Page 322 - Fundamentals of Magnetic Thermonuclear Reactor Design

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RF DEMO-S, and the Japanese Helium Cooled Solid Breeder (JA HCSB) proj-
ects (carried out in the EU, Russia and Japan, respectively). Projects with a simi-
lar ideology are underway in the USA, China and Korea. They employ tritium
breeding lithium ceramic pebbles and an 8–10 MPa helium flow as a coolant.
There are three design versions of the breeder elements. In the first version,
breeder ceramic material is placed inside externally helium-cooled tubes (the
‘breeder-in-tube’ configuration); in the second, helium flows inside the tubes,
and the breeder material is outside, with tubes oriented poloidally or radially.
In the third one, pebble bed ceramic material is placed between helium-cooled
panels. The ceramic breeder consists of a layer of pebbles of the same diam-
eter or different diameters. The pebble bed fill factor is ∼63% in the first case,
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and ∼82% in the second case. The lithium ceramics enrichment with Li is
40%–90%, and its temperature application window is 300–1000°С, depending
on the ceramics type.
The ceramic breeder is expected to last until an 11%–20% lithium burn-up.
A purge stream of a helium-hydrogen mixture is ran through the ceramic mate-
rial at ∼100 Pa to extract the tritium. Tritium transfer lines have diffusion barri-
ers, intended to reduce tritium losses.
A RAFM steel is utilised as a structural material. It has a durability of 70–
2
90 dpa (≤10 MW year/m ). Beryllium in the form of either pebbles or layers
of porous material acts as a multiplier. The temperature application window is
300–710°С for the Be pebbles and 400– 550°С for the porous material. Helium
cooling the FW and the BZ has the same parameters.
In the EU HCPB test blanket project, a lithium ceramics pebble bed is placed
between helium-cooled panels on the inside (Fig. 10.2). Beryllium pebbles oc-
cupy the space between those panels on the outside. In the Russian blanket
design, the BZ channels are a coaxial assembly of 28-mm dia. tubes with 1-mm-
thick walls (Fig. 10.3).

FIGURE 10.2 Schematic diagram of the European helium-cooled ceramic tritium breeding
blanket.