Neutron flux measurement channels

Neutron flux measurement channels (KNI channels) are one of our stable and long-term products. KNI channels have been supplied by ŠKODA JS to VVER nuclear power plants since 1989. The original design with detectors from the Russian company POZIT was replaced in 1996 by design with detectors from the American company IST (now Mirion Technologies).

Neutron flux measurement channels

Self-powered detectors with a rhodium (Rh) emitter are used to determine the power distribution in the core of VVER reactors. The detectors are designed to check the distribution of neutron flux density along the height and radius of the core by constantly converting neutron radiation into electric current. The signal from these detectors is led to a measuring apparatus, which processes this signal and thus transmits in real time basic information about the state of the core and the primary circuit and important parameters of the secondary circuit. The KNI channel consists of a neutron flux measurement channel armature and the Rh self-powered detectors. The KNI armature ensures the deployment of the Rh self-powered detectors, protects the detectors from the influence of the primary circuit coolant and hermetizes the channel outlets from the reactor. The detectors are located in the reactor core in assemblies called neutron flux measurement channels. The KNI channels pass through the nozzles of the block of protective tubes and are inserted into the core at 36 coordinates (in the VVER 440 reactor) or at 64 coordinates (in the VVER 1000 reactor). Each channel contains 7 detectors, which are evenly distributed along the height of the core.

At ŠKODA JS, we have been continuously producing and supplying these products since 1989. During that time, we have not only delivered over 800 KNI channels to both Czech nuclear power plants, but also over a thousand pieces to Jaslovské Bohunice in Slovakia and Paks in Hungary.

In 2020, we signed several contracts for the supply of KNI channels to both Czech nuclear power plants. We will gradually supply over 80 KNI channels to the Temelín NPP in several stages. To Dukovany NPP, we gradually supply almost 30 pieces of KNI.

Interesting numbers

9867 mm – max. total length of the KNI for VVER 440 reactors (produced in 6 various designs)
12290 mm – total length of the KNI for VVER 1000 reactors (produced in one design)
2000 more than two thousand KNIs delivered since 1989