DTU Risø Campus Technical University of Denmark


Sequential simulation

Sequental simulation is used when the reaction volume is exposed to changing physical conditions such as irradiation quality and intensity like cooling water in nuclear reactors or in cases where solutes are added or subtracted at some stages.

A sequential simulation is executed with a Chemsimul Job, "name".csj. The job consists of a number of *.csc files. Each of these files can be used in a simulation.
A Chemsimul Job can be repeated by changing the number of job cycles, the default is one cycle.

The job will be performed in a linear time scale by joining the simulation time steps. The end concentrations of each step are used as start concentrations in the following step. You must remember to mark Save final concentrations in the Output Control for each case.

All the steps in a sequental simulation ( a Chemsimul Job) must be identical with respect to chemical reactions and exchange reactions. It is not required that the rate constants are identical. An exchange reaction can be made inoperative by setting the rate constant to zero.

Furthermore it is required that the Graphics setup must be identical in all steps.

How to build a Chemsimul Job file

As an example we consider the radiation chemistry of a fusion reactor cooling system.

The cooling water in a fusion reactor is circulated through several layers of piping with different doserates and fractions of gamma, alfa and neutron irradiation. Each layer may have its own radiation time, total dose and G-values. A number of simulation cycles may be performed until the concentrations reach steady state.

Three steps in the fusion reactor cooling system are used in example testiter.csc.

The files testiterG2.dat and testiterG3.dat contain the G-values for step 2 and step 3 respectively.

The reaction scheme was abbreviated to allow simulation with the demo version of Chemsimul. The complete reaction scheme is given in iter1.csc.

The files are found in the zip-package SequentialSimulation.zip

You may create the job by following these steps:

  1. Open Chemsimul
  2. Click "File"
  3. Choose "New Chemsimul Job"
  4. Find and mark testiter.csc
  5. "open"
  6. Mark step 1 and Choose "Copy a step"
  7. Mark step 2 and Choose "Edit step"
  8. Select the tab "Irradiation"
  9. Change "Total Dose" to 240 Gy
  10. Click "Add from file"
  11. Mark testiter_G2.dat and "Open"
  12. Click "Accept all"
  13. Select the tab "Identification and Job Control"
  14. Mark step 2 and Choose "Copy a step"
  15. Choose "Yes" to save testiter_2.csc
  16. Mark step 3 and Choose "Edit step"
  17. Select the tab "Integration Parameters"
  18. Change "Final Time of Simulation" to 1.5 s
  19. Select the tab "Irradiation"
  20. Change "Total Dose" to 1870 Gy
  21. Change "Total Duration of Irradiation" to 1.5 s
  22. Click "Add from file"
  23. Mark testiter_G3.dat and "Open"
  24. Choose "Accept all"
  25. Select the tab "Identification and Job Control"
  26. Choose "Run Job"
  27. Save testiter_3.csc
  28. Save testiter.csj
  29. Now look at "Graphics Output"
  30. Click menu "Show" and Choose "Show Saved Concentrations"
  31. This table contains start and end concentrations for each step.

Note that you can choose to repeat the simulation by selecting the number of "Job Cycles"


  • Peter Kirkegaard
    Applied Mathematician, Ph.D.
    DTU - Risø Campus, Roskilde, Denmark
  • Erling Bjergbakke
    Bjergbakke Chemical Consulting
    Roskilde, Denmark
  • Jens V. Olsen
    System Programming Analyst
    DTU - Risø Campus, Roskilde, Denmark
  • Webmaster 5 Jul 2016