Diatribes of Jay

This is a blog of essays on public policy. It shuns ideology and applies facts, logic and math to economic, social and political problems. It has a subject-matter index, a list of recent posts, and permalinks at the ends of posts. Comments are moderated and may take time to appear. Note: Profile updated 4/7/12

17 March 2011

Japan’s Nuclear Disaster: Reason for Hope

Watching the treble disasters in Japan as they deepen has been heartbreaking. While northeastern Honshu struggles to dig out from the devastation wrought by a record earthquake and tsunami, snow falls on the victims, and several Fukushima nuclear reactors teeter toward meltdown. Bad news has continued to escalate on all fronts.

The nuclear disaster is the most terrifying. Unlike demolished homes, roads, and power lines, radioactivity is invisible. It can proliferate literally at the whim of the wind. But now the authorities seem to have a sensible plan.

All along, the basic problem has been getting cooling fluid into the reactor cores and cement blockhouses that store spent fuel. There is no electric power for that purpose because the nuclear plants successfully shut down, and the tsunami put the backup generators out of commission. So the service pumps that normally circulate cooling water were useless, and workers had to resort to portable generators and applying coolant with portable pumps on fire trucks.

Imagine pumping water into a huge, sealed containment vessel through a safety valve designed only to release high-pressure radioactive hydrogen and steam, and that only sporadically. That’s not an easy task. Then heat from spent fuel in adjacent tanks began to evaporate the water in them, creating an entirely separate risk. In some ways that risk was more ominous, since the spent fuel, unlike the reactor cores, has no containment vessel other than the cement blockhouse that surrounds it.

That’s why Tepco’s reported attempt to get real power to the site from elsewhere makes sense. If power can be restored to the plants, normal circulation of coolant might resume. There is a risk that partial meltdowns and hydrogen/steam explosions may have destroyed or damaged necessary pipes, valves or controls. But the best way to circulate cooling water is through internal systems designed for that purpose, not to force it into a system designed to be impregnable, through orifices never designed for that purpose.

Once electric power to the plant is restored, all or most of the instruments and gauges telling workers what is happening inside the reactors may work again. In addition, workers can attempt to get cooling back on line from inside the control room, which is heavily shielded. There they can work with reduced exposure to radioactivity and hence for longer hours.

Initially, the control room was probably next to useless without electric power for lighting, instruments or controls. One use of the portable generators brought in was no doubt to power the control room to get an idea what was happening inside the reactors. The fact that authorities have now decided to apply full external power suggests that the mobile generators were not robust enough to run all the cooling pumps, but were strong enough to provide encouraging news from the control room.

Finally, the spent-fuel tanks, whose tops have blown off and are open to the air, are amenable to helicopter-drops of water. That approach can proceed separately and independently. As long as the tanks are not burning continuously, the helicopter crews might find ways to reduce their exposure to radioactivity while filling up the tanks. (I presume authorities have made every effort to seal the helicopters and to provide some sort of temporary internal overpressure while they are flying over or through suspected sources of radioactive gas and particles. A few SCUBA tanks with appropriately adjusted regulators might do the job.)

Since the plants were designed to provide their own electric power, there probably were no separate lines bringing external power to them. But power lines designed to draw power out of the plants’ own generators can be used to get power to the control room and normal equipment from other, still functioning remote power plants in Japan. Power can flow either way.

So despite its many setbacks and several adjacent reactors, Fukushima is still far from Chernobyl. There are multiple and escalating risks. But the reactor cores still have heavy steel containment vessels, which didn’t exist at Chernobyl. They seem to be mostly, if not entirely, intact.

So if the pumps, pipes and valves for cooling water still work, this plan has a greater chance of success than anything I’ve seen described in the news so far. For the sake of Japan, its beleaguered people, and an anxious, watching world, I hope the plan works.

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