Movable in-core neutron detectors for pressurized water reactors

In pressurized water reactors, flux mapping can be carried out by means of a movable in-core neutron detector. The authors have developed such a detector, consisting of a fission chamber and integral drive cable. The article explains, by means of test results, the plateau characteristics, neutron sensitivity, gamma-ray sensitivity, insulation resistance, linearity, stability, resistance to temperature cycling and resistance to neutron exposure. These detectors are already in use in commercial PWRs, and results have been excellent. (auth.)