Serpent

https://serpent.vtt.fi/docs
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Serpent is a Monte Carlo neutron and photon transport code used for reactor physics, fusion...
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### Example: Define Source from File

Source: https://serpent.vtt.fi/docs/user_guide/detectors.html

This example shows how to define a source using a previously generated source file 'src1.inp'. The '-1' for the fraction indicates that all particles from the file should be used as the source.

```plaintext
src S1 p sf "src1.inp" -1
```

--------------------------------

### Initialize command-line plotter

Source: https://serpent.vtt.fi/docs/user_guide/geometry_plotting.html

Displays the initial prompt upon starting the command-line plotter.

```text
Command line plotter started...

[ 0.00000 0.00000 0.00000 ] XY >
```

--------------------------------

### Example Coefficient Matrix Definition

Source: https://serpent.vtt.fi/docs/user_guide/automated_gc.html

A practical example of a coefficient matrix defining 11 restart points and 54 branch combinations.

```text
coef 11 0 0.1 1 3 5 10 15 20 30 40 50
3 nom Blo Bhi
3 nom Clo Chi
3 nom Flo Fhi
2 nom CR
```

--------------------------------

### Example: Calculate Inward Current and Write to Source File

Source: https://serpent.vtt.fi/docs/user_guide/detectors.html

This example demonstrates calculating the inward particle current for a cylindrical surface detector and writing the scored particles to a source file named 'src1.inp'. The '-1' for the detector name and fraction indicates all particles.

```plaintext
surf S1 cyl 0.0 0.0 2.5 -5.0 5.0
det D1 p ds S1 -1 df "src1.inp" -1
```

--------------------------------

### Invoke Particle Disperser Routine

Source: https://serpent.vtt.fi/docs/user_guide/particle_disperser.html

Example of running the particle disperser interactively via the command line.

```bash
~/projects/serpent2$ sss2 -disperse

Random particle distribution file generator launched...

Enter volume type: 1 = sphere
                   2 = cylinder
                   3 = cube
                   4 = annular cylinder
                   5 = cuboid
                   6 = parallelepiped
                   7 = spherical shell
                   8 = conical frustum

1

Enter sphere radius (cm): 2.5
Enter number of particles (> 1) or packing fraction (< 1): 15000
Enter particle radius (cm): 0.0455
Enter particle universe: F

More particles? (y/n): n

Enter file name: part1.inp

Use grow and shake algorithm? (y/n): n

Randomizing 15000 particles for initial sampling...

Overlapping particles:   4156 / 15000 pf = 0.06537 / 0.09043
Overlapping particles:   2045 / 15000 pf = 0.07810 / 0.09043
Overlapping particles:   1127 / 15000 pf = 0.08363 / 0.09043
Overlapping particles:    639 / 15000 pf = 0.08658 / 0.09043
Overlapping particles:    369 / 15000 pf = 0.08820 / 0.09043
Overlapping particles:    213 / 15000 pf = 0.08914 / 0.09043
Overlapping particles:    128 / 15000 pf = 0.08966 / 0.09043
Overlapping particles:     70 / 15000 pf = 0.09001 / 0.09043
Overlapping particles:     40 / 15000 pf = 0.09019 / 0.09043
Overlapping particles:     23 / 15000 pf = 0.09029 / 0.09043
Overlapping particles:     12 / 15000 pf = 0.09036 / 0.09043
Overlapping particles:      8 / 15000 pf = 0.09038 / 0.09043
Overlapping particles:      4 / 15000 pf = 0.09040 / 0.09043
Overlapping particles:      3 / 15000 pf = 0.09041 / 0.09043
Overlapping particles:      2 / 15000 pf = 0.09042 / 0.09043

Writing final distribution to file "part1.inp"...

15000 particles, packing fraction = 0.09043
```

