Patent Number: 048184713
Section: abstract

A Local Power Range Monitor (LPRM) string is employed between BWR fuel assemblies arranged in side-by-side spaced positions. The string has a hollow tube and neutron detectors located therein at spaced axial locations and being adapted to provide local power monitoring information. The hollow string tube is adapted to receive a neutron flux sensitive probe for calibrating the detectors. Each fuel assembly has an outer hollow tubular channel surrounding fuel rods and spacers disposed within and axially along the channel and about the fuel rods. The spacers are composed of a material incapable of producing a localized change in neutron flux. Elements in the form of strips of a neutron absorber material are attached to the exterior of the channel of each fuel assembly at a respective corner thereon and located axially at different known positions therealong and adjacent to the hollow string tube. The material composing the strips is capable of producing a localized change in neutron flux such that, upon passage of the probe through the hollow string tube and past the strips, the probe will sense the neutron flux change being produced by each of the strips and thereby the position of the probe can be tracked as it is moved through the string tube.