Fukushima: in hindsight, could the crisis have been prevented?
Today, with increasing concerns about radiation leaks, and very little progress in stabilizing the reactor cores, the situation seems to be deteriorating. I am wondering, however, if some of the radiation figures we are seeing are really major increases, or just a result of better monitoring — more instruments in the field, and more systematic deployment. In the early days, the workers were too busy to spend a lot of time on monitoring, and most detectors were offline. Clearly, there is a buildup of contaminated water in the lower levels of the reactor buildings, and the nearby spillover trench; but this can only be expected, considering how indiscriminately they have been using whatever water was available to keep the fuel rod temperatures more or less under control. It also seems inevitable that a lot of this contaminated runoff will reach the ocean, as it is already within 50-60 meters. At present the primary radioactive material seems to be iodine 131, which has a short half-life of only eight days. There is a report of trace amounts of plutonium, presumably from reactor 3, but it is not clear how it might have escaped. The stabilization of the reactor cores remains the first priority, so it is likely that a certain amount of radiation release will continue, as an unavoidable side effect of these efforts.
In an ideal situation, we would not have radiation leaks at all, it goes without saying. So, looking backward, is there any way this ongoing near-catastrophe could have been prevented? I have to say “yes†— both before the fact, at the plant design level; and after the fact, in the early response stages. I am going to save the discussion of the former for another time, and address the actions of the plant managers in the first days after the quake.
What happened on March 11
According to the NOVA special, the Fukushima reactors automatically went into shutdown when the quake hit. This was apparently a deliberate safety measure (whether it was a good idea is a question I will explore later). While it takes a long time for the reactor cores to actually cool, at this point they were no longer generating electricity. Diesel-powered generators automatically kicked in to provide power for lighting, controls, and the crucial cooling pumps. It is not clear whether the plant was cut off from the national electric grid by the effects of the earthquake itself, or by the later tsunami, but for the purposes of this reconstruction I will assume the connection was knocked out by the earthquake. At any rate, for this brief period between the earthquake and tsunami, the situation was under control.
We all know what happened next — the tsunami flooded the diesel generators, which cut off all power to the plant. It isn’t clear whether the generators were damaged, completely destroyed, or merely quit due to temporary submersion, but the result was the same. The plant shifted to emergency battery power, but this was sufficient for only eight hours of operation. By approximately midnight, the critical function of pumping cool water through the reactor vessels to cool the fuel rods had stopped, leading to elevated core temperatures and the possibility of meltdown. Most reports have focused on this failure (for good reason), but I would like to call attention to another malfunction that I think actually initiated the downward spiral: the secondary containment structures also had a cooling and ventilation system, which, of course, was also without power.
The purpose of the secondary containment was to capture any releases from the reactor vessel in case of malfunction; therefore it was equipped with a sophisticated ventilation and filtering system. The filters were designed to capture any radioactive particles, and to harmlessly vent any hydrogen gas buildup. Highly-explosive hydrogen gas is a known byproduct of overheated fuel rods. The problem was that, with no electric power, they had a situation with both overheating fuel rods and a non-functioning ventilation system (I have to say this certainly looks like a design flaw).
As the fuel rod temperatures increased, the cooling water in the reactors turned to steam, increasing the pressure in the vessels. In order to prevent the reactor vessels from bursting (which would have been a first-class calamity), the plant managers were forced to release steam into the secondary containment structures. This steam contained both radioactive contaminants, and hydrogen gas.
March 12: fatal inaction?
This was the situation in the early morning hours of March 12. The site personnel had probably been on the job for 12-18 hours; transportation and communications were disrupted throughout the region; many people were probably in a state of psychological shock. TEPCO headquarters in Tokyo probably had very little understanding of the situation at the plant, and the government oversight agencies even less. Workers were preoccupied with cooling the reactor cores — I believe they were in the process of introducing seawater to replace the water that had boiled off. In the confusion, the issue of hydrogen buildup seems to have been overlooked. Then, the roof blew off Reactor Building #1.
For all the reasons mentioned above, I can scarcely blame anyone for this particular disaster. As I said, it seems to have been a secondary result of a faulty design that allowed two sequential safety systems to fail for the same cause. But you could also argue that this hydrogen explosion should have been anticipated; after all, they knew they were venting the core, and the system had been designed with the understanding that this venting could release explosive hydrogen. Regardless, it seems inexcusable that the explosion in reactor 1 was followed by explosions in Building 4 (the same day), Building 3 (March 14) and Building 2 (March 15). Given that the possibility of a hydrogen explosion was well-known, not to mention conclusively demonstrated on March 12, it seems to me that some kind of effort should have been undertaken to vent the secondary containment buildings; either by manually opening roof vents, or even sending work crews to remove sections of roof or walls if necessary.
I am harping on this point because, in hindsight, these hydrogen explosions are the primary reason the reactors have not been stabilized, and why there are continuing problems with cooling and with radiation releases. Look at this video of one of the damaged reactor buildings — try to imagine how difficult it must be for workers trying to reestablish lighting, control and cooling systems in this apocalyptic, radioactive landscape of steaming, twisted metal. I would go so far as to say that if it weren’t for the damage caused by these explosions, the reactors would all be under control by this time (as are reactors 5 and 6, which did not suffer explosions).
Tough choices
One possible reason why no attempt was made to ventilate the secondary containment buildings was that this would release a certain amount of radiation. In the immediate aftermath of the earthquake/tsunami, it is understandable that TEPCO managers would be reluctant to do so; in fact, in normal circumstances, a deliberate release would be almost unthinkable, given the sensitivity to any mention of radioactivity that is understandably widespread in the Japanese populace. But my contention is that a deliberate release at this point (to be more precise, it would have had to have been an ongoing release over a week or more) could have prevented the enormous destruction of infrastructure which is currently handicapping the recovery efforts and endangering the workers; infrastructure that, ironically, had survived the earthquake and tsunami intact.