Plutonium spotted far from Fukushima 08 Mar 2012 | 14:11 GMT | Posted by Geoffrey Brumfiel | A paper out today in the journal Scientific Reports shows evidence that radioactive plutonium spread tens of kilometres from the Fukushima Daiichi nuclear plant. The new work could lead people to believe that there is a health risk, but that is not the case. Plutonium is a radioactive element that is made inside nuclear reactors. Unlike some of the other contaminants to come from Fukushima, it is not volatile, and it is much harder for plutonium to escape from a nuclear reactor during a meltdown. That doesn’t mean it can’t happen: when Chernobyl’s Unit 4 reactor exploded in 1984, it released a large quantity of plutonium into the surrounding environment. Plutonium can be dangerous. When it decays, it usually releases heavy particles such as electrons and helium nuclei. These particles aren’t particularly dangerous outside the body, but if plutonium is ingested they can cause genetic damage. The new paper shows that minute quantities of plutonium from Fukushima have spread far from the plant. In samples taken to the northwest and in the J-Village, where workers live, the authors found trace amounts of plutonium in the surface soil (see map). Looking at the ratio of plutonium-241 to plutonium-239, they were able to conclude that the plutonium came from Fukushima rather than other sources, such as old nuclear-weapon tests. The additional exposure from inhaling this loose plutonium at the S2 site is around 0.5 millisieverts (mSv) over 50 years. This dose — 0.5 mSv over half a century — is five times higher than the government’s current estimate for plutonium exposure from the accident, but it doesn’t mean there’s a health risk. Over the same period, the average person on Earth would receive 120 mSv from natural sources of radiation. Even for those who worry about low-dose radiation, it’s safe to say that this additional plutonium exposure won’t have an impact. Nevertheless, the measurements are interesting. The distances at which the team finds the material imply that plutonium was ejected during the hydrogen explosions in the first days of the crisis. And the relatively low levels (around 10,000 times lower than Chernobyl) suggest that the heavily shielded concrete casings around the reactors did offer some protection from the worst of the fallout. There’s another reason this work is important. As we report this week, mistrust is running high among residents in Japan. Independent measurements such as these are extremely important in providing residents and evacuees with the information they need to get on with their lives. In this case, the measurements show little additional risk. But news of plutonium, no matter how small, will no doubt be dispiriting to the residents of Fukushima.
9.0级地震引发的日本福岛核电站危机已经有2个多月了,法国科学家2011年5月23日在《环境与科技》( Environmental Science Technology 2011 45 (10), p 4193)网站发表了一项最新研究报告,对于福岛核电站事故对其电厂附近的野生生物的影响进行评估,指出有些物种可能已经吸收到的辐射剂量远超过敏感物种的安全水平。 这项报告由法国辐射防护与核安全研究所(French Institute of Radioprotection and Nuclear Safety)的 Jacqueline Garnier-Laplace, Karine Beaugelin-Seiller以及Thomas G. Hinton合作完成。这也是首次对福岛核事故的生态后果作出的评价。关心福岛核事故的朋友们不妨可以看看Garnier-Laplace和她的同事研究报告。 原文下载: http://doc.sciencenet.cn/upload/file/20116374917265.pdf
一般认为,会导致以下连锁反应: 日本福岛核危机-全球核电建设低迷-中国谨慎建设核电-电动汽车电能来源依赖火电-失去电动汽车节能环保的意义! ① 日本福岛核危机:引发全球在建、拟建核电项目的搁置。我国近年地震等地质灾害频发,因此,我国核电的发展将可能受到影响。 ② 中国的电能来源:主要以煤电为主(80%),其他(约20%):核电、风电、水电、太阳能发电等。 ③ 而火电的煤炭利用效率(用于火力发电的煤炭占全年煤炭使用量的1/5左右)很低,首先煤炭转化为电能,再输送(电能损耗),再给电动汽车充电,电能再经机械转化为汽车的推动力,这个过程的能量损耗比直接采用内燃机(汽油或柴油,甚至是天然气、代用燃料,如酒精等)的效率要低。这意味着对环境的污染并没有实质改善,因此,也就失去了通过电机拖动方式代替内燃机推动方式的意义。 ④ 另外,电动汽车本身的技术也存在瓶颈,例如:电池技术、充电技术等。 因此,综合以上分析,可以预见,在短期内: a)内燃机仍然将作为主要的汽车动力来源方式,尤其是中重型商用车、客车,解决石油危机的可能方式有可能转向可再生的代用燃料内燃机; b)对于电动汽车的发展,可以考虑采用风能、太阳能的利用,但这受地理条件和气候的影响和限制; c)对于氢电池,存在储存和使用的安全问题,造价也高,而且氢的收集也是一个问题(不能依靠电能分解)。