Journal of Materials Science

, Volume 55, Issue 6, pp 2454–2461 | Cite as

Optimization on producibility improvement and the recycling process of neutron multipliers for fusion applications

  • Jae-Hwan KimEmail author
  • Masaru Nakamichi
Electronic materials


Beryllium and beryllium intermetallic compound (beryllide) pebbles have been regarded as a neutron multiplier in an international thermonuclear experimental reactor (ITER), as well as a demonstration (DEMO) fusion reactor. A novel fabrication process of the beryllide pebbles has been successfully established by combining the plasma sintering and rotating electrode processes. However, owing to the brittleness of beryllides, their granulation yield is approximately 70%, which does not generally satisfy the requirement, whereas the fragments (designated to be not spherical) with 30% are generated as by-products. To improve the granulation yield and in considering a new recycling process, a novel step on fundamental experiments was adopted to confirm feasibility on the recycling process using the same plasma sintering and rotating electrode processes. Because the formation of oxidized surface and neutron-induced defects in these materials is anticipated, these defects should be eliminated during the recycling process. The plasma sintering process is known to remove impurities on powder surfaces by applying a pulse current, whereas the rotating electrode process (REP) is a granulation process that uses arc melting at a temperature higher than the melting point. Hence, a feasibility test on the recycling process was performed by applying this process with the fragments for the pebbles simulated as the used pebbles. In the case of mixture ratios of 1:1 and 2:1 for the mixed powders and fragments, respectively, and the powders pulverized by 100% fragments, the rods produced through plasma sintering were successfully fabricated even if several areas with low density are identified. Not all rods were broken during the REP, indicating granulation results with similar size distribution and yield. Regarding the oxygen contents of as-received pebbles, fragments, and rod and pebbles produced with 100% fragments, the plasma sintering effect on impurity cleaning is therefore not significant, whereas the REP evidently leads to remarkable reduction of oxygen as impurity.



This work was supported by JSPS KAKENHI Grant No. 18K05006.


  1. 1.
    Someya Y, Tobita K, Hiwatari R, Sakamoto Y (2018) Joint special design team for fusion demo, fusion DEMO reactor design based on nuclear analysis. Fusion Eng Des 136:1306–1312CrossRefGoogle Scholar
  2. 2.
    Dombrowski DE (1997) Manufacture of beryllium for fusion energy applications. Fusion Eng Des 37:229–242CrossRefGoogle Scholar
  3. 3.
    Kim J-H, Nakamichi M (2018) Fabrication and characterization of crushed titanium–beryllium intermetallic compounds. J Nucl Mater 498:249–253CrossRefGoogle Scholar
  4. 4.
    Nakamichi M, Kim J-H, Yonehara K (2013) Novel granulation process of beryllide as advanced neutron multipliers. Fusion Eng Des 88:611–615CrossRefGoogle Scholar
  5. 5.
    Nakamichi M, Kim J-H (2014) Development of advanced neutron multipliers for DEMO blankets. Fusion Sci Technol 66:157–162CrossRefGoogle Scholar
  6. 6.
    Chakin V, Rolli R, Moeslang A, Kurinskiy R (2015) Tritium and helium release from highly neutron irradiated titanium beryllide. Fusion Eng Des 98–99:1728–1732CrossRefGoogle Scholar
  7. 7.
    Kurinskiy P, Kim J-H, Nakamichi M (2019) Fabrication and characterization of Be12V pebbles with different diameters. Fusion Eng Des (in press)Google Scholar
  8. 8.
    Reimann J, Abou-Sena A, Brun E, Fretz B (2013) Packing experiments for beryllium pebbles for the fusion reactor HCPB Blanket. In: Proceedings of the 11th IEA international workshop on Beryllium technology. pp 89–102Google Scholar
  9. 9.
    Li CX, An XZ, Yang RY, Zou RP, Yu AB (2011) Experimental study on the packing of uniform spheres under three-dimensional vibration. Powder Technol 208:617–622CrossRefGoogle Scholar
  10. 10.
    Baule A, Makse HA (2014) Fundamental challenges in packing problems: from spherical to non-spherical particles. Soft Matter 10:4423–4429CrossRefGoogle Scholar
  11. 11.
    Donev A, Cisse I, Sachs D, Variano E, Stillinger F, Connelly R, Torquato S, Chaikin P (2004) Improving the density of jammed disordered packings using ellipsoids. Science 303:990–993CrossRefGoogle Scholar
  12. 12.
    Lu P, Li S, Zhao J, Meng L (2010) A computational investigation on random packings of sphere-spherocylinder mixtures. Sci China Phys Mech Astro 53:2284–2292CrossRefGoogle Scholar
  13. 13.
    Haji-Akbari A, Engel M, Keys AS, Zheng X, Petschek RG, Palffy-Muhoray P, Glotzer SC (2009) Disordered, quasicrystalline and crystalline phases of densely packed tetrahedral. Nature 462:773–777CrossRefGoogle Scholar
  14. 14.
    Sasamoto T, Hara H (1976) Change in impurity contents in magnesia after vaporization in vacuum. Yogyo-Kyokai-Shi 84(9):40–43Google Scholar
  15. 15.
    Suzuki A, Mishin Y (2005) Atomic mechanisms of grain boundary diffusion: low versus high temperatures. J Mater Sci 40:3155–3161. CrossRefGoogle Scholar
  16. 16.
    Roth J, Wampler WR, Oberkofler M, van Deusen S, Elgeti S (2014) Deuterium retention and out-gassing from beryllium oxide on beryllium. J Nucl Mater 453:27–30CrossRefGoogle Scholar
  17. 17.
    Nakamichi M, Kim J-H (2014) Fabrication of beryllide pebble as advanced neutron multiplier. Fusion Eng Des 89:1304–1308CrossRefGoogle Scholar
  18. 18.
    Kurinskiy P, Kim J-H, Nakamichi M (2018) Granulation of Be12V pebbles using the rotating electrode method. Fusion Eng Des 137:177–181CrossRefGoogle Scholar
  19. 19.
    Kim J-H, Nakamichi M (2015) Comparative study of sinterability and thermal stability in plasma-sintered niobium and vanadium beryllides. J Alloy Compd 638:277–281CrossRefGoogle Scholar
  20. 20.
    Klemenkov M, Hoffmann J, Kurinskiy P, Kuksenko V, Vladimorov P, Chakin V, Moslang A (2016) TEM characterization of irradiated beryllium. In: European microscopy congress proceedings. pp 880–881Google Scholar
  21. 21.
    Keys LK, Moteff J (1970) Neutron irradiation and defect recovery of tungsten. J Nucl Mater 34:260–280CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Fusion Energy Research and Development DirectorateRokkasho Fusion Institute, National Institutes for Quantum and Radiological Science and TechnologyAomoriJapan

Personalised recommendations