Severe physical restrictions and high radiation levels make the region under the pressure vessel of a Boiling Water Reactor (BWR) a challenging environment for the removal of control rod drive (CRD) assemblies. Under contract to a Westinghouse subsidiary, Foster-Miller developed a new method for removing and installing these CRD assemblies using a "rigid chain" concept. Each of two chains is driven through a sprocket during installation, creating a back to back rigid chain arrangement - a self-standing, load bearing component that ensures adequate load support during the CRD exchange sequence. This system is modular and rugged. Fast setup is achieved by lightweight modular design. Its simplicity and effectiveness have led to rapid acceptance at BWRs in the United States and Switzerland including: Detroit Edison's Fermi Station; Washington Public Power Supply System's WNP-2 station; and Kernkraftwerk Liebstadt in Switzerland.
