Reactor structure material and method for reducing corrosion of reactor structure material

In this invention, the followings can be used to prevent stress corrosion cracking of reactor structure material, such as: reducing the injection quantity of hydrogen for preventing stress corrosion cracking and injection quantity of noble metals to reduce the transportation of radioactivity to the turbine system; reducing as much as possible the quantity of excess hydrogen in an off-gas system; minimizing the adhesion quantity of rare metals on fuel material surface; suppressing the production of loose particulate iron produced on fuel material surface; and lowering the corrosion potential of the reactor primary system material without increasing oxidation and hydrogenation of fuel materials. A photocatalyst material such as n-type semiconductor 1 is adhered on metal parent material 2 such as stainless steel or inconel of welding material. Hydrogen concentration in rector water is raised if necessary, and current is generated to flow in the metal parent material from the photocatalyst material due to the irradiation of light and radiation existing in the reactor so as to lower corrosion current. One or more kinds among Pt, Rh, Ru or Pd can be adhered on the surface of the optical catalyst material.