Short-Term Hydrogen Production Issues for Iter

Gaeta, Michael J.; Merrill, B.J.; Bartels, H.-W.; Laval, Carine Rachel; Topilski, L.

doi:10.13182/fst97-a19877

Cited by 16 publications

(6 citation statements)

References 3 publications

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“…For the test at 1100°C, the CO generation rates increase with exposure time and experience a fall off as the sample is consumed. 2 , and CO generation rates that are primarily dependent on the test temperature. The H 2 and CO 2 generation rate curves for NB31 at 800 to 1000°C were slightly different from those for NS31 at these temperatures.…”

Section: Measurements and Resultsmentioning

confidence: 99%

“…This accident type is of concern because steam interactions with hot carbon can produce significant quantities of hydrogen. As discussed by Clark et al [1], the primary steam reactions with graphite are as follows: Assessment of the consequences of such accident scenarios is typically done by means of accident model simulation [2] and the use of experimentally-derived chemical reactivity data for the various forms of carbon fiber composites that may be used in advanced tokamaks.…”

Section: Introductionmentioning

confidence: 99%

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Physical Characterization and Steam Chemical Reactivity of Carbon Fiber Composites

Anderl¹,

Pawelko²,

Smolik³

2001

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Section: Measurements and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Physical Characterization and Steam Chemical Reactivity of Carbon Fiber Composites

Anderl¹,

Pawelko²,

Smolik³

2001

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“…Moreover, the steam can react with the hot surfaces [1] and some non-condensable gases (hydrogen and oxygen gases due to the water radiolysis or thermolysis) may be mixed in it. The presence of noncondensable gases can drastically modify the phenomenon of condensation: air mixed in the steam DCC has been only marginally studied and only in atmospheric conditions [2].…”

Section: Figure 1: Section View Of the Vvpssmentioning

confidence: 99%

Effect of non-condensable gas in steam condensation at sub-atmospheric pressure condition

Giambartolomei

Pesetti

Raucci

et al. 2022

J. Phys.: Conf. Ser.

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In the International Thermonuclear Experimental Reactor (ITER), a postulated Loss Of Coolant Accident (LOCA) in the Vacuum Vessel (VV) has to be managed with a pressure suppression system working at sub-atmospheric pressure. The operating conditions considerably differ from those experienced in the fission nuclear power plants such as BWR, since the ITER Tokamak works at very low pressure conditions and can withstand a maximum pressure of 0.15 MPa. For this reason, the pressure value must not exceed 10 kPa for a water temperature of 30 °C inside the Vapour Suppression Tanks (VSTs) that are the fundamental components of the Vacuum Vessel Pressure Suppression System (VVPSS). During a LOCA some non-condensable gases (mainly hydrogen and oxygen gases due to the water radiolysis or thermolysis) may be mixed in the steam and this could impair the condensation efficiency. In order to investigate the effects of non-condensable gas on DCC, we conducted a research program funded by ITER Organization at the laboratory of the University of Pisa: we designed and built a small-scale experimental rig to study the steam Direct Contact Condensation (DCC) with the presence of non-condensable gas and simulate the behaviour of a VST. Since DCC can occur with different characteristics, we ran 12 closed mode tests exploring all condensation regimes injecting a certain mass of air with the steam discharged in the subcooled water. The tests started at the saturation pressures corresponding to water temperatures ranging from 40 °C to 80 °C and ended when the free space volume reached the atmospheric pressure. From the analysis of the data acquired during the tests we observed that the condensation efficiency remained higher than 95%. We observed that despite this, the presence of a certain quantity of non-condensable gas has negative aspects on condensation: the condensation regime never reaches stability (the regimes quickly shift towards instability). Furthermore, the presence of air triggers a turbulence of the flow which interferes with the transfer of heat from the steam to the water. Not only the introduction of air into the flow increases linearly the pressure above the water head but its high temperature further contributes to the pressure increase. The air mixed with the flow also forms eddies that can trap the steam and transport it out of the water, preventing it from condensing. Apart from condensation, the most noticeable problem is the rapid increase in pressure inside the condensation tank.

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“…For fusion, with its metal dusts, safety analyses have recognized the issue that the dust layer will likely react before the solid wall materials. Gaeta (1997) calculated steam reactions with 50 micron beryllium dust, for invessel LOCA events, and found that the reaction would generate ~2 kg of hydrogen gas in the vacuum vessel for ITER. Rhein (1965) and There is little industrial testing information published about steam reactions; apparently there are few industrial situations where metal powders or dusts contact a steam atmosphere.…”

Section: Combustion In Gases Other Than Airmentioning

confidence: 99%

Dust Combustion Safety Issues for Fusion Applications

Cadwallader¹

2003

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This report summarizes the results of a safety research task to identify the safety issues and phenomenology of metallic dust fires and explosions that are postulated for fusion experiments. There are a variety of metal dusts that are created by plasma erosion and disruptions within the plasma chamber, as well as normal industrial dusts generated in the more conventional equipment in the balance of plant. For fusion, in-vessel dusts are generally mixtures of several elements; that is, the constituent elements in alloys and the variety of elements used for in-vessel materials. For example, in-vessel dust could be composed of beryllium from a first wall coating, tungsten from a divertor plate, copper from a plasma heating antenna or diagnostic, and perhaps some iron and chromium from the steel vessel wall or titanium and vanadium from the vessel wall. Each of these elements has its own unique combustion characteristics, and mixtures of elements must be evaluated for the mixture's combustion properties. Issues of particle size, dust temperature, and presence of other combustible materials (i.e., deuterium and tritium) also affect combustion in air. Combustion in other gases has also been investigated to determine if there are safety concerns with "inert" atmospheres, such as nitrogen. Several coolants have also been reviewed to determine if coolant breach into the plasma chamber would enhance the combustion threat; for example, in-vessel steam from a water coolant breach will react with metal dust. The results of this review are presented here.ii SUMMARY This report presents some data on metal dust explosions, and limits of metal dust combustibility. Fusion experiments generate armor tile and metal-component dusts during plasma-material interactions, and these dusts accumulate in the vacuum vessel. The safety issues with these dusts are examined here. The dusts tend to be chemically toxic, neutron activated, and may contain tritium if the fusion experiment uses tritium fuel. Past chemical reaction work has examined the oxidation-driven mobilization of solid wall materials, because these materials comprise the majority of the in-vessel inventory. The dust may actually react before the bulk wall materials due to its higher surface area and its dispersion in the vacuum vessel volume. Loss of vacuum accident (LOVA) modeling has shown that dust can be lofted within the vacuum vessel by inrushing air, and there are a number of possible ignition mechanisms energetic enough to initiate a dust deflagration event. The ignition mechanisms identified here are electrostatic discharge, radiant heating of particles, laser ignition, and plasma heating antenna arcing. Since the fusion conditions are elevated temperature and dust-air mixtures at one atmosphere pressure, industrial studies also apply to fusion LOVA dust analyses.Most of the metal dusts require reasonably high temperatures for autoignition (i.e., 500 -700°C), or spark ignition energies in the 1 millijoule range. Metal dusts will deflagrate, that is, combust with a subs...

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Short-Term Hydrogen Production Issues for Iter

Cited by 16 publications

References 3 publications

Physical Characterization and Steam Chemical Reactivity of Carbon Fiber Composites

Physical Characterization and Steam Chemical Reactivity of Carbon Fiber Composites

Effect of non-condensable gas in steam condensation at sub-atmospheric pressure condition

Dust Combustion Safety Issues for Fusion Applications

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