This is the lastest update from the UK's Chief Scientific Advisor, Sir John Beddington.
Over the past few days, there has been continuing concern about the situation at Fukushima, particularly in light of yesterday's amendment to British travel advice to "consider leaving" Tokyo, which has also been the advice of many other countries.
"Sir John Beddington explained: At the beginning of this week, our concerns were mainly about possible meltdowns in the reactors. What the Japanese were doing was entirely proportionate to the situation and, even in our worst case scenarios, such as extreme weather conditions, there was nothing remotely to worry about. There were two main reasons why we changed the British travel advice.
1. Fuel Ponds
If the fuel ponds that hold spent fuel rods were allowed to dry out, especially the pond in reactor number 4, the emissions would be highly radioactive. We worried that radiation would start coming out as a result of fire or minor explosions and this would cause more radiation than that coming from the reactors themselves. This is one of the reasons it was more important to be more precautionary around the Fukushima plant, and that was why the recommendation was adopted to extend the evacuation zone to 80km. We discussed this with our scientific colleagues in America and they agreed. There is STILL no massive danger but we wanted to be precautionary.
2. Worst Case Scenario
The British Prime Minister asked us to look at the plausible "worst case scenario" combined with unfavourable weather conditions, particularly with regards to Tokyo. I repeat that this is HIGHLY UNLIKELY. Even if our plausible worst case scenario happened, the danger to Tokyo would be modest. Although radiation would increase for a short time - no longer than 48 hours - the effects on human health would be mitigated by staying indoors not opening windows. For people living in Tokyo, immediate concerns can be allayed. If the UK were to find any traces of radiation, they would inform Tokyo of when the plume is due in order for people to take precautions. This is NOT the current situation; this is only assuming the worst case scenario. Both of our worst case scenarios (explosions in reactors and extreme weather conditions) are unlikely.
To sum up, regarding the precautionary zone around the plant it was sensible to be precautionary, but even in worst case scenario, we are not worried about the human health risks. The US and France have heard these conclusions and they share our opinion.
Q: Is there any chance of contamination in Tokyo?
Sir John: Implications to people in Tokyo - none.
Question from the BritishSchool: Given that the reactor was contained but then suddently there was an explosion, how long do you foresee a dangerous situation continuing for?
Sir John: The key issue is whether or not the Japanese can get sufficient water into the holding pond on reactor 4 and continue to get water into other holding ponds. In the case of reactors, adequate water is needed to keep them cool. That is critical. In terms of when we can all relax - this is dependent on how successful the Japanese are at cooling the reactors and ponds. When that begins to happen we can relax. In a week or so we will know if we really have to worry or not. In addition, afterwards, there are enourmous problems of clean up and that could take years.
Question from David Warren: Can you clarify about the contamination of food and water?
Sir John: We have been working with our colleagues in DEFRA and the food standards agency in the UK. The message is to avoid food grown around the region of the plant of course. Normal sewage filtration processes take out radioactivity. If this was dangerous to anyone outside of Fukushima, the Japanese authorities would react and advise. In Chernobly the risks were significant - more dramatic and worrying, but even the risks were negliible for water because of filtration. Bottled water is always safe. Any problems related to tap water will not be connected with radiation but rather the sewage coming from broken pipes. In conclusion, microbiology is more of a concern than radiation. As for food in shops - in cartons, tins, bottles or boxes, there is no problem whatsoever. It would be unwise to eat food produced from gardens in the region. Anything left in the open air in Fukushima, dont eat.
Q: You now advise to "consider leaving" - at what stage would you change that to "leave"?
Sir John: Only in the worst case scenarios. The reason we said "consider leaving" - there are major disruptions to transportation and supply chain in the whole of Japan. We are NOT advising that people leave due to the risk of radiation. Even IF a plume were to reach Tokyo, it would not pose major health risks.
Q: What does plausible worst case mean? Is there an implausible worst case?
Sir John: Implausible - all reactors and all ponds go up at the same time and extreme weather conditions bring the plume to Tokyo; it's not sensible to consider this.
Q: How do we know if the Japanese government is telling the whole story?
Sir John: There would be a series of explosions at the reactors - the Japanese government cannot hide that if it were to be the case.
Q: Why is the French giving different advice?
Sir John: Their advice is not based on science.
Q: Any reason for people in Tokyo to take potassium iodide? Children, pregnant mothers?
Sir John: The Health Protection Agency is on the line. If we are looking at the "worst case scenario" it would be sensible for pregnant women, children and nursing mothers to take stabilising drugs as their thyroids are more sensitive radioactive iodine. However there is no need for anyone in Tokyo to take these drugs now. If necessary, there would be plenty of warning for people in Tokyo to take the tablets.
Finally, we are continuing to monitor this situation every day, with nuclear and health experts."
Keep safe and stay calm!
Our thoughts, prayers, and hopes for a quick recovery are with all those who have been affected by this crisis.
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