Design of the Information Processing Unit of the Ferd (Fuel Element Rupture Detector) System of EBR-II

In the detection of fuel element cladding failures in sodium-cooled reactors of high power density, it is desirable to discriminate between different types of such failures. Cladding rupture signals consist of count rate excursions, whose shape or "signature" is expected to depend on the type of cladding failure; the duration of these phenomena is expected to amount to a few minutes, and possibly include "spikes" of 0.1 sec. The accurate recording of such signals requires a display system bandwidth of the order of 100 cps; at the same time, no display or record is normally required except during an excursion. The system devised to meet these requirements inscribes counts directly on a continuous loop of magnetic recording tape and also presents them to a "prompt" count rate meter. After a short delay, the tape is read into another count rate meter which drives a fast oscillograph; the readout system is turned on only when the prompt CRM signal exceeds a predetermined level. The record thus consists of pre-signal background during the write-readout delay plus slightly less than 5 min of excursion signal, on two channels.