1. Tritium Recovery in HCPB blanket for DEMO and ITER
Aim of the work
to make a review on the possible TES and CPS processes for HCPB-DEMO, in the light of the need to propose for ITER processes and technologies “DEMO relevant”
to propose design data and operative conditions for TES and CPS in HCPB-DEMO 2003
to carry out a preliminary discussion on the tritium processing in HCPB-TBM in the context of ITER FEAT
Italo Ricapito, Bologna (Italy), May 2006

2. Tritium Recovery in HCPB blanket for DEMO and ITER
TOPICS
briefly on HCPB-DEMO 2003 design
tritium permeation rate into HCS loop from HCPB-DEMO 2003
TES candidate processes for HCPB-DEMO 2003
CPS candidate processes for HCPB-DEMO 2003
considerations on the tritium management strategy in HCPB-TBM
proposals for the next R&D activities

3. Possible flow-diagram for the HCPB-DEMO tritium cycle
He coolant, Q2 + QTO
Q2 to TRS or ISS
TES
He purge, Q2 + Q2O H2
Q2O to WPS
HCS
CPS SG BL
HCPB
blanket
Steam to turbine
Impurities to WGPS
H2, H2O
LEGENDA
HCS: Helium Cooling System
TES: Tritium Extraction System
TRS: Tritium Recovery System
ISS: Isotope Separation System
CPS: Cooling Purification System
WPS: Water Processing System
WGPS: Waste Gas Processing System
SG: Steam Generator

4. Input data used for the calculation
HCPB-DEMO 2003: tritium permeation rate into HCS
Input data used for the calculation
tritium generation rate: 385 g/d
tritium implantation and permeation from FW: neglected (W coating)
TES global efficiency: 0.9
He purge flow= 8000 Nm3/h, 0.4 kg/s*
HT partial pressure in HCS loop: 0.8 Pa,  0.75 Ci/kg**
diffusivity and Sieverts’ constant for Eurofer 97 from literature
recombination coefficient Krec : 1E-26 1E-29 m4 /s***

5. HCPB-DEMO 2003: tritium permeation rate into HCS
Considerations on the assumed input data
* With respect to the HCPB-DEMO 95, a reduction of the He -purge flow-rate has been considered, with a consequent lower load to ISS still keeping a relatively low HT partial pressure in the purge gas stream
** HT partial pressure in HCS loop was fixed as compatible with the limit of environmental tritium release through the steam generators (by permeation + leakage) of 20 Ci/d
*** The assumed range of the recombination coefficient corresponds to experimental data for bare (1E-26 m4/s) and oxidized Eurofer 97 in different conditions

6. HCPB-DEMO 2003: tritium permeation rate into HCS

7. TES for HCPB-DEMO 2003 TES feed stream in HCPB-DEMO 2003
He mass flow-rate (kg/s)
0.4
Volumetric flow-rate at NPT (Nm3/h)
8000
Pressure (atm)
1.1
Temperature (K)
873
HT molar fraction
1.610-5, 16 vppm
HT partial pressure (Pa)
1.8
H2 partial pressure (Pa)
110
HTO molar fraction
510-7, 0.5 vppm*
Q2O molar fraction
1.6510-5, 16.5 vppm
Q2O partial pressure (Pa)
* It is assumed that only 3% of tritium is present in HTO form

8. TES for HCPB-DEMO 2003
Different processes have been proposed in the past to remove tritium (HT and HTO forms) from He purge. The most conceptually different are:
Process A: Cold Traps + TSA (Temperature Swing Adsorption), mainly developed by FZK for HCPB-DEMO 95
Process B: TSA + VPSA (Vacuum Pressure Swing Adsorption), mainly developed by Canadian experts (Sood, Ruthven, Kveton) for HCPB-TBM
Process C: Oxidiser + cold trap (or TSA)
Process D: TSA + Q2 permeators

9. TES for HCPB-DEMO 2003
Process A (FZK proposal for HCPB-DEMO 95): cold traps +TSA
Cold traps E100 for Q2O removal; TSA (columns A100) for Q2 removal;

10. TES for HCPB-DEMO 2003
Main characteristics of the FZK process for TES in HCPB-DEMO 95
Cold trap temperature
173 K
Q2O molar fraction at the cold trap outlet
< 1 vppm
TSA temperature in adsorption phase
77 K
TSA temperature in regeneration phase
160 K
% of He flow-rate in regeneration phase on the feed flow-rate
 15 %
TSA pressure in adsorption and regeneration phases
1 atm
Duration of the TSA cycle
12 h (6+6)
Global Efficiency in tritium removal
> 90 %

