FirstEnergy Corp. has started testing to make sure its Davis-Besse nuclear plant is airtight.

The pressure test, which started Monday and should be over by the end of the week, is a crucial step in the Akron utility's efforts to restart Davis-Besse.

The company said Davis-Besse may be ready to restart in May, pending approval from the Nuclear Regulatory Commission. The company has pushed back the restart date numerous times since the plant in Oak Harbor, about 25 miles east of Toledo, first closed down in February 2002.

The procedure that started Monday, called an integrated leak rate test, is designed to make sure that the steel vessel that surrounds the nuclear reactor isn't leaking air into the outside environment. The steel vessel is made of 1 ½-inch-thick steel and is surrounded by a massive concrete containment chamber.

FirstEnergy had to cut out part of the containment vessel last summer to replace the corroded vessel head that sat on top of the reactor. The NRC requires that all nuclear plants undergo the same type of test every 10 years. Davis-Besse last did the test in 2000, but will repeat the process because of the repairs.

The plant has to pass more tests before being allowed to restart, including checking for coolant leaks at the bottom of the reactor. The company found large rust stains on the bottom of the vessel, but could not determine if the rust was caused by coolant leaks at the top of the vessel or from nozzles underneath.

The coolant leak test probably won't take place before May. FirstEnergy said it wants to use a camera-equipped robot to examine the highly radioactive vessel bottom, but NRC officials have questioned whether that alone will detect any small leaks.

The robotic camera has better than 20/20 vision, FirstEnergy spokesman Todd Schneider said.

``We really don't need NRC approval for this test. But we'll work with them,'' he said. ``We will satisfy the NRC's concerns before going forward.''

The company also is looking at how to resolve a possible clogging problem involving two pumps that would recirculate reactor coolant in an emergency. FirstEnergy engineers found that it's possible small debris could clog the devices, called high- pressure injection pumps.

The company may not have to make any pump modifications, Schneider said. But it may install filters that would prevent debris from entering the pumps, or put in new pumps not susceptible to clogging, he said. The issue is not expected to significantly delay getting the plant ready to restart, he said.

The NRC will hold three meetings April 15 in Ohio involving Davis-Besse. The first meeting, 9 a.m. at Davis-Besse, will involve the plant's radiation protection program. Afterward, there will be two meetings at the Camp Perry Clubhouse in Port Clinton. The meeting at 2 p.m. will give NRC officials an update on where FirstEnergy is in the restart process. The last meeting, which starts at 7 p.m., is aimed at updating the public on Davis-Besse issues.