Hydrogen Isotope Research Center - Toyama Univ.

Data Base for Tritium Solid Breeding Materials (Li₂O, Li₂TiO₃, Li₂ZrO₃ and Li₄SiO₄) of Fusion Reactor Blankets --- Yoshiaki FUTAMURA

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1. Introduction

  In designing and evaluating the breeding blanket of nuclear fusion reactor, there must be the data for various properties of blanket materials such as tritium breeding material, neutron multiplier, construction material, cooling material, purge gas and so on. Among various properties, physical and thermal, mechanical, chemical stability and compatibility, tritium solubility and transport, irradiation effects, afterheat characteristics, thermal cycling effects, waste disposal, and other miscellaneous properties of breeding materials are very much important.
  Lithium contained ceramics such as Li₂O, Li₂TiO₃, Li₂ZrO₃ and Li₄SiO₄ are recently considered as promising candidate tritium breeding materials for fusion reactor blankets. Up to this time, authors have endeavored to collect and to compile data for various properties of those materials from as many sources as possible. Moreover, rearranged data in matrix is formed in order to construct better database and to be easily used.
  This up-to-date database are the summary of the our previous reports and newly collected data after the latest report.^{1),2),3),4),5)} This database can make it clear on what properties of any breeding material there are no information, few and limited information, uncertainties, and good information. Hence the present status of existing data can be recognized from this database. Then it can become clear what property of any breeding material, will need more investigations in future.
  In case of collecting data, the main required functions and characteristics for solid breeding materials, and some samples of operating conditions for fusion reactor blankets are taken into considerations. Those contents are shown in Table 1-1, and 1-2, respectively.

<Table 1-1 Main required functions and characteristics for solid breeding materials.>

Function	Required characteristics
Good tritium production and Breeding characteristics	High lithium content Efficient release/recovery of produced tritium
Proper breeder temperature Control	High thermal conductivity
Good integrity	Good neutron irradiation resistance High mechanical strength and high durability Good chemical stability Good compatibility with other materials
High safety	Low activation Low reactive with coolant
Fabrication	Mass production at a low price Easy treatment

<Table 1-2 Major operating conditions of breeding materials of a fusion reactor.>

-	ITER	SSTR
Breeding material	Li2ZrO3	Li2O
Li burn-up (%)	~5	10~30
Nuclear heat generation (MW/m3)	~50	~90
Temperature range (°C)	300~750	450~950
Structural material	SS316 LV-IG	RAF (F82H)
Multiplier material	Be	Be
Environmental gas	He gas (~0.1MPa)	He gas (~0.1MPa)

Notes :

ITER : International Thermonuclear Experimental Reactor.

SSTR : Steady State Tokamak Reactor.

  So this database ca be expected to be very useful and helpful for designing and evaluating breeding blankets.
  However, owing to the limitation of our research and search activity, there may be still oversight of existing data. So the authors are very much grateful for being notified existing data as well as bring assisted for collecting the data and/or supplied with them. Only with such collaboration, we can construct the complete database for breeding blanket materials.