11. TES for HCPB-DEMO 2003 Process B: TSA + VPSA TSA VPSA Vacuum pump
Gas to gas heat
exchanger
cooler
Dryer
Regeneration
loop
300K
90K
77K
1 atm
10 atm.
800K
320 K
Heat N2 c
ooler
Vacuum
pump
HT to ISS
280 K
77 K H2
addition
Cold box
TSA
VPSA
Process B:
TSA + VPSA

12. TES for HCPB-DEMO 2003
In the process B (Canadian proposal for HCPB-TBM):
Q2O is removed from He purge by a TSA system, operated at room temperature in the adsorption phase and at 300 °C in regeneration under a purified He stream
Q2 is subsequently removed from He by a VPSA system, operated at 77 K in the adsorption step and under vacuum at 77 K in the regeneration phase

13. Duration of the VPSA cycle: some minutes
TES for HCPB-DEMO 2003
VPSA system
Q2 to TRS or ISS H2
He+Q2
purified He to blanket
Adsorption column V1 V6 V3 V2 V4 V5 VP
To impurity detritiation
Process steps
Feed pressurisation (all valves closed except V1), lasting some minutes
Adsorption at 77 K and 1-2 MPa (all valves closed except V1, V3)
Co-current blow-down (all valves closed except V2, V4)
H2 addition (all valves closed except V6)
Co-current evacuation (all valves closed except V2, V5)
Duration of the VPSA cycle: some minutes

14. H2 adsorption isotherm on 5A zeolite at 77 K
TES for HCPB-DEMO 2003
H2 adsorption isotherm on 5A zeolite at 77 K
Need to operate the VPSA columns at high pressure in the adsorption phase (1-2 MPa)

15. Process C: OXIDATION + COLD TRAP (or TSA)
TES for HCPB-DEMO 2003
Process C: OXIDATION + COLD TRAP (or TSA)
Q2 is oxidised to Q2O by external addition of O2 or by internal oxidation on CuO/Cu2O
Q2O, at a partial pressure of about 110 Pa, is removed by cold traps or TSA

16. TES for HCPB-DEMO 2003
Process D: TSA + Q2 permeators

17. TES for HCPB-DEMO 2003
CONSIDERATIONS ON THE REQUIRED TES EFFICIENCY
TES total efficiency in tritium removal higher than 0.9 is not necessary because there is not need to decrease furtherly the HT partial pressure in the He purge stream and, consequently, the tritium permeation rate
TES efficiency of 0.9 refers to the overall tritium removal removal from He purge, both as Q2 and Q2O. Nevertheless, a Q2O removal efficiency for processes A and B higher than 94 % is required in order to make possible a correct operation of the downstream cryogenic adsorption processes

18. Comparison /1: TES for HCPB-DEMO 2003
for Q2O removal, cold traps can achieve lower dew points than TSA, although a moisture molar fraction less than 1 vppm at the outlet gas stream is not required
Q2O molar fraction at the feed stream is very low, around 17 vppm: the possibility to operate at the required efficiencly both cold traps and TSA for a relatively high flow-rate with a so low moisture molar fraction at the feed stream must be experimentally verified

19. Comparison /2: TES for HCPB-DEMO 2003
for Q2 removal VPSA is much more compact than TSA
VPSA has a smaller tritium inventory because of the smaller adsorbent beds;
VPSA operation is much more complex than TSA
for Q2 removal under TES operative conditions, TSA is more technologically mature than VPSA

20. Comparison /3: TES for HCPB-DEMO 2003
Q2 removal by Pd-Ag permeators is not suitable for TES application because the relatively low Q2 partial pressure in the feed stream
Process of Q2 oxidation + Q2O removal by cold traps or TSA (operated at room temperature) is the simplest one and the most common in industrial applications
Process A (FZK concept for HCPB-DEMO 95) and process C (Oxidation + cold traps or TSA) are the most reliable options

21. CPS for HCPB-DEMO 2003 CPS: THREE MAIN FUNCTIONS
removal of the tritium permeated from the blanket;
He purification from impurities and erosion/corrosion products;
addition of a proper amount of H2O and H2 in order to adjust the oxygen potential in the HCS loop.

22. CPS for HCPB-DEMO 2003
He coolant flow-rate CPS to be processed by CPS, being CTO the tritium concentration at the SG inlet, P the tritium permeation rate from the blanket and CPS the CPS efficiency (DF: tritium decontamination factor):

23. CPS for HCPB-DEMO 2003
Required feed flow-rate to be processed by CPS as a function of tritium permeation rate for different decontamination factor in tritim removal

24. CPS for HCPB-DEMO 2003 Reference data input for CPS in HCPB-DEMO 2003
Gas stream temperature at CPS inlet: 773 K
Gas stream pressure: 8 MPa
T permeation rate into HCS loop: g/d
Total CPS efficiency in the tritium removal: 0.90
He flow-rate in CPS: Nm3/h
HT partial pressure at SG inlet: 0.8 Pa (0.1 vppm, 0.75 Ci/kg)
H2 partial pressure: 500 Pa (62 vppm)
H2O partial pressure: 50 Pa (6 vppm)

