A. Sagara

S. Fukada

National Institute for Fusion Science (NIFS-Repository)

ternTritium storageTritium permeation barrierFlibe flow rate 2.2m3/sReferences(1) S. Fukada, A. Sagara, et aI., Fus. Eng. Des., 61-62(2002) 783-788.(2) S. Fukada, A, Sagara, et aI., Fus. Sci. Technol., 41(2002) 1054-1058.(3) S. Fukada et aI., Proc. ANS/TOFE meeting,Washington D.C., (2002).heat exchanger and the trItIUm recovery system aresurrounded by a stagnant Flibe (or Flinak) layer, thetritium leak rate became 1.6 Ci/day. The rate was withinthe permissible level. If there is other reliable tritiumbarriers, e.g. alumina film, with a degradation factor of10 6, it will be also effective. A by-pass system candecrease a flow rate of Flibe passing through the tritiumrecovery system, and therefore it can make their sizesmall. However, it was found to be not good from a viewpoint of tritium leak. We needed to lower all the tritiumlevel in Flibe coolant down to the premissible level.Even if we used any of the three recovery systems, themost serious tritium leak occurred at the secondarycoolant loop of the heat exchanger. The rate was 34kCi/day and was thousand times higher than thepermissible level. It is necessary to develop a new conceptto enclose tritium in the secondary loop. The largesttritium inventory source was 34 kCi/ton in a stainless-steel structural material. That in Flibe was much smallerthan it. We need to search for a new material with lowinventory.Fig. 1 A liquid blanket (Flibe) loop systemSecondaryTritium permeation barrierHeat exchanger§ 4. A Study on the System of TritiumRecovery from a Liquid Blanket of aFusion ReactorFukada, S. (Kyushu University), Sagara, A.A liquid blanket was applied to the conceptual designof FFHR-II because of advantages of a self-cooled,simple structure. The molten salt blanket showed goodperformances of low MHD effect, TBR > 1 with theaddition of Be, low induced radioactivity, low tritiuminventory and low reactivity with oxygen or water vapor.However, there were few design studies on tritiumrecovery from the molten salt blanket. In the presentstudy, we investigated the tritium recovery system as adesign study of the NIFS collaboration work ofFFHR-II.Necessary conditions imposed on the tritium recoveryfrom the molten salt blanket are as follows; (1) all tritiumgenerated in the blanket (1.8 MCi/day) is transferred by aFlibe coolant and is recovered by a tritium removalsystem under a steady-state operation, (2) permissibletritium leak to the environment should be less than 10Ci/day that was tentatively set in the present study, (3)simple apparatus and easy to operate, (4) operation overthe melting temperature, (5) high operation safety and touse materials compatible with HF and (6) operation undera low oxygen impurity condition. Additional assumptionsfor the design are; (7) no isotope effect in physicalproperties, (8) no decomposition of Flibe by a VxB force.We here focused on whether or not tritiumcan be recovered by a permeation window, acounter-current He-Flibe extraction towerand a vacuum disengager that are in arealistic scale [1-3].Fig. 1 shows a typical configuration of aplasma chamber, a blanket, tritium recoverysystem and a heat exchange consisting afusion reactor system. The tritium generationrate was estimated 1.8 MCi/day. Most ofthem is removed by the tritium recoverysystem and others inevitably leak throughwalls of tubing lines, the tritium recoverysystem and the heat exchanger. If there wasno barrier for the tritium leak, the leak ratewas estimated 35 kCi/day. Since the valuewas huge, it was impossible to lower thetritium leak rate below 10 Ci/day withoutany tritium barrier. On the other hand, if theTable 1 Tritium recovery rate and tritium leak rate with or without by-pass or tritium permeation barrier(l)a =1 (no by-pass) (2)a =1 (Flibe barrier) (3) ex = 0.1rr generation rate in blanket 1,800kCiJday 1,800kCi/day 1,800kCi/dayrr concentration in Flibe 5xl0-4wppm (lkPa) 5xl0-4wppm (lkPa) 5x10-3wppm (lOkPa)tIn T recovery system 1,765kCiJday 1,766kCiJday 1,44lkCiJdayrr leak through line from blanket to IRS lkCVday ICi/day 10kCildayrr leak through secondary flow 34lkCilday 34kCi/dayT Leak from heat exchanger lOCi/day lOCi/day 9JkCildayT leak through line from HX to blanket lOCi/day lOCi/day 30CildayT inventory in sus 316 8kCiJton 8kCi/ton 30kCiJton246

A Study on the System of Tritium Recovery from a Liquid Blanket of a Fusion Reactor

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