NESC9673 WAPPA.

1. NAME OR DESIGNATION OF PROGRAM:  WAPPA.

3. DESCRIPTION OF PROGRAM OR FUNCTION

WAPPA the Waste Package Performance Assessment program, is intended to serve as a tool for evaluating both the relative and the absolute performance of waste package design concepts, for guiding or selecting a preliminary design among conceptual designs, and for support of licensing activities. WAPPA is a barrier degradation code for a nuclear waste  package in a geologic repository. The WAPPA model includes five distinct degradation process models (radiation, thermal, mechanical, corrosion, and leaching), which are driven internally by waste decay and externally by repository stress and fluids. The modeling approach is barrier-integrated and process-sequential, allowing modification of the entire waste package by the sequential operation of five process models within each time-step. The process models are coupled at the system level via state and coupling variables. The penetration of water into the waste package and its effects on the barriers it contacts are tracked radially inwards. The WAPPA model describes and predicts the temporal and spatial extent of the loss of containment capability for each barrier and for the entire waste  package, on any time scale up to one million years after isolation.
Input includes the radial geometry and material properties of each component, degradation rates for each process modeled, and time-dependent boundary conditions (fluid flux, mechanical stress, and temperature) as the waste package/repository interface. The output quantifies the residual state of integrity of waste package components as a function of time and calculates the heat and radionuclide fluxes output to the repository. Other output at each calculation time point includes: the temperature and nuclide concentration profiles internal to the waste package, residual mass  fractions of radionuclides in the wasteform and residual waste mass  fraction, and various barrier status degradation indices andparameters. In addition, summary output includes the total mass for  each nuclide output to the repository and the barrier's status history used to pinpoint times of failure.

4. METHOD OF SOLUTION:

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM:

6. TYPICAL RUNNING TIME:  The sample problem required 16 CPU seconds.

NEA-DB executed the test case included in this package  on a VAX-11/780 computer in 285 seconds of CPU time.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

The fluid flux required as an input boundary condition to WAPPA can be calculated by STFLO (NESC 9852) as a function of time and stored in the geology- specific boundary conditions file. Similarly, the DOT-BPMD (NESC 9833) program can be  used at the front-end to simulate time-dependent temperatures at the waste package/repository boundary.

10. REFERENCES:

- INTERA Environmental Consultants, Inc.:
  WAPPA: A Waste Package Performance Assessment Code.
  ONWI-452  (April 1983)

11. MACHINE REQUIREMENTS:

1156 pages (VAX-11/780).

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  VMS.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHORS

          G. Kilshtok
          Office of Nuclear Waste Isolation
          Battelle Project Management Division

File name	File description	Records
NESC9673_01.001	Information file	92
NESC9673_01.002	WAPPA FORTRAN source	12844
NESC9673_01.003	Sample input	21
NESC9673_01.004	Sample output (FT06)	1910
NESC9673_01.005	Material codes	16
NESC9673_01.006	Repository boundary conditions	8
NESC9673_01.007	R-Gamma buildup factors and G-ray X-sct	17
NESC9673_01.008	ORIGEN2 data	139
NESC9673_01.009	Thermal properties	85
NESC9673_01.010	Mechanical properties	7
NESC9673_01.011	Fluid independent corrosion properties	20
NESC9673_01.012	Fluid dependent corrosion properties	160
NESC9673_01.013	Corrosion enhancement factors	20
NESC9673_01.014	Wasteform leach properties	1
NESC9673_01.015	Backfill leach properties	1
NESC9673_01.016	Nuclide transport properties	24