Abstract: A warning system for traffic routes at an avalanche danger hillside is provided wherein the hillside ground is divided in an assumed avalanche falling direction, thus into a series of areas which are e.g. about 30 meters wide. These areas each have at least one associated indication device with an electronic signal output, and the signals of the indication device are fed to a memory which, for a downhill correct sequence of the signals, energizes an avalanche alarm and releases the alarm when, by virtue of the stored experience data, there is no longer a risk below the avalanche area. The indication devices receive an electronic signal output of a receiver for the reflected waves of at least one radar transmitter, and these signals from the indication device are fed to an electronic logic circuit which, for a downhill correct sequence of the signals energizes and releases an avalanche alarm in accordance with the snow movement on the hillside.

Abstract: A method of testing the circulation of a bulk charge of fuel elements in the core of a pebble bed type of nuclear reactor comprises increasing the electrical conductivity of a number of fuel elements and then injecting the marked elements into a bulk charge of other unmarked elements having a lower electrical conductivity at predetermined positions in the core of a nuclear reactor and a measured times. The marked fuel elements are subsequently detected electromagnetically as they are carried in the bulk charge of unmarked elements through an electromagnetic field generated by a detection and measurement station. The elements are marked by including a material having a greater electrical conductivity than the remainder of the element and this material may be coated on the surface of the elements or incorporated in the body of the elements.