Search

This study investigates sorption and diffusion of Cs in two potential host rocks (granite from Kinmen Island and basalt from Penghu Island) by using batch and through-diffusion methods in order to establish a reliable safety assessment methodology. These methods were applied to crushed and intact rock samples to investigate the actual geological environment. According to solid-phase analysis, including X-ray diffraction, elemental analysis, auto radiography, and polar microscopy, the sorption component primarily contained iron-magnesium (Fe-Mg) minerals in basalt and granite. Moreover, the distribution coefficient ( K) of Cs in various concentrations (~10-10 M) obtained from batch tests indicated a higher sorption capacity in basalt than that in granite because of the 10% Fe-Mg mineral content. The diffusion of Cs in both crushed granite and basalt reached steady state after 110 days, and the apparent diffusion coefficients ( D) were 2.86 × 10 and 1.82 × 10 m/s, respectively. However, the value of D for Cs in intact rocks was estimated to be 1.45 × 10 m/s in granite and 0.56 × 10 m/s in basalt, lower than the values obtained using crushed rocks. In addition to the microporous structure (major sorption minerals), it showed that the major retardation of Cs depended on the porosity (θ) of compacted media, according to through-diffusion tests. In fact, the solid/liquid ( S/ L) ratio decreased as is the case when switching from batch to column experiments and the sorption effect on minerals became even more negligible in retardation of radionuclide migration. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of this paper aimed at the characterization of metallic composition and surface analysis on the cruds of fuel rods for unit-1 of boiling water reactor (BWR-6) at Kuosheng Nuclear Power Plant in Taiwan. The inductively coupled plasma- atomic emission spectroscopy (ICP-AES) and gamma spectrometry were carried out to analyze the corrosion product distributions and determine the elemental compositions along the fuel rod under conditions of hydrogen water chemistry (HWC) switched from normal water chemistry (NWC) of plant site in this study. Most of the crud consisted of the flakes and irregular shapes via SEM morphology. The XRD results showed that the loosely adherent oxide layer was mostly composed of hematite (α-Fe2O3) with amorphous iron oxides. The parameters of reactor water chemistry and the available mathematical model for crud deposition were utilized to interpret the chemistry effects on such crud deposition behavior. The fuel surface of this plant appeared to be one with the lower crud deposition. [Copyright &y& Elsevier]

ivity concentrations using gamma-ray spectrometer and distributions of natural radionuclides in soil samples collected were investigated to assess the environmental radioactivity and characterization of radiological hazard. The average concentrations of U, Th series and K in the 5 cm depth soil were 22.53, 33.43 and 406.62 Bq kg, respectively, which was within world median ranges in the UNSCEAR 2000 report. The average absorbed dose rate estimated by soil activity and annual effective doses were 49.32 nGy h and 60.48 μSv, respectively. Since the soil is an important building material, the mean radium equivalent activity ( Ra), external ( H) and internal ( H) hazard index using various models given in the literature for the study area were evaluated as 101.72 Bq kg, 0.27 and 0.34, respectively, which were below the recommended limits. The effects of pH value, conductivity, true density and textural properties of soil samples on the natural radionuclide levels were also studied. The application of cluster analysis (CA) and principal component analysis (PCA), coupled with Pearson correlation coefficient analysis, were utilized to analyze the data, identify and clarify the effects of physico-chemical properties on natural radioactivity levels. The CA and PCA results showed that the former method yielded three distinctive groups of the soil variables whereas the latter one yielded the number of variables into three factors with 87.5% variance explanation. [ABSTRACT FROM AUTHOR]

