Lynchburg, VA--Inserting or retracting rod cluster control assemblies (RCCAs) regulates the rate of nuclear fission in the core of a nuclear reactor. Typically, the RCCA comprises 16 to 24 control rods, each one pinned and lock-welded at its upper end to a "spider assembly" that couples to a drive mechanism.
Problem: Due to flow-induced vibrations, mating components may cause the cladding of some control rods to wear. Current rod cluster control assemblies must be replaced as a whole, even when only one rod needs repositioning or replacement.
Solution: A fastening system that allows repositioning or re-placement of individual control rods to allow continued use of the RCCA.
Douglas Attix of Framatome Cogema Fuels believes his design accomplishes this goal. Key aspects include:
Screwing the control rod into the spider boss brings the cap's spring-loaded blade into contact with the coupling's slotted face. Each time the blade aligns with a slot, it "clicks" in. Additional torque causes the blade to "cam out" of the slot and click into the next. When the desired position is reached, installation is complete.
Because the control rod is restrained from rotation upon application of less than a prescribed amount of torque, vibration and other small forces will not rotate the coupling with respect to the boss. Furthermore, control-rod installation, repositioning, or removal from the assembly can occur remotely under water at the reactor site.
Additional details…Contact Douglas Attix, Framatome Cogema Fuels, P.O. Box 10935, Lynchburg, VA 24506-0935, (804) 832-2728.
In addition to the engineers mentioned on these pages, three others also won Edmund Scientific telescopes. They are: Margaret Lowen, of Fluid Management, a unit of IDEX Corp.; and Lev Freiden, of Patriot Sensors and Controls Corp. We will report on their innovative projects in a subsequent issue.