Chapter 9
Fuel Retention in a Reactor with Full
C-Wall and Full W-Wall and Its Recovery
9.1 Introduction
Because of the limited resources and radio-hazardousness of Tritium (T), accounting
for T fuel inventory in a fusion reactor system and its reduction/recovery are key
engineering issues for establishment of a D-T fusion reactor as an energy source.
Among all components and subsystems in a fusion reactor system, T retained in
a reactor vessel is the largest and most difficult to account or quantify, and also
hard to recover. Although T retention in other subsystems, such as exhaust, blanket,
refinement, isotope separation, storage, fueling, and piping must be also quantified,
it is not directly correlated to plasma material interactions (PMI) and is not discussed
here. Many reviews and textbooks on T management in a fusion reactor have been
published. One can refer a textbook entitled “Tritium fuel for fusion reactors” [1]
as an example. Techniques for handling T have been well established. Nevertheless,
the amount of T used in a reactor is quite huge compared to conventional T handling
systems and no PMI data relating to T fuel are available. Hence, PMI data based
on H and D are used for investigation of PMI in a reactor using D and T as the
fuels. Since the mass differences among H, D, and T are quite large, their behavior
in plasma material and PMI should be significantly different from each other as
introduced in Sect. 7.6 in Chap. 7. Although isotope effects clearly appear in physical
and chemical phenomena in plasma confinement, PMI, and behavior in materials,
for examples, better confinement, lager sputtering and less permeation, for heavier
isotopes, respectively. Fortunately or unfortunately, however, PMI data themselves
include rather large uncertainty (or error). This makes it difficult to discuss the isotope
effect appeared in PMI quantitatively. Hence some uncertainty, within a factor, cannot
be excluded in the estimation of the fuel retention in reactor based on PMI data of
H and D in this chapter and the isotopic effects would be considered only when the
effect exceeds the square root mass dependence of
√
3 for H and T and
√
2 for D
and T.
This chapter focuses on T retention in a reactor vessel in particular how the retention piles up under long operation or under steady-state operation. The estimation
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
T. Tanabe, Plasma-Material Interactions in a Controlled Fusion Reactor, Springer Series
in Plasma Science and Technology, https://doi.org/10.1007/978-981-16-0328-0_9
161
Fuel Retention in a Reactor with Full
C-Wall and Full W-Wall and Its Recovery
9.1 Introduction
Because of the limited resources and radio-hazardousness of Tritium (T), accounting
for T fuel inventory in a fusion reactor system and its reduction/recovery are key
engineering issues for establishment of a D-T fusion reactor as an energy source.
Among all components and subsystems in a fusion reactor system, T retained in
a reactor vessel is the largest and most difficult to account or quantify, and also
hard to recover. Although T retention in other subsystems, such as exhaust, blanket,
refinement, isotope separation, storage, fueling, and piping must be also quantified,
it is not directly correlated to plasma material interactions (PMI) and is not discussed
here. Many reviews and textbooks on T management in a fusion reactor have been
published. One can refer a textbook entitled “Tritium fuel for fusion reactors” [1]
as an example. Techniques for handling T have been well established. Nevertheless,
the amount of T used in a reactor is quite huge compared to conventional T handling
systems and no PMI data relating to T fuel are available. Hence, PMI data based
on H and D are used for investigation of PMI in a reactor using D and T as the
fuels. Since the mass differences among H, D, and T are quite large, their behavior
in plasma material and PMI should be significantly different from each other as
introduced in Sect. 7.6 in Chap. 7. Although isotope effects clearly appear in physical
and chemical phenomena in plasma confinement, PMI, and behavior in materials,
for examples, better confinement, lager sputtering and less permeation, for heavier
isotopes, respectively. Fortunately or unfortunately, however, PMI data themselves
include rather large uncertainty (or error). This makes it difficult to discuss the isotope
effect appeared in PMI quantitatively. Hence some uncertainty, within a factor, cannot
be excluded in the estimation of the fuel retention in reactor based on PMI data of
H and D in this chapter and the isotopic effects would be considered only when the
effect exceeds the square root mass dependence of
√
3 for H and T and
√
2 for D
and T.
This chapter focuses on T retention in a reactor vessel in particular how the retention piles up under long operation or under steady-state operation. The estimation
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
T. Tanabe, Plasma-Material Interactions in a Controlled Fusion Reactor, Springer Series
in Plasma Science and Technology, https://doi.org/10.1007/978-981-16-0328-0_9
161