Cookies on the BBC website We use cookies to ensure that we give you the best experience on our website. We also use cookies to ensure we show you advertising that is relevant to you. If you continue without changing your settings, well assume that you are happy to receive all cookies on the BBC website. However, if you would like to, you can change your cookie settings at any time. Find out more BBC Accessibility links Skip to content Skip to local navigation Accessibility Help BBC iD Sign in BBC navigation News Sport Weather iPlayer TV Radio More… Search term: BBC News Science & Environment Home World UK England N. Ireland Scotland Wales Business Politics Health Education Sci/Environment Technology Entertainment & Arts 12 April 2011 Last updated at 12:09 Share this page Email Print Share Facebook Twitter Fukushima: As bad as Chernobyl? Comments Richard Black By Richard Black Environment correspondent, BBC News The Chernobyl (l) and Fukushima (r) plants The Fukushima (r) incident is now rated on a par with Chernobyl (l)... but will it prove to be that bad? Continue reading the main story Japan quake Fukushima report: Key points Fukushima glimpse How plant was stabilised What went wrong? Chernobyl is regularly labelled the worlds worst nuclear accident - and with good reason. A working reactor caught fire, explosively. Radioactive debris was sent 30,000 feet into the air - the height at which airliners conventionally fly. Some of that debris came down thousands of kilometres away, in concentrations strong enough to prohibit the eating of meat and the drinking of milk produced locally. The upgrading of Japans Fukushima incident to a level seven - the maximum - on the International Nuclear and Radiological Event Scale (INES) puts it on a par with Chernobyl. And a spokesman for Tokyo Electric Power Company (Tepco), which runs the plant, suggested it could even end up being worse than Chernobyl. This, though, appears to be a minority view among engineers - both those who generally support nuclear power, and those who have in the past voiced criticisms. Continue reading the main story Worlds worst nuclear incidents Level 7: Chernobyl, Ukraine, 1986 - explosion and fire in operational reactor, fallout over thousands of square kilometres, possible 4,000 cancer cases Level 7: Fukushima, 2011 - tsunami and possibly earthquake damage from seismic activity beyond plant design. Long-term effects unknown Level 6: Kyshtym, Russia, 1957 - explosion in waste tank leading to hundreds of cancer cases, contamination over hundreds of square kilometres Level 5: Windscale, UK, 1957 - fire in operating reactor, release of contamination in local area, possible 240 cancer cases Level 5: Three Mile Island, US, 1979 - instrument fault leading to large-scale meltdown, severe damage to reactor core Timeline: nuclear accidents The classification of seven means theres a leak of radiation into the wider environment; and although itll be interpreted as being the same as Chernobyl, its not the same, said Paddy Regan, professor of physics at the UKs University of Surrey. The amount of radiation release is a lot less, and the way its released is very different. The Chernobyl fire was putting lots of radioactive material into the atmosphere and taking it over large distances; here, there have been a couple of releases where theyve vented [gas from] the reactor, and then released some cooling water. Don Higson, a retired Australian nuclear safety specialist, was more pithy. To my mind, [rating Fukushima equivalent to Chernobyl] would be nonsense, he said. In the month following the Chernobyl explosion, he said, 134 workers were hospitalised with acute radiation sickness and 31 died. The equivalent figures for Fukushima are none and none. (Although workers have been taken to hospital with radiation burns, this is not the same as acute radiation sickness.) Two units So why the uprating? Continue reading the main story “Start Quote The potential for atmospheric release is very large, with 250 tonnes of material sitting in that pond” John Large Nuclear consultant What it does not mean is that things have got worse at the plant; in fact, conditions appear to be markedly more stable than in the days following the Tohoku earthquake and tsunami, although not completely under control. Rather, Japans Nuclear and Industrial Safety Agency (NISA) has re-analysed data from the incident and decided that collectively the releases of radioactivity mean it slots into a level seven categorisation. The manual for agencies using the INES scale, published by the International Atomic Energy Agency (IAEA), runs to 218 pages. One of the criteria for evaluating the severity of an incident is the total release of radioactive material. This is derived by first adding up the amounts of each different radioactive isotope released, then multiplying each by a conversion factor related to the characteristics of that particular isotope, then adding up all of the resulting numbers. Radioactivity is measured in becquerels (Bq); a million million of these is a terabecquerel (TBq). A level seven rating is defined as An event resulting in an environmental release corresponding to a quantity of radioactivity radiologically equivalent to a release to the atmosphere of more than several tens of thousands of TBq of Iodine-131. NISA puts the Fukushima figure at 370,000 TBq of Iodine-131 equivalent; the Nuclear Safety Commission, which has a more over-arching role in the Japanese system, says 630,000 TBq. Testing for radiation Japanese authorities have acted very differently from their Soviet counterparts in 1986 Either way, its clearly beyond the threshold for classification as an INES level seven event, although an order of magnitude lower than the 5.2 million TBq released from Chernobyl. But that tells you nothing about the danger