1. Tritium Research in TITA Information Required
November 23, 2018
Tritium Research in TITA Information Required
Dai-Kai Sze, UCSD
Phil Sharpe, INL
Presented at the
US-ITER TBM Meeting
UCLA, LA, CA
Feb , 2007
November 23, 2018

2. November 23, 2018
Proposed Tritium Research Activities in TITAN Collaboration (formerly known as JUPITER-III)
Involved Parties considered several issues that require attention for progress in developing successful and Plasma-facing Components and PbLi Blankets :
1. Key technical items for tritium behavior in PFCs:
Plasma-driven permeation behavior and effect of surface conditions
Irradiation and implanted He effects on retention and permeation
Mixed materials retention behavior
2. Key technical items for tritium in blanket systems:
Solubility in PbLi
Recovery methods from PbLi and He flows
Transport barriers resistant to thermal cycling and irradiation
Permeation behavior at very low partial pressures over metals
November 23, 2018

3. TITAN Task 1-1: Fuel behavior in Plasma-facing Components
November 23, 2018
TITAN Task 1-1: Fuel behavior in Plasma-facing Components
Plasma driven permeation/Tritium retention (TPE)
- Mono-materials (W, RAF) non-irradiated & irradiated
- Mixed-materials, Duplex materials (Be on W, W on RAF)
Mixed-material PSI W/Be systems (PISCES)
- Formation conditions
- PMI behavior using D & He plasma
- W sputtering & evaporation, hot spot formation, etc.
- Surface modification
Effects of Helium on Tritium retention/permeation and mixed material formation (PISCES and TPE)
TITAN Task 2-1: Tritium Behavior in Irradiated PFC Materials
Plasma- and gas-driven permeation in irradiated W
Transport properties of irradiated Be/RAFS bonds
- Influence of He and bubble formation
- Intermetallic formation and dynamics of bond characteristics
November 23, 2018

4. TITAN Task 1-2: Tritium Behavior in Liquid Breeder Blankets
November 23, 2018
TITAN Task 1-2: Tritium Behavior in Liquid Breeder Blankets
Solubility of T in PbLi at Blanket Conditions
- Measurement of tritium solubility at low partial pressures (required for tritium inventory control)
- Explore possible deviance from Sievert’s Law (indicative from other LM results, e.g. Li)
Concentration Effects of T Permeation in Structural Materials
- Linear vs. Sievert’s behavior? Devise measurement for dissociation/ recombination rates
- Explore influence of surface characteristics and treatment
Tritium Extraction from PbLi at Blanket Conditions
- Measure mass transport across liquid-vapor interface for vacuum disengagement or window permeator designs
November 23, 2018

5. What information do we need?
November 23, 2018
Solubility of tritium in LiPb
Efficient tritium recovery method
Development of reliable tritium diffusion barrier
Establish the pressure dependency of tritium permeation.
November 23, 2018

6. Tritium solubility
November 23, 2018
Most tritium solubility measurements were done by using hydrogen at high H2 partial pressure.
It was assumed that the Sievert’s law applies and extrapolated to much lower tritium partial pressure (< 1 Pa).
For most liquid metals, the hydrogen obeys Sievert’s law only at rather low tritium partial pressure.
Force fitting the Sievert’s law may result large error if extrapolated to very low partial pressure.
November 23, 2018

7. Tritium solubility uncertainty
November 23, 2018
Early comparison observed a two order of magnitude difference in Sievert’s constant from different measurements.
Recent report at the St. Petersburg workshop suggested a factor of 18 difference between the new results and the reference solubility.
November 23, 2018

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10. Work Required
November 23, 2018
It is important to establish the complete phase diagram between T and LiPb.
Depends on the tritium concentration, the partial pressure /concentration can either obey, or not obey, the Sievert’s law.
We need to measure the tritium solubility down to a partial pressure << 1 Pa.
For such a low partial pressure and low concentration, it is necessary to use tritium for measurement and control purpose.
STAR is set up to do this.
November 23, 2018

11. Tritium recovery
November 23, 2018
Much work has been done, mainly in EC, to develop an efficient tritium recovery process.
However, the efficiency of the recovery process is only about 20%.
The target recovery efficiency is about 75%.
Improvement of the EC process, or the development of a new process, will be necessary.
November 23, 2018

12. What can we do?
November 23, 2018
Permeation window is a possible process to recover tritium from LiPb.
Permeation depends on the square root of tritium partial pressure. Therefore, tritium solubility information will be necessary to the permeation method.
Surface contamination is a key concern for tritium permeation.
Are there other methods?
November 23, 2018

13. Permeation coating
November 23, 2018
There have been much efforts on development of tritium permeation coating to reduce tritium permeation by about a factor of 100.
This goal has not been reached for a large surface area.
Some reported that permeation reduction factor can be much reduced under irradiation.
Under TITAN program, Japan side will develop coating, and US side will test the effectiveness of the coating.
November 23, 2018

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15. Tritium permeation
November 23, 2018
The usual assumption is that tritium permeation is proportional to the square root of tritium partial pressure.
Theoretical prediction is that, at low pressure, tritium permeation will be proportional to the tritium partial pressure.
This pressure dependence of tritium permeation is important for tritium control, and the tritium recovery method based on permeation window.
TITAN will investigate the pressure dependence on permeation at low tritium partial pressure.
November 23, 2018

16. Conclusion
November 23, 2018
There is not sufficient information on many tritium related issues for the LiPb system.
One of the key problems is that we do not have the complete T/LiPb phase diagram.
To do experiments at a hydrogen partial pressure relevant to the blanket condition, tritium has to be used.
STAR will be a key facility to do this work.
The results from this work will be useful for all the LiPb based blankets.
The permeation barrier development will be useful of other type of blankets, such as He-cooled and water-cooled solid breeder blankets.
November 23, 2018