After the Davis-Besse NPP near Toledo, Ohio is shut down for refueling on February 28, a routine inspection finds problems similar to those that nearly caused a serious incident in 2002. At least 16 critical parts are cracked or flawed, potentially allowing acidic cooling water to leak onto and corrode the steel containment vessel. In 2002, corrosion was found to have eaten a pineapple-sized hole through the 6-inch wall of the vessel. Only a thin stainless steel inner lining prevented release of pressurized coolant. (See Incident #922.)
Todd Schneider, a spokesman for the plant's owner FirstEnergy, says repairs are under way and the company hopes to be able to restart the plant in July. A team from the NRC is on site to monitor the complicated repairs to the reactor head and upgrades to other control systems. The Union of Concerned Scientists has petitioned the NRC to keep the plant offline until FirstEnergy can prove the cracking will not recur.
After the 2002 incident, Davis-Besse was shut down for two years. The reactor head was replaced with one from a plant at Midland, MI that had never operated. However, that uses the same nickel-steel alloy as the original head. A head with tubes made of a different alloy has been ordered from Europe, but its delivery date is uncertain.
Rajender Pal, a 35-year-old scrap dealer, dismantled a gamma irradiator and cut open the cobalt-60 capsule from the scrapped machine. He died earlier this month from multiple organ failure caused by radiation poisoning after being exposed at Delhi's Mayapuri scrap yard. Seven co-workers were also exposed and hospitalized. Two will require bone-marrow transplants. Hundreds of dealers operate at the scrap yard, and it is surrounded by densely-populated residential areas. Police cordoned off a ten-square-mile area during the cleanup.
The machine was discarded by a chemistry laboratory at the University of Delhi. It was imported from Canada in 1970 and had not been used since 1985. Deepak Pental, vice-chancellor of the University, said the active life of the material had been miscalculated.
Didier Louvat, a nuclear waste specialist with the International Atomic Energy Agency, told The New York Times that the Mayapuri case was the most serious instance of radiation exposure anywhere in the world since 2006.
When instruments show pressure dropping in the "SCRAM" system at Perry NPP in Ohio, the reactor operators manually shut down the plant. No radiation is released and the plant is not damaged.
Todd Schneider, a spokesman for the plant's owner FirstEnergy, said the operators were being conservative. NRC rules forbid a plant to operate without a working SCRAM system, and call for a shutdown if the problem cannot be fixed within 20 minutes.
An earthquake of magnitude 9.0 offshore of the Japanese coastal city of Sendai strikes at 1446 local time (0546 GMT). Within minutes, a tsunami as much as 30 feet high sweeps ashore. Much of the port area of Sendai is destroyed as the wave reaches six miles inland. Power is out over much of the area 400km north of Tokyo and thousands are feared dead.
The quake triggers the prompt shutdown of five nuclear power plants in the area. At the Fukushima nuclear plant, the tsunami knocks out the backup diesel generators being used to power the cooling pumps after main power failed. There is still enough residual heat in the cores of the three operating reactors there to cause problems. (Three others were already shut down for inspections.) Mobile generators are brought in, but cannot be connected to the plant systems because the connectors do not match.
On Saturday, 12 March, the Unit 1 reactor suffers a hydrogen explosion after the core is vented to relieve pressure as residual heat cannot be removed fast enough. One worker dies and four others are injured by the blast. Little radiation is released; the wind carries it out to sea. A second explosion, at Unit 3, occurs on Monday, 14 March, injuring 11 people. At reactor #2, a third explosion occurs early in the morning on Tuesday, 15 March.
Concern then turns to the spent-fuel pools, which also are not getting cooling water. It is believed that enough water boiled away from the pool at reactor 4 to expose the tops of fuel rods, which then generates hydrogen causing a fourth explosion. Radiation in the area reaches dangerous levels, but quickly dissipates. As Japanese authorities struggle to keep the situation under control, fears mount that this could be a worse crisis than Three Mile Island, affecting other countries.
On Wednesday, 16 March, a second fire occurs at #4. (The head of the U.S. NRC says the spent-fuel pool is completely dry; Japanese officials deny this.) Also, there are reports of trouble at #5 & #6, previously OK. Measures being considered are to fill the pools from a distance using riot-control water cannons, or to drop it from buckets under helicopters flown by JDF members. The latter depends on low radiation counts.
In recognition of the cumulative effects to be expected from this disaster, on 12 April 2011 it was upgraded to INES Level 7 — a major accident. The death toll stands at ???