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Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
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August 4–7, 2024
Marco Island, FL|JW Marriott Marco Island
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Latest News
Vogtle-3 shuts down for valve issue
One of the new Vogtle units in Georgia was shut down unexpectedly on Monday last week for a valve issue that has since been investigated and repaired. According to multiple local news outlets, Georgia Power reported on July 17 that Unit 3 was back in service.
Southern Company spokesperson Jacob Hawkins confirmed that Vogtle-3 went off line at 9:25 p.m. local time on July 8 “due to lowering water levels in the steam generators caused by a valve issue on one of the three main feedwater pumps.”
Aaron E. Craft, Jeffrey C. King
Nuclear Technology | Volume 172 | Number 3 | December 2010 | Pages 255-272
Technical Paper | Photon and Neutron Transport and Shielding | doi.org/10.13182/NT10-A10934
Articles are hosted by Taylor and Francis Online.
A survey of neutron-attenuating materials is conducted, followed by a systematic optimization of the radiation shield configuration for the Affordable Fission Surface Power System. Water, borated water, boron carbide, boron-doped beryllium, zirconium hydride, and lithium hydride are evaluated for neutron shielding, and tungsten is considered for gamma shielding. Lithium hydride, borated water, and boron carbide are selected for further consideration, and radial, upper axial, and lower axial shield sections are developed separately from these materials and then combined to form complete shields. Two competing effects determine the optimal position of the tungsten layer: increasing secondary gamma production due to fast neutron scattering when the tungsten layer is placed closer to the core, and radially increasing mass when placed farther from the core. The optimal position of the tungsten layer is found for each shield configuration and material. The as-landed configuration of each radiation shield allows a maximum dose of 5 rem/yr to an outpost 1 km from the reactor core. The shield also protects the SmCo magnets in the alternators of the Stirling power converters, allowing a maximum dose of 2 Mrad gamma and 1014 n/cm2 fast neutron fluence to the magnets over the 8-yr design lifetime. A minimum mass is found for each shield section while meeting these dose limits. The radial shield section is cylindrical, and the upper and lower axial shield sections are conical in shape. Axial shields with a range of pitch and thickness are analyzed, and the optimal shapes of the upper and lower axial shields for each material are found. The three sections of the shield are combined to form a complete shield. The lithium hydride shield is the lightest of the final shields at 6215 kg. The borated water shield is the second lightest at 6663 kg, which is 448 kg more than the lithium hydride shield. The boron carbide shield is the most massive at 8315 kg, which is 2100 kg more than the lithium hydride shield.