Polykast is a dry-mix material widely used for casting into closed containers. Polykast is field-castable and provides excellent and cost effective neutron shielding. It has a very high hydrogen content - 6% greater than that of water - and contains boron to suppress radiation from capture-gamma rays. SWX-259 has 0.9% boron, while SWX-259Z-4 contains 4% boron for better thermal neutron attenuation. Polykast has been used in a variety of shielding wall barriers, and even an entire four-foot thick roof for a cyclotron facility.
No special tools or skilled labor are needed, Polykast only requires mixing with water. It sets up within 30 minutes of casting into a strong solid material. Sealing the container immediately after casting maximizes the water, and hence the hydrogen, content. This material may be poured in as many layers as required, as each layer bonds readily to the previous one. 56 lbs of dry-mix powder will cast one cubic foot.
The recommended temperature limit for Polykast is 150° F (66° C). When held at this temperature for extended periods, it loses only about 7% of its hydrogen content. Even at 300° F (149° C), it retains 80% of its hydrogen. Polykast is available in multiples of 165 pounds and has a shelf life of six months, under dry storage conditions. Other formulas are available to increase boron content.
Boron-Silicone is a fire-resistant, heat-resistant, field-castable elastomer with a high hydrogen content (67% of water's). It is self-extinguishing and will withstand temperatures up to 400° F (205° C) for extended periods while retaining 90% of its hydrogen. Boron-Silicone contains 1% boron for thermal neutron capture and the suppression of capture-gammas.
Other boron concentrations can be supplied upon request.
SWX-237-0 Poly-Substitute is a boron free version of the standard silicone elastomer mix, boasting the same physical properties, including the high hydrogen content and self-extinguishing nature. It is frequently used when fire and temperature restrictions prevent the use of HDPE.
Although this is a solid material, its resiliency will minimize any impact due to secondary missile formation. Its density is 1.59 g/cc (99 lbs./cu ft).
Boron-Silicone is available in a variety of shapes and sizes. For example, Shieldwerx has provided large pre-cast rings for use as a biological neuron shield for coolant recalculating lines. The material has also been used in the manufacture of
large fuel transportation and as reactor cavity shield
plugs where the customer cast 9,000 pounds of the material, on-site, for use as a sacrificial shield. Another customer cast the Silicone Mix into shipping containers for spent fuel storage.
SWX-237 2" samples
High temperature resistance is a frequent requirement for power reactor shielding. Kretekast is a refractory material designed to retain a significant portion of its shielding properties at temperature up to 450°F (230°C). This material will maintain its physical integrity at temperatures up to 1900°F (1038°C). In addition, this rugged material is completely non-combustible and can be easily cast in the field. Its compressive strength is 1000 psi (90 BAR).
Kretekast is well suited to attenuate the neutron flux from power reactors by the inclusion of hydrogen and boron in the forms of temperature-resistant additives. It incorporates approximately three times as much hydrogen as ordinary concrete, making the material far superior for neutron shielding applications. The hydrogen concentration - which moderates fast neutrons - is approximately one-half that of water. The refractory matrix also provides good resistance to heat.
Standard Kretekast has a boron content of 1.6% and type 277Z-5 contains 5%. It is also available in other concentrations of boron or can be made to be boron-free and used as a poly-substitute.
Type 277 is offered in the form of dry mix for casting in place, but can also be supplied in pre-cast shapes. Customers often use 277 in the ES-3100 storage casts. It is readily shaped with ordinary concrete-strength power tools (e.g., band saws or drills). Kretekast Dry Mix is available in 300 pound (136kg) drums.
Quantities Required to Cast One Cubic Foot:
Type Dry Mix
237 99 lbs
259 56 lbs
277 96 lbs
On-site casting is sometimes the only way to achieve the desired shielding. Our castable shielding products can be used to fill walls, surround spent fuel and withstand enormous pressures and temperatures.
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