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Helium-Cooled, Flibe Breeder, Beryllium Multiplier Blanket

Ralph W. Moir, Joseph D. Lee, R. Carroll Maninger, William S. Neef, Jr., Albert E. Sherwood, David H. Berwald, Jackson H. DeVan, Jungchung Jung

Fusion Science and Technology

Volume 8 / Number 1P1 / July 1985 / Pages 133-148


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The concept described for the blanket surrounding a fusion reaction chamber is based on the use of molten fluoride salts to convert fusion energy into electricity and to breed the tritium fuel for the fusion power plant. Helium cools the first-wall and the blanket internals, which consist of a bed of beryllium balls in which neutrons are multiplied. The neutrons are used to breed tritium and also to release extra energy in exothermic nuclear reactions. Tritium is bred in the molten Flibe salt (LiF + BeF2) that flows slowly (∼0.1 m/s) in steel tubes and is removed from the salt and the helium by processing both streams. Because the solubility of tritium in Flibe salt is so low, there is a strong driving force for tritium permeation. A 10-µm-thick tungsten permeation barrier, deposited by chemical vapor deposition on the salt-carrying tubes, is proposed for preventing excessive tritium permeation into the helium stream. A 1-mm-thick aluminum jacket on the steel steam generator tubes is proposed to prevent excessive tritium permeation into the steam system. Flibe salt has safety advantages with respect to large accidents in that it will not react with air or water, in contrast to liquid lithium. For the first time, a method is proposed for recycling solid material in fusion blankets. To accomplish this, beryllium pebbles were chosen because the pebbles can be loaded into the blanket after manufacturing and, to accommodate radiation-induced swelling, can be moved periodically by flowing. Once the balls have reached their radiation damage lifetime, they can be removed from the blanket for refabrication and recycle.

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