Abstract: Aqueous characteristics and activity concentrations of U/Th-series radionuclides were investigated in the birthplace of hokutolite – the Peito Hot Spring Area in Taiwan. Water samples were taken in 12 locations from the hot spring pond and the Peito Creek in this study. Temperature, acidity and redox potential exhibited similar trends decreasing from the hot spring pond toward downstream Peito Creek. The aqueous environment of this area existed in an acidic and oxidative state and was found influenced by hot spring water drawing and wastewater discharge. Major ions in water were Fe3+, Ca2+, Sr2+, Ba2+, Pb2+, Cl− and SO4 2−, which (except for Ba2+) generally varied with sampling locations in a tendency similar to those of temperature, acidity and redox potential. U/Th-series radionuclides were examined by α spectrometry while 226Ra were determined with ICP-QMS. Th-series was found predominant over U-series in this area. Activity concentrations of 238U (0.09±0.02 to 2.69±0.13pCi/L) and 234U (0.10±0.02 to 2.64±0.13pCi/L) were similar and the activity ratios for 234U/238U were greater than unity. For 230Th and 226Ra, the activity concentrations were respectively 0.07±0.03 to 0.86±0.06pCi/L and 0.17±0.02 to 1.49±0.06pCi/L, which led to activity ratios of 230Th/234U lower than unity while those of most 226Ra/230Th greater than unity. In Th-series, the activity concentrations of 232Th (0.06±0.02 to 0.90±0.06pCi/L) and 230Th were similar at the sampling area. Apparent disequilibria were discovered between 228Ra and 232Th resulting from abundant 228Ra (6.01±0.41 to 10.5±0.8pCi/L). The variation for activity concentration of 228Th (0.43±0.06 to 9.26±0.18pCi/L) with sampling locations was similar to that of 232Th. However, significant disequilibria were discovered between 228Th and 232Th. The reported data contribute to the assessment of radionuclides distribution and the investigation of hokutolite recovery in the studied area. [Copyright &y& Elsevier]

Abstract: Relationships between aquatic parameters and nuclide activities of uranium/thorium-series as well as radiochemical processes occurred in Peito Hot Spring Area were investigated in this research. Artificial mixing of tap water with channeled spring water were found causing temperature decrease, lowering Ra2+ concentration and inhibiting hokutolite crystallization. A novel mechanism was derived from this work to interpret the vanishment of hokutolite, which could also be applied in studying radiochemistry, migration of the radionuclides as well as the recovery and conservation of hokutolite. [Copyright &y& Elsevier]

The continued use of nuclear energy has come into question due to the difficulties in managing radioactive waste, and public opposition has increased since the Fukushima nuclear disaster in March 2011. Nonetheless, the novel spent nuclear fuel (SNF) management technologies proposed indicate new pathways toward facilitating the environment and the sustained use of nuclear energy. The reprocessing and recycling of SNF provides an alternative to direct geological disposal. In this article, we examine the current status and strategic alternatives of radioactive waste management in Taiwan. [ABSTRACT FROM AUTHOR]

Uranium- and thorium-series isotopes are able to dissolve in hot spring waters and decay into radon, which could potentially cause health risk of the public. Besides, several environmental investigations can be carried out by measuring radon concentrations in hot spring waters. Accordingly, the measurement of radon in hot spring water is a significant issue. A practical method for measuring radon in hot spring water was developed by using a silicon semiconductor detector, RAD-7. The overall effect of detection efficiency and radon leakage of the measuring system were examined to calibrate the measured concentration of radon in hot spring waters. In addition, the effect of water temperature and pH on emanation of radon from standard 226Ra solutions as well as that of the measuring time on precision of the measurement were investigated. The correlation among temperature, pH and emanation of radon was then obtained. Further, the established method was applied to in-situ measurement to investigate the concentration of radon in hot spring waters from different geological areas in Taiwan. According to the percent error of the measurement, the measuring time for environmental samples was set as 50 min. The overall effect of radon leakage and detection efficiency of the measuring system was estimated to be 99.19 ± 7.47% with a standard rock source of 222Rn from NIST. Standard sources of 222Rn were prepared from 226Ra standard solutions with different pH values. The 226Ra standard solutions were sealed and stand for 38 days in a 250 mL vial specific for the RAD-7. After measured by the WAT250 mode of the RAD-7, the data were measured as (52.5 ± 8.9)%∼(83.6 ± 11.0)% of the prepared concentration of 222Rn (from 226Ra). The emanation rate of 222Rn from standard solution under pH 1.44–9.07 was (53.2 ± 6.9)% ∼(84.3 ± 11.1)% and decreased with pH to a minimum value at 7.00. Moreover, the effect of temperature increases with pH. High correlated trend curves (r2 = 0.9829–0.9999) for 222Rn emanation rate versus pH under different temperature were obtained. A smooth curved surface fitted by the MATLAB for emanation rate of 222Rn was accordingly derived. The 222Rn concentrations in waters of the Beitou Hot Spring (acid-digestion sulfate spring on sedimentary rock strata), Wulai Hot Spring (sodium bicarbonate spring on metamorphic rock strata), Choshuitan (sodium bicarbonate spring on mudstone strata) and Zhaori Hot Spring (acid-digestion sulfate spring on andesite strata) were measured with RAD-7 by WAT250 for 50 min and then calibrated by 222Rn emanation rate estimated above, which were 215 ± 37 (Bq/m3), 6797 ± 1073 (Bq/m3), 2124 ± 577 (Bq/m3) and 26644 ± 2768 (Bq/m3). • A practical method for measuring Rn in hot spring water was developed. • Correlation among water temperature, pH and emanation of Rn was obtained. • A smooth curved surface fitted by the MATLAB for Rn emanation was derived. • This method was applied to in-situ measurement of Rn in hot spring waters in Taiwan. [ABSTRACT FROM AUTHOR]