25. CPS for HCPB-DEMO 2003 CPS PROCESS, PROPOSED by FZK FOR HCPB-DEMO 95
STEAM GENERATOR O2
OXIDISER
HE1
423 K
CPS PROCESS, PROPOSED by FZK FOR HCPB-DEMO 95 2
filter
H2, H2O
HE2
250 K
cooler/cold trap 2
to WPS
150 K
adsorbent beds 2
to WGPS
77 K

26. CPS for HCPB-DEMO 2003 REMARKS ON THE REFERENCE CPS PROCESS/1
the oxidizer unit contains a metal catalyst (Pt)
the adsorbent material for the removal of impurities and not oxidised Q2 is 5A zeolite
the adsorption phase of the CPS final purification step is carried out at 8 MPa and LN temperature
the regeneration technique of the adsorption process consists of: depressurisation at ambient pressure, heating at room temperature, counter-current He flow

27. CPS for HCPB-DEMO 2003 REMARKS ON THE REFERENCE CPS PROCESS/2
the need to keep a high efficiency of the oxidation step, not less than 94 %, is a critical issue
unusual pressure for the adsorption process;
possible very high feed flow-rate to be processed
amount and type of impurities may have a strong effect on the regeneration step of the adsorption process (higher temperature could be required)

28. Alternative processes
CPS for HCPB-DEMO 2003
Alternative processes
“Internal” Q2 oxidation by a CuO/CuO2 reactor, Q2O removal by adsorption process (in hybrid configuration, high P and room T in adsorption, atmospheric P and high T in regeneration), cryogenic MSB for impurity removal or cold traps
no Q2 oxidation: Q2O removal by adsorption process + Q2 (and impurities) removal by VPSA operated at room temperature

29. TRITIUM MANAGEMENT IN HCPB-TBM
HCPB-TBM in ITER FEAT
NT-TBM
TM and PI-TBM
Duty cycle
0.25
Burn pulse length (s)
450
Tritium generation rate during pluses (mg/d) 92 96
Average daily tritium generation rate (mg/d) 22 23
He coolant mass flow (kg/s)
0.750.88
0.610.72
He coolant pressure (MPa) 8
Helium coolant temperature (°C, in-out)

30. TRITIUM MANAGEMENT IN HCPB-TBM
HCPB TBM: purge gas characteristics at TES inlet (from DDD)
He flow-rate (Nm3/h)
12.1
He pressure (MPa)
0.11
H2 partial pressure (Pa)
110
HT partial pressure at the blanket outlet (Pa)
0.4
Q2O (mainly H2O) partial pressure at the blanket outlet (Pa)

31. TRITIUM MANAGEMENT IN HCPB-TBM
HCPB TBM: input data for HCS and CPS (from DDD)
Average daily tritium permeation rate from HCPB-TBM (g/d) 12
HT partial pressure in HCS loop (Pa)
0.3
H2 partial pressure in HCS loop (Pa)
300
H2O partial pressure in HCS loop (Pa) 36
He flow-rate in CPS (Nl/h)
107

32. TRITIUM MANAGEMENT IN HCPB-TBM
DEMO relevant
TES and CPS for HCPB-TBM
“Ad hoc” designed
Tritium extraction from He purge gas and from He coolant can be accomplished by TES or CPS derived from DEMO.
As an alternative, the possibility to extract tritium from He purge and coolant directly in a simpler and more compact system should be carefully evaluated.
The second option appears attractive especially for the short pulse scenario (burn pulse of 450 s).

33. TRITIUM MANAGEMENT IN HCPB- TBM
TES for HCPB-TBM, “DEMO relevant”

34. TRITIUM MANAGEMENT IN HCPB-TBM
CPS for HCPB-TBM, “DEMO relevant”

35. TRITIUM MANAGEMENT IN HCPB-TBM
Tritium Measurement System proposed by FZK

36. SUITABLE R&D ACTIVITIES
ITER focused
First step: evaluation of the actual need of dedicated TES and CPS as derived from DEMO, for both short and long burn pulse scenario
influence of oscillating tritium generation on the TES and CPS feed streams: time constant for tritium desorption from the ceramic breeder; time constant for tritium permeation from TBM into TBM-HCS
possibility to operate the system batch-wise, using suitable buffer tanks
adaptability of TMS to TES and CPS tasks

37. SUITABLE R&D ACTIVITIES
ITER focused
Second step: if TES and CPS to be tested in ITER FEAT are derived from DEMO, their further development should be performed in parallel for HCPB-TBM and HCPB-DEMO blankets, following the same methodology.

