Are reactors in Japan related to those in Illinois?
The nuclear situation in Japan is still developing and you might wonder: Does Illinois have the same kind of nuclear reactors?
Yes, we do. According to the U.S. Nuclear Regulatory Commission – nuclear power plants’ primary regulator – the reactors that have been venting gas and radioactive steam are boiling water reactors with Mark I containment, commonly called Mark I BWRs. There’re 23 of these in the United States, and Illinois is home to four of them. The Quad Cities Generating Station northeast of Moline has two Mark I BWRs (GE BWR-3 models with some modifications). Another pair (GE BWR-3 models) resides at Dresden Generating Station, southwest of Joliet.
The reactors’ owner, Exelon, and the NRC say there’s no cause for concern: Illinois’ nuclear reactors are humming along normally. But the fact that Illinois reactors haven’t been affected by catastrophic floods or earthquakes doesn’t satisfy critics of the nuclear industry. They point out that the 40-year-old design has a fundamental shortcoming common to reactors of their age; if left alone, reactors can remain hot for days or even weeks after they’re shut down.
Typically, station operators will cool a reactor by circulating water throughout its container, but the process requires electricity – from the grid, batteries or backup generators. When power’s not available, there’s no way to pump water and it’s possible that a reactor’s core can melt, burn through containers and, following that, release radioactive gas, steam and smoke into the air. In Japan, the tsunami knocked out power in a wide region, and backup diesel generators did not perform properly.
NRC documents suggest the likelihood of a repeat situation in Illinois is low. Power stations are expected to survive earthquakes that are at least as strong as the last recorded tremor. Stations are also expected to survive major floods. NRC documents show the Quad Cities plant should be able to shut down safely in the presence of a 1,000-year deluge, and the station made it through 1993’s massive flood along the Mississippi River. The Dresden station is expected to survive any flooding along the nearby Illinois River.
The U.S. has never had an accident on the scale of what we're seeing in Japan, and the lower-level incidents we have had did not involve Mark I BWRs. Still, the nuclear industry hopes to build new reactors that are less susceptible to meltdowns than 60s-era devices. Some designs employ so-called passive cooling, which would allow reactors to dissapate reactor heat without backup power. None has ever been built in the U.S., though there’re several in the planning stage.
Exelon didn’t answer questions about whether it intends to replace Illinois’ Mark I BWRs (which have been running for four decades) with new reactors that have passive cooling systems. But decisions made by the company suggest it has no intention of swapping new reactors for old ones. The Chicago-based company asked for – and received – permission to run one of the Dresden reactors until 2029. Permission to operate the station’s other reactor runs out in 2031. The company can operate both Quad City reactors until 2032. The company is also investing millions in technology that would wring more power out of all four Mark I reactors.