Patent Number: 040070859
Section: summary

BACKGROUND OF THE INVENTION This invention relates to nuclear reactor fuel elements. It has been proposed that nuclear reactor fuel elements of the kind in which nuclear fuel material is enclosed in a protective sheath should be individually identifiable by providing within each sheath an insert which is unique to that fuel element. Such inserts may conveniently be provided with markings whereby a digital output train of pulses can be produced, on passage of the fuel element through an activated eddy current head, for example, and de-coding equipment can readily be devised to accept these sequential pulses. However this is a time dependent function and if the position of the markings is to be correctly identified it is essential to control strictly the relative movement of insert and marking detector. This may be difficult. SUMMARY OF THE INVENTION According to the present invention an insert for a nuclear reactor fuel element whereby the fuel element may be individually identified bears an array of markings at spaced positions to produce a series of signals on presentation of the insert to a detector responsive to each marking and further markings at some only of said positions to vary the series of signals produced on presentation to the detector. The insert can thus provide both clock pulses from the array of markings at spaced positions and numerical identification pulses from the further markings to ensure uncritical time dependence when the insert is passed through a detector. Also according to the invention is a nuclear reactor fuel element comprising nuclear fuel material within a protective sheath and including within the sheath an insert in accordance with the preceding paragraph. Preferably the insert is a bar of metal in which all the markings are holes extending through the bar, the further markings being at right angles to the array at spaced positions. As an alternative to holes the markings may be grooves with the further markings provided by deepening the grooves. The bar may be hollow, that is tubular in form. For the further markings which are to provide the individual identification a binary coded decimal system is preferred, that is one in which four markings are provided for each decade to represent 8, 4, 2, and 1. A further marking may also be provided similarly to provide a lead-in pulse for each decade.