Page 336 - Fundamentals of Magnetic Thermonuclear Reactor Design

314 Fundamentals of Magnetic Thermonuclear Reactor Design

Self-recovering CaO, AlN, Y O -based coatings or multilayer cermet barri-
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ers are candidate electrically insulating materials. ITER is a unique opportunity
to see if their function is affected by the MFR’s severe environment, which is
impossible to do through off-reactor experiments or with fission reactors. The
environment includes factors, such as the fusion neutron fluxes, liquid metal
flows, magnetic field, heat load at the DEMO-S blanket level, thermal cyclic
loading, impact of the purification and chemical control system, and the need
for maintaining a given liquid metal content.
A number of the ITER and DEMO-S parameters characterising different
impacts are close, although some cannot be obtained simultaneously (e.g. the
coolant flow rate and temperature rise magnitude). The neutron fluence is much
lower in ITER than in DEMO-S, and additional tests, using a stronger neutron
source may be needed, if the fluence impact on the electrically insulating barrier
is substantial.
Thermal Mechanical Characteristics. Because the TBMs and the DEMO-
S blanket have virtually the same geometry and coolant temperature/pressure,
one can reliably simulate the temperature and mechanical stress fields in TBM
blanket internal elements, as well as in side and rear walls. From the thermal
mechanics perspective, the cyclic mode of the ITER operation is more stressful
than the DEMO-S continuous operating mode. This increases the reactor com-
ponent’s cyclic strength margin.

10.5.2 Characteristics of Test Blanket Modules
Each ITER member state has proposed by the end of 2008 two design versions
of the test blanket module, except for the Indian TBM Team with one version
(Tables 10.5 and 10.6) [3,9,11–18]. The first one stipulates the use of existing
materials and technologies. The second aims at tomorrow’s materials and tech-
nologies and is encumbered with many difficulties. The proposed TBMs are of
course consistent with the member countries’ blanket concepts.
There are two TBM groups based on two breeder blanket concepts. Group
one includes helium- or water-cooled ceramic blankets. They use ferritic or fer-
ritic/martensitic steels as structural material, a ceramic breeder in the form of
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Li SiO or Li TiO pebbles (with a 40%–90% Li enrichment) and beryllium
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(porous material or pebbles) as a multiplier.
The coolant pressure is 15 and 8 MPa for water and helium, respectively,
and the temperature range is 280–325°C and 300–500°C for water and helium,
respectively. A purge stream of helium with a small percentage of hydrogen at
0.1–0.15 MPa is used to extract the tritium.
Group two is represented by modules employing a liquid metal (PbLi or Li)
as a tritium breeder, and helium, liquid metal or a combination of the two as a
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coolant. The breeder is up to 90% enriched with Li. The module generally oc-
cupies around one-half of the test port void space in the toroidal direction and
has a maximum possible radial dimension. One exception is the Russian version