In pool neutron radiography of a BWR control blade

The control blades of boiling water nuclear power reactors (BWR) are an important part of their safety system. The blades are formed of an array of stainless steel tubes filled with boron carbide as a neutron absorber. It became obvious that these blades could lose effectiveness before the end of their mechanical design life. Stress corrosion cracking will occur at a certain exposure and tritium and boron carbide can be lost to the coolant. The latter will reduce effectivity of the control blades. A nondestructive method to detect significant boron losses would be of help to assess the quality of the blades. Neutron radiography has been used on such a control blade. (Auth.)