Results 1 - 10 of 367
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[en] This device attenuates the noise of cooling water droplets falling out of trickling plates below a spray facility. In this manner expensive noise-attenuating cranks or embankments around the cooling tower become unnecessary. Noise attenuation is achieved by a catching device closely above the water reservoir. Instead of falling vertically on the water surface, the droplets hit the inclined surfaces of a horizontal grid. A number of such plane or slightly curved surfaces are placed together with little inclination against the vertical (250 to 300, with a maximum of 450) at such a distance that no drop can hit the water surface directly, i.e. unattenuated. In a second type of design also the capacity of the cooling water pumps and with it the investment and operating cost is reduced. For instance, about 2000 kW are saved by higher arrangement of the catching device, closely below the trickling components. (RW)
[de]Diese Vorrichtung daempft den Laerm der aus Rieselplatten unter einer Spruehvorrichtung fallenden Kuehlwassertropfen. Hierdurch entfallen aufwendige geraeuschdaempfende Kulissen oder Erdwaelle um den Kuehlturm. Die Geraeuschdaempfung gelingt durch eine Abfangeinrichtung dicht ueber dem Wasserbecken. Anstatt senkrecht auf die Wasserflaeche fallen die Tropfen auf die schraeg gestellten Flaechen eines horizontalen Rostes. Zahlreiche solche ebene oder leicht gekruemmte Flaechen stehen mit geringer Neigung gegen die Vertikale (250 bis 300, max. 450) in solchem Abstand nebeneinander, dass kein Tropfen direkt, d.h. ungedaempft, auf die Wasserflaeche treffen kann. In einer zweiten Ausfuehrung werden auch die Kuehlwasser-Pumpleistungen und damit Investitions- und Betriebskosten reduziert. Beispielsweise rund 2000 kW werden eingespart durch hoehere Anordnung der Abfangeinrichtung dicht unter den Rieselbauten. (RW)
[en] New technological approaches need to be in place to address such concern which has significantly deteriorated public confidence in nuclear power. Such technological approach must be capable of systematically mitigate the consequence of severe nuclear accidents involving radioactivity release. An example of such approach is spray technology. In case of an accident involving radioactivity release to the environment, it may possible to deploy spray system to quickly respond to the released radioactivity and to minimize the impact of accidental releases on humans and the environment. During early phase of Fukushima nuclear accident mitigation process, water spray operations were carried out through fire trucks and military helicopters, but the primary concern of such operations was to cool down the reactor and to extinguish the fire and not to minimize the spread of radioactive materials. The aim of this research is to investigate spray technology for effective and efficient capturing of fission products released from leaked/damaged nuclear reactor to the environment. For this purpose, a systematic approach with in depth information about release phenomena and spray features will be required. Based on the information regarding release phenomena including types of materials and their amount and size, release locations, release conditions such as rates, velocities, temperature, etc., requirements for spray application is being developed including spray material types (foam, mist etc.), spray solution additives, flow rates, pressure, drop size, spray coverage area and spray duration, etc. Subsequently the efficiency and effectiveness of spray system to reduce the Dispersion of radioactivity in the environment during the course of severe accident can be characterized. This paper is a summary of our initial investigation for the use of spray technology to reduce the consequence of severe nuclear accident. An experimental investigation of iodine removal efficiency in a spray chamber is demonstrated. The spray solution of pH 13 was prepared by adding 0.5 % NaOH and 0.2 % Na2S2O3. At constant carrier gas flow rate, the iodine removal efficiency was found to increase with increasing the spray flow rate
[en] Based on the research results at home and abroad, this paper provides a brief summarisation and comments on the heat transfer characteristics, mechanisms, strengthening way and affecting parameters of spray cooling. Some theoretical models for critical heat flux are presented. And the development direction of spray cooling is proposed according to the cooling requirements of high power lasers. (authors)
[en] Spray–wall interaction is an important process encountered in a large number of existing and emerging technologies and is the underlying phenomenon associated with spray cooling. Spray cooling is a very efficient technology, surpassing all other conventional cooling methods, especially those not involving phase change and not exploiting the latent heat of vaporization. However, the effectiveness of spray cooling is dependent on a large number of parameters, including spray characteristics like drop size, velocity and number density, the surface morphology, but also on the temperature range and thermal properties of the materials involved. Indeed, the temperature of the substrate can have significant influence on the hydrodynamics of drop and spray impact, an aspect which is seldom considered in model formulation. This process is extremely complex, thus most design rules to date are highly empirical in nature. On the other hand, significant theoretical progress has been made in recent years about the interaction of single drops with heated walls and improvements to the fundamentals of spray cooling can now be anticipated. The present review has the objective of summarizing some of these recent advances and to establish a framework for future development of more reliable and universal physics-based correlations to describe quantities involved in spray cooling.
[en] High speed video imaging and an inverse heat conduction problem algorithm were used to observe and measure the effect of the angle between the nozzle and surface of a skin phantom on: (a) surface temperature; (b) heat flux q; and (c) overall heat extraction Q during cryogen spray cooling (CSC). A skin phantom containing a fast-response temperature sensor was sprayed with 50 ms cryogen spurts from a commercial nozzle placed 30 mm from the surface. The nozzle was systematically positioned at angles ranging from 5 deg. to 90 deg. (perpendicular) with respect to the phantom surface. It is shown that angles as low as 15 deg. have an insignificant impact on the surface temperature, q and Q. Only exaggerated angles of 5 deg. show up to 10% lower q and 30% lower Q with respect to the maximal values measured when nozzles are aimed perpendicularly. This study proves that the slight angle that many commercial nozzles have does not affect significantly the CSC efficiency. (note)
[en] The MAAP4 code was benchmarked against the hydrogen mixing experiment in a full-size nuclear reactor containment. This particular experiment, designated as E11.2, simulated a small loss-of-coolant-accident steam blowdown into the containment followed by the release of a hydrogen-helium gas mixture. It also incorporated external spray cooling of the steel dome near the end of the transient. Specifically, the objective of this bench-mark was to demonstrate that MAAP4, using subnodal physics, can predict an observed gas stratification in the containment
[en] According to the present invention in one aspect there is provided a nuclear fuel element comprising a cluster of nuclear fuel rods supported with their axes parallel in spaced apart relationship by transverse grids so as to define interspaces for the axial flow of coolant and having at least one of the interspaces occupied by an axially extending auxiliary coolant conduit with lateral holes through which auxiliary coolant is sprayed into the cluster and including deflection means extending from a transverse grid and located in a position in front of the holes for deflecting coolant spray onto parts of the fuel rods inaccessible to auxiliary coolant, and the deflecting means being constituted by a target plate secured to a grid and with a face of the plate positioned in the trajectory of one or more jets of auxiliary coolant from the auxiliary coolant conduit, the target plate depending vertically from a grid between two rows of nuclear fuel rods, the rods in each row being spaced at a uniform pitch, said face of the target plate being directed towards the auxiliary coolant conduit, said face being bounded by two parallel longitudinal edges which are separated by a width of plate substantially equivalent in distance to half the pitch of the nuclear fuel rods. (author)
[en] For the safety of spent nuclear fuel assemblies stored in storage pool in the extreme condition where the water is lost completely, a passive spray cooling technique was designed, and its effectiveness has been validated by a functional experiment. The spray cooling characteristics of the spent fuel assembly have also been investigated by the experiment.