A gas shut-off valve is a security component used in the intelligent gas meter. The gas shut-off valves used by Osaka Gas Co. are characterized by : (1) a 100% retrieval rate within ten years after installation of the gas meter, (2) an established retrieval procedure, and (3) a single model complying with identical specifications. Taking advantage of these features, the authors have developed a reuse method for gas shut-off valves. Specifically speaking, the accelerated deterioration test conditions have been established as a statistical procedure has been developed for determining the reusability rate, and the criterion for evaluating reusability has been clarified.

Recycled products have been prepared with immiscible waste plastics and their effects on the radiation shield were examined. The results obtained were as follows: Radiation dosage in the air decreased exponentially rapidly even in the absence of the shield materials. Recycled products having 15~24cm thickness showed apparently radiation shield effect and dosage decreased to ca. 40~60% at 30cm distance from radiation sources.