Design of ITER neutron yield monitor using microfission chambers

We propose a microfission chamber system which will be installed near the first wall region of ITER as the neutron yield monitor. This system has a wide dynamic range of 10(10) with a temporal resolution of 1 ms and is easily calibrated by a neutron transport calculation. The U-234 (80%) + U-235 (20%) fission chamber, the lifetime of which is about four times longer than that of the U-235 chamber, can be used in ITER for one third of the ITER lifetime. We expect that these detectors will be operated in a high magnetic field near the first wall of ITER. Four sets of the detectors will be installed in the large side port and three blanket modules. Techniques for the replacement of those detectors are discussed. (C) 1997 Elsevier Science S.A.