Neutron Transport Analysis for In-vessel Diagnostics in ITER

Nuclear transport analysis using the MCNP code and heat analysis using a general purpose Finite Element Method code ANSYS 11, respectively, have been carried out for in-vessel components of the microfission chamber (MFC) and the poloidal polarimeter. The nuclear heating rates of the MI cable and the exhaust pipe of the MFC are highest in the gap between two adjacent blanket modules and decrease at greater distances from the gap. Heat analysis using the nuclear heating rate calculation indicates that the maximum temperature of the exhaust pipe can be lowered by changing the distance between two cooling clamps. The nuclear heating rates of the first mirrors of the poloidal polarimeter in the upper port plug are high (> 1 W/cc), and the radiation shield could reduce this rate only by a factor of 2 ~ 4. This heating likely is caused by the effect of streaming neutrons due to an overlap of the beam lines. However, it has been found that the nuclear heating rate can be reduced by reducing the diameter of the beam transmission line.