| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1881495 | Radiation Measurements | 2012 | 7 Pages |
Water in soil affects the dose rate in sedimentary media. First it dilutes the radioelements, and second the mass stopping power as well as photon interaction cross sections are greater in water than in typical sediment constituents (Aitken, 1985). Here the effect of moisture on the gamma dose rate is investigated using Monte Carlo simulations based on the GEANT4 toolkit. Dose deposition processes are studied on the scale of individual grains in modelled well-sorted sediments: detailed tracking of gamma rays and secondary electrons shed light on the relative importance of the different interaction modes at stake, as a function of grain size, porosity and fraction of saturation of the sediments, as well as the energy of gamma rays. A description of the specifically designed GEANT4 codes is provided, followed by a comprehensive analysis of the phenomena. It is shown that geometry effects, specifically grain size and compactness, have a great impact on gamma dose rates received by sediment grains and that these can be quantified in the case of very simple grain assemblages. For a better accuracy in retrospective dosimetry dating methods, morphological features of the sediments that influence dose rates should be characterized and their influence on dose rate studied; Monte Carlo transport codes seem to be the favoured tools for that purpose.
► Monte Carlo simulations allowed us to study dose deposition processes in sediments. ► Simulation tools are presented and their performance is discussed. ► Beyond matrix effects, geometry parameters are of paramount importance. ► Grain/pore size is the most important parameter in such grain scale effects.
