1. magnetic confinement - ENEA - Fusione

3. FUSION TECHNOLOGY 101
3.10 International Fusion Material
Irradiation Facility (IFMIF)
[3.48] S. Tosti et al.,
Testing of a catalytic
membrane reactor (CMR)
for decomposition of
tritiated water from
breeder blanket purge
gas in a closed loop pilot
plant, ENEA Internal
Report FUS TN BB-TS-
R-003 (2001)
[3.49] S. Tosti et al., Fus.
Eng. Des. 49–50, 953
(2000)
[3.50] S. Tosti et al,
Method of bonding thin
foils made of metal alloys
selectively permeable to
hydrogen, particularly
providing membrane
devices, and apparatus
for carrying out the
same, European Patent EP
1184125 A1 (2001)
[3.51] S. Tosti et al., Pd-
Ag membrane reactors
for water gas shift
reaction, to be published
in Chem. Eng. J.
[3.52] A. Basile et al,
Sep. Purif. Technol. 25,
549 (2001)
[3.53] S. Tosti et al.,
Characterization of thin
wall Pd-Ag rolled
membranes, to be
published in Int. J.
Hydrogen Energy Science
Fig. 3.42 - Measured
conversion values for the
water gas-shift reaction.
Two data acquisition systems for the tests at the cyclotron were developed at ENEA
Frascati: a) pulse mode based on a PCI card and LabVIEW software, with inputs for
8 channels and counting frequency up to 10 MHz; b) current mode based on CAMAC
modules and LabVIEW software. The neutron code SAND-II (for analysis of the
neutron activation data taken in the irradiation experiment) was implemented.
3.11.1 Tritium recovery from tritiated water
3.11 Fuel Cycle
The activities carried out concern the development, production, and testing of rolled
Pd-ceramic membranes and membrane reactors for the water gas-shift reaction
[3.48].
A pilot plant for testing membranes and membrane reactors in operating conditions
relevant to a “closed loop process” [3.49] for tritium recovery from tritiated water
was assembled.
The Pd-Ag rolled sheets were used to fabricate permeator tubes by a new welding
procedure. This new technique, an alternative to the inert gas tungsten arc welding
previously used, avoids the formation of thermal stressed zones along the permeator
tubes [3.50]. The rolled membranes were tested at 135-360°C with a hydrogen
transmembrane pressure in the range of 130-180 kPa and hydrogen flow rates up to
1.02×10 -4 mol s -1 . Complete hydrogen selectivity and good chemical and physical
stability were observed in long-term tests. The membrane reactors were tested at 325-
330°C, with a feed pressure of 100 kPa with reference to the water gas-shift reaction
CO+H 2 O⇔H 2 O+CO 2 .
High reaction conversion values in the range 95-99% (above the equilibrium value,
about 80%) for the water gas-shift reaction were measured, and the effects of the flow
rate and excess water in the feed stream were evaluated [3.51, 3.52]. The excess water
in the feed flow rate produces an increase in the reaction yield, according to the
theoretical analyses. Figure 3.42 reports three cases:
• equimolar feed ratio (CO=H 2 O);
• excess water (H 2 O=0.6, CO=0.4);
• excess water and the presence of a reaction product (H 2 O=0.3, CO=0.5, CO 2 =0.5).
The tests on the membrane reactors have demonstrated the applicability of
membrane technologies for the decomposition of tritiated water from breeder
blanket purge gas as well as for hydrogenation or dehydrogenation processes
involving the use or
Reaction conversion (%)
99
98
97
96
95
0
CO=H 2 O=0.5
CO=0.4 H 2 O=0.6
CO=0.2 H 2 O=0.3 CO 2 =0.5
4 . 10-5 8 . 10-5 1.10-4
CO feed flow rate (mol/s)
production of extremely
pure hydrogen.
In addition, the effect of
contaminants on the
interaction of hydrogen
gas with palladium and
the modification of the
membrane surface were
studied by characterising
the Pd-Ag rolled
membranes in long-term
tests [3.53].