Steam Chemical Reactivity of Be Pebbles and Be Powder
TL;DR: In this paper, the results of chemical reactivity experiments for Be pebbles (2-mm and 0.2mm diameter) and Be powder (14-31 pm diameter) exposed to steam at elevated temperatures were reported.
Abstract: This paper reports the results of chemical reactivity experiments for Be pebbles (2-mm and 0.2-mm diameter) and Be powder (14-31 pm diameter) exposed to steam at elevated temperatures, 350 to 900°C for pebbles and 400 to 500°C for powders. We measured BET specific surface areas of 0.12 m 2 /g for 2-mm pebbles, 0.24 m 2 /g for 0.2-mm pebbles and 0.66 to 1.21 m 2 /g for Be powder samples. These experiments showed a complex reactivity behavior for the material, dependent primarily on the test temperature. Average H 2 generation rates for powder samples, based on measured BET surface areas, were in good agreement with previous measurements for fully-dense CPM-Be. Rates for the Be pebbles, based on measured BET surface areas, were systematically lower than the CPM-Be rates, possibly because of different surface and bulk features for the pebbles, especially surface-layer impurities, that contribute to the measured BET surface area and influence the oxidation process at the material surface.
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TL;DR: In this article, the principal types of materials that have some role in safety are recalled, which either represent a potential source of hazard or contribute to the amelioration of hazards; in each case the related issues are reviewed.
Abstract: Fusion power holds the promise of electricity production with a high degree of safety and low environmental impact. Favourable characteristics of fusion as an energy source provide the potential for this very good safety and environmental performance. But to fully realize the potential, attention must be paid in the design of a demonstration fusion power plant (DEMO) or a commercial power plant to minimize the radiological hazards. These hazards arise principally from the inventory of tritium and from materials that become activated by neutrons from the plasma. The confinement of these radioactive substances, and prevention of radiation exposure, are the primary goals of the safety approach for fusion, in order to minimize the potential for harm to personnel, the public, and the environment. The safety functions that are implemented in the design to achieve these goals are dependent on the performance of a range of materials. Degradation of the properties of materials can lead to challenges to key safety functions such as confinement. In this paper the principal types of material that have some role in safety are recalled. These either represent a potential source of hazard or contribute to the amelioration of hazards; in each case the related issues are reviewed. The resolution of these issues lead, in some instances, to requirements on materials specifications or to limits on their performance.
33 citations
TL;DR: The technical challenges resulting from the choice of water coolant and the differences in approach and assumptions that lead to different design decisions amongst researchers in this field are summarized.
25 citations
TL;DR: A review of results of some fusion safety studies performed in Russia during 1996-2000 (after the 6th IAEA Technical Committee Meeting on ‘Developments in Fusion Safety’) is reported in this paper.
11 citations
01 Nov 2001
TL;DR: In this paper, thermogravimetric experiments were conducted to study the beryllium pebbles' behavior when exposed to air in the temperature region 400-900 °C.
Abstract: In the design of the European Helium-Cooled Pebble Bed (HCPB) Blanket, the use of beryllium as a neutron multiplier in the form of a pebble bed is foreseen. In the development of the pebble bed, kinetic data are needed for the reaction between the beryllium pebbles and air. Therefore, thermogravimetric experiments were conducted to study the pebbles' behaviour when exposed to air in the temperature region 400–900 °C. The material tested consisted of beryllium pebbles produced by the Rotating Electrode Method. At temperatures up to 700 °C, the reaction kinetics is approximately parabolic, although a deviation from parabolic behaviour is observed after approximately 6000 s of air exposure. Above 700 °C, a combination of paralinear and accelerating behaviour is observed. From the experimental results the appropriate rate constants were determined by curve fitting.
9 citations
TL;DR: In this paper, the authors present the results of a screening investigation that compares the oxidation rates of tungsten, molybdenum, carbon fiber reinforced composites (CFC), CFC and beryllium in the temperature range 300-700°C.
8 citations
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24,580 citations
TL;DR: In this paper, the influence of neutron irradiation effects and annealing on the chemical reactivity of beryllium exposed to steam was investigated, and the results indicated that the porosity network of irradiated and unirradiated Be increased with the anneal temperature.
32 citations
TL;DR: In this paper, the reaction rates for fully dense and porous 88% dense beryllium in steam between 600 and 1230°C were determined for the porous material were 200 times higher than those for solid material at comparable temperatures.
20 citations
TL;DR: In this article, the influence of neutron irradiation effects on the chemical reactivity of beryllium exposed to steam was investigated, and the results indicated a significant enhancement in the chemical reactionivity at 700°C.
Abstract: This paper reports the results of an experimental study to determine the influence of neutron irradiation effects on the chemical reactivity of beryllium exposed to steam. The study entailed measurements of the following: (1) swelling of irradiated Be specimens annealed at temperatures ranging from 450°C to 1200°C, (2) hydrogen generation rates for unirradiated Be control specimens exposed to steam at temperatures from 450°C to 1200°C, and (3) hydrogen generation rates and tritium mobilization rates for irradiated Be exposed to steam at temperatures from 450°C to 700°C. For irradiated Be, swelling occurred at temperatures above 600°C and it increased to about 56% for an anneal temperature of 1200°C. Tritium and 4He were released concurrently from specimens that were annealed at 800°C and above. Steam-Be reactivity measurements for the control specimens were consistent with previous work at temperatures above 700°C, and the new measurements extended the reactivity database down to 450°C. Steam-reactivity measurements for irradiated Be were comparable to control specimens for 600°C and below, but, they indicated a significant enhancement in the chemical reactivity at 700°C.
14 citations
TL;DR: In this paper, an experimental system developed to investigate steam-metal reactions important to fusion technology is described, which is configured specifically to measure hydrogen generation rates and can be used for measuring hydrogen generation rate.
Abstract: This paper describes an experimental system developed to investigate steam-metal reactions important to fusion technology. The system is configured specifically to measure hydrogen generation rates...
11 citations