[en] The Fuel Cycle and Materials Administration (FCMA) in Taiwan announced a Supplementary Regulation for Classification of Low Radioactive Wastes, as well as the Regulation for Disposing of Low Radioactive Wastes and its Facility Safety Management in July 17, 1997, and September 10, 2003, respectively. The latter regulation states that in the future, before delivering low-level radioactive waste to a final land disposal site, each waste drum must specify the nuclide activity and be classified as class A, B, C or greater than C. The nuclide activity data for approximately 100,000 drums of low-level radwaste at the Lan-Yu temporary storage site accumulated in 1982-1995, therefore, must be established according to the above regulations. The original waste database at the Lan-Yu site indicates that the data were absent for about 9% and 72% of Co-60 and Cs-137 key nuclide activities, respectively. One of the principal tasks in this project was to perform whole drum gamma radioactivity analysis and contact dose rate counting to establish the relationship of dose-to-curie (D-to-C) of specific waste stream to derive gamma radioactivity of counting drums for 2 trenches repackaged at the Lan-Yu site. Utilizing regression function of Microsoft Excel and collected gamma data, a dose-to-curie relationship for the whole-drum radwaste is estimated in this study. Based on the relationship between radioactivity of various nuclides and the surface dose rate, an empirical function of the dose rate (Dose) associated with product of nuclide activity (Curie) and energy (Energy), CE is set up. Statistical data demonstrated that 838 whole drums were counted employing D-to-C approach to classify other 3,279 drums, and only the contact dose rate was detected for roughly 75% of the drums to estimate gamma radioactivity of whole drums, which can save considerable cost, time, and manpower. The 4,508 drums were classified as A and 7 drums as C after repackaging was complete. The estimation of D-to-C relationship was near 80% in those sorted drums. This methodology can provide a simple, easy and cost-effective way for inferring gamma nuclide activity. (authors)

[en] We report on the performance of small gap MSGCs. The maximum gain for small gap MSGCs is about 1000. Small gap MSGCs with anode width of 3 μm at low rate (similar 10 Hz/mm²) have good operational stability. The gas gain varies less than ±1% during a 20 h period. (orig.)

[en] This study was conducted using batch and column methods in order to investigate the sorption and diffusion of cesium (Cs) for two potential host rocks in Taiwan: argillite from Taitung site and granite from Kinmen Island, with the purpose of establishing a reliable safety-performance assessment methodology for the final disposal of spent nuclear fuel. The methods were applied on crushed rock samples to simulate the in-situ geological environment. The mineral component and basic characteristics of the host rock samples were obtained using solid-phase analyses, i.e., X-ray diffraction (XRD), elemental analysis, N₂-BET surface area analysis, and cation exchange capacity (CEC). Furthermore, the distribution coefficients (K_d) of Cs were obtained using batch tests with various sample grain size. The results showed that higher sorption capacities were found for argillite than granite; due to the higher clay mineral content in the argillite. Experiments for diffusion of Cs both in crushed argillite and granite were also conducted. The apparent diffusion coefficients (D_a) were analysed and plotted as accumulating curves, respectively. However, the values estimated for the diffusive results (D_a) of Cs in argillite were revealed to be lower than those of granite. In addition, the diffusive results showed that the major retardation factor (R_f) of Cs was dependent upon the micro-porous structure of the tested media, e.g., a decrease in constrictivity (δ) and an increase in tortuosity (τ). The solid/liquid ratio, in fact, decreased, as it was in the case when switching from the batch method to a through-diffusion experiment, of which the analysis results indicated that the sorption effect on the minerals was even more negligible in regard to the retardation of radionuclide migration. (authors)