Energetic Analysis of Experimental Behavior of Molten SnxLiy When Impacted by a Vertical Column of Water
Abstract The SnxLiy and PbxLiy, alloys are being considered as liquid breeding materials for fusion reactor applications. Thus, it is important to understand the safety implications associated with inadvertent contact with water used in an indirect cycle. In an effort to study this interaction, experiments have been conducted with these molten alloys when impacted with a vertical 2.4-m-tall column of water at 30 and 60°C. The qualitative behavior of Sn75Li25 was compared under similar conditions with other candidate molten metals, specifically tin, lead, and a lead-lithium alloy, Pb83Li17. Multiple pressure spikes were produced with Sn and Pb, while essentially only one initial pressurization followed by a few strongly damped minor peaks was observed with the different alloys containing lithium. Results with tin-lithium are quite similar to pure tin and lead behavior. Dynamic pressure traces from the physical and chemical reactions are discussed and used to compare the energetics associated with the two different alloys. The pressure traces were used to calculate experimental impulses, which represent the energetics of the reactions. The impulse ratio of the experimental and the theoretical values increased in the tests of alloys containing lithium. (Hydrogen production from lithium-water reactions was quite rapid and copious.) In contrast, hydrogen production with tin-lithium was modest and quite similar to the lead-lithium alloy. It was found that the metal-water interactions of Pb83Li17 and Sn75Li25 are quite similar and have significantly reduced energetics from those of pure lithium and other reactive metals being considered.
Liquid metal chemical reaction safety in fusion facilities
Safety implications of chemical reactions associated with postulated accident conditions with liquid metals (LM's) are discussed, along with possible prevention and mitigation techniques. The safety issues for handling lithium or 17Li83Pb are complex. However, enough is known to conclude that either LM can be safely used in deuterium—tritium fusion facilities if certain solutions can be implemented in designs at acceptable cost. The overall safety objective is to prevent significant accidental chemical reactions when possible and to mitigate the consequence of reactions that do occur. Passive design features should be used to limit maximum accident consequences, either facility damage from energy release or public health effects from radioactivity mobilization. Also, the total risk (consequence and frequency) of accidental chemical reactions should be limited. Available data on safety-related LM chemical reactions are reviewed, and the implications of reaction severity are indicated. Design suggestions and recommendations are offered to help meet safety objectives in LM fusion facilities. These suggestions are influenced by (a) the facility fluence, (b) the LM inventory, (c) the desired level of inherent/passive safety, and (d) the cost/benefit of design suggestions. Assuming a commercial-scale facility with large LM inventory with a goal of high levels of passive safety, recommendations for lithium designs include using nitrogen (rather than air) as the building atmosphere and a high reliability barrier covering concrete. Suggestions for either lithium or 17Li83Pb include eliminating water cooling within the building.
Influence of filler addition, storage medium and evaluation time on biaxial flexure strength and modulus of adhesive systems
Abstract Objective. This study evaluated the effects of filler addition, storage medium and time on biaxial flexural strength and flexural modulus of six adhesive systems. Materials and methods. The adhesives were either unfilled resins: Single Bond, Prime&Bond 2.1 and One-Step; or filled resins: Single Bond Plus, Prime&Bond NT and One-Step Plus. Resin discs of each product (0.5 mm thick × 6.0 mm diameter) were prepared using silicon molds (n = 10). The discs were stored dry, in water, mineral oil or ethanol for 1 week or 3 months before biaxial flexural testing. Data were statistically analyzed by 3-way ANOVA and Tukey's post-hoc test (α = 0.05). The specimens were tested in a universal testing machine at 1.27 mm/min until failure occurred. Results. In general, the storage in ethanol led to significantly lower flexural strength and flexural modulus values than the other storage conditions for all adhesives in both storage periods. Filler addition increased flexural strength and flexural modulus for Prime&Bond NT, when it was stored dry or in water for 1 week. For Single Bond Plus, the filler addition resulted in higher flexural modulus, when it was stored for 1 week in oil and in ethanol. No significant differences in flexural modulus were observed between One-Step and One-Step Plus in any storage medium. Conclusions. Results suggested that filler addition does not necessarily have to increase the flexural strength and flexural modulus. Ethanol and oil storages tended to yield opposite effects.