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Blanket Chapter | 10 311

TABLE 10.4 Comparison of ITER TBMs and DEMO-S Blanket Parameters
Parameters ITER TBMs DEMO-S blanket
Reactor operation mode Pulsed Stationary
2
Number of pulses (cycles) 3000 10 –10 3
5
Cycle characteristic, i.e. plasma burn/ 400/1800 10 …10 6
pause time (s)
2
Neutron flux FW load (MW/m )
Average 0.78 2.52
Peak 3.4
2
Fast neutron fluence (MW year/m ) 0.1 (expected) 10–15
0.3 (maximum)
2
Heat flux FW load (MW m )
Average 0.25 (expected) 0.4
Peak 0.5 (design) 0.7
Blanket module dimension (m)
Radial 0.015–0.626 0.5–1.0
Poloidal ∼1.7 2–7.3
Toroidal 0.5–0.65 1–1.5
Coolant
Helium pressure (MPa) 8 8–10
Temperature range (°C) 300–500 220–500
Liquid metal temperature range (°C) 300–550 350–700
Coolant flow rate (m/s)
Helium 45–67 22–115
Lithium 0.45 2.2
Rate of tritium breeding in Li–V blanket
3
Specific rate (mg/s m ) 0.03 0.4
Full rate (mg/s) ∼10 −3 3.09

The much lower neutron flux FW load and fast neutron fluence in ITER
compared to DEMO-S are to result in an adequate decrease in the following:
l tritium breeding specific rate (per unit volume of the BZ),
l fast neutron fluence in structural materials,
l density of radiation energy release.

To obtain a meaningful physics and engineering information, the TBM test-
ing in ITER should be complemented with material science research under
more intense neutron radiation.