7.1 Tritium Production Using Coated Lithium Particles

Fig. 7-1 Concept of coated lithium particles
Ceramic coated lithium particles are inserted into a graphite sleeve and contained in a graphite block before an irradiation test is performed in the HTTR.

Fig. 7-2 Tritium release from coated lithium particle
The figure indicates that tritium is easily released after heating the lithium particles coated by alumina (Al2O3) with LiAlO2 as a nucleus.

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Fig. 7-3 The position of an irradiation test for a graphite sleeve
Coated lithium particles are to be tested in the side reflector of the HTTR after having been contained in a graphite sleeve and capsule.

A method for producing tritium using the High Temperature Engineering Test Reactor (HTTR) is proposed. From the viewpoint of chemical stability, particles which have LiAlO2 as a nucleus and coatings of ceramics such as Al2O3, SiO2 and ZrO2 are used as shown in Fig. 7-1. The coated particles are produced by the same method as the coated particle fuel for the HTTR. In the case of coating by Al2O3, for example, double coating is conducted. It was found that when the coated particles were irradiated below 1,000 K little tritium comes out after heating at 1,000 K but is easily released after heating above 1,400 K, as shown in Fig. 7-2. It was confirmed that no chemical reactions of the ceramic coating with the nucleus occur and the coated particles are chemically stable at temperatures which are expected to be in the irradiation range of coated lithium particles. Moreover, the tensile strength of the second coating layer is predicted to be maintained up to 1,100 K. It is necessary to confirm the mechanical integrity by actual irradiation tests in the future. Figure 7-3 shows the position of the irradiation test in the in-core section of the HTTR.
Coated lithium particles are used in the blanket of a fusion reactor to produce tritium.

Reference
K. Yamashita et al., Development of Ceramic-Coated Lithium Particles for Tritium Production Tests in High Temperature Engineering Test Reactor, Nippon Genshiryoku Gakkai-Shi, 40 (1), 65 (1998).

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