Radioactive decay source, practical example
The radioactive decay source mode was implemented in Serpent 2.1.24 for the purpose of radiation transport calculations involving activated materials. The source term is determined by:
- Isotopic material compositions, either user-defined or obtained from a previous burnup / activation calculation
- Decay constants of radioactive nuclides read from ENDF format decay data file
- Emission spectra read from ENDF format decay data file
The radiation types in version 2.1.28 and earlier are limited to discrete photon emitting reactions. Work on continuum reactions, neutron emission and bremsstrahlung from beta decay is under way.
The radioactive decay source mode is most conveniently used with burnup or activation calculation, in which case the radioactive material compositions can be read from a binary restart file (see the set rfw and set rfr options). In such case the same input can be used for both calculations without major modifications. Serpent converts the isotopic material compositions in the neutron transport calculation into elemental compositions for the following photon transport calculation, and source rate normalization is carried out automatically based on the total emission rate.
The radioactive decay source mode has been tested in radiation shielding calculations involving a transport cask containing irradiated fuel and shut-down dose rate calculations for the ITER fusion reactor.
- ^ Sirén, P. and Leppänen, J. "Expanding the Use of Serpent 2 to Fusion Applications: Development of a Plasma Neutron Source." In proc. PHYSOR 2016. Sun Valley, ID, May 1-6, 2016.
- ^ Leppänen, J. and Kaltiaisenaho, T. "Expanding the Use of Serpent 2 to Fusion Applications: Shut-down Dose Rate Calculations." In proc. PHYSOR 2016. Sun Valley, ID, May 1-6, 2016.