Overpressure

About: Overpressure is a research topic. Over the lifetime, 3236 publications have been published within this topic receiving 34648 citations.

Simulations of the hydrogen migration out of intermediate-level radioactive waste disposal drifts using tough2

Abstract: Corrosion and radiolysis processes cause hydrogen to be generated in a repository for intermediate-level radioactive waste (ILW) for at least 10’000 years after the closure of the facility. Two model configurations have been used for the TOUGH2 simulations to investigate the impact of the hydrogen in terms of the pressure build-up and the gas saturation level in the disposal drift and in the surrounding argillaceous rock formation. 1. Cross-section (2D) through the disposal drift, perpendicular to its axis: The overpressure caused by the hydrogen has been found to be less than the expected frac pressure, for the production rate and scheme considered. 2. Longitudinal vertical section (3D) through the disposal, access and main drifts: The flow of gas/water from the disposal drift through/around the sealing plug in the access drift has been found to have limited impact on the overpressure inside the disposal drift.

Method for verifying the tightness of a tank system in a motor vehicle

Abstract: A method for verifying the tightness of a tank system, wherein an overpressure or a negative pressure is introduced into the tank system by means of a pressure source and the time curve of at least one operating parameter of the pressure source is detected when the overpressure/negative pressure is introduced up to a first point in time or until a first pressure level is reached, whereupon said operating parameter time curve is compared with an expected time curve for a tight tank. A lack of tightness is deduced if the detected time curve deviates from the diagnostic curve by at least one predefined value. The invention is characterized in that the overpressure/negative pressure in the tank system is raised until a second point in time or second pressure level is reached, and the pressure source is detected once again and compared with another expected time curve for a tight tank.

Two-step wireline log analysis of overpressure in the Bekapai Field, Lower Kutai Basin, Indonesia

Abstract: As part of our effort to improve pore-pressure estimation in diagenetically altered mudstones, we have used wireline logs to estimate disequilibrium compaction and unloading contributions to the hard overpressure encountered in the Bekapai Field, Lower Kutai Basin. The maximum vertical effective stress that the overpressured mudstones have experienced is estimated from the density log using Dutta9s relationship between vertical effective stress and void ratio. The sonic–density cross-plot is then used to estimate the sonic reference trend: that is, the expected sonic response if the mudstones were currently at maximum vertical effective stress. Finally, comparison of the sonic log with the sonic reference trend gives the unloading contribution to overpressure using Bowers’ unloading relationship between the vertical effective stress and velocity. In spite of poor data quality, fair results were obtained showing a steady increase in disequilibrium compaction overpressure below the top of the sharp pressure ramp. Immediately below the pressure ramp, the unloading contribution to overpressure dominates, with gas generation being the most likely cause. Our interpretation explains the pressure and wireline log data in this deltaic setting satisfactorily, resolving a debate on overpressure-generation mechanisms in the shelfal area of the basin that has been ongoing for 25 years.

Nucleation of Ice by Mechanical Shock

Abstract: THE frequent occurrence of heavy rainfall shortly after lightning has prompted speculation on mechanisms by which a lightning stroke might increase precipitation from clouds. One possibility is that supercooled cloud droplets are frozen by the pressure wave generated by the lightning stroke. Goyer1 estimated that the instantaneous pressure in a lightning channel would generate a shock wave equivalent to that produced by the detonation of primacord (detonating fuse). In some field experiments2, he detonated a vertical length of primacord about 100 feet from the supercooled plume of Old Faithful geyser (Yellowstone National Park, USA) and observed that a shower of ice pellets 0.5 to 1 mm in diameter fell from the plume. The calculated overpressure at the plume, being only 7 mbar, was insufficient to disrupt individual cloud droplets, so that it seemed that the supercooled cloud droplets had been induced to freeze by the passage of the shock wave. Some support for this proposal was obtained from laboratory experiments3 in which supercooled water contained in small tubes was induced to freeze by the passage of a shock wave having an overpressure of about 70 mbar.

Influence of the geometry of protective barriers on the propagation of shock waves

Abstract: The protection of industrial facilities, classified as hazardous, against accidental or intentional explosions represents a major challenge for the prevention of personal injury and property damage, which also involves social and economic issues. We consider here the use of physical barriers against the effects of these explosions, which include the pressure wave, the projection of fragments and the thermal flash. This approach can be recommended for the control of major industrial risks, but no specific instructions are available for its implementation. The influence of a protective barrier against a detonation-type explosion is studied in small-scale experiments. The effects of overpressure are examined over the entire path of the shock wave across the barrier and in the downstream zone to be protected. Two series of barrier structures are studied. The first series (A) of experiments investigates two types of barrier geometry with dimensions based on NATO recommendations. These recommendations stipulate that the barrier should be 2 m higher than the charge height, the thickness at the crest should be more than 0.5 m, while its length should be equal to twice the protected structure length and the bank slope should be equivalent to the angle of repose of the soil. The second series (B) of experiments investigates the influence of geometrical parameters of the barrier (thickness at the crest and inclination angles of the front and rear faces) on its protective effects. This project leads to an advance in our understanding of the physical phenomena involved in the propagation of blast waves resulting from an external explosion, in the area around a protective physical barrier. The study focuses on the dimensioning of protective barriers against overpressure effects arising from detonation and shows the advantage of using a barrier with a vertical front or rear face.