Laurent Desorgher IRA Requirements from radioprotection and radiophysics

Laurent Desorgher, IRA Requirements from radioprotection and radiophysics : activation and dose calculation

List of simulation requirements • Tallying of the ambiant dose equivalent H*(10) for shielding design + error estimation • Computation of activation in bunker therapy by protons, neutrons, and gammas • Definition of irradiation profile • Dose H*(10) resulting from radioactive decay at different time windows

Conversion of fluence through a volume into ambiant of equivalent dose H*(10) =Equivalent dose at 1 cm depth Aligned irradiation field Sphere ICRU Ci(E) = conversion coefficient of fluence into H*(10) computed for protons, e-, gammas, neutrons by Monte Carlo et published in ICRP 74 Fi(E) =fluence over a 3 D grid computed by Monte Carlo

Example computation of H*(10) for protontherapy • Conversion in Geant 4 and FLUKA of neutron, gamma, proton, en electron in H*(10) • Use of conversion coefficients from ICRP 74 • Enregistrement of H*(10) on a 3 D grid of 25 x 25 cm 3

Geant 4 requirement for H*(10) computation • Possibility to multiply the fluence through volume or surface over a 3 D grid by a user defined function of energy for different types of particle • We have implemented our own solution in Geant 4 scoring • Some solution seems to be available in GAMOS • In general an uncertainty estimation of the scoring values in Geant 4 would be of great benefit • Possibility to filter the tally computation in fonction of time window • Important to assess the dose from decay of activated materials or radioactive source at different time windows

Requirements for simulation of radioactive decay • The two simulation cases are activation study and simulations of radiation source in radioprotection, radiotherapy, … The requirements are : • Correct production of activated nuclei by nuclear spallation • Is there a validation of this physics in Geant 4? • Simulation of decay of radioactive source is essential • In general good secondary spectrum • Validation case by case with DDEP data

Requirements for simulation of radioactive decay • Possibility to define the user irradiation profile • Shielding study for beam line • Possibility to compute radioactive decay in user defined time windows for activation study • Solution of the Bateman equation in the code • Some validation of the GEANT 4 biasing mode are ongoing • Possibility to filter the tally computation in fonction of time windows for assesment of H*(10) from activated material

Validation of gamma, Xrays emission spectrum for 137 Cs computed with GEANT 4

Radioactive decay in biasing mode in GEANT 4 • Integration of the Bateman equation • Possibility to force the radioactive decay in user defined time windows

Gamma spectrum of 99 Mo after 3 hour