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

070
progress report
2010
15 cm radius); b) neutron and gamma spectra at the
detector location; c) analysis of the components of the
collided neutron spectrum.
The estimation of neutron spectra and
collided–to–uncollided ratio(C/U) is useful to evaluate
the neutronic performance of the HRNS collimator in
both configurations (i.e. variation of the background with
the distance inside the cavity) and to characterize the
radiation field inside it. Figure 3.29 shows the C/U values
for 15 cm and 5 cm radius: the latter option is more
effective in the collimation, especially in the front regions.
Neutron spectra for 15 cm and 5 cm radii at the detector
position are shown in figure 3.30.
Figure 3.28 – The HRNS inside the port plug: in pale
blue the concrete collar
Collided/uncollided
1.6
1.2
0.8
0.4
0.0
800
5 cm radius
15 cm radius
1200
1600
Distance from the torus axis (cm)
Figure 3.29 – Collided to uncollided ratio at different
positions along the HRNS collimator: 15 cm (red) and
5 cm (black) radius
Neutron flux (n cm2/MeV/source n)
10 -10
10 -12
10 -14
0 10 20
Energy (MeV)
Figure 3.30 – Neutron spectra at the detector position
D for 15 cm (dotted blue) and 5 cm (straight black)
radius
In order to fully characterize the radiation field at the
detector position D, photon flux and spectra have been
evaluated as well. The absolute values of the gamma flux
are: 5.32×10 8 γ/cm 2 /s and 3.29×10 9 γ/cm 2 /s for 5 cm
and 15 cm radius respectively .
The collided spectrum at the detector position has been
analyzed in order to isolate the contribution due to
different zones of the torus (inboard and outboard zones).
The results obtained show that a large contribution to the
collided neutron spectrum is due to the particles scattered
only by the inboard side, which penetrate into the
collimator, thus reaching the detector position. These
results confirm the effectiveness of the port plug shielding
capability [3.11].
Three–dimensional neutronic analysis of the ITER
in–vessel coils
In the frame of the contract ITER/CT/09/4100001120
a complete neutronic analysis has been performed for the
design of the in–vessel coil systems by using the MCNP5
code in a full 3–D geometry. A detailed geometry of edge
localised mode (ELM) and vertical stabilizing (VS) coils
based on the last design specifications has been integrated
into the last version of 40° ITER Alite MCNP model
(fig. 3.31).
cm
800
400
0
VS upper
Upper ELM
Central
ELM
Lower
ELM
-400
VS lower
Figure 3.31 – Vertical section of Alite–4
MCNP model with In–vessel coils
-800
-800
-400
0
cm
400 800