ITERの簡易モデルを用いたMCNPコードによるITERの仮想真空容器内中性子計測
Synthetic In-vessel Neutron Diagnostics for ITER by using the MCNP
Code with Simplified ITER Model

8P67西谷健夫1)、石川正男2)、CHEON MunSeong3)、HONG SeongHee3)、
RODIONOV Roman4)、DI SARRA Silvia5)、KRASILNIKOV Vitaly5)
著者名 NISHITANI Takeo1) , ISHIKAWA Masao2), CHEON MunSeong3), HONG
SeongHee3), RODIONOV Roman4), DI SARRA Silvia5), KRASILNIKOV Vitaly5)
著者名

所属略称 (1)名大、(2)QST、(3)KFE、(4)RFDA、(5)ITER機構
所属略称 (1)Nagoya Univ., (2)QST, (3)KFE, (4)RFDA, (5)ITER Org.
It is important to predict the diagnostics output prior to thereal plasma experiment. We have established a synthetic
in-vessel neutron diagnostics for ITER by using theMCNP code with a simplified ITER model. By using thesynthetic in-vessel neutron diagnostics, we can evaluate
the response of those neutron diagnostics against thechange of the plasma parameters.
The precise MCNP model of an ITER 40 degrees
sector, the so-called C-model [1], is provided by the ITER
Organization, however, it is very heavy and takes a longtime to simulate the response of in-vessel neutron
diagnostics. We have performed simplified 20 degrees and360 degrees ITER models as the synthetic in-vessel
neutron diagnostics [2], which include neutron flux
monitors (NFM) in an equatorial port, micro fission
chambers (MFC), diverter neutron flux monitors (DNFM),
and a neutron activation system (NAS).

Port plugà

Fig. 1 Schematic views of the ITER 20 degrees sector model forthe in-vessel neutron diagnostics.

Figure 1 shows the schematic views of the 20 degrees
sector model, which includes Toroidal Field Coils (notshown in Fig.1). In this model, all in-vessel neutron
diagnostics are assumed to be installed in the same sector.
The equatorial port (EQ) plug with NFM is imported fromthe EQ#1 detailed structure of the C- model. Shielding
blankets are modeled with armor plates and homogenizedshielding blocks. The model of the divertor cassette has acontinuous structure in the toroidal direction.
A benchmark calculation has been performed forneutron spectra at MFCs and DNFMs to confirm thevalidity of the simple model. It is found that neutron
spectra at MFCs by the simple model agree well withthose by C-model. However, neutron spectra at DNFMs
by the simple model are a little bit under estimationcompared with those by C-model.
The absolute calibration of the detection efficiency
for the total neutron yield in the whole plasma is one of
the most important issues in neutron diagnostics. In ITER,
compact D-T neutron generators will be used as a neutron
source for the neutron calibration, where the neutron
source will move in the vacuum vessel. Here, thesimulation for the neutron calibration using a compact DT neutron generator is investigated by MCNP calculations
with the simplified model.
Table 1 list the detection efficiencies of NFM,
DNFM and MFC for the ITER standard plasma, anidealistic 14 MeV line source, and the compact D-T
neutron generator moving on the plasma axis where thegenerator is facing to the radial direction. Detection
efficiencies of NFM and DNFM for the neutron generator
are 30% and 10% overestimate against those for thestandard plasma, respectively. On the other hand, thedetection efficiency of MFC is 6% under estimate againstthat for the standard plasma.
Table 1. Detection efficiencies of NFM, DNFM and MFC.
Detection efficiency (counts/souce)
Diagnostics Standard plamsa 14MeV line source Neut Generator
NFM
1.04E-08
1.19E-08
1.34E-08
DNFM(U-235)
2.83E-11
2.92E-11
3.08E-11
MFC(lower)
2.73E-11
2.44E-11
2.57E-11[1] D. Leichtle et al., Fusion Eng. Des., 136, 742-746 (2018).
[2] L. Bertalot et al., J. Isntrum., 7, C04012 (2012).