Tritium Breeding Blanket
Part II: Coolant
Properties,
Shielding, and
Tritium Breeding
Ratio
Nicholas Alfred
NRE 4610-A :Intro to Fusion
Dec 7th, 2015
500
Why Li17Pb83
• High density [~9015 kg/(m^3)] [1] (and therefore a high
mass flow rate can be obtained at lower velocities)
• High thermal conductivity [~18.58W/(m*K)] [1] (and
therefore a more uniform temperature distribution in
the coolant channel)
• Modest specific heat [~187.2J/(kg*K)] [1] (which allows
it to remove the heat from the system while staying
under the melting point of the ODS structural material)
• Combines the tritium breeding and coolant system to
reduce system complexity
• Pb provides n-2n and Li-6 provides Li(n,α)T [2] reactions
• At the eutectic point so the melting temperature is at
its lowest [3]
Blanket Shielding
density
material (g/m^3)
Molecular
weight (g/mol)
Region
thickness (m)
avg. crossattenuation
section (m^2) [5] factor
entering flux exit flux
He
5.76E+03 [4]
4.00E+00
1.80E-02
3.66E-28
8.82E-01
1.47E+17
1.29E+17
ODS Steel
7.64E+06 [6]
4.75E+01
1.80E-02
3.24E-28
5.05E-01
1.29E+17
6.53E+16
He
5.76E+03
4.00E+00
3.50E-03
3.66E-28
9.76E-01
6.53E+16
6.38E+16
SiC
3.21E+06
4.01E+01
1.00E-02
2.90E-28
8.14E-01
6.38E+16
5.19E+16
LPb
4.80E+05
1.73E+02
4.55E-01
5.59E-28
3.15E-02
5.19E+16
1.63E+15
SiC
3.21E+06
4.01E+01
1.00E-02
2.90E-28
8.14E-01
1.63E+15
1.33E+15
He
5.76E+03
4.00E+00
3.50E-03
3.66E-28
9.76E-01
1.33E+15
1.30E+15
ODS Steel
7.64E+06
3.41E+02
1.80E-02
3.24E-28
8.20E-01
1.30E+15
1.06E+15
He
5.76E+03
4.00E+00
1.80E-02
3.66E-28
8.82E-01
1.06E+15
9.38E+14
MHD Pressure drop in the Breeder
• Conductivity of coolant = 7.213*10^7 S/m [1] which means
it will be heavily affected by the magnetic field without
insolation by the SiC tubes.
• With the tubes the pressure change per unit length due to
the flowing coolant affected by the magnetic field is in the
order of 10^(-4) Pa/m [2] which can be neglected
compared to the frictional pressure drop per unit length
𝑃 𝑀𝐻𝐷 = 𝐿𝑉𝐵⊥ 2 σ𝑓
𝑃(𝑀𝐻𝐷)
𝑃𝑎
~ 10−4
𝐿
𝑚
𝐶
2𝑡σ𝑠
2 ∗ 0.01 ∗ 0.001
−13
,C =
=
=
9.695
∗
10
𝐶+1
𝐷σ𝑓 0.286 ∗ 7.213 ∗ 107
Tritium Breeding Ratio and Doubling
Time
• From estimations in
the downtime and
from the loss of
tritium due to decay
and processing, the
TBR was estimated to
be 1.2 for the system.
[7]
• The time to double
this amount of
tritium is 2 years
assuming no
downtime or loss of
tritium that is
produced in the
blanket to the rest of
the system. [2]
References
• [1] Zinkle, S. J “Summary of Physical Properties for
Lithium, Pb-17, and (LiF)nBeF2 Coolants” Sandia
National Lab, July 1998.
• [2] Stacey, W.M. Fusion Textbook
• [3] Jauch, U, et al. “Thermophysical Properties in the
System Li-Pb.” Institut für Material-undFestkörperforschung. Sep. 1986.
• [4] Todreas, N. E, et al. “Nuclear systems thermal
hydraulic fundamentals second eddition – revised
printing volume 1” (2012).
References Cont.
• [5] Cross-secton database
http://www.kayelaby.npl.co.uk/atomic_and_nuclear
_physics/4_7/4_7_2.html, accessed on Nov 28th
2015.
• [6] ODS data page
https://www.ipp.mpg.de/1532493/P93A.pdf,
accessed on Nov 30, 2015.
• [7] Wong, CPC, et al. “An overview of dual coolant
Pb-17Li breeder…” Fusion Engineering and Design 81
(2006).