26aD61P
鉛リチウム合金の熱的物性評価に関する研究
Study on thermophysical properties of lead lithium alloy
近藤正聡,
Masatoshi KONDO

野澤貴史
Takashi NOZAWA

東工大原子炉研
日本原子力研究開発機構
Tokyo Institute of Technology Japan Atomic Energy Agency

Liquid lead lithium alloy (Pb-Li) is one of thecandidates of the tritium breeders of fusion reactors. The
thermophysical properties of the alloy, such as thermalconductivity, specific heat, viscosity and density, areessential to design the fusion blanket system. Some of
the thermophysical properties of the alloy are reported in
the previous papers [1-2]. However, the available datafor the thermal conductivity is quite limited. The thermalconductivity is obtained by the equation;
λ=ρCPα(1),where ρ is the density, Cp is the specific heat and α is thethermal diffusivity of the alloy.
The purpose of the present study is to make clear thethermal conductivity of the Pb-Li alloys having the Liconcentrations in the range between 0 and 30 atom% atvarious temperatures. In the present work, the density,
the specific heat and the thermal diffusivity of the alloys
are evaluated based on the previous studies and theexperimental data newly obtained in the current work.
Then, the thermal conductivity as functions of the Liconcentration and the temperature is evaluated.

2. Evaluation of density of Pb-Li alloys.
The Pb-Li alloys having various Li concentration were
fabricated in the previous study [3]. The density data of
the alloys in a solid state was obtained by means of theArchimedean method with the samples fabricated. The
equation of the densities at the room temperature as afunction of Li concentration (0at% < χLi < 28at%) isobtained asρ(300K) [kg/m3]=-6.02×10-2×χLi+11.3(2).

The density of the alloy in a liquid state is evaluatedbased on the previous studies [4]. The density as thefunctions of the temperature (673K < T < 823K) and theLi concentration (0 at%< χLi <30at%) is described in theequation;
ρ[kg/m3]=(-6.34×10-2)×χLi+11.4-1.19×10-3T(3).

3. Evaluation of thermal diffusivity of Pb-Li
alloys
The thermal diffusivities of Pb-5Li, Pb-11Li and
Pb-17Li were measured by means of laser flash method
using ULVAC TC-9000 with the samples in ref. [3]. Thetemperature dependence of the thermal diffusivity islarger at higher Li concentration in the alloys. The
dependence of Li concentration on the thermaldiffusivity is larger at higher temperature. For example,
the equation for the thermal diffusivity of Pb-17Li at thetemperature between 573K and 773K is obtained as,
αPb-17Li[cm2/s]=3.46×10-4T-1.05×10-1(4).

4. Evaluation of specific heat of Pb-Li alloys
The specific heats of Pb-10Li and Pb-25Li werealready obtained in the previous study [4]. The specificheat is larger at the higher Li concentration. Theapproximation curves were obtained based on the data of
the previous report [4]. For example, the specific heat at873K is described in the equation;
CP(873K)[kJ/kgK]=4.64×10-5χLi2+8.83×10-4χLi+0.144(5).

5. Evaluation of thermal conductivity of Pb-Li
alloys
The thermal conductivities of Pb-Li alloys at thetemperature between 573K and 873K were evaluatedbased on the data in the previous studies and obtained in
the current work. The thermal conductivities are shownin Fig. 1. The thermal conductivity of Pb-17Li at thetemperature of 673K, 773K and 873K are higher thanthose of Pb, Pb-5Li and Pb-11Li. The thermal
conductivity of Pb-17Li had larger temperaturedependence than those of Pb, Pb-5Li and Pb-11Li.
Thermal conductivity [W/mK]

1. Introduction

35

By extraporation from Eq. (3)30873K
773K

25673K

2015573K

Ref.[5] at 625K

1002

4681012141618

Li concentration [at%]Fig. 1 Thermal conductivity of Pb-Li alloys as functionsof Li concentration and temperature
Reference[1] E. Mas de les Valls, et al., J. Nucl. Mater., 376,353-357 (2008).
[2] M. Kondo, et al., Fus. Eng. Des., 88, 2556- 2559
(2013).
[3] Y. Nakajima, et al., Fus. Eng. Des., in press.
[4] J. Saar et al., J. Phys. F, 17, 305-314 (1987).
[5] B. Schulz, Fus. Eng. Des., 14, 199-205 (1991).