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The Radiation Protection and Shielding Division is developing and promoting radiation protection and shielding aspects of nuclear science and technology — including interaction of nuclear radiation with materials and biological systems, instruments and techniques for the measurement of nuclear radiation fields, and radiation shield design and evaluation.
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ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
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Penn State and Westinghouse make eVinci microreactor plan official
Penn State and Westinghouse Electric Company are working together to site a new research reactor on Penn State’s University Park, Pa., campus: Westinghouse’s eVinci, a HALEU TRISO-fueled sodium heat-pipe reactor. Penn State has announced that it submitted a letter of intent to host and operate an eVinci reactor to the Nuclear Regulatory Commission on February 28 and plans to engage with the NRC on specific siting decisions. Penn State already boasts the Breazeale reactor, which began operating in 1955 as the first licensed research reactor at a university in the United States. At 70, the Breazeale reactor is still in operation.
R. L. Crowther, J. W. Weil
Nuclear Science and Engineering | Volume 3 | Number 6 | June 1958 | Pages 747-757
Technical Paper | doi.org/10.13182/NSE58-A25508
Articles are hosted by Taylor and Francis Online.
The presence of a large, sharp resonance at 1 ev in Pu240 results in the effective pile cross section for this isotope being very much larger than the true thermal cross section. Furthermore, the narrowness of this resonance causes the absorption of epithermal neutrons in Pu240 to be strongly self-shielded. Consequently, the effective cross section of Pu240 will be a function of reactor spectrum and of the Pu240 concentration at any given time. The significance of this effect can be appreciated by noting that the effective cross section of this isotope is frequently more than twice the effective thermal value. An approximate method of calculation has been applied to long term reactivity problems. The importance of the resonance augmentation and concentration dependence of the Pu240 cross section is particularly evident in the first few thousand Mwd/t and causes significant changes in the reactivity required to reach any longer burnout. Sample calculations are presented and comparisons with the Canadian experimental determinations of the effective Pu240 cross section are made. An effective constant Pu240 cross section is presented which will yield approximately correct burnout results when used in conventional irradiation studies.
