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Nuclear Criticality Safety
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Las Vegas, NV|Mandalay Bay Resort and Casino
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Fusion Science and Technology
Latest News
Zap Energy hits 37-million-degree electron temperatures in compact fusion device
Zap Energy announced April 23 that it has reached 1-3 keV plasma electron temperatures—roughly the equivalent of 11 to 37 million degrees Celsius—using its sheared-flow-stabilized Z-pinch approach to fusion. Reaching temperatures above that of the sun’s core (which is 10 million degrees Celsius temperature) is just one hurdle required before any fusion confinement concept can realistically pursue net gain and fusion energy.
Z. D. Whetstone, K. J. Kearfott
Nuclear Technology | Volume 176 | Number 3 | December 2011 | Pages 395-413
Technical Paper | Radiation Transport and Protection | doi.org/10.13182/NT10-118
Articles are hosted by Taylor and Francis Online.
This research was conducted to determine the optimal way to shield a compact, isotropic neutron source into a beam for active interrogation neutron systems. To define the restricted emission angle and to protect nearby personnel when stand-off distances are limited, shielding materials were added around the source. Because of limited space in many locations where active neutron interrogation is employed, a compact yet effective design was desired. Using the Monte Carlo N-Particle Transport Code, several shielding geometries were modeled. Materials investigated were polyethylene, polyethylene enriched with 10B, water, bismuth, steel, nickel, INCONEL® alloy 600, tungsten, lead, and depleted uranium. Various simulations were run testing the individual materials and combinations of them. It was found that at a stand-off distance of 1.5 m from the source, the most effective shielding configuration is a combination of several layers of polyethylene and steel. Without any shielding, the dose is 3.71 × 10-15 Sv/source particle. With a shielding consisting of multiple layers of steel totaling 30 cm thickness interspersed with several layers of polyethylene totaling 20 cm thickness, the dose drops to 3.68 × 10-17 Sv/emitted neutron at radians opposite the shield opening. The layered shielding approach is more effective at reducing dose equivalent and neutron fluence than shields made out of single continuous layers of the same material and thicknesses. Adding boron to the polyethylene and substituting tungsten for steel would make the shielding more effective but would add mass and cost.