2018

Kaltiaisenaho, Toni

ln this report, a beta bremsstrahlung model implemented in Serpent Monte Carlo code is described. The beta spectrum model includes a theoretical shape factor for beta transitions. The transition types, energies and intensities are read from an ENDF format decay data file. A simple approximation for the Fermi function is used. Bremsstrahlung photons emitted by beta particles are created with a thick{arget bremsstrahlung approximatíon.<br/>The implemented beta bremsstrahlung model ís compared to Geant4 Monte Carlo code in a simple fuel pin geometry for Sr-90 and Y-90. A reasonably good agreement is obtained in the peak regions of the bremsstrahlung spectra. Serpent underestimates the spectra in the highenergy regions, which is most likely due to the limitations of the thick{arget bremsstrahlung approximation. The beta spectrum model is also compared to RADAR beta spectrum data for a few nuclides by calculating effective dose rate around a fuel pin. The dose rates calculated with the Serpent beta spectrum model are a few percent higher on average.