--------------------------------

### Run-time Output for Density Adjustment

Source: https://serpent.vtt.fi/docs/user_guide/geometry.html

Example of the console output showing the calculated density adjustment factors for specific materials.

```text
Calculating material volumes by sampling points...

x-dimensions : -1.07277E+01 1.07277E+01 cm
y-dimensions : -1.07277E+01 1.07277E+01 cm
z-dimensions : 0.00000E+00 2.14550E+01 cm

Estimated calculation time: 0:00:02
Realized calculation time : 0:00:03

 - Density of material fuel adjusted by factor 1.00787 (err 0.00046)
 - Density of material cool adjusted by factor 1.00529 (err 0.00027)
 - Density of material clad adjusted by factor 0.95083 (err 0.00087)

 OK.
```

--------------------------------

### Source Convergence Acceleration Output

Source: https://serpent.vtt.fi/docs/user_guide/criticality_simulation.html

Example of the run-time output generated when the source convergence acceleration solver is active.

```Text
...

Iterating initial fission source:

Running source batches for iteration loop  1 / 10...
Completed in 15.7 seconds.

Running response matrix solver...
Completed in 10.1 seconds.

Running source batches for iteration loop  2 / 10...
Completed in 16.5 seconds.

Running response matrix solver...
Completed in 10 seconds.

...

Running source batches for iteration loop 10 / 10...
Completed in 15.9 seconds.

Running response matrix solver...
Completed in 9.26 seconds.

Sampling initial source...
OK.

...
```

--------------------------------

### Run Case Matrix Calculations

Source: https://serpent.vtt.fi/docs/user_guide/automated_gc.html

Command-line examples for running specific history calculations, individual momentary variations, and all variations in sequence.

```bash
sss2 cm_example -omp 128 -casematrix CASE1 2 -1
```

```bash
sss2 cm_example -omp 128 -casematrix CASE1 2 18
```

```bash
sss2 cm_example -omp 128 -casematrix CASE1 2 0 -coe
```

--------------------------------

### Material Volume Output Format

Source: https://serpent.vtt.fi/docs/user_guide/mc_volumes.html

Example of the content generated in the .mvol file, which can be included in the main input file.

```text
 1 % --- Material volumes:
 2
 3 % Produced Fri Jul 11 23:29:36 2025 by MC volume calculation routine by
 4 % sampling 100000000 random points in the geometry.
 5
 6 set mvol
 7
 8 fuel1           0 2.89150E+00 % (0.001)
 9 fuel2           0 2.31671E+01 % (0.000)
10 fuel3           0 8.68416E+00 % (0.000)
11 fuel4           0 5.78933E+00 % (0.001)
12 fuel5           0 2.89435E+00 % (0.001)
13 fuelG           0 8.68194E+00 % (0.001)
14 clad            0 1.63054E+01 % (0.000)
15 chan            0 1.47919E+01 % (0.000)
16 cool            0 9.62999E+01 % (0.000)
17 mode            0 5.27520E+01 % (0.000)
```

--------------------------------

### Interpret Run-time Output

Source: https://serpent.vtt.fi/docs/user_guide/external_source_simulation.html

Example of the standard output generated during a photon transport simulation batch.

```Text
...

------------------------------------------------------------

Serpent 2.2.2 -- Photon transport simulation

Title: "Photon test case"

Source batch 35 / 200 (500000 histories per batch)

Running time :                  0:00:02
Estimated running time :        0:00:14
Estimated running time left :   0:00:12

Estimated relative CPU usage :  1169.5%

(O4) (OMP=12)
------------------------------------------------------------

...
```

--------------------------------

### Material volumes file format

Source: https://serpent.vtt.fi/docs/user_guide/mc_volumes.html

Example content of an .mvol file generated by the volume calculation routine.

```text
 1% --- Material volumes:
 2
 3% Produced Sat Jul 12 00:08:53 2025 by MC volume calculation routine by
 4% sampling 100000000 random points in the geometry.
 5
 6set mvol
 7
 8fuel1           1 2.89150E+00 % (0.001)
 9fuel2           5 2.89641E+00 % (0.001)
10fuel2           4 5.79307E+00 % (0.001)
11fuel2           3 5.79119E+00 % (0.001)
12fuel2           2 2.89649E+00 % (0.001)
13fuel2           1 5.78992E+00 % (0.001)
14...
15clad            0 1.63054E+01 % (0.000)
16chan            0 1.47919E+01 % (0.000)
17cool            0 9.62999E+01 % (0.000)
18mode            0 5.27520E+01 % (0.000)
```

