Patent Number: 041845145
Section: summary

The invention relates to a valve system for actuation or de-actuation of a device, and more particularly to a valve system incorporating single failure protection logic. Valve systems for applications such as actuation or de-actuation of a control rod assembly of a nuclear reactor are known in the art. However, prior known valve systems for reactor scram applications have not incorporated the single failure criteria which protects against spurious action in case of a single failure, nor allowed for testing of the valves during normal operational conditions without either causing or preventing the safety action as required by the reactor protective systems. SUMMARY OF THE INVENTION The present invention provides a simple valve system, which incorporates single failure protection logic for a control rod system of a nuclear reactor, by means of three independent input signals combined in a function commonly known as two-out-of-three logic, which meets the above-mentioned single failure criteria while allowing testing of the actuating valves during normal operation of the reactor protective systems. Using the input signals as independent and redundant actuation/de-actuation signals, a single failure, or failure of the corresponding valve assembly or valve set, will neither prevent the desired action nor cause the undesired action of the associated mechanism. Therefore, it is an object of the invention to provide a valve system which incorporates a single failure protection logic. A further object of the invention is to provide a valve system which allows actuation or de-actuation of a device by means of three independent input signals combined in a function known as two-out-of-three logic. Another object of the invention is to provide a valve system wherein a single signal failure, or failure of the corresponding valve, will neither prevent the desired action nor cause the undesired action of an associated mechanism. Another object of the invention is to provide a valve system which allows testing of the system valves during normal operational conditions without either causing or preventing the action as required by the associated mechanism. Other objects of the invention will become readily apparent from the following descriptions and accompanying drawings.