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2026 ANS Annual Conference
May 31–June 3, 2026
Denver, CO|Sheraton Denver
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Christmas Light
’Twas the night before Christmas when all through the house
No electrons were flowing through even my mouse.
All devices were plugged by the chimney with care
With the hope that St. Nikola Tesla would share.
R. W. Conn, T. Y. Sung, M. A. Abdou
Nuclear Technology | Volume 26 | Number 4 | August 1975 | Pages 391-399
Technical Paper | Reactor | doi.org/10.13182/NT75-A24440
Articles are hosted by Taylor and Francis Online.
The induced radioactivity and afterheat in five recently presented fusion reactor blanket designs have been calculated. These designs differ in the choices of structural material, coolant, and neutron multiplier. Nevertheless, the radioactivity levels at shutdown after a 2-yr operation are within a factor of 4 of each other and are clustered at ∼1 Ci/W(th). However, the long-term radioactivity (>200 yr) is greatest for niobium structures and least for aluminum. For niobium, the level of long-term activity is ∼5 × 10−5 Ci/W(th), whereas for aluminum, the level drops to ∼10−7 Ci/W(th) just several weeks after shutdown. This last result will be modified by the inclusion of trace elements and impurities. Afterheat levels are found to vary from to 5% of the thermal operating power, depending on design and the choice of structural material. Importantly, however, the afterheat power density is only ∼0.2 W/cm3 at most and this is roughly a factor of 10 to 60 less than the afterheat power density in fast breeder reactors. Biological hazard potential (BHP) values are calculated for all designs by the pessimistic approach of dividing the activity in Ci/kW(th) by the lowest maximum permissible concentration value, in Ci/km3 of air, given in U.S. Atomic Energy Commission rules, Title 10, Part 20. In all cases, the BHP nevertheless drops below 1 km3/ kW(th) 20 yr after shutdown following a 2-yr operation. The key isotopes contributing to radioactivity, afterheat, and BHP are listed for future reference.