  Meneley, K.  O. Ott,  and E.  S. Wiener,  Fast
Reactor Kinetics - The QX1 Code, ANL-7769, March 1971.
             D. A. Meneley, ANL Intra-Laboratory Memorandum, March
1972.

11. MACHINE REQUIREMENTS

450K byte memory, input, output, and punch datasets, a maximum of 2 cross section datasets, and a maximum of 6 scratch datasets

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:   OS/360.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

   The
IBM360/75 version is overlayed. Edition 6 of QXI includes a steady-  state restart capability, a more satisfactory iteration procedure for feedback problems, and a simplified dump file facility.

15. NAME AND ESTABLISHMENT OF AUTHOR

                 D. A. Meneley*
                 Applied Physics Division
                 Argonne National Laboratory
                 9700 South Cass Avenue
                 Argonne, Illinois  60439
*Present address-Ontario Hydro
                 Toronto, Ontario, Canada

File name	File description	Records
NESC0474_01.001	LIBRARY DATA	5609
NESC0474_01.002	SOURCE PROGRAM (F4)	6643
NESC0474_01.003	JCL+OVERLAY,DD CARDS	33
NESC0474_01.004	SAMPLE PROBLEM	192
NESC0474_01.005	OUTPUT LIST OF SAMPLE PROBLEM	8363