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Division Spotlight
Human Factors, Instrumentation & Controls
Improving task performance, system reliability, system and personnel safety, efficiency, and effectiveness are the division's main objectives. Its major areas of interest include task design, procedures, training, instrument and control layout and placement, stress control, anthropometrics, psychological input, and motivation.
Meeting Spotlight
Utility Working Conference and Vendor Technology Expo (UWC 2024)
August 4–7, 2024
Marco Island, FL|JW Marriott Marco Island
Standards Program
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 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. 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.”
Alan H. Wells, Albert J. Machiels
Nuclear Technology | Volume 176 | Number 3 | December 2011 | Pages 387-394
Technical Paper | Radiation Transport and Protection | doi.org/10.13182/NT11-A13315
Articles are hosted by Taylor and Francis Online.
According to the U.S. Nuclear Regulatory Commission's guidance based on concerns for potential channeling of neutrons between absorber particles, the criticality safety of transportation systems should not rely on credit for >75% of the boron in fixed neutron absorbers. The 75% efficiency (or effectiveness) factor was first formulated in 1987 for a cask to transport spent fuel from the Fermi Unit 1 (Fermi-1) fast breeder reactor. Fermi-1 fuel was highly enriched (25.6 wt%), and a critical condition could possibly be achieved in a dry environment. The 75% factor was later expanded to include low-enriched light water reactor (LWR) spent fuel, although the latter cannot achieve a critical state without the presence of a moderator. Under flooded conditions, the net effect of channeling is significantly reduced because the neutrons are nearly isotropically scattered by the moderator and impact the neutron absorber from all possible directions. Under dry conditions or under conditions representative in neutron attenuation measurements for absorber qualification, the neutrons impact the absorber mostly perpendicularly, and neutron channeling is maximized. The effect of neutron channeling for the Fermi-1 fuel and for a typical LWR fuel shipment was quantified using a methodology developed to apply experimental transmission data to calculations of the neutron angular distribution at the neutron absorber sheet, yielding the strength of the neutron channeling effect for a particular fuel type and cask basket geometry. These analyses show that neutron absorber qualification via a collimated neutron transmission measurement conservatively bounds the neutron channeling effect. Further imposition of a 75%-only credit leads to an overly conservative amount in neutron absorbers. For transport applications of LWR spent fuel, this results in increased costs with no measurable benefits to criticality safety.