ABSTRACT
A laser-induced-breakdown-spectroscopy (LIBS) experiment with a unique double-pulse setup and operated in low-pressure (3 kPa) He ambient gas is performed to study the detection of light elements, such as hydrogen (H) and deuterium (D), as well as elements of high excitation energies, such as fluorine (F) and chlorine (Cl), which are usually difficult to detect using ordinary LIBS techniques. A nanosecond Nd:YAG laser operated in its fundamental wavelength with energy of 54 mJ is focused onto the Al target to generate the He plasma. Another picosecond Nd:YAG laser operated in its fundamental wavelength with energy of 2 mJ is focused onto the sample surface and activated 2 µs before the operation of the nanosecond laser. The application to polyvinyl chloride (PVC) and polytetrafluoroethylene (PTFE) samples produces sharp and high-intensity Cl- and F-emission lines. Meanwhile, the sharp and well-resolved H-D-emission lines with merely 0.18 nm wavelength separation are also clearly detected from a zircaloy sample. Further measurement of a set of zircaloy samples containing different concentrations of D yields a linear calibration curve with a zero intercept. The detection limit of D is found to be about 10 ppm.
ABSTRACT
A crucial safety measure to be strictly observed in the operation of heavy-water nuclear power plants is the mandatory regular inspection of the concentration of deuterium penetrated into the zircaloy fuel vessels. The existing standard method requires a tedious, destructive, and costly sample preparation process involving the removal of the remaining fuel in the vessel and melting away part of the zircaloy pipe. An alternative method of orthogonal dual-pulse laser-induced breakdown spectrometry (LIBS) is proposed by employing flowing atmospheric helium gas without the use of a sample chamber. The special setup of ps and ns laser systems, operated for the separate ablation of the sample target and the generation of helium gas plasma, respectively, with properly controlled relative timing, has succeeded in producing the desired sharp D I 656.10 nm emission line with effective suppression of the interfering H I 656.28 nm emission by operating the ps ablation laser at very low output energy of 26 mJ and 1 µs ahead of the helium plasma generation. Under this optimal experimental condition, a linear calibration line is attained with practically zero intercept and a 20 µg/g detection limit for D analysis of zircaloy sample while creating a crater only 10 µm in diameter. Therefore, this method promises its potential application for the practical, in situ, and virtually nondestructive quantitative microarea analysis of D, thereby supporting the more-efficient operation and maintenance of heavy-water nuclear power plants. Furthermore, it will also meet the anticipated needs of future nuclear fusion power plants, as well as other important fields of application in the foreseeable future.
ABSTRACT
During a preliminary survey on xerophthalmia in North Sumatra, Indonesia, a total of 1754 children of 0-6 years of age were examined clinically as well as with a vital staining technique, using Rose-Bengal 1%-Fluorescein sodium 1% eyedrops. Differences in prevalence were found between children from the rural villages, from Gunung Pamela rubber estate and from one Health Centre and two kindergartens in Medan town. None of the children in the estate and in Medan had Bitot spots or acute corneal involvement; conjunctival xerosis (XIA) was found in 28% among boys and 11% among girls at the rubber estate, whereas in Medan only 1% had XIA. In the village, the calculated minimum point prevalence rates for X1B, X2 + 3 and XS were respectively 0.29%, 0.16% and 0.45% for age-group 0-6 years, sexes combined. According to WHO criteria xerophthalmia should, therefore, be considered of public health importance in the rural area visited. The potential use of the vital staining technique in early diagnosis of xerophthalmia is discussed. WHO criteria for assessment of the magnitude of the xerophthalmia problem as well as the guidelines for xerophthalmia surveys from the International Vitamin A Consultative Group have been analysed in this survey as a casestudy.
