Technical Design Report Super Fragment Separator

2.4.A6.2.2 Shielding against direct radiation
DRAFT
The shielding of the Super-FRS has been calculated in two parts. The first part of the Pre-Separator
with very strong radiation was simulated with the heavy ion transport code FLUKA [43,44].
In the production target up to 50% of the primary beam can react. But even these ions emerge from
the target and the primary beam and most fragments are dumped inside the first part of the
Pre-Separator, mainly in the beam catchers. For the realistic FLUKA simulation different scenarios
where considered in which the beam after having passed the production target hits each beam
catcher. Hitting mainly one catcher represents the worst case scenario for the nearby shielding. The
cross section of the shielding around one of the beam catchers is depicted in Figure 2.4.163. A
similar cross section is required in the whole first part of the Pre-Separator where the primary beam
may be dumped. The effective dose rates resulting mainly from fast neutrons were calculated
according to Ferrari and Pelliccioni [119].
Figure 2.4.163: Cross section of the radiation shielding in the first part of the Pre-Separator. The result of a
FLUKA simulation of the whole area shows the dose rate during highest intensity primary beam operation
with 10 12 238 U/s hitting one of the beam catchers after having passed the production target. The reduction of
fast neutrons by the inner iron and outer concrete shielding reduces the effective dose rates to a level below
0.5 µSv/h.
For the rest of the Super-FRS tunnel an analytical model has been developed. It is based on the
measurements of double differential neutron yields originated from a 1 GeV/u uranium beam
hitting a thick iron target, dose values can be estimated via the following formula:
e d ⋅ρ
1 −
H ( r,
ϑ)
= H I
( )
0(
ϑ)
⋅ ⋅ λ ϑ
2 ⋅
r
The dose (rate) H ( r,
ϑ)
is derived from the angular dependent constants ) ( H and ) (ϑ λ , the
0 ϑ
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