--------------------------------

### View material definition output

Source: https://serpent.vtt.fi/docs/user_guide/materials.html

Example of the isotopic composition table printed in the [input].out file for a defined material.

```Text
Isotopic composition (non-zero densities):

-------------------------------------------------------------------
Nuclide    a. weight   temp      a. dens      a. frac      m. frac
-------------------------------------------------------------------
92234.03c  234.04093  300.0  1.23985E-06  1.80000E-05  4.68048E-05
92235.03c  235.04395  300.0  1.65406E-04  2.40134E-03  6.27090E-03
92238.03c  238.05078  300.0  2.27936E-02  3.30914E-01  8.75210E-01
 8016.03c   15.99492  300.0  4.59205E-02  6.66667E-01  1.18473E-01
      sum                    6.88807E-02  1.00000E+00  1.00000E+00
-------------------------------------------------------------------
```

--------------------------------

### View Adaptive Search Mesh Statistics

Source: https://serpent.vtt.fi/docs/user_guide/geometry.html

Example output showing the dimensions, depth levels, cell count, and memory allocation of a generated search mesh.

```text
Adaptive search mesh:

 - Dimensions: x = [-119.9, 119.9]; y = [-120.0, 120.0]; z = [0.0, 488.6];
 - Depth: 9 5 4 2
 - 9212777 mesh cells
 - 83.4% of volume consists of pre-assigned data
 - 1.90 Gb of memory allocated for search mesh
 ...
```

--------------------------------

### Configure Micro-Depletion with set mdep

Source: https://serpent.vtt.fi/docs/user_guide/gc_generation.html

Example demonstrating the configuration of a simple Pu-239 production chain using the set mdep input option.

```Serpent
1% -- Simple Pu-239 production chain:
2
3set mdep 0 4.62E+02 1 fuel
4
5922380 16 922380 18 922380 102  % (n,2n), fission and capture for U-238
6932390 16 932390 18 932390 102  % (n,2n), fission and capture for Np-239
7942390 16 942390 18 942390 102  % (n,2n), fission and capture for Pu-239
```

--------------------------------

### Define a tabulated source spectrum

Source: https://serpent.vtt.fi/docs/user_guide/sources.html

Example of defining a source spectrum with five energy bins using the sb parameter.

```text
1% -- A completely made-up source spectrum for demonstration:
2
3src S1
4sb 5 0
51.0 0.0
62.0 2.0
74.0 1.0
85.0 3.0
99.0 1.0
```

--------------------------------

### Configure Source Convergence Acceleration

Source: https://serpent.vtt.fi/docs/user_guide/criticality_simulation.html

Example input for the 'set sca' option to accelerate fission source convergence using a response-matrix-based solver.

```Serpent Input
1% -- Apply source convergence acceleration:
2
3set sca 10          % 10 outer iterations
41                   % Single batch of source neutrons per outer iteration
51                   % Cartesian mesh
6-268.80 268.80 25   % 25 cells in x-direction
7-268.80 268.80 25   % 25 cells in y-direction
8-4.64 442.41 22     % 22 cells in z-direction
95 5 5               % 5x5x5 sub-mesh
```

--------------------------------

### View Isotopic Composition Output

Source: https://serpent.vtt.fi/docs/user_guide/materials.html

Example of the isotopic composition table generated in the [input].out file, showing isotopes marked with thermal scattering data.

```Text
Isotopic composition (non-zero densities):

-------------------------------------------------------------------
Nuclide    a. weight   temp      a. dens      a. frac      m. frac
-------------------------------------------------------------------
 1001.03s    1.00782  300.0  6.65517E-04  6.66667E-03  1.00767E-03 S
 1002.03s    2.01410  300.0  6.58862E-02  6.60000E-01  1.99366E-01 S
 8016.03c   15.99492  300.0  3.32758E-02  3.33333E-01  7.99626E-01
      sum                    9.98275E-02  1.00000E+00  1.00000E+00
-------------------------------------------------------------------
```

