Abstract: There is provided a method and apparatus for electric-arc welding, in which an alternating current of positive and negative pulses is supplied to produce an electric arc between a welding electrode and a workpiece. The ratio of the durations of the positive and negative pulses of welding current is arranged to be changed in response to a signal from a sensing device adapted to sense a change in a characteristic of the electric arc so as to provide optimum welding current for changed welding conditions. The ratio of the amplitudes of the positive and negative pulses may also be varied in response to a signal from a sensing means.

Abstract: A nuclear reactor fuel element has within its protective sheath an insert whereby it may be uniquely identified. The insert bears an array of markings at spaced positions to produce a series of clock pulses on presentation of the insert to a detector responsive to each marking and further markings at some only of the spaced positions to vary the series of signals produced on presentation of the insert to the detector, thereby providing numerical identification pulses.