Shielding materials

KNK-n (Germany) gray iron high density concrete 

PEC (Italy) nikel reflector elements and B4C shield elements high density concrete 

JOYO (Japan) stainless steel graphite, concrete 

DFR(UK) steel and borated graphite,top plugs only borated graphite concrete 

BOR-60 (Russian Federation) stainless steel cast iron and high density concrete 

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Elastomeric shield materials (ESM) have been developed as low density flexible ablators for low shear appHcations (49). General Electric s RTV 560 is a foamed silicone elastomer loaded with silicon dioxide [7631-86-9] and iron oxide [1317-61 -9] particles, which decomposes to a similar foam of Si02, SiC, and EeSiO. Silicone resins are relatively resistant to thermal decomposition and the silicon dioxide forms a viscous Hquid when molten (50) (see... 

Exposure is minimized by ehoiee of souree, by duration of exposure, by distanee from souree (at 1 m die radiation level is redueed almost 10-fold), and by shielding. The greater die mass per unit area of shield material die greater die shielding effieieney. Whereas a- and (3-partieles pose few problems (die former ean be absorbed by, e.g., paper and die latter by 1 em Perspex) y- and X-rays are not eompletely absorbed by shield material but attenuated exponentially sueh dial radiation emerging from die shield is given by ... 

D, is the dose rate emerging from a shield of thiekness t u is the linear absorption eoeffieient of shield material. 

Table 11.5 Approximate half-thickness values for a selection of shield materials and y-emitters...

Combining Tr + Tr for a point source gives equation 8.3-10. Radiation is attenuated by the distance from the source, the shielding material for the type of radiation and the thickness of shield that it must penetrate. 

Tabulated buildup factors depend on the type of primary radiation, the energy, E, of the primary radiation, the charge, Z, atomic number, A, and thickness of the shielding material. 

The next factor in the shield design is to design for prevention of fragment penetration of the shield material. 

Time and shielding can be merged into a single factor. The shelters described in Section 5.2.1 (walls, basements, etc.) really serve as shields from radiation, heat, fallout, and even from the air blast and flying debris. At the moment of explosion, radiation and heat travel at the speed of light and expose unshielded victims. At the instant of realization that a nuclear weapon has exploded, an individual should move as quickly as possible to a location behind a rugged shielding material. 

Shielding material can be brick, concrete, steel, wood, or even the earth. Ideally, the shielding material will not collapse from the explosion or air blast or burn from the heat. If available, an underground shelter is the best option to avoid the air blast, thermal burns, initial radiation, and fallout. However, most victims do not have time to be terribly selective about where to seek shelter. The innermost rooms of a building may be the only shelter available. While they do not provide the same level of shielding as an underground basement, they provide more protection than an open environment. Seek the best shield in the immediate vicinity and stay there at least several minutes until the initial radiation and heat subside. 

Because the neutron direction is known, the FNAP approach does not require the use of coUimators to focus the incident beam and there is no need to pulse the source. However, as the neutrons are emitted in an essentially isotropic distribution, many neutrons still fail to impact the target bag and neutron shielding is needed in aU directions surrounding the source and bag regions. In addition, the scattering of the neutrons in the shielded material along with the resulting inelastic and capture... 

The U.S. Department of Energy (DOE) found the cost to dispose of depleted uranium hexafluoride ranged from 4 to 12 billion. As an alternative to disposal, INEEL developed a concept of converting depleted uranium into an oxide aggregate material for use in cement. This cement material is known as Ducrete cement and is used as a shielding material (D202937, p. 1). 

Radiation shielding materials Optical and electronic devices... 

Examples of conductive ABS polymer composites include electromagnetic shielding materials (56,57) and electrically conductive composite plastic sheets, which may be used for packaging of integrated circuit devices (58,59). 

Here four factors are seen as the major contributors to the detector background rate. They are (a) the cosmic ray shield, (b) the atmosphere surrounding the detector, (c) the detector itself, and (d) the cosmic rays. For the cosmic ray shield about the detector, it is advisable to use old or virgin lead, that is, lead that was purified over 100 years ago, thus allowing any 210Pb present to decay. One should expect 1 cpm/g shield material. Iron can also be used in constructing the detector... 

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