The Geothermal Valley Hot Spring Area of Beitou in Taiwan is celebrated for is discovery of hokutolite. Ascribed to abundant radioisotopes of uranium- and thorium-series from igneous stratum in this area, the radioactivity and background radiation is important to be investigated for nearby inhabitants. In this study, measurements were carried out for gross α/β activities, radium-isotope and tritium activities in water, major naturally occurring radionuclides in soil, sludge and plants, and radon-isotope activities in air. The ambient dose rate, effective dose rate, direct radiation dose from surface of the ground as well as the annual effective dose to the public was estimated. Gross α/β activities detected in hot spring water indicated that the hot spring water is undrinkable in this area. Gamma activity in water was mainly from daughters of 228Ra and 226Ra, which decreased downstream the Beitou Creek. The activity of 3H was lower than the minimum detectable activity (MDA) at the sampling sites. The 7Be and 137Cs were rare in soil. Potassium-40 was measured in sludge, and 7Be and 4K were found in plants. Cobalt-60 was

The nuclear facilities at Institute of Nuclear Energy Research (INER) had been successively decommissioned and decontaminated over the recent years. Since dismantling was a complex task, to achieve the main goal was minimization of radioactive waste production and required the set-up of procedures, criteria of free release, strict follow-up and traceability at all steps. This study gave an overview of the efforts on non-destructive assay (NDA) of relatively large volumes of waste and the sampling of contaminated waste with radiochemical analysis was utilized to determine the radionuclide vectors. The experiences of free release planning and measurement of a very low level radioactivity with high throughput for scrapped metal at the INER and the technical achievements in this research could offer a reference of decision-making by the competent authority.

Activity concentrations and distributions of natural and man-made radionuclides in soil samples collected around nuclear power plant IV, Taiwan, were investigated for five years to assess the environmental radioactivity and characterisation of radiological hazard prior to commercial operation. The activity concentrations of radionuclides were determined via gamma-ray spectrometry using an HPGe detector. Data obtained show that the average concentrations of the (238)U and (232)Th series, and (40)K, were within world median ranges in the UNSCEAR report. The (137)Cs ranged from 2.46 +/- 0.55 to 12.13 +/- 1.31 Bq kg(-1). The terrestrial absorbed dose rate estimated by soil activity and directly measured with a thermoluminescence dosemeter (excluding cosmic rays), and the annual effective doses, were 45.63, 57.34 nGy h(-1) and 57.19 microSv, respectively. Experimental results were compared with international recommended values. Since the soil in this area is an important building material, the mean radium equivalent activity, external and inhalation hazard indices and the representative level index using various models given in the literature for the study area were 98.18 Bq kg(-1), 0.27, 0.34 and 0.73, respectively, which were below the recommended limits. Analytical results demonstrate that no radiological anomaly exists. The baseline data will prove useful and important in estimating the collective dose near the new nuclear power plant under construction in Taiwan.