--------------------------------

### Cylindrical Mesh Detector Examples

Source: https://serpent.vtt.fi/docs/user_guide/detectors.html

Demonstrates cylindrical mesh detectors with full radial, angular, and axial binning, and a variant with only radial binning.

```plaintext
 1% -- Cylindrical mesh detector with radial, angular and axial binning:
 2
 3det D1 dn 1
 4       0.0 100.0 100  % 100 radial bins between 0 and 100 cm
 5       0.0 360.0 36   % 36 angular bins between 0 and 360 degrees
 6       0.0 100.0 100  % 100 axial bins between z = 0 and 100 cm
 7
 8% -- Cylindrical mesh detector with radial binning only:
 9
10det D2 dn 1
11       0.0 100.0 100  % 100 radial bins between 0 and 100 cm
12       0.0 360.0 1    % single angular bin
13     -1E18  1E18 1    % single axial bin covering the full z-dimension

```

--------------------------------

### Interpret external source simulation runtime output

Source: https://serpent.vtt.fi/docs/user_guide/external_source_simulation.html

Example of the runtime output displaying multiplication, analog k-eff, and source k0 for a subcritical system.

```text
...

------------------------------------------------------------

Serpent 2.2.2 -- Neutron external source simulation

Title: "Godiva (subcritical modification)"

Source batch 150 / 200 (50000 histories per batch)

Running time :                  0:03:51
Estimated running time :        0:05:15
Estimated running time left :   0:01:24

Estimated relative CPU usage :  1187.6%

Multiplication   = 6.0394E+01 (0.00259)
k-eff (analog)   = 0.98343 +/- 0.00004  [0.98334  0.98351]
k0    (source)   = 1.23859 +/- 0.00052  [0.98334  0.98351]

(O4) (OMP=12)
------------------------------------------------------------

...
```

--------------------------------

### Define Guide Tube Pin Geometries

Source: https://serpent.vtt.fi/docs/user_guide/automated_gc.html

Defines pin structures for empty guide tubes and rodded guide tubes using material compositions.

```Serpent
 1% -- Empty guide tube:
 2
 3pin GTU
 4cool        0.56134
 5zirc4       0.60198
 6cool
 7
 8% -- Rodded guide tube:
 9
10pin ROD
11AIC         0.43310
12steel       0.48387
13cool        0.56134
14zirc4       0.60198
15cool
```

--------------------------------

### sample - See description in Serpent Wiki

Source: https://serpent.vtt.fi/docs/syntax/index.html

This input card's functionality is described in the Serpent Wiki.

```APIDOC
## sample

### Description
See description in Serpent Wiki.

### Method
INPUT CARD

### Endpoint
sample

### Notes
- Refer to the Serpent Wiki for detailed information on the 'sample' input card.
```

--------------------------------

### Invoke Control Rod Insertion Branch

Source: https://serpent.vtt.fi/docs/user_guide/automated_gc.html

Replaces the empty guide tube universe with the rodded guide tube universe and updates the CR variable.

```Serpent
1% -- Insertion of control rods:
2
3branch CR repu GTU ROD
4          var CR 1
```

--------------------------------

### Define 3x3 Guide Tube Lattice

Source: https://serpent.vtt.fi/docs/user_guide/geometry.html

Defines a 3x3 lattice for control rod guide tubes, using universe 'T' for the tube and 'W' for water. This lattice is nested within the fuel rod lattice.

```plaintext
1% -- 3x3 guide tube lattice:
2
3lat X 1 0.0 0.0 3 3 5.14
4
5T W T
6W T W
7T W T


