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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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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.
Jeffrey C. King, Leonardo de Holanda Mencarini
Nuclear Technology | Volume 208 | Number 7 | July 2022 | Pages 1137-1148
Technical Paper | doi.org/10.1080/00295450.2021.2004870
Articles are hosted by Taylor and Francis Online.
A low-enriched-uranium (LEU)–fueled space reactor could avoid the security and proliferation concerns inherent with highly enriched uranium (HEU)–fueled space nuclear reactors. Recent LEU-fueled space reactor designs include a moderator to reduce the size and mass of the reactor core. This paper considers shadow shield options for an unmoderated HEU-fueled space reactor and a moderated LEU-fueled space reactor. Both reactors are kilowatt-class reactors, producing 15 kW(thermal) of thermal power over a 5-year operational lifetime. Based on the shielding required to meet established dose limits [a neutron fluence of less than 1014 n/cm2 (1 MeV equivalent in silicon) and a gamma-ray dose of less then 1 Mrad in silicon], the moderated LEU-fueled space reactor will require a thicker shadow shield than the unmoderated HEU-fueled space reactor. The thinner reflector of the moderated LEU-fueled reactor results in more neutrons reaching the shadow shield at higher energies compared to the unmoderated HEU-fueled reactor. The presence of a significant reflector in most space reactor designs means that the core spectrum is relatively unimportant in terms of shadow shield design, as the reflector thickness has a much stronger impact on the neutrons and gamma rays reaching the shadow shield. Based on the results presented in this paper, the mass optimization of moderated LEU-fueled space nuclear reactors should always consider the coupled effects of the core, the reflector, and the shielding.