(1)
Lithium lead (LiPb) has been proposed for use both as multiplier and tritium generating material in the blankets of fusion power plants. LiPb eutectic permits the use of moderately enriched or natural Li and has a relatively low cost in comparison with other tritium generating and multiplier materials.
17Li-83Pb eutectic was chosen among possible LiPb compositions because of its lowest melting temperature and its adequate stability. Low melting temperatures provide an easier operation of the loop and allow for out-of-blanket tritium extraction either in batch or continuous modes.
Critical issues for 17Li-83P are the compatibility with structural materials and the high tritium pressure in the liquid. Continuous tritium extraction is possible if the eutectic is kept at temperatures 300-350 C in the blanket, which is still satisfactory for compatibility with stainless steel but requires protection to restrict tritium permeation to the water coolant.
GENERAL PROPERTIES - (17Li-83Pb)
Solubilities
Solubilities of Ni, Mn, Cr and Fe in the temperature range ~500-700 K are between 1-10 appm, and slightly higher for Fe. Oxygen solubility is extremely small.
Reactivity
The reactivity of 17Li-83Pb with air, steam and water is low. The H2 production rate is typically about two orders of magnitude lower than in lithium metal. In the presence of steam the rise in temperature of 17Li-83Pb was negligible.
DATA AND CORRELATIONS
Data from refs [1, 2] are presented in Table 1. Other thermophysical properties as functions of temperature are:
Density [[rho]] in g/cm3:
(1)
(2)
Thermal diffusivity a in cm2/s:
(3)
(4)
Thermal Conductivity k in W/m-C:
(5)
(6)
Specific heat capacity c in J/kg-C:
(7)
(8)
Viscosity in mPa-s:
(9)
Thermal expansion coefficient [[alpha]] in m/m-C:
(10)
with
the universal gas constant, all temperatures in degrees Celcius (C) and
subscripts s=solid, l=liquid. Equations (1), (3), (5), (7) and (10) are valid
in the temperature range 25-230 C and Eqs (2), (4), (6), (8) and (9) in the
range 240-350 C.
TABLE 1 Thermophysical properties of 17Li-83Pb in the solid state
T C [[rho]](s, a(s,l) [[nu]] k(s,l) C(s,l) [[eta]] [[alpha]]
l) kg/m3 cm2/s W/m-K J/kg-K mPa-s (10-6)
m/m-K
25 10217.7 0.1796 26.4610 147.3 20.163
50 10185.4 0.1789 27.1962 150.5 22.630
100 10120.8 0.1769 28.6662 158.1 27.600
150 10056.3 0.1752 30.1362 169.8 31.890
200 9991.7 0.1734 31.6062 183.9 34.410
210 9978.8 0.1731 31.9002 186.9 35.160
220 9965.9 0.1727 32.1942 190.0 35.460
230 9953.0 0.1724 32.4882 193.1 35.120
Thermophysical properties in the liquid state
240 9587.0 0.0680 12.0048 190.30 0.1875109
250 9570.0 0.0693 12.2008 190.20 0.1875011
265 9545.0 0.0713 12.4948 190.10 0.1874871
280 9520.0 0.0732 12.7888 190.00 0.1874739
295 9495.0 0.0752 13.0828 189.80 0.1874614
310 9470.0 0.0771 13.3768 189.70 0.1874495
325 9444.5 0.0791 13.6708 189.50 0.1874382
340 9419.0 0.0810 13.9648 189.40 0.1874275
350 9402.6 0.0823 14.1608 189.30 0.1874206
ks (W/m-K) kl (W/m-K)
Temperature (C)
Figure 1: Thermal conductivity of 17Li-83Pb in both the solid and liquid state.
cs (J/kg-K) cl (J/kg-K)
Temperature (C)
Figure 2: Specific heat of 17Li-83Pb in both the solid and liquid state.
[[rho]](s,l) (kg/m3) [[alpha]] (10-6 m/m-K)
Temperature (C)
Figure 3: Density (liquid and solid state) and coefficient of thermal expansion of 17Li-83Pb.
a(s,l) (cm2/s) [[eta]] (mPas)
Temperature (C)
Figure 4 : Thermal diffusivity (solid and liquid state) and viscosity of 17Li-83Pb.