Abstract
The paper discusses the servicing of nucleonic instruments under factory conditions and considers some of the problems which have arisen in the British Atomic Energy Project. The annual failure rates of some of the standard instruments are given and attention is called to the component failures. It is noted that much progress has been made in improving the reliability and life of some of the newer components, e.g. Geiger-Muller counters, and that the failure rates are highest for the more orthodox components, e.g. thermionic valves and resistors. Experiences are quoted from British, American and Canadian sources. Reviewing the analyses presented, an attempt is made to lay down a number of guiding principles to follow when designing complete instruments.