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Hydrogen peroxide (H2O2), an oxidizer produced by water radiolysis, is considered one of the main contributors to corrosion of the stainless steel (SS) components in the cooling system of nuclear reactors. The detailed understanding of this chemical system is however still missing. The present research aimed to study the effects of H2O2 on 304 SS. The surface morphology and the chemical composition of the SS specimens after experiment were examined using Scanning Electron Microscope – Energy Dispersive X-ray (SEM-EDX). The change in atomic % of Fe, Cr, Ni, and O as a function of temperature will be reported. The corrosion type and possible corrosion products will be proposed and discussed.

In this study, a prototype of commercialized-style radiation shielding blocks based on natural rubber mixed with radiation shielding substance (i.e. lead and tungsten compound) was developed. The gamma shielding test was carried out using 137 Cs (662 keV) source and 60Co (1173, 1332 keV) source. The results reveal that based on the gamma attenuation property and forming capability, the optimum formula was a shielding block with 60% lead oxide, which was able to completely shield gamma radiation (> 99%). In comparison with a radiation shielding block with lead oxide, a radiation shielding block with tungsten oxide showed similar characteristics. Due to the higher price of tungsten oxide, natural rubber block with lead oxide is preferred. However, with an environmental concern, natural rubber block with tungsten oxide is selected. Moreover, it was found that the mechanical properties of these radiation shielding blocks (including hardness, tensile strength and elongation at break) were reduced with increasing of the amount of radiation shielding substance mixed in the radiation shielding blocks. However, the reduction of these mechanical properties does not affect the actual utilization since these radiation shielding blocks are normally not subjected to any strong force or pressure. In addition, the SEM images showed the uniform dispersion of radiation shielding substances in the rubber block texture.

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The handheld X-ray fluorescence spectrometer (hXRF) was applied to major element analysis in the geological samples and the results were compared with the results of the wavelength dispersive X-ray fluorescence spectrometer (WDXRF). In addition, the analytical compositions were confirmed by X-ray diffractometer (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). In the case of pXRF analysis, eight geological reference materials were used to calibrate the analytical method and four known concentration samples were used to prove the method. In research, ten geological samples from Phuket province, Thailand were collected with different depths corresponding to O horizon (0-0.1 m), A horizon (0.1-0.3 m), B1 horizon (0.3-1.0 m), B2 horizon (1.0-2.0 m), C1 horizon (2.0-3.0 m), C2A horizon (3.0-5.0 m), C2B horizon (5.0-8.0 m), C3 horizon (8.0-12.0 m), D horizon (12.0-20.0 m) and RK horizon (> 20.0 m). The elemental analysis results showed that the pXRF results were matched well with that WDXRF results. The concentration range in ten samples were Si (18-22 wt%), Al (12-15 wt%), Fe (1-4 wt%), K (0.4-3.2 wt%) and Ti (0.2-0.4 wt%). The concentration of some elements such as Ca and Mg on those ten samples are low and they are unable to analysed by hXRF. The XRD patterns revealed that all samples consisted of quartz, kaolinite, halloysite, illite, vermiculite and biotite.

Abstract. The measurement of moisture content in soil is based on the principle of neutron back scattering. In this principle, when fast neutrons emitted from a radioactive source collide with hydrogen atoms their energies are much greater reduced than colliding with other elements. The number of slowed down neutrons, hence, represents the number of hydrogen atoms present in the vicinity of the source. As water is the main contributor of hydrogen atoms in a soil medium, the moisture content in soil, therefore, can be measured based on this principle. An in-house developed probe containing a source of fast neutrons and a slow neutron detector was inserted into soil at different depths under the ground level. The probe was made of high density polyethylene and connected to a suitably calibrated detection system by a single cable. The moisture content was determined from the slow neutron count rate. The results of field measurement tests were reported and discussed.

The performance of neutron tomography facility at the Thai Research Reactor TRR-1/M1 is studied. Thermal neutron beams with a flux of 106 n/cm2/s are employed to radiate on a standard sample, so-called Strip B, in the test. The neutron irradiating on samples were detected by a neutron-to-photon conversion plate. After that, the low-energy photons were guided to a charge coupled device (CCD) to obtain a digital image. During the experiment, a rotation stage was used to rotate the sample in order to measure the attenuated/scatted neutrons at different angles with respect to the sample geometry. The angle-varied images were then processed via a reconstruction software to create a 3-dimension (3D) image (tomography). The result shows that an image of 0.5 mm-diameter cadmium wire could be observed by employing our facility, but the sharpness of the 3D image is still needed to be further improved.