Monday, March 14, 2011

Can Nukes and Quakes Co-exist?

The operators at the Fukushima Unit 1 Nuclear power plant in northern Japan must have realized that a bad day was about to turn into a very bad day when they turned on the emergency core cooling system – and it failed to start. They tried to start the second backup generator, and it failed to start too.

That set off a mad scramble to try to keep ahead of falling water levels, hydrogen explosions, radiation venting and a multitude of other obstacles in hopes of preventing a complete collapse of the reactors ‘ over heated cores, a race which, as of this writing, they are losing.

When the Great Miyagi Earthquake with an intensity of 9 on the Richter Scale hit the coast of northern Japan, Unit 1 and its two sister reactors were up and running and producing electricity. They automatically shut down, as is customary in all such cases even when there is a relatively minor tremor.

(Three other units in the complex were already down for serving and refueling and had not figured strongly in this episode. However, a fire broke out Tuesday morning in Unit-4. The core is said to be empty, but spent fuel is stored on site).

So far so good. But it is necessary to keep cooling water circulating through the core even in shut down mode; otherwise, the fuel will begin to overheat from the decay of the numerous strongly radioactive elements that are created by the nuclear chain reaction. If heating continues, the fuel might melt.

Electricity is the Achilles heel of nuclear power. It is needed to run the pumps that keep the cooling water through the core. Normally, the plant would simply take power off of the regional power grid. But because of the earthquake there was a regional blackout.

That contingency had been foreseen, which is why nuclear power stations have backup diesel generators and backups to those generators, sometimes as many as four per plant. What planners failed to account for was that the resulting tsunami would take out the generators needed to run the back up generators. Next move? Improvise.

The government has been rushing generators of all kinds to Fukushima in order to keep pumping water into the core. Some of them have proved to be too weak to be of much use. One apparently was destroyed in a hydrogen explosion at a neighboring plant. The situation complicated by the fact that airports are under water, rail lines are twisted and some roads are impassable.

Everyone understands that Japan, sitting right on the so-called Pacific Rim of Fire, is very prone to earthquakes. The country has made a huge bet that it can build nuclear reactors that are strong enough to withstand even the strongest shaking. It has 54 nuclear power plants supplying roughly 30 percent of the nation’s electrical energy.

In fairness it can hardly be argued that Japan has been cavalier about the prospects of an earthquake (some anti-nuclear groups might beg to differ). Indeed, even before last Friday’s tremor, Japan had experienced a two recent major quakes that severely impacted its nuclear program though not causing any radiation leakage.

In July 2007 a major quake struck of the coast of the Sea of Japan near where the Tokyo Electric Power Co. has seven huge reactors (largest concentration of civilian plants in the world). Although only slightly damaged, the regional authorities have been very cautious about restarting them. Three units are still out of commission, nearly four years after the quake.

Then in August 2009 another large quake struck in Suruga Bay south of Tokyo near where the Chubu Electric Power Co. has five nuclear power plants. One plant, which experienced unusually high shaking, has only recently returned to service. At one time about 12 nuclear power plants were out of service contributing to Japan’s miserable capacity factor(the percentage of time a reactor is operating).

The event on the Sea of Japan resulted in a general strengthening of seismic standards and some refitting. Chubu decided to decommission two of its older plants near Suruga Bay because they deemed it uneconomical to bring them up to current seismic standards.

But all of this attention was focused on ground movement and protecting the containment. That a tsunami might take out the entire emergency core cooling system at half a dozen plants at once apparently was not a contingency that received much attention..

Masashio Goto, a former engineer who worked on containment designs for Toshiba before he became more critical of nuclear power, says he believes it is possible to design a containment system that can withstand even the most severe earthquake. But, as everyone is now learning, an earthquake-related hugely increases the problems and ability to recover.

Consider some of the problems that the operators at Three Mile Island in 1979 and Chernobyl in 1984, the two previous most severe nuclear incidents, did not have to contend with: total electric power blackout, airports submerged, rail and highway systems severely damaged or totally destroyed, ports closed.

About 170,000 people living within 20 kilometers of the stricken reactors were advised to evacuate. As the situation worsened Tuesday the government extended the evacuation area to 30 km and advised residents to at least stay indoors and “hang up laundry inside.”

Should a meltdown at any one or all six Fukushima Daiichi plants spew out more radiation, then the imperative to move people will be greater. Already about half of the Japanese armed forces have been mobilized to help in the quake-nuclear relief. The USS Ronald Reagan aircraft carrier has moved to the vicinity and presumably can help as the navy did during the Indonesian tsunami.

The reactors at Fukushima are very old. Unit-1 was commission exactly 40 years ago this month, and by modern standards employs horse-and-buggy technology (though, of course, upgraded). There are new reactor designs being implemented that eliminate the need for generators to keep the core cooled by using natural convection to circulate cooling water.

In theory, these advances in reactor design should make them safer and more earthquake resistant. Intellectually, it should be possible for nukes and quakes to coexist. Whether the Japanese, not to mention other people in the world, buy into this argument, however, remains to be seen.


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