to people. Becquerels are a measure of the rate of radioactive decay; if one atomic nucleus decays per second, that is defined as one becquerel. By contrast, sieverts - another unit commonly used during the last months reporting - measure the likely medical impact of the radiation to which an individual is exposed. And a huge number of becquerels does not automatically translate into a huge amount of sieverts. Its hard to make a comparison between Three Mile Island, Chernobyl and Fukushima because the radioactive release is different and so is the population, said John Large, a UK-based independent nuclear engineer. In Ukraine and Belorussia (now Belarus) it was primarily a rural population, whereas in Japan youve got a highly sophisticated public living in fairly dense population groups. And the way the state intervenes is different. With Chernobyl, loads of workers were brought in with no concern for their health - but Japans a democracy. In some quarters, Japans swift decision to establish an exclusion zone, initiate monitoring of people and food, and dispense iodine tablets has received praise - and the volume of advice and warnings issued to the public has been very different from the silence that pertained after Chernobyl, despite criticisms from other quarters over the quality and timing of some of the Japanese advice. Not spent Nuclear experts are cautioning, however, that the situation at Fukushima is still very much in play. Where most attention has centred on reactors 1, 2 and 3, there is also concern about the spent fuel pond in reactor building 4. In the week following the tsunami, it became clear that the pond was running dry, meaning that fuel rods would have heated up. This meant likely degradation of their zirconium alloy cladding, the possible release of hydrogen, and - by Tepcos admission - the risk that a nuclear chain reaction could begin. The potential for atmospheric release is very large, with 250 tonnes of material sitting in that pond, said Dr Large. If you were to have an energetic event you could have a very large release indeed. The priority is, as it has been all along, to restore adequate coolant to the fuel ponds and the reactors themselves - while hoping that earthquake aftershocks and bad weather do not hamper operations any more. Radiation levels Your comments More on This Story Japan quake Analysis Fukushima report: Key points Fukushima glimpse How plant was stabilised What went wrong? Protest as reactor restarts Nuclear Fears Nuclear industry scuppered? Cruise finds Fukushima pollution Q&A: Health effects of radiation Fukushima v Chernobyl On the ground Images of then and now Grief of survivors Loss and recovery in numbers Signs and stories of hope Video Reports Inside crippled Fukushima plant Watch Inside meltdown reactor Watch Related Internet links INES NISA Tepco (in English) IAEA - Fukushima The BBC is not responsible for the content of external Internet sites Comments Sign in with your BBC iD, or Register to comment and rate comments All posts are reactively-moderated and must obey the house rules. Be the first to comment Share this page Share Facebook Twitter Email Print More Science & Environment stories RSS LaunchSpaceX rocket return test ends in crash US company SpaceX says its experiment to bring part of its Falcon rocket down to a soft landing on a floating sea platform did not work - but its cargo mission to the space station remains on track. Bent time tips pulsar out of view Unusual number of UK flowers bloom Top Stories French soldier patrol near the Eiffel Tower in Paris as part of security measures following the attack on the offices of Charlie Hebdo magazine - 9 January 2015Crisis meeting over Paris attacks AirAsia divers recover black box Boyhood takes Golden Globe honours Terrorism Bill needs to be changed Cameron warns of legacy of debt Features Mans waist being measuredWeight and see How personalised diets can help slimming CompositeOne died, one survived Two mothers, two sons and the Pakistan school massacre PenguinFrozen out Should tourists be banned from visiting the Antarctic? Hala ModdelmogFast-food queen How the death of her mother drove one woman to triumph in business Elise and her baby Anderson in December 2014Hope and ambition Haiti youth speaks of aspirations, five years on from quake Most Popular Shared 1: Huge crowds at Paris unity rally 2: London goes Tricolore in Paris tribute 3: La Dolce Vita star Anita Ekberg dies 4: The mother of Japanese whisky 5: Englands forgotten railway stations Read 1: Apology for Muslim-only Birmingham 2: AirAsia QZ8501: Divers recover black box flight recorder 3: Boyhood takes Golden Globe honours 4: Paris attacks: Hollande to hold security meeting 5: The fast-food queen who triumphed over adversity 6: First Milk payment to dairy farmers delayed by two weeks 7: Jaguar to create 1,300 UK jobs as firm launches SUV model 8: Gay question to recruits defended by MoD 9: David Cameron warns of legacy of debt 10: Terrorism Bill needs to be changed to protect citizens rights Video/Audio 2: How Paris march unfolded - in 60 secs Watch 3: New AirAsia underwater video released Watch 4: Golden Globes: The highlights Watch 5: BBC News Channel Watch 6: Charlie Hebdo support at the Globes Watch 7: Video links Paris gunman to IS Watch 8: Huge numbers at Paris unity rally Watch 9: Thatcher bust unveiled in Falklands Watch 10: Health fears over train toilet waste Watch Services Mobile Connected TV News feeds Alerts E-mail news About BBC News Editors blog BBC College of Journalism News sources Editorial Guidelines BBC links Mobile site Terms of Use About the BBC Privacy Accessibility Help Cookies Contact the BBC Parental Guidance BBC Copyright © 2015 BBC. The BBC is not responsible for the content of external sites. Read more.
Posted on: Mon, 12 Jan 2015 07:49:18 +0000