Radon emanation coefficient study of a geological sample

The radon atom can escape from the material it was formed in by direct recoil or by diffusion. It then enters either an inter or intra-granular space. Next, the radon atom can migrate by diffusion or convection in order to reach the atmosphere. The emanation coefficient is defined as the ratio between the number of radon atoms that escape from the matrix and the total number produced in the entire material. We propose to define a protocol in order to measure this emanation coefficient by a differential gammametric method. This method consists in determining the concentration of the short, half-life progenies of radon (essentially lead-214 and bismuth-214) through measuring their gamma-ray intensities in a hermetic cell before and after radioactive equilibrium. The first gamma measurement results give us the quantity of radon trapped in the solid matrix. A second analysis, after 13 days, gives the total production of the progenies, and thus the total radon in the sample. The measurements of a sample that is both dried and saturated are necessary to estimate the radon emanation potential. The influence of the fluid in the porous space is discussed in a theoretical way. This approach is applied to a geological sample and compared with the experimental results

Track etch velocity and chemical damages induced by ions in a cellulose nitrate detector

We sum up here the results obtained on a cellulose nitrate detector (LR 115). LR 115 was irradiated with ions from proton and oxygen ions in the energy range 1–10 MeV/amu. Each irradiated sample consisted of a stack of several detectors (about 20–30) each 12$\mu$ thick. So chemical damages were studied according to the energy lost in each detector. Broken bonds were identified and quantified using infrared spectroscopy. In the same time we develop the same approach as proposed by Katz R. for the nuclear emulsion response. This approach is based on the hit theory, where the hits are produced by the secondary electrons removed by the incoming ion. Using this approach, neglecting any differences in the initial electron energy spectra and in the temporal aspect of energy deposition, it is surprising to simulate, with the very same parameters, the chemical cross sections from protons and oxygen ions

Chemical Bonds Broken in Latent Tracks of Light Ions in Plastic Track Detectors

When a swift ion is slowed down through a plastic detector it creates a latent track. In nuclear track detectors, this latent track can be specifically etched by an appropriate chemical solution. This enlargement process is due to a higher etch velocity (VT) along the ion\u27s path than in the non-damaged part of the detector. The etched track velocity is definitely linked to the damage created by the incoming ion in the detector material. A relationship between the physical parameters of the energy deposition and the variation in this etched track velocity with the ion energy cannot easily be explained. We present here our study on the chemical damage created by several ions in a cellulose nitrate type detector and our first attempt to simulate them by the use of the hit theory

Uranyl sorption species at low coverage on Al-hydroxide: TRLFS and XAFS studies

International audienceDetailed understanding of the respective roles of solution and surface parameters on the reactions at uranyl solution/Al-(hydr)oxide interfaces is crucial to model accurately the behaviour of U in nature. We report studies on the effects of the initial aqueous uranyl speciation in moderately acidic solutions, e.g. of mononuclear, polynuclear uranyl species and/or (potential) U(VI) colloids, on the sorption of U by large surface areas of amorphous Al-hydroxide. Investigations by Extended X-ray Absorption Fine Structure (EXAFS) and Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS) reveal similar U coordination environments on Al-hydroxide for low to moderate U loadings of sorption samples obtained at pH 4–5, independently of the presence of mononuclear or polynuclear aqueous species, or of the potential instability of initial solutions favoring true U-colloids formation. EXAFS data can be interpreted in terms of a dimeric, bidentate, inner-sphere uranyl surface complex as an average of the U surface structures. TRLFS data, however, provide valuable insights into the complex U surface speciation. They indicate multiple uranyl surface species under moderately acidic conditions, as predominant mononuclear and/or dinuclear, inner-sphere surface complexes and as additional minor species having U atoms in a uranyl (hydr)oxide-like coordination environment. The additional species probably occur as surface polymers and/or as adsorbed true U colloids, depending on the aqueous U concentration level (1–100 μM). These results are of importance because they suggest that Al-hydroxide surface characteristics strongly control uranyl surface species in moderately acidic systems

Polyvinyltoluene scintillators for relative ion dosimetry: An investigation with Helium, Carbon and Neon beams

We present a dosimeter prototype, devoted to ion beam dosimetry, tested with Helium, Carbon and Neon ions having an equivalent range in water of 150 mm. A polyvinyltoluene based plastic scintillator is used to convert the deposited energy into scintillation, a measurement probe and a long optical fibre guide the light to a photon counting unit. Using 10–40 μm thick scintillators we show that the dosimeter gain is enough to provide useful measurements, the ion-induced scintillation can be interpreted using a model taking into account the energy deposited by secondary electrons. For a practical purpose it is shown that a linear relationship can be established between the scintillation signal and the relative dose