```

--------------------------------

### Critical Spectrum Calculation Example (LWR)

Source: https://serpent.vtt.fi/docs/user_guide/gc_generation.html

Example input for critical spectrum calculation using the FM method for an LWR. It specifies no micro-group structure (uses default 168-group) and a single batch for improved convergence.

```input
1% -- Critical spectrum calculation:
2%
3%    No micro-group structure specified: use default 168-group structure
4%    Single batch for improved convergence and performance
```

--------------------------------

### Example ACE Cross Section Directory File Entries

Source: https://serpent.vtt.fi/docs/user_guide/nuclear_data.html

These examples demonstrate the structure of lines within an ACE format cross section directory file. Each line defines a nuclide or element with its associated data and file path.

```text
   1001.00c   1001.00c  1   1001  0    1.007825    0  0  /xs/data/100100JF32.ace
    H-1.00c   1001.00c  1   1001  0    1.007825    0  0  /xs/data/100100JF32.ace
   8016.03c   8016.03c  1   8016  0   15.994915  300  0  /xs/data/801603JF32.ace
   O-16.03c   8016.03c  1   8016  0   15.994915  300  0  /xs/data/801603JF32.ace
  40000.06c  40000.06c  1  40000  0   91.219625  600  0  /xs/data/4000006EB68.ace
 Zr-nat.06c  40000.06c  1  40000  0   91.219625  600  0  /xs/data/4000006EB68.ace
  92235.09c  92235.09c  1  92235  0  235.043952  900  0  /xs/data/9223509JF32.ace
  U-235.09c  92235.09c  1  92235  0  235.043952  900  0  /xs/data/9223509JF32.ace
  95342.09c  95342.09c  1  95242  1  242.059419  900  0  /xs/data/9534209JF32.ace
Am-242m.09c  95342.09c  1  95242  1  242.059419  900  0  /xs/data/9534209JF32.ace
  95242.09c  95242.09c  1  95242  0  242.059419  900  0  /xs/data/9524209JF32.ace
 Am-242.09c  95242.09c  1  95242  0  242.059419  900  0  /xs/data/9524209JF32.ace
 Np-237.30y 93237.30y   2  93237  0  239.10201     0  0  /xs/llldos1
  93237.30y 93237.30y   2  93237  0  239.10201     0  0  /xs/llldos1
   lwj3.03t   lwj3.03t  3      0  0    1.007828  374  0  /xs/data/sssth1
   grj3.16t   grj3.16t  3      0  0   12.001096  700  0  /xs/data/sssth1
```

--------------------------------

### Configure Activation Steps

Source: https://serpent.vtt.fi/docs/user_guide/burnup_calculation.html

Use the dep input card with actstep to maintain previous reaction rates for activation calculations.

```Serpent
1% -- Run a single time step to obtain transmutation reaction rates:
2
3dep daystep 1
4
5% -- Continue with activation steps (maintain previous reaction rates):
6
7dep actstep 1 1 1 1 1 1
```

--------------------------------

### Utility and File Management Options

Source: https://serpent.vtt.fi/docs/user_guide/running_overview.html

Additional command line options for handling depletion files, restart files, and particle tracking.

```APIDOC
## Other Command Line Options

### Description
Utility options for reading binary depletion files, managing restart files, and generating particle track files.

### Parameters
#### Command Line Options
- **-rdep** (flag) - Optional - Read binary depletion file from previous calculation and print new output according to inventory list.
- **-rfw** (flag) - Optional - Write restart file with current compositions and stop.
- **-trackfile** (integer) - Optional - Write particle tracks in file for a given number of particle histories.
```

--------------------------------

### Define a track-length detector

Source: https://serpent.vtt.fi/docs/user_guide/detectors.html

Example of defining a super-imposed track-length detector using the dtl parameter.

```Serpent
1% -- Track-length detector:
2
3det D4 dtl S1
```

--------------------------------

### Run Serpent Simulation

Source: https://serpent.vtt.fi/docs/user_guide/running_overview.html

The general syntax for running Serpent is to provide the input file name followed by optional command-line arguments. Ensure the input file path is correct.

```bash
sss2 INPUT [ OPTIONS ]
```

