The Nuclear Regulatory Commission has told companies that operate nuclear reactors that they may need to carry out further inspections of pressurized water reactor heads in which corrosion or other problems have been found.

NRC's bulletin, issued Aug. 9, comes in the wake of major corrosion found in the vessel head at the Davis-Besse nuclear plant in Oak Harbor, Ohio, as well as discoveries of cracked and leaking vessel head penetration nozzles at several other reactors.

In August of last year, the commission sent a bulletin to licensees about the problems discovered in nozzles. Nuclear utilities responded with information about their inspecting the vessel heads. Then, in March, after the corrosion was found at Davis-Besse, NRC mandated that licensees provide more information about their inspection programs.

The latest notice says that inspections that rely mostly on visual checks may not be enough. It says that volumetric or surface examinations also may be needed. Some acceptable types of inspections include using ultrasound, electric currents and liquid dyes to determine if metal structures are cracked or corroded, NRC says.

NRC staffers have scheduled a meeting with industry officials about the new bulletin on Aug. 23 at commission headquarters in Rockville, Md. Other interested parties may listen to the meeting by using a toll-free number. (See for details.)