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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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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
The RAIN scale: A good intention that falls short
Radiation protection specialists agree that clear communication of radiation risks remains a vexing challenge that cannot be solved solely by finding new ways to convey technical information.
Earlier this year, an article in Nuclear News described a new radiation risk communication tool, known as the Radiation Index, or, RAIN (“Let it RAIN: A new approach to radiation communication,” NN, Jan. 2025, p. 36). The authors of the article created the RAIN scale to improve radiation risk communication to the general public who are not well-versed in important aspects of radiation exposures, including radiation dose quantities, units, and values; associated health consequences; and the benefits derived from radiation exposures.
Ashlea V. Colton, Blair P. Bromley, Daniel Wojtaszek, Clifford Dugal
Nuclear Science and Engineering | Volume 186 | Number 1 | April 2017 | Pages 48-65
Technical Paper | doi.org/10.1080/00295639.2016.1273021
Articles are hosted by Taylor and Francis Online.
Thorium, a fertile nuclear fuel that is nearly three times as abundant as uranium, represents a long-term energy source that could complement uranium and eventually replace it. To facilitate the gradual transition from uranium-based fuels to thorium-based fuels, it may be advantageous in the near term to introduce small amounts of thorium (˂7% of the total fuel mass) into uranium-based fuels in pressure tube heavy water reactors (PT-HWRs). Downblending natural or slightly enriched uranium dioxide with thorium dioxide for fuel pellets placed at the ends of the fuel stack of a conventional 37-element fuel bundle could help reduce axial power peaking for fresh fuel, while incorporating thorium dioxide into the central element of the fuel bundle could reduce coolant void reactivity (CVR).
A series of two-dimensional lattice physics simulations was carried out as part of conceptual scoping studies to evaluate the potential performance and safety characteristics of uranium-based fuel bundles with small amounts of thorium fuel added. The simulation results were complemented by an approximate model for evaluating the potential economic characteristics. The cases studied involve modifications to fuel composition, central element materials, and the addition of thorium dioxide to the fuel stack. In addition, a set of preliminary three-dimensional MCNP simulations was performed where fuel bundles were modeled to assess the effect of thorium end pellets and graded axial enrichment on end power peaking.
Results suggest it should be possible to incorporate thorium into the fuel cycle using existing 37-element fuel bundle geometry. Advantages to incorporating thorium include a reduction in the CVR through a thorium central element, breeding of small amounts of 233U, maintaining front-end fuel costs at or below the price of natural uranium (NU) fuel, and maintaining maximum linear element ratings within 6%of those achieved using NU 37-element fuel.