--------------------------------

### Define Variable Power History

Source: https://serpent.vtt.fi/docs/user_guide/burnup_calculation.html

Example of changing normalization power levels across multiple depletion intervals.

```Serpent
 1% -- Burn 30 days at full 300 MW power:
 2
 3set power 300E6
 4dep daystep 0.5 0.5 1 1 2 5 10 10
 5
 6% -- Shut down for 10 days:
 7
 8set power 0.0
 9dep daystep 0.5 0.5 1 1 2 5
10
11% -- Power to 50% for 30 days:
12
13set power 150E6
14dep daystep 0.5 0.5 1 1 2 5 10 10
```

--------------------------------

### Include external input files

Source: https://serpent.vtt.fi/docs/user_guide/general_input.html

Use the include card to modularize input descriptions or share common parameters across multiple calculation cases.

```text
include “ _FILE_ ”
```

--------------------------------

### Configure External Source Simulation

Source: https://serpent.vtt.fi/docs/user_guide/external_source_simulation.html

Use these input cards to set up an external source simulation in a supercritical system. The 'set tcut' option is crucial for limiting simulation time due to exponential population growth.

```input
 1% -- Run external source simulation:
 2
 3set nps 1000000
 
 5% -- Isotropic point source at origin (E = 1 MeV by default):
 6
 7src SRC1 sp 0 0 0
 
 9% -- Delayed neutron emission on:
10
11set delnu 1
12
13% -- Additional options:
14
15set tcut 0.5E-6  %  Time cut-off to 0.5 microseconds
16set nbuf 10000   %  Increase neutron buffer size
17set bala 1       %  Switch on OpenMP load balancing.

```

--------------------------------

### Define Cooling Period with Decay Interval

Source: https://serpent.vtt.fi/docs/user_guide/burnup_calculation.html

Example of appending a decay interval to a burnup calculation to simulate a cooling period.

```Serpent
1% -- Depletion interval in cumulative burnup steps:
2
3dep butot 0.1 0.5 1 5 10 15 20 25 30 35 40 45 50
4
5% -- Decay interval in incremental time steps:
6
7dep decstep 365 365 365 365 365
```

--------------------------------

### Compile Serpent VTT with Makefile

Source: https://serpent.vtt.fi/docs/installation/compiling.html

Automates the build process using the standard Make utility. The compilation should produce an executable named 'sss2' without errors or warnings.

```bash
~/src/serpent2$ make -j
gcc -Wall -ansi -ffast-math -O3 -Wunused -DOPEN_MP -fopenmp -pedantic -fpic -c addbranching.c
gcc -Wall -ansi -ffast-math -O3 -Wunused -DOPEN_MP -fopenmp -pedantic -fpic -c addbuf.c
gcc -Wall -ansi -ffast-math -O3 -Wunused -DOPEN_MP -fopenmp -pedantic -fpic -c addbuf1d.c

... 
gcc -Wall -ansi -ffast-math -O3 -Wunused -DOPEN_MP -fopenmp -pedantic -fpic -c zaitoiso.c
gcc -Wall -ansi -ffast-math -O3 -Wunused -DOPEN_MP -fopenmp -pedantic -fpic -c zdis.c
gcc -Wall -ansi -ffast-math -O3 -Wunused -DOPEN_MP -fopenmp -pedantic -fpic -c zonecount.c
gcc addbranching.o addbuf.o addbuf1d.o ... zaitoiso.o zdis.o zonecount.o -lm -fopenmp -lgd -o sss2
Serpent 2 Compiled OK.
~/src/serpent2$

