Conversion of Mesh Tally Using Gridconv from MCNP Output + Software Requirements

In the realm of scientific and technical simulations, the Monte Carlo method is heralded as a powerful tool for the analysis and modeling of intricate processes. Among the diverse instruments utilized in this method, mesh tally stands out for its exceptional accuracy and capability to provide detailed information.

What is a Tally?

In Monte Carlo simulations, a tally refers to the measurement and aggregation of information such as the number of collisions, energy absorbed, and other physical characteristics of particles at specific points or regions within the simulation model. Tallies offer statistical data from simulations, facilitating the analysis and interpretation of results.

Types of Tallies

• F1 Tally: Number of collisions with surfaces.

• F2 Tally: Flux through surfaces.

• F4 Tally: Average number of particles in volumes.

What is Mesh Tally?

A mesh tally is a specialized form of tally wherein the simulation region is subdivided into a grid of smaller cells. This subdivision, arranged in a mesh-like structure, enhances the accuracy of data collection. Mesh tallies are particularly valuable for complex simulations that necessitate detailed information.

Differences Between Tally and Mesh Tally

• Precision: Mesh tally offers higher accuracy by subdividing the region into smaller cells.

• Detail: Mesh tally provides more information about local variations within the simulation region.

• Application: Mesh tally is suitable for complex simulations requiring precise information at various points, while simpler tallies are employed for more general measurements.

Applications of Mesh Tally

• Medical Simulations: For assessing radiation dose in cancer treatments.

• Nuclear Reactor Design: For optimizing the design and safety of reactors.

• Radiation Shielding Calculations: For designing radiation shields and evaluating safety.

Mesh Tally Output and Result Analysis

Mesh tally serves as a potent tool for more precise and detailed analysis in Monte Carlo simulations, aiding researchers and engineers in obtaining more reliable results.

Converting Mesh Tally Data to Readable Text Files Using Gridconv

Gridconv transforms mesh and radiography outputs into inputs for external graphical programs. The mdata file generated by the MCNP software is in ASCII format, meaning its information is not directly viewable.

To convert this data into a readable file, Gridconv software is required. The conversion process is detailed below.

1. Download and Install Gridconv Software:

   • If you do not have the software, it can be downloaded.

2. Open Gridconv Software:

   • After launching the software, the following message is displayed:

    

   Enter the type of data file: mdata or mctal.
   <default=mdata>:
   

   • Specify the type of input file. The default is set to mdata. Press Enter to proceed to the next step.

3. Enter the Name of the Input File:

    

   Enter name of input file. <default=mdata>:
   

   • Specify the name of the input file. The default name is mdata. If the input file name differs, type the name and press Enter.

4. Specify Binary File Type:

    

   Is this a binary data file? y/n
   <default=yes>:
   

   • If the file is not binary, enter n and press Enter.

5. Create Text File:

    

   Do you wish to create a text file? y/n
   This file is portable to any system.
   <default=no>:
   

   • To create a text file, enter y and press Enter.

6. Enter the Name of the Output File:

    

   What do you want to name your file?
   <default=mdata>:
   

   • Specify the name of the output file. For instance, enter mdata.txt. Here, the mdata file is converted to a text format as mdata.txt.

Content of Mesh Tally File

The mesh tally file contains the following information:

1. Program Title: Name and description of the program or simulation.

2. Grid Information: Configuration specified in the input file and the grid structure of the simulation area.

3. Desired Output: Data from the simulation, including mesh tally results.

4. Output Errors: Errors and warnings encountered during output generation.

Using the Mesh Tally File in MATLAB

For using this file in MATLAB, follow these steps:

1. Remove Extraneous Parts: Delete unnecessary sections, retaining the output section as a table.

2. Load Data into MATLAB: Utilize the load command to read the data and convert it into a matrix for further analysis and visualization.

MATLAB Commands for Loading Data

Assuming the mesh tally data is saved as a text file (e.g., mdata.txt), follow these detailed steps:

1. Save Data as Text File:

   • Ensure the data is saved in a structured format in mdata.txt.

2. Read Data Using load Command:

   matlab

   % Load data from text file
   data = load('mdata.txt');
   
   % Assume columns 1 and 2 are coordinates, and column 3 is the dose
   x = data(:, 1);
   y = data(:, 2);
   dose = data(:, 3);
   

3. Create Matrix and Plot Dose Contour:

   matlab

   % Create a grid of points
   [X, Y] = meshgrid(unique(x), unique(y));
   
   % Interpolate dose data
   Z = griddata(x, y, dose, X, Y);
   
   % Plot contour
   contourf(X, Y, Z);
   title('Dose Contour in Reactor Geometry');
   xlabel('X-axis');
   ylabel('Y-axis');
   colorbar; % Show color scale
   

Explanation of Commands:

• load Command: Loads data from the text file mdata.txt into a variable in MATLAB.

• meshgrid Command: Creates a grid of coordinate points X and Y.

• griddata Command: Interpolates the dose data based on x and y coordinates to create a matrix Z.

• contourf Command: Plots the dose contour based on X, Y, and Z values.

By following this method, you can load mesh tally data as a matrix in MATLAB and plot the dose as a contour. This enables detailed analysis and visualization of the simulation data, enhancing the accuracy and comprehensiveness of your findings.