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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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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.”
Peter S. Jackson, Patrick J. Williams
Nuclear Technology | Volume 121 | Number 1 | January 1998 | Pages 70-80
Technical Paper | Human Factors | doi.org/10.13182/NT98-A2820
Articles are hosted by Taylor and Francis Online.
Most commercial pressurized water reactors with alloy 600 steam generator tubes are susceptible to stress-induced corrosion at locations such as the tube sheet transition, the tube-to-tube support structure interface, U-bend regions with high localized stresses, and to a lesser extent, free-span locations between supports where deposits or manufacturing defects have caused accelerated local attack. Under postulated main steam-line break (MSLB) accident conditions (and in rare instances during normal operation), some leakage of reactor coolant inventory through these cracks occurs. The result is an iodine source term to the environment.A simplified probabilistic iodine release model has been developed that is different from previous conservative deterministic models, which were developed for the routine steam generator tube rupture analysis, which is performed as part of a plant's safety analysis. The model described herein was developed to calculate the probability that the iodine release for MSLB-induced steam generator leakage will result in thyroid and whole body doses that do not exceed the criteria in 10CFR100 for the projected condition of the plant's steam generator tubes after a specified period of full-power operation.This simplified probabilistic model treats the intrinsic statistical nature of the projected population of degraded tubes, the probability of leakage for multiple degradation mechanisms, and the probability distributions for iodine release for a preexisting spike and a coincident spike.Results from applying this methodology to data from a plant with substantial steam generator degradation indicate that steam generators with multiple degradation mechanisms can be operated safely for normal operating cycles. Safely, in this case, means without a significant probability of exceeding thyroid and whole body dose criteria under normal operation and postulated accident conditions.