```

--------------------------------

### Define Surface Detectors in Serpent

Source: https://serpent.vtt.fi/docs/user_guide/detectors.html

Example demonstrating the definition of a spherical surface and associated surface current and flux detectors.

```Serpent
 1% -- Surface used with the surface detectors (sphere centred at the origin):
 2
 3surf S1 sph 0.0 0.0 0.0 5.0
 4
 5% -- Surface current detectors:
 6
 7det D1 ds S1 -1  % Particle current entering the sphere
 8det D2 ds S1  0  % Net flow of particles through the sphere
 9det D3 ds S1  1  % Particle current exiting the sphere
10
11% -- Surface flux detector:
12
13det D4 ds S1 -2  % Integral particle flux over the sphere
```

--------------------------------

### Display command-line plotter help

Source: https://serpent.vtt.fi/docs/user_guide/geometry_plotting.html

Lists available commands for the plotter interface by entering 'h'.

```text
[ 0.00000 0.00000 0.00000 ] XY > h

List of commands:

exit : exit plotter
file : set output file name
qp   : toggle quick plot mode on/off [off by default]
bou  : boundary mode [0 = none, 1 = cell, 2 = material, 3 = both]
pix  : set image size in pixels
orig : set origin
rgb  : set material color [name and RGB values]
max  : reset to maximum dimensions
sq   : set square shape
box  : set plot area [bounding box coordinates]
ax   : set plot axis [xz, yz or xy]
zo   : zoom out [optional factor]
zi   : zoom in [optional factor]
w    : move west [optional distance]
s    : move south [optional distance]
n    : move north [optional distance]
e    : move east [optional distance]
u    : move up [optional distance]
d    : move down [optional distance]
imp  : WW mesh [0 = off, 4 = lin cell, 5 = log cell, 6 = lin src, 7 = log src]
par  : set particle type for WW mesh plot [n = neutron, p = photon]
ene  : set particle energy for WW mesh plot [in MeV]
```

--------------------------------

### Define a U235 fission source

Source: https://serpent.vtt.fi/docs/user_guide/sources.html

Example of defining a fission source using the sr parameter for a specific nuclide and reaction.

```text
1% -- U235 fission source in fissile materials:
2
3src S1 sr 92235.09c 18 se 5E-08 sm fiss
```

--------------------------------

### Example of a fatal calculation error

Source: https://serpent.vtt.fi/docs/user_guide/general_input.html

Displays the format of fatal errors occurring during simulation routines, which should be reported to the development team.

```text
***** Thu Feb 25 15:05:16 2025

 - Version          = 2.2.2
 - MPI task         = 0
 - OpenMP thread    = 22
 - RNG parent seed  = 1456405516

Fatal error in function LevelScattering:

Now, I am become Death, the destroyer of worlds!

Simulation aborted.
```

--------------------------------

### Define Pin-cell Burnup Calculation

Source: https://serpent.vtt.fi/docs/user_guide/burnup_calculation.html

Example of a complete pin-cell burnup input file using cumulative burnup steps for depletion.

```Serpent
 1set title "Pin-cell burnup calculation"
 2
 3% -- geometry:
 4
 5nest 0
 6fuel cyl 0 0 0.412
 7clad cyl 0 0 0.475
 8cool sqc 0 0 0.665
 9outside
10
11set bc 3
12
13% -- Materials:
14
15mat fuel  -10.045 burn 1 vol 0.5333
16 8016.09c  -1.18500E-01
1792234.09c  -2.37996E-04
1892235.09c  -2.67788E-02
1992238.09c  -8.54483E-02
20
21mat clad   -6.560
2240000.06c  -0.9791
2350000.06c  -0.0159
2426000.06c  -0.0050
25
26mat cool   -0.7569   moder lwtr 1001
27 1001.06c  -1.11878E-01
28 8016.06c  -8.87791E-01
29 5010.06c  -6.05254E-05
30 5011.06c  -2.70164E-04
31
32therm lwtr lwe7.12t
33
34% -- Cross section, decay and fission yield data:
35
36set acelib "s2v0_endfb71.xsdata"
37set declib "s2v0_endfb71.dec"
38set nfylib "s2v0_endfb71.nfy"
39
40% -- Run in criticality source mode:
41
42set pop 20000 500 20
43
44% -- 40 kW/kgU power density:
45
46set powdens 40.0E-3
47
48% -- Depletion history with a single interval in cumulative burnup steps:
49
50dep butot 0.1 0.5 1 5 10 15 20 25 30 35 40 45 50
51
52% -- Isotope list for inventory calculation:
53
54set inventory 531350 541350 922350 942390 942400 942410
```

