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Division Spotlight
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.
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
Virginia utility considers SMRs
Dominion Energy Virginia has issued a request for proposals from leading nuclear companies to study the feasibility of putting a small modular reactor at its North Anna nuclear power plant.
While the utility says it is not a commitment to build an SMR at the site, the RFP is “an important first step in evaluating the technology and the North Anna site to support Dominion Energy customers’ future energy needs consistent with the company’s most recent Integrated Resource Plan.”
E. Teuchert, K. A. Haas, H. J. Rütten, Yuliang Sun
Nuclear Technology | Volume 102 | Number 2 | May 1993 | Pages 192-195
Technical Paper | Nuclear Reactor Safety | doi.org/10.13182/NT93-A34816
Articles are hosted by Taylor and Francis Online.
In high-temperature reactors (HTRs), ingress of water introduces positive reactivity. Normally, this is controlled by the reactor itself, but in hypothetical situations, there could be a need for an active support by the control system. Calculational research identifies three reasons for the reactivity change caused by the water: (a) a negative contribution by the absorption of the hydrogen, (b) a positive contribution by the softening of the neutron energy spectrum, and (c) a reduction of the neutron leakage losses due to a shift in the neutron flux local distribution. By increasing the carbon/heavy metal ratio, the reactivity effect can be reduced to almost zero or even to negative values. In the modular pebble-bed HTR, this effect can be accomplished in a simple manner. By adding 25% of graphite spheres to the regular batches of feed fuel elements, the neutron spectrum effect is reduced, and the fractional absorption of hydrogen is increased; thus, the maximum excess reactivity is limited to 0.3%. The effect on economy and safety is negligible.