1. magnetic confinement - ENEA - Fusione

3. FUSION TECHNOLOGY 79
3.5 Neutronics
system to reach useful energy resolution will be tested during D-D and D-T
operations at JET.
3.5.4 Evaluation of neutron cross sections for fusion materials (EFF
project)
The correct design of a fusion reactor requires the availability of a complete nuclear
database extending up to 20 MeV in neutron energy. The ENEA Fusion and Applied
Physics Divisions participated in the European Fusion File (EFF) Project by updating
neutron cross-section data. In 2001, the carbon and oxygen cross sections were
newly evaluated on the basis of the latest experimental and theoretical findings. The
neutron capture cross sections were re-evaluated in the entire range of 10 -5 eV up to
20 MeV of incident neutron energy. Model calculations based on state-of-the-art
nuclear structure and nuclear reaction models were employed together with a global
analysis of the latest experimental information. Inverse photo-neutron reaction data
were utilised to cover the energy range above a few MeV. These data and the model
calculations were used for the transitions leading to excited states of residual nuclei.
The resulting nuclear cross-section data were compiled and organised into ENDF 6
nuclear data format. The files were integrated with complete existing data libraries
(including all the reaction channels other than capture). For 12 C, the JENDL 3.2 file
was chosen as a basis; for 16O, the JEF-2 file was selected. The data files were made
available to the community for testing. Preliminary tests were done with standard
format checking codes (FIZCON, PSYCHE, and CHECKR).
3.5.5 Neutronics benchmark experiment on SiC (EFF project)
[3.37] P. Batistoni et al.,
Measurements and
analysis of reaction rates
and of nuclear heating in
SiC, Final report of task
TTMN-002 (1)-001,
Report FUS- TEC- MA-
NE-R-2001
Fig. 3.14 - The SiC block in
front of the FNG target.
Silicon carbide (SiC) is one of the candidate structural materials for a fusion reactor
because it has excellent low-activation, low-decay-heat properties. To validate the
SiC neutron cross-section data in the EFF library, a benchmark experiment was
started in 2000 at FNG. A block of sintered SiC (457 mm x 457 mm, 711-mm thick, 470
kg total weight, 127 pieces) lent to ENEA by JAERI was used (fig. 3.14). The
experiment was completed in 2001 in collaboration with TUD, FZK and the Josef
Stefan Institute of Ljubljana [3.37].
Several nuclear quantities, including neutron and gamma-ray spectra, nuclear
heating and activation rates, were measured at different penetration depths inside
the block irradiated with 14-MeV neutrons (up to about 58 cm, corresponding to
about 10 mean free paths for 14-MeV neutrons). The measurements were compared
with the same quantities calculated using MCNP-4C and the deterministic 2-D code
DORT with EFF-2.4, the new evaluated cross sections for Si-28 included in EFF-3.0,
and the international FENDL-2 and Japanese JENDL-FF nuclear data libraries.
Comparison shows that the
European files and JENDL-
FF well reproduce the
measured quantities, within
the total uncertainty, while
FENDL-2 tends to
significantly under-estimate
the fast neutron flux, as
shown in figure 3.15 where
the C/E values are given for
the neutron flux in the
energy range E > 10 MeV.
The experiment was also
used to validate, through
deterministic and Monte