--------------------------------

### Input Cards Overview

Source: https://serpent.vtt.fi/docs/syntax/index.html

Provides an overview of the input parser and general rules for using input cards.

```APIDOC
## Input Cards Overview

### Description
Input cards are processed sequentially by the parser. The start of a new card signifies the end of the previous one. It is crucial to ensure that user-provided arguments do not conflict with reserved card names to prevent errors.

### General Rules
- Input cards are processed one at a time.
- The beginning of a new card marks the termination of the preceding card.
- Avoid using reserved input card names as arguments for any input card.
```

--------------------------------

### Cartesian Mesh Detector Example

Source: https://serpent.vtt.fi/docs/user_guide/detectors.html

Defines a 2D Cartesian mesh for pin-wise fission power distribution. Integrates results over the z-direction.

```plaintext
1% -- Pin-wise fission power distribution in a 17x17 PWR fuel assembly
2
3det D1 dr -8 void
4       dx -10.8 10.8 17
5       dy -10.8 10.8 17

```

--------------------------------

### Define materials using various input conventions

Source: https://serpent.vtt.fi/docs/user_guide/materials.html

Demonstrates defining natural uranium fuel using mass fractions, stoichiometries, and atomic densities, along with setting the cross-section library.

```Serpent
 1% -- Uranium oxide fuel defined using mass fractions:
 2
 3mat fuel1 -10.295
 4
 592234.03c  -4.68049E-05
 692235.03c  -6.27089E-03
 792238.03c  -8.75210E-01
 8 8016.03c  -1.18473E-01
 9
10% -- Uranium oxide fuel defined using stoichiometries:
11
12mat fuel2 -10.295
13
1492234.03c   0.000054
1592235.03c   0.007204
1692238.03c   0.992742
17 8016.03c   2.000000
18
19% -- Uranium oxide fuel defined using atomic densities:
20
21mat fuel3  sum
22
2392234.03c   1.23985E-06
2492235.03c   1.65406E-04
2592238.03c   2.27936E-02
26 8016.03c   4.59205E-02
27
28% -- Cross section directory file:
29
30set acelib "s2v0_jeff32.xsdata"
```

--------------------------------

### Define Case Matrix Input Card

Source: https://serpent.vtt.fi/docs/user_guide/automated_gc.html

Example input card configuration for a case matrix including historical and momentary variations.

```text
1casematrix CASE1
23 BH1 BH2 BH3
311 0 0.1 1 3 5 10 15 20 30 40 50
43 nom Blo Bhi
53 nom Clo Chi
63 nom Flo Fhi
72 nom CR
```

--------------------------------

### Define Detector - Basic Syntax

Source: https://serpent.vtt.fi/docs/user_guide/detectors.html

Basic syntax for defining a detector with name, particle type, and optional parameters. Use 'n' for neutrons and 'p' or 'g' for photons.

```input
det NAME [ PART ] [ dv VOL ] [ dt OPT ... ] [ dhis HOPT ] [ da AMAT FLX ] ...
```

--------------------------------

### Slurm script for OpenMP calculation

Source: https://serpent.vtt.fi/docs/user_guide/parallelisation.html

Example Slurm batch script for running an OpenMP parallel calculation with 128 CPU cores.

```bash
#!/bin/bash
#SBATCH -o log.txt                 # Slurm output
#SBATCH --job-name=OpenMP_test     # Job name
#SBATCH --ntasks=1                 # Run a single MPI task
#SBATCH --cpus-per-task=128        # Number of CPU cores per task
pwd; hostname; date                # Log working directory, host and date
~/bin/sss2 -omp 128 inp > inp.log  # Serpent excution line

```
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