The main goal of the project is to improve the understanding of the basic problem in radiation protection, namely risk estimates after exposure to low doses of various types of ionizing radiation at dose rates that occur at work places, in the normal living environment, around nuclear facilities and in diognostic medicine. The project aims to achieve better quantification of dose-time-effect surfaces for age, sex, sensitivity, etc. dependent radiation risks at doses below 10mSv by photons, neutrons, alpha particles and beta particles and incorporated radionuclides.
Presently, in radiation protection, the concept of a linear, no-threshold hypothesis for low dose/dose-rate risk assesment is applied. This hypothesis is increasingly being questioned. The present scientific basis for or against this hypothesis is far from bieng satisfactory. Neither advances in radio-epidemiological studies nor advances in basic radiation biological studies will ever be able to alone resolve this problem. The only feasible scientific pathway to tackle this problem forms the core element of this project, namely a quantitative synthesis of basic biological, medical, etc. information on mechanisms leading to somatic radiation effects at low doses in the form of mechanistic, mathematical models for radiation carcinogenesis.
The project consists of five work packages: a) critical processes and data evaluation, b) primary damage models, c) repair consequence models, d) development of mechanistic cancer models and, e) conclusions for radiation protection applications. There are nine partners from different universaties and institutions of Europe. PSI is participating in the work-packge number two, i.e. WP2, namely primary damage models. The primary task of PSI consists of generating cross-section data libraries for different types of radiation and also developing/improving stochastic tracking methods to calculate detailed dose distributions in materials with elements ranging from Z=1 to 100 and covering the entire energy range of 1eV to 100GeV.
During the last year, for the period ending 31.12.2001, efforts have continued for the generation and verification of the cross-section data for e- and e+. Data for Bremsstrahlung, elastic scattering and ionization have been generated at PSI for the entire 1eV to 100GeV range and covering all the elements from Z=1 to 100. For speeding up calculations with a stochastic code, it is desirable to include fit coefficients for the secondary radiation energy spectra and angular distributions in the database. After several critical checks, the methodology to obtain fit coefficients has been finalized. Considerable progress has been made in developing the theory and calculational scheme for the generation of excitation data for e- and e+. The future plan consisits of generating the excitation data and fit coefficients, thus completing the task of creating a usable database in the stochastic code being employed, namely GEANT. The final form of the database will include elastic scattering, ionization, excitation, Bremsstrahlung, relaxation spectra and fit coefficients for e-and e+ and in addition annihilation data for e+. For efficient transportation of charged particles in GEANT, efforts will be directed towards developing and integrating an appropriate condensed history tracking method.