Ion motions, involving atomic collisions within the solid and fluid phases are simulated using a three-dimensional Monte Carlo algorithm, which is based on the principles of ion scattering and electronic interactions with the moving ion. The recoil range distributions of radon, thorium and radium are calculated from this algorithm, which are then used to compute the emanating powers of these elements for synthetic porous media. The synthetic porous media are generated using the turning bands method, from which a fractal dimension of the recoil surface area can be obtained. The depletions of thorium and radium from the solid phase are calculated based on the effective recoil surface area, and expressions describing emanation of daughter ions through successive recoil, from $\rm\sp{238}U$ to $\rm\sp{222}Rn$ and from $\rm\sp{232}Th$ to $\rm\sp{220}Rn$ are developed. The recoil emanation-rate ratios under conditions of zero adsorption and complete adsorption of radon, thorium and radium are calculated for a saturated medium. For the isotopes within the same decay chain, it is predicted that the daughters usually should have higher measured radioactivities than the parents. It is found that the recoil supply rates and emanation rates increase slightly with porosities because the effective recoil surface area increase with porosities. Recoil release rates under varying degrees of saturation are also examined. It is found that the recoil emanation rate under saturated conditions is much larger than the emanation rate under dry conditions due to the intense embedding in a dry sample. For a moisture content of 10% or more, the recoil emanation rates quickly approach the emanation rate associated with saturated conditions, and with 30$\sim$40% moisture content, the emanation rate essentially equals that under saturated conditions. A recoil experiment was conducted to / demonstrate that the recoil effect does occur in a natural sample, and could cause radioactive depletion on the sample surface. / Source: Dissertation Abstracts International, Volume: 56-07, Section: B, page: 3658. / Major Professor: David J. Furbish. / Thesis (Ph.D.)--The Florida State University, 1995.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77508 |
| Contributors | Sun, Hongbing., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 241 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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