Controls shielding

Nuclear Applications. Powder metallurgy is used in the fabrication of fuel elements as well as control, shielding, moderator, and other components of nuclear-power reactors (63) (see Nuclearreactors). The materials for fuel, moderator, and control parts of a reactor are thermodynamically unstable if heated to melting temperatures. These same materials are stable under P/M process conditions. It is possible, for example, to incorporate uranium or ceramic compounds in a metallic matrix, or to produce parts that are similar in the size and shape desired without effecting drastic changes in either the stmcture or surface conditions. OnlyHttle post-sintering treatment is necessary. 

Static dissipative grades covers, guards, access panels, machine windows and doors, static control shields, glove boxes, electronic equipment, process instrumentation, conveyor line covers, clean room windows and doors, partitions and pass through modules... 

Fig. 2.59.1. Partial view of the plant shown in the schematic drawing in Fig. 2.58. 1, Chamber 2, door and temperature controlled shield 3, swiveling cover, if manipulator is not in use 4, temperature controlled shelves ...

A TSR administrative control for the hydraulic shield door keys required to operate the keyed locks will effectively control shield door operations. In addition, a TSR administrative control will be used to preclude personnel access to the north end of Room 112 when the Room 109/Zone 2A shield door is down. 

Overlapping temperature-controlled shields (not on top not on bottom if the condenser is below the chamber) ... 

The reactor refueling system (RRS) provides the means of receiving, storing, transporting, and handling reactor core assemblies. Fuel, control, shield, reflector, and ultimate shutdown assemblies are handled by the RRS for all core configuration operations. 

The isotope boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons. Boron nitride has remarkable properties and can be used to make a material as hard as diamond. The nitride also behaves like an electrical insulator but conducts heat like a metal. 

Standard commercial iastmmentation and control devices are used ia fluorine systems. Pressure is measured usiag Bourdon-type gauges or pressure transducers. Stainless steel or Monel constmction is recommended for parts ia contact with fluoriae. Standard thermocouples are used for all fluorine temperature-measuriag equipment, such as the stainless-steel shielded type, iaserted through a threaded compression fitting welded iato the line. For high temperature service, nickel-shielded thermocouples should be used. 

One feature of reprocessing plants which poses potential risks of a different nature from those ia a power plant is the need to handle highly radioactive and fissionable material ia Hquid form. This is necessary to carry out the chemical separations process. The Hquid materials and the equipment with which it comes ia contact need to be surrounded by 1.5—1.8-m thick high density concrete shielding and enclosures to protect the workers both from direct radiation exposure and from inhalation of airborne radioisotopes. Rigid controls must also be provided to assure that an iaadvertent criticahty does not occur. 

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