By staff writers
From: news.com.au
March 17, 2011
 A man is scanned for radiation at a temporary scanning center for residents living close to the quake-damaged Fukushima nuclear power plant, March 16, 2011 / AP |
Is the world on the brink of a nuclear disaster? Eight experts give their opinion on the nuclear crisis in Japan, and their overwhelming message is to remain calm.
On the risk of nuclear rain in Australia
Dr Pradip Deb is Senior Lecturer in Medical Radiations at the School of Medicals Sciences, RMIT University.
“I completely disagree with this. Radiation exposure in Japan is mainly gamma radiation which is not 'material' that can be dissolved in water. It’s electromagnetic energy like light or ultraviolet rays. Gamma radiation cannot mix with water or anything else. So I do not think anybody will have any extra problem besides the normal ones if it’s raining just because of the incident in Japan.”
On public safety
Sir John Beddington, Chief Scientific Officer for the UK government
"If the Japanese fail to keep the reactors cool and fail to keep the pressure in the containment vessels at an appropriate level, you can get this ... dramatic word 'meltdown'. What a meltdown involves is the basic reactor core melts, and as it melts, nuclear material will fall through to the floor of the container. There it will react with concrete and other materials.
"Remember this is the reasonable worst case, we don’t think anything worse is going to happen. In this reasonable worst case you get an explosion. You get some radioactive material going up to about 500m up into the air. Now, that’s really serious, but it’s serious again for the local area.
"If you then couple that with the worst possible weather situation ... and you had maybe rainfall which would bring the radioactive material down - do we have a problem? The answer is unequivocally no. Absolutely no issue.
"The problems are within 30 km of the reactor. And to give you a flavour for that, when Chernobyl had a massive fire at the graphite core, material was going up not just 500m but to 30,000ft (10km). It was lasting not for the odd hour or so but lasted months, and that was putting nuclear radioactive material up into the upper atmosphere for a very long period of time. But even in the case of Chernobyl, the exclusion zone that they had was about 30km. And in that exclusion zone, outside that, there is no evidence whatsoever to indicate people had problems from the radiation.
"This is very problematic for the area and the immediate vicinity and one has to have concerns for the people working there. Beyond that 20 or 30km, it’s really not an issue for health.”
Prof Steve Jones, independent nuclear and environmental consultant.
"The radiation dose rates reported so far from the vicinity of the plant are consistent with a significant release of radioactvity, but so far on a scale very much lower than Chernobyl. However, without an estimate of the quantity of individual radionuclides released, or measurements of radionuclide concentrations in air or in deposits on the ground, it is not possible to make any very meaningful estimates of the possible radiation dose to affected members of the public."
Dr Richard Wakeford, Dalton Nuclear Institute and Visiting Professor of Epidemiology, University of Manchester.
“Words like ‘apocalypse’ and ‘catastrophe’ used about the situation at the Fukushima nuclear power plant are utterly inappropriate for the position there, as far as the radiation exposure of members of the public are concerned. No expert would use terms like these to describe the situation at Fukushima.
“To put radiation doses into context, many Japanese undergo CT scans for cancer screening purposes, and these scans produce radiation doses of about 10 millisieverts (10,000 microsieverts) - much more than they are receiving from the Fukushima reactors.
“Radiation sickness and other early effects of radiation exposure are caused by high doses of radiation (about 1,000 millisieverts - 1,000,000 microsieverts).”
On the safety of the public in Tokyo
Prof Paddy Regan, Professor of Nuclear Physics at the University of Surrey.
“Tokyo is approx 200km from the edge of the Fukushima site. This means that, assuming that any radiation is spread out evenly if was to get airborne, the dose of radiation would be 1 part in approximately 40,000 of that seen at the edge of the plant (assumes that the edge of the plant is 1 km from the source). If this radiation kept up at this level for a full year (also extremely unlikely), this would translate to an ADDITIONAL dose of approximately 0.2 mSv/year for people in Tokyo (or about the same as a chest X-ray and about 1/10th of the annual dose UK people get from the environment).
Even the max values quoted so far (spikes at approx. 200 msV/hour briefly at one on the reactors) translate to a maximum of approx. 40 mSv per year which is approx. 20msV, but still below the dose likely to cause significant increases in cancer.”
Prof Malcolm Joyce, Professor of Nuclear Engineering at Lancaster University."The spread of airborne contamination is unlikely to be evenly distributed because this depends on the transport mechanism - i.e. whether via smoke or steam, the altitude the contamination reaches before significant dispersion takes place and the time period over which the contamination is evolved - as John Beddington commented earlier in the week, concerning the important distinction between this incident and Chernobyl. I would expect the activity to be dispersed as a plume, probably teardrop-shaped but obviously this is very dependent on the prevailing winds. These currently appear to be away from Tokyo. There are well-established simulation models to predict these plume dynamics.
"In the unlikely event that the plume were to drift the 200km in the direction of Tokyo, given the direction of prevailing winds and the scale of the plume which is much, much smaller than Chernobyl, there would be a second potential issue associated with the deposition and ingestion of the very short-lived iodine isotopes.”
On the general situation
Dr. Philippe Blondel, Deputy Director, Centre for Space, Atmospheric & Oceanic Science, University of Bath.
"The magnitude of the Japanese earthquakes and the main resulting tsunami are apparent from the immense scale of devastation and from the fact that all countries around the Pacific were affected. For example, the tsunami waves were still more than 1 m high when they reached New Zealand, having travelled the 8,000 km in about 12 hours. And they even reached Antarctica, albeit much reduced in height. The current fears about nuclear safety should not shadow the huge plight of the refugees and the difficulties of on-going search and rescue operations. They are taking place in the background of regular earthquakes, some of them associated to tsunami alerts. The Japanese Meteorological Agency estimated on Monday that the next 3 days would see a 40% probability of large aftershocks (more than magnitude 5), reducing to 20% from 17-20 March. Current activity supports their predictions."
On staff safety
Tony Roulstone, Course Director, MPhil in Nuclear Energy, Department of Engineering, University of Cambridge.
"When the levels were 1000mSV it was understandable that people were withdrawn. The radiation levels now seem to be fluctuating at a level well below this high level and TEPCO seems to be managing the dose and risk of its staff in light of the serious situation. The current sea water cooling arrangement for units 1/2/3, while perhaps effective, could be called a jury rig and needs monitoring and management. If the station staff continue to do this the natural reduction of the fission product (decay) will allow the core to cool. Currently the fission product heating is about 1/300th of the prior core power - and falling. As we have seen with the interruption of cooling to unit 2 on Monday, continuous cooling is the top priority.”
- The experts were interviewed by the Australian Science Media Centre (AusSMC).
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