Prime pagine RA2010FUS:Copia di Layout 1 - ENEA - Fusione

technology programme (cont’d.)
progress report
2010
071
In a first stage, the blanket/manifold original description
was not modified: the coils cut across the interposing
structures. In a second stage, manifolds have been
simulated in front of poloidal coils located behind gaps
(fig. 3.32). Poloidal, radial and toroidal variations of all
relevant nuclear parameters are provided, as well as
detailed nuclear heating tables useful for thermal analysis.
In the original configuration (without front manifolds) the
total nuclear power deposited on ELM coils is ∼3 MW. The
peak nuclear parameters obtained on the conductor are:
nuclear heating 1.7 W/cm 3 and damage 0.4 dpa.
Concerning the insulator: maximum cumulative dose is
4210 MGy, dose rate 211 Gy/s and neutron fast fluence
3.45×10 20 n/cm 2 . For stainless steel components, the
He–production peak is 6.5 appm.
Nuclear parameters show a great spatial variation. Peak
values are found in limited zone close to the blanket gaps:
figure 3.33 shows the toroidal profile of the nuclear heating
in the upper toroidal ELM front components. The peak
corresponds to the poloidal gap. An increase of about 50%
is obtained in this zone with respect to the parts of the coils
far from the gap.
Figure 3.34 shows the radial profile of the nuclear heating
in CuCrZr in the toroidal coils of lower ELM coils and
connecting poloidal segments with and without a front
manifold. Without a front manifold, the ratio between
nuclear heating values in front and rear coils is about 0.3.
By comparing top and bottom toroidal results, the nuclear
heating in the bottom coils shielded by blanket modules is
about 50% of that in the top. With a front manifold, the
radial profile exhibits a steeper variation: the ratio between
rear and front coil nuclear heating values drops to 0.2. The
increase due to the manifold is about 60% due to the
presence of water and large void space. The increase in the
other quantities is lower than that in nuclear heating except
for Helium production in the zones behind the manifold.
Regarding the impact on the vacuum vessel reweldability,
the He–production value does not exceed that of the
original configuration (max He–production 0.6 appm).
With heterogeneous manifold located in front of the
poloidal coils, the He–production exceeds the limit but
only in zones where the rewelding is not foreseen.
Comparing the nuclear loads on CuCrZr and C10700 for
the conductor and of spinel and MgO for the insulator, no
significant variations are found. Hence, the neutronic loads
on these materials can be considered as non relevant issues
for selecting these components.
Activation analysis has been carried–out with FISPACT
2007 by using the neutron spectra calculated in 3–D with
MCNP5 and the safety scenario SA2. Total neutron fluxes
vary from 7.3×10 12 n/cm 2 /s in the more shielded segment
to 5.1×10 13 n/cm 2 /s on the nose of the connecting coils in
the gap between blanket modules. Figure 3.35 shows the
dose rate versus time after irradiation in the front part of
the connecting segment. At the shutdown, peak specific
Poloidal segment of ELM coils
Figure 3.32 – Radial section of MNCP model of ITER.
Poloidal ELM coils in the configuration a) without
front manifold and b) with manifolds
Nuclear heting (W/cm 3 )
1.6
1.2
0.8
0.4
0.0
SS support-front
SS envelope
MgO insulator
Water
CuCrZr
conductor
0 30 60 90 120
Toroidal position (cm)
Figure 3.33 – Nuclear heating toroidal profile of the
front coil and front support of upper ELM toroidal
top coils
Nuclear heating (W/cm 3 )
2
1
0
4
Tor top lower ELM
Tor bottom lower ELM
Pol no front manifold
Pol + front manifold
8 12 16 20
Distance from the VV (cm)
Figure 3.34 – Nuclear heating on CuCrZr radial
profile in lower ELM coils and poloidal connecting
segments with and without front manifold
Contact dose rate (sv/h)
10 4 CuCrZr
C10700
MgO
10 2
Spinel
SS
10
10 -2
10 -4
10 -6 Min Hour Days Month Year
10 -8 10 -4 10
10 2
Time after irradiation (years)
Figure 3.35 – Peak contact dose rate versus time
after irradiation in the most irradiated coil