Containment shields

Control exposures by engineering techniques, e.g. containment, shielding, ventilation (consider need for in-duct filters to remove contamination prior to exhausting to atmosphere), backed up by systems of work and personal protection including approved respirators where necessary. 

Dewar Any cryogenic container shielded by a vacuum-insulated space. 

The solvent has a bulk diamagnetic susceptibility that is dependent on the shape of the sample container. Thus, the solvent in a spherical container shields the solute to an extent that is slightly different from the shielding afforded by the solvent in a cylindrical container. The shielding is... 

There have been two major accidents (Three Mile Island in the United States and Chernobyl in the former Soviet Union) in which control was lost in nuclear power plants, with subsequent rapid increases in fission rates that resulted in steam explosions and releases of radioactivity. The protective shield of reinforced concrete, which surrounded the Three Mile Island Reactor, prevented release of any radioactivity into the environment. In the Russian accident there had been no containment shield, and, when the steam explosion occurred, fission products plus uranium were released to the environment—in the immediate vicinity and then carried over the Northern Hemisphere, in particular over large areas of Eastern Europe. Much was learned from these accidents and the new generations of reactors are being built to be passive safe. In such passive reactors, when the power level increases toward an unsafe level, the reactor turns off automatically to prevent the high-energy release that would cause the explosive release of radioactivity. Such a design is assumed to remove a major factor of safety concern in reactor operation, see also Bohr, Niels Fermi, Enrico AIan-HATTAN Project Plutonium Radioactivity Uranium. 

Any drop test should be conducted with the contents of the package simulated to its maximum weight. More than one drop may be necessary to evaluate all possible drop attitudes. It may also be necessary to test specific features of the package such as hinges or locks to ensure that containment, shielding and nuclear criticality safety are maintained. 

Intermediate heat sink - Air in containment, shielding water... 

The rather limited ranges of humidity, and ambient temperature and pressure preclude the positive determination of their effects on the total heat transfer to uninsulated liquid oxygen systems. It maybe concluded, however, from this study, that the controlling mechanism for heat transfer to this type of system is the outer boundary layer. In this domain, the majority of heat is transferred by convection and is primarily dependent on the temperature of the frost surface. Tlie heat transferred by radiation, though appreciable, is relatively independent of temperature and time. Container shielding could substantially decrease this quantity. Water vapor condensation accounts for but a small part of the total heat transferred and decreases to a negligible amount with increased time. 

Main control room emergency habitability system air storage cylinders (though these air cylinders are housed in the radiological auxihary building, they are included within the containment/shield building fire area). 

Environmental qualification of the safety significant SSCs within the Containment/Shield Building ensure that key safety function delivery will not be affected by extreme ambient temperature. 

The nuclear island structures include the containment (the steel containment vessel and the containment internal structure) and the shield and auxiliary buildings. The containment, shield and auxiliary buildings are structurally integrated on a common basemat, which is embedded below the finished plant grade level. 

One shortcoming of the system is that after 72 hours the Passive Containment Cooling Water Storage Tank (PCCWST) on top of the Containment Shield Building needs to be refilled. This requires active pumping. A seismically qualified tank and diesel driven pumps are to be added to the Auxiliary Building, to provide a supply of water to the PCCWST adequate for 7 days post accident (see Section 8.4.3.9 for more details). 

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