a b s t r a c tExposure of polytetrafluoroethylene (PTFE) to a-radiation was investigated to determine the physical and chemical effects, as well as to compare and contrast the damage mechanisms with other radiation types (b, g, or thermal neutron). A number of techniques were used to investigate the chemical and physical changes in PTFE after exposure to a-radiation. These techniques include: Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and fluorescence spectroscopy. Similar to other radiation types at low doses, the primary damage mechanism for the exposure of PTFE to a-radiation appears to be chain scission. Increased doses result in a change-over of the damage mechanism to cross-linking. This result is not observed for any radiation type other than a when irradiation is performed at room temperature. Finally, at high doses, PTFE undergoes mass-loss (via small-fluorocarbon species evolution) and defluorination. The amount and type of damage versus sample depth was also investigated. Other types of radiation yield damage at depths on the order of mm to cm into PTFE due to low linear energy transfer (LET) and the correspondingly large penetration depths. By contrast, the a-radiation employed in this study was shown to only induce damage to a depth of approximately 26 mm, except at very high doses.

In this study, actinide oxides (plutonium, uranium, neptunium, and americium oxides) were imaged to enable characterization of their morphology, particle size, cathodoluminescence (CL) signal, and trace elemental content using a scanning electron microscope equipped with a cathodoluminescence detector. Unexpectedly, neptunium oxide (NpO 2 ) powder was found to have two unique CL signals [1][2][3]. The NpO 2 powder was analyzed via energy dispersive spectrometry to identify which elements were present with the hope of determining the origin of the two CL signals. This analysis determined that magnesium (Mg), chlorine, and calcium (Ca) were the elements that caused the multiple CL signals. These samples were also analyzed in the electron microprobe. While undergoing electron probe microanalysis (EPMA), some of the particles could be seen fluorescing in the optical microscope on the microprobe, see Figure 1. An attempt was made to capture an image of the fluorescing NpO 2 particle prior to determining the distribution of neptunium via wavelength dispersive spectroscopy. This particle was damaged by the beam after a short time, see Figure 2.These initial studies have resulted in the need to expand the research project and develop the use of CL element distribution imaging. Since some materials emit CL signals, i.e. characteristic secondary electron excitation in the visual light spectrum, it is expected that CL can be used as another technique to identify trace elements [4]. Based on the initial study, it is anticipated that CL imaging will be faster than traditional EPMA mapping. However, to ensure that the CL signals have been correctly identified, the next analysis will be verification of the CL signals using elemental standards. Once the CL signals are verified, CL imaging of fuel pellets can be used to reveal the distribution of the actinide elements as well as the non-actinide elements. These analyses will confirm that CL imaging can be a viable tool and provide complementary data to supplement traditional mapping techniques.