Input syntax manual

From Serpent Wiki
Revision as of 18:53, 17 November 2015 by Jaakko Leppänen (Talk | contribs)

Jump to: navigation, search


This page will contain the whole input syntax of Serpent 2

This is a reference to one article [1]

This is another reference to the same article [1]

Input cards

mat (material definition)

surf (surface definition)

cell (cell definition)

det (detector definition)


Input options

set pop

set pop <npg> <ngen> <nskip> [ <keff0> <btch> ] 

Sets parameters for simulated neutron population in criticality source mode. Input values:

<npg> number of neutrons per generation
<ncyc> number of active generations
<nskip> number of inactive generations
<keff0> initial guess for k-eff
<btch> batching interval

The simulation is first run for a number of inactive generations to allow the fission source to converge. This is followed by a number of active generations, during which the results are collected. The statistics are divided in batches, and by default each generation forms its own batch.


  • Using the pop card sets the mode to criticality source simulation. External source simulation is invoked using set nps.
  • Convergence of fission source can be monitored using Shannon entropy (input parameters set his and set entr).
  • See detailed description on the statistical effects of batching.

set nps

set nps <ppb> [ <btch> ] 

Sets parameters for simulated particle population in external source mode. Input values:

<ppb> number of particles per batch
<btch> number of batches

The simulation is for a number batches using the given batch size.


  • Using the nps card sets the mode to external source simulation. Criticality source simulation for neutrons is invoked using set pop.
  • Running an external source simulation requires a source, defined by the src card. Source definition also sets the transported particle type.
  • Neutron external source simulations are limited to sub-critical systems, unless time cut-off (set tcut) or generation cut-off (set gcut) is invoked
  • Neutron external source simulations in multiplying systems may require adjusting the neutron buffer (set nbuf)

set delnu

set roulette


  1. ^ Leppänen, J. "Development of a new Monte Carlo reactor physics code." D.Sc. Thesis, Helsinki University of Technology, 2007. (VTT Publications 640)