38. SUITABLE R&D ACTIVITIES
DEMO focused
Three main areas of R&D have been identified
Q2 permeation into HCS and through SG structural materials
TES technologies (mainly optimisation of adsorption processes)
CPS technologies

39. SUITABLE R&D ACTIVITIES
Q2 permeation through the blanket and SG structural materials
detailed modelling of Q2 permeation from the blanket into HCS: correct geometry and operative conditions have to be considered
detailed modelling of Q2 permeation through steam generators: suitable geometry and operative conditions have to be considered
extensive experimental campaign aimed at the evaluation of the recombination coefficient (or PRF of oxide layers on He side) for the system Q2-EUROFER and Q2-INCOLOY for different values of Q2O/Q2 molar ratios

40. SUITABLE R&D ACTIVITIES
TES development for DEMO: feasibility of the Q2O removal step
experimental verification of the feasibility to operate cold traps or MSB with high efficiency in removing Q2O at very low concentration (less than 20 vppm) from a He gas stream.

41. SUITABLE R&D ACTIVITIES
TES development for DEMO: Q2 removal, basic studies (Q2-zeolite interaction)
determination of the pure Q2 adsorption isotherm at 77 K on different types of zeolites: 3A, 4A, 5A (all of them are fully available on the market)
determination of the multicomponent adsorption equilibria at 77 K for He-Q2 mixture in the range of foreseen Q2 partial pressure on the above mentioned zeolites;
correlation of the experimental data with suitable models of multicomponent adsorption equilibria: extended Langmuir, IAS (Ideal Adsorption Solution model), RAS (Real Adsorption Solution model).
determination of the kinetics of Q2 adsorption at 77 K on zeolites 3A, 4A ,5A.

42. SUITABLE R&D ACTIVITIES
TES development for DEMO: Q2 removal, process study
construction of an experimental apparatus on lab-scale in order to study the process performance in adsorption and regeneration phase: PILATUS loop in TL-FZK, or similar, is a suitable option
realisation of a computing code able to correlate the experimental data coming from the previous activity and to carry out the process scale-up to higher He flow-rate and different Q2-Q2O composition
optimisation of the process in a suitable loop on pilot plant scale: integration in EBBTF should be suitable

43. SUITABLE R&D ACTIVITIES
R&D activities: flow-diagram of the activities for adsorption process optimisation
Experimental determination of adsorption isotherms
of pure components
Experimental determination
of multicomponent adsorption equilibria
Experimental determination of adsorption kinetics: diffusion in macro and micropores
Data correlation with multicomponent adsorption models
Dynamic simulation model
Experimental results on lab scale apparatus
Design of full scale system
Experimental results on pilot plant

44. SUITABLE R&D ACTIVITIES
CPS processes for DEMO: Q2O removal
a comparative investigation, based on small scale experiments, of the performance of the catalytic oxidation process of Q2 to Q2O by external O2 addition and the alternative “internal” oxidation by a reactive CuO/Cu2O bed under conditions relevant for HCPB-DEMO 2003;
a comparative investigations on cold trap and molecular sieve performance for Q2O removal, again by small scale experiments. For this activity it is recommended to operate with the total pressure, linear velocity and gas composition as close as possible to those foreseen in CPS for HCPB-DEMO.

45. SUITABLE R&D ACTIVITIES
CPS processes for DEMO: impurity removal
First of all, it appears necessary to provide a quantitative prediction of such impurities and their concentration in the HCS loop. Experience gained in the frame of advanced gas-cooled fission reactors should be considered in detail.
Thereafter, small scale experiments on different adsorption process configuration should be accomplished in a suitable facility on lab-scale.
Optimisation of the process has to be carried out on a pilot plant scale: integration in EBBTF should be a good opportunity

46. Summary of the main results/1
a value of 8000 Nm3/h of He purge flow-rate is proposed for HCPB-DEMO 2003, about 35 % less than in the previous HCPB- DEMO 95
the tritium permeation rate from the blanket into HCS loop was estimated in the range of 0.1 10 g/d
Q2-Q2O composition at in the purge gas stream at the TES inlet was provided, as a consequence of points a) and b)
differently from the past, a total TES efficiency in tritium removal of 0.9 is proposed but the efficiency in Q2O removal must be not less than 0.94

47. Summary of the main results/2
e) among different candidate processes two of them (FZK process and Q2 oxidation + cold trap or MSB) appear as the most attractive for TES application
main design data for CPS have been provided (gas stream flow- rate and composition, CPS efficiency in tritium removal), consistent with a HT partial pressure in the HCS loop of 0.8 Pa
possible candidate processes for CPS have been considered: the main concern arise from the removal of impurities by cryogenic adsorption processes
suitable R&D activities in the field of Q2 permation, TES and CPS have been proposed and the related flow-diagram for a systematic study and optimisation of adsorption processes provided