As the days pass, the Fukushima incident is evolving from a crisis with the potential to turn catastrophic, into an expensive, dangerous, long-lasting mess. And while being a long way from the ‘apocalypse’ predicted by the EU Energy Commissioner Gunther Oettinger, – it seems to be much worse than I had imagined.
It could easily have been much worse. The New York Times spoke to scientists who model nuclear reactors, and predict what is happening inside by what is coming out. One team calculated core temperatures had reach 2,250 °C, and another that temperatures reached 2,700 °C. At these temperatures, almost every substance is molten, and so the centre of the reactors was, at some stage, probably a molten radioactive blob. The fraction of the core which melted is not known, but when melted, the relative disposition of nuclear fuel can lead to spontaneous criticality – in which nuclear reactions re-start and cannot be controlled.
Additionally, the widespread deposition of Iodine-131 (which is a by product of the fission process) is an indicator that during the crisis, the volatile contents of the core were allowed to reach the external environment. Thankfully it appears that very little of the heavy metals in the core have leaked.
The International Atomic Energy Authority have a Fukushima update page and pleasingly, an archive of update pages so one can see how things appeared as events unfolded. Currently (3rd April) all the reactors are being cooled with around 8 cubic metres per hour of water and are at temperatures between 100 °C and 260 °C. So it seems the situation – though grave – is stabilised , if not yet ‘under control’.
From the IAEA data on 17th and 26th March I read that injuries in the accident are:
- 2 subcontractor employees are injured, one person suffered broken legs and one person whose condition is unknown was transported to the hospital;
- 2 people are missing; [It is now known these people were killed by the tsunami]
- 2 people were “suddenly taken ill”;
- 2 TEPCO employees were transported to hospital during the time of donning respiratory protection in the control centre;
- 4 people (2 TEPCO employees, 2 subcontractor employees) sustained minor injuries due to the explosion at Unit 1 on 11 March and were transported to the hospital; and
- 11 people (4 TEPCO employees, 3 subcontractor employees and 4 Japanese civil defense workers) were injured due to the explosion at Unit 3 on 14 March.
- Radiological Contamination
- 17 people (9 TEPCO employees, 8 subcontractor employees) suffered from deposition of radioactive material to their faces, but were not taken to the hospital because of low levels of exposure; They have received doses between 100 and 180 millisievert.
- One worker suffered from significant exposure during “vent work,” and was transported to an offsite center;
- 2 policemen who were exposed to radiation were decontaminated; and
- Firemen who were exposed to radiation are under investigation.
Things could easily have been much worse.
The doses that people have received are relatively low, but some of radiation levels outside the plant are worrying. From IAEA log on 1st April, I read:
The IAEA monitoring team made additional measurements at 9 locations West of Fukushima-Daiichi nuclear power plant. The measurement locations were at distances of 30 to 58 km from the Fukushima nuclear power plant. The dose rates ranged from 0.4 to 2.3 microsievert per hour.
A dose rate of 0.4 microsievert per hour equates to an annual dose of 3.5 millisievert – which would typically double a person’s exposure for a year. This would not concern me. However a dose rate of 2.3 microsievert per hour equates to an annual dose of 20 millisievert – which is a significantly high dose. It will be interesting to see how measurements evolve. If this contamination is from Iodine 131, then it will quickly decay to Xenon with a half-life of 8 days. Other volatile substances created within the reactor include Caesium-137, which has a half-life of 30 years and so will linger considerably longer.
It doesn’t matter if coal is worse. Many articles (e.g. this from the Washington Post) point out that coal is dirty and dangerous – killing thousands of people every year and releasing massive amounts of radioactivity and mercury into the environment. And that’s not to mention the carbon dioxide! In this context , they argue, nuclear power is reliable, clean and safe.
These are good points, and well made. But they miss the central issue. Nuclear power is dangerous in a different way. If this accident had been worse than transpired – but within the range of possibilities – then it could have distributed not iodine and caesium – but long-lived highly radioactive metals such as uranium and plutonium, across hundreds of square kilometres of Japan – perhaps even approaching Tokyo. This has thankfully not happened, but only because of a considerable amount of good fortune.
Current nuclear power technology requires that humans are always able to control the reactor environment, providing cooling and controlling the reactor gain. Although the events which precipitated this accident were extreme, they were entirely foreseeable , and indeed foreseen. And 6 nuclear reactors shared the same site meaning that an incident at one could create and incident at its neighbours Nuclear reactors in which critical accidents are ‘unlikely’ are, in my opinion, unacceptable. Accidents are inevitable, but it is technically possible to create intrinsically safe reactors in which it is genuinely impossible for one failure – or many – to create a critical disaster. Why aren’t we building them?