Thursday, August 25, 2011
Ron Smith: Fukushima: the consequences
At the moment of the earthquake, only three of the Fukushima reactors were in operation. All three immediately went in to automatic shutdown, as they were programmed to do. However, the cores of shutdown reactors (reactors where fission is not longer taking place) still contain fission products, which continue to decay and produce heat. They thus need continuous cooling. The genesis of the problem at Fukushima was, because of damage caused by the earthquake and tsunami, that this cooling could not be maintained. Electrical power was lost and back-up arrangements were damaged. There is also evidence that essential pipe-work, serving the reactor cores, was also damaged. The net effect of this was a meltdown of the overheated fuels rods, which damaged the reactor containment structures. This made maintaining cooling even more difficult, since water that was inside was able to escape.
Overheated fuel rods were then the catalyst for the decomposition of such water as was present, and the production of hydrogen. This in turn was the cause of a build-up of pressure and, when the pressure was released, the accumulation of hydrogen in reactor buildings 1, 2 and 3. This inevitably resulted in a series of explosions as the hydrogen/air mixtures ignited. Hydrogen also accumulated in reactor-building 4. In this case it was the result of a loss of cooling capability in relation to spent fuel that had already been removed from reactor 4 and was being held in an associated spent-fuel pool in the reactor building. The release of gas from the over-heated reactors and the subsequent explosions, and the escape of contaminated water from the containment vessels caused extensive contamination of the region around the Fukushima plant, both land and sea.
This was the immediate and direct consequence. The plant operators now (five months later) have recovered temperature control of the (very) damaged reactors and the spent-fuel pool but there is still some risk of contaminated water escaping into the sea. No further aerial escapes are taking place but there are hotspots in the region of the plant, which raise questions about the extent to which evacuated persons may be permitted to return anytime soon.
There was another notable feature of the March 11 events at Fukushima and that was a high and persisting level of media frenzy about the danger of what was happening. Five months later, commentary on the Japanese earthquake and tsunami still seems to revolve around Fukushima, notwithstanding that the event as a whole seems to have killed some 25,000 persons, whilst the nuclear events at Fukushima-Daiichi killed nobody and that is very likely how matters will remain, notwithstanding the extensive radioactive contamination of land and water.
What happened at Fukushima is very different, in terms of causation, from what occurred, some twenty-five years ago at Chernobyl, but the events are similar. Both rated a ‘7’ (‘major accident’ – the highest rating) on the IAEA International Nuclear Event Scale, and both entailed extensive contamination of the local environment. In the Chernobyl case we know (from the report of the international Chernobyl Panel) what the long term health consequences were for people living in the vicinity and they are negligible (see my ‘The significance of Chernobyl’, 24/5/2010).
Notwithstanding this, the public perception of these events (Chernobyl and Fukushima) is very different. Nuclear accidents are seen as unacceptably and irredeemably dangerous. There is, thus, another consequence of the incident at Fukushima and that is a renewed clamour for the total abolition of nuclear power. As is well known, the German government has already announced the phasing out of nuclear power by 2022. Similarly, referenda in Switzerland and Italy have come out strongly against civilian nuclear power generation. Italy presently has no nuclear capability but, until Fukushima, was planning the construction of 10 units. It seems clear that it will abandon those plans and possible, perhaps likely, that Switzerland will phase out its present capability.
On the other hand, the United States is planning to add modestly to its stock of 104 power reactors. Similarly France (which generates nearly 80% of its electricity by nuclear means) will add to its existing stock. Something similar applies to South Korea, Finland, Russia and the United Kingdom. The really interesting cases are China and India. The former presently has 14 operating reactors but it is building or planning to build 208. The corresponding figures for India are 20 and 63. Overall figures from the World Nuclear Association suggest that 548 new reactors will be added to the approximately 440 presently operating. Some of these present plans will undoubtedly change and public sentiment may be a significant factor in some these cases.
Japan, itself, is the really interesting case. In a recent public opinion survey, fully 75% expressed themselves in favour of ending the use of nuclear power. In addition, the Japanese Prime Minister, Mr Naoto Kan, has recently expressed regret about his support for the Japanese nuclear industry and spoken about a ‘phase-out’. For all that, I am not sure that it will happen. As is well-known, Japanese policy, both domestic and foreign has been conditioned for nearly a century by anxieties about energy security. Japan has no oil and no coal and no gas. Since the oil shocks of the early 1970s, nuclear power has been the answer. Japan has an enormous investment in its nuclear infrastructure, including 55 reactors. Notwithstanding his position on the nuclear issue, Mr Kan’s demise as Prime Minister is predicted almost daily. It may be that his successor will be more cautious and that economic and security considerations will ultimately prevail. Kipling’s advice about ‘keeping your head, whilst all about you are losing theirs’, seems very apposite here.
at 11:13 AM