Fabrication of micro capsule containing fluorescent magnetic particles for advanced inspection of heat exchanger tubes

Ito, Fuyumi; Nishimura, Akihiko  

Stress corrosion cracking sometimes occurs in the heat exchanger tubes of aging nuclear power plants. At the present time, Eddy Current Testing (ECT) is used to inspect these heat exchanger tubes. When symptoms of corrosion or cracks are found on the inside wall of the tubes, they are usually repaired. As repaired tubes increase in number, the cost of repair work rises considerably. Therefore, discovering tiny cracks has the purpose of ensuring not only progress on safety but also economical benefit. Cracks are observed not only by ECT but also by Magnetic particle Testing (MT), which facilitates visual observation. In the case of MT, a dispersed liquid with magnetic particles is applied to a magnetized sample. However, this dispersed liquid could potentially enter inside the crack. To solve this problem, this paper proposes that magnetic particles be contained inside a micro capsule, this capsule calls Magnetic Particle Micro Capsule (MPMC).