FuelMeltANCHOR Iterative Solving Macro to Determine LHGR to Melt Will MacFee under direction of Andrew Proffitt

Why do we need it? Fuel melt LHGR needed for fuel performance analysis. Iterative method to determine the LHGR necessary to melt fuel time consuming. Automation increases efficiency.

What are the inputs? Original Input file from deck and its respective folder location. Folder location where FRAPCON executable is stored. Initial LHGR Guess Time step for melt (if examining a single time step)

What are the inputs? (Continued) Axial Profile for Ramp Axial Profile for Peak FRAPCON Run time FRAPCON Version

Input Screen

How Does It Work? Loads in an unedited FRAPCON input file. Uses the Average LHGR to find melt at time steps in burn-up history. Time steps used are the last time step, time step intervals of 5, and the first time step. Starts at the last time step and iterates backwards, carrying LHGR for melt as initial guess for subsequent previous time step.

How Does It Work? (Continued) Adds 10 time steps of .001 days leading up to time at time step of interest. Increases LHGR using even intervals to iteration guess. First 9 time steps have Axial Profile of Ramp Iteration guess has Axial Profile of Peak Ignores burn-up history beyond time step of interest

How Does It Work? (Continued) Starting from initial guess, iterates upwards by 0.5 kw/ft. After finding an output file with melt, subtracts 0.5 kw/ft from guess then iterates up by 0.1 kw/ft. After finding melt again, subtracts 0.1 kw/ft from guess then iterates up by 0.01 kw/ft.

How Does It Work? (Continued) After finding melt at the 0.01 kw/ft iteration, this is considered the melting point. Then iterates back to next time step of 5 using previous LHGR to melt as initial guess.

How Does It Work? (Continued) Run time changes based on input file. Larger burn-up history, longer run time. Each time step takes an average of 10 iterations to find melt. FRAPCON run time most dominant time determination.

Initial Verification Done on generic CE16x16 SONGS input file. Verified against method done by hand. Method done by hand was 5 new time steps increasing at .01 GWd/mtU beyond intended time step.

Initial Verification (Continued) New input file created from FRAPCON Auto Input Generator for each time step studied. Iterated only peak to find fuel melt. Begun Verification against Official Power-to-Melt curves used in the past.

Average LHGRs CE16x16 Time Step Time (Days) LHGR ANCHOR (kw/ft) LHGR Hand (kw/ft) Difference (kw/ft) 1 0.17 23.30 0.76 23.34 -0.04 5 52.59 23.64 53.05 23.60 0.04 10 142.86 23.32 143.33 23.11 0.21 15 236.15 22.90 236.62 22.66 0.24 20 330.19 22.48 330.67 22.18 0.30 25 424.43 22.06 424.91 21.73 0.33 30 519.72 21.65 520.21 21.34 0.31 35 619.32 21.28 619.83 21.00 0.28 40 721.97 20.96 722.48 20.70 0.26 45 827.34 20.68 827.87 20.44 50 938.4 20.43 938.94 20.22 55 1069.67 20.17 1070.27 20.01 0.16 56 1100.41 20.13 1101 19.97

Peak LHGRs CE16x16 Time Step Time (Days) LHGR ANCHOR (kw/ft) LGHR Hand (kw/ft) Difference (kw/ft) 1 0.17 24.28 0.76 24.33 -0.05 5 52.59 24.64 53.05 24.60 0.04 10 142.86 24.30 143.33 24.09 0.21 15 236.15 23.87 236.62 23.62 0.25 20 330.19 23.43 330.67 23.12 0.31 25 424.43 22.99 424.91 22.65 0.34 30 519.72 22.56 520.21 22.24 0.32 35 619.32 22.18 619.83 21.89 0.29 40 721.97 21.84 722.48 21.57 0.27 45 827.34 21.55 827.87 21.30 50 938.4 21.29 938.94 21.07 0.22 55 1069.67 21.02 1070.27 20.85 56 1100.41 20.98 1101 20.81