福岛

Posted onJan.07, 2014inBasic Science,Fukushima,福岛,Health,Junk Science,meltdown,Nuclear energy,Pacific Ocean,公共安全,辐射,风险,ScienceWonk Blogby

愚蠢的一致性

Emerson一致性是好的 - 知道某些事情通常会随着时间的流逝而保持恒定。例如，我们总是可以指望重力将我们牢固地固定在地面上。政客通常在骗和自我服务。我可以指望放射性持续衰减。等等。当然，并非所有的一致性都是好的 - 正如爱默生所指出的那样，“愚蠢的一致性是小政治家，哲学家和神圣的小思想的妖精。”我们还可以依靠美国公众始终质疑进化是否真正发生。我们中的许多人都知道，我们的完美主义者老板将始终坚持再进行一轮评论和编辑，然后再将文件出门出门。我们总是会发现那些显然为他们缺乏知识而感到自豪的人。而且我们可以预期，某些类别的博客作者将继续将世界末日视为近乎视野。 It is this latter category I’d like to talk about this time – particularly the batch that continues to insist that the reactor accident at the Fukushima Dai’ichi site is going to kill millions.

Before launching into this piece I’d like to point you to awonderful counter-exampleof what I just said – a blog posting by oceanographer and University of Washington professorKim Martini. I have been accused of being part of the pro-nuclear and/or pro-radiation lobby because of my long years of experience as a radiation safety professional – Dr. Martini told me that she became interested in this topic, researched it herself, and came to her conclusions independently of the nuclear energy and radiation safety professionals. In short, she is scientifically competent, intelligent, and has no reason to be biased either pro- or anti-nuclear.

最新一轮的福岛愚蠢是欺诈tention that Americans need to evacuate the West Coast because of an apparently imminent release from one or more of the affected reactors and/or the Reactor 4 spent fuel pool. There are also those who blame the Fukushima accident for massive starfish die-offs, for sick animals along the Alaskan coast, and more – all of which (according to the good Dr. Martini) are far from accurate. And anti-nuclear activist Helen Caldicott has gone as far as to state that the entire Northern Hemisphere might need to be evacuated if things get as bad as she fears and the Unit 4 spent fuel pool collapses. So let’s see what the facts are, what the science can tell us, and what the real story might be.

Can the melted reactors go critical?

There have been predictions that the ruined reactor cores will somehow achieve criticality, producing more fission products and spreading more contamination into the water. While this is not strictly speaking impossible it is highly unlikely – sort of like saying that it is remotely possible that Bill Gates will leave me his fortune, but I’m still contributing to my 401(k) account. To achieve criticality (to a nuclear engineer or a reactor operator, “criticality” simply means that the reactor is operating at a constant power) requires reactor fuel that’s enriched to the right percentage of U-235, a critical mass of the uranium (enough to sustain a chain reaction), and it has to be in a configuration (the critical geometry) that will permit fission to occur. Also important in most reactors is a moderator – a substance such as water that will slow neutrons down to the point where they can be absorbed and cause the U-235 atoms to fission. In reactors such as the ones destroyed in Fukushima require all of these components to achieve criticality – take away any one of them and there will be no fission chain reaction.

毁坏的反应堆核心符合其中的一些要求 - 因为它们在事故发生时一直在运行，我们知道它们的次数足够丰富。被水（海水或地下水）包围，它们也可能浸入主持人中。但是没有临界几何形状，核心无法维持裂变链反应。因此，问题是这些核心是否可以偶然地陷入关键的几何形状。答案是它极不可能。

例如，考虑制造核反应堆核心的工程和设计。Granted, much of this design goes into making the reactors as efficient and as cost-effective to operate as possible, but the fact is that we can’t just slap some uranium together in any configuration and expect it to operate at all, let alone in a sustained fashion. In addition, reactors keep their fuel in an array of fuel rods that are immersed in water – the water helps slow the neutrons down as they travel from one fuel element to the next. A solid lump of low-enriched uranium has no moderator to slow down these neutrons; the only moderated neutrons are those that escape into the surrounding water and bounce back into the uranium; the lumps in a widely dispersed field of uranium will be too far apart to sustain a chain reaction. Only a relatively compact mass of uranium that is riddled with holes and channels is likely to achieve criticality – the likelihood that a melted core falling to the bottom of the reactor vessel (or the floor of the containment) would come together in a configuration that could sustain criticality is vanishingly low.

How much radioactivity is there?

首先，让我们从可以释放到海洋的放射性量开始。它来自于此的是在芯上发生的铀裂变，直到被反应器关闭为止 - 铀本身略有放射性，但每个分裂的铀原子都会产生两个放射性原子（裂变片段）。当反应堆被中子轰击时，反应堆的材料会变得放射性，但是这些金属非常耐腐蚀，不太可能溶解到海水中。然后，当非侵蚀U-238捕获中子时，在反应堆芯中形成的prutanic元素，例如p和美国的裔元素。其中一些tranuranics具有较长的半衰期，但是长的半衰期意味着核素仅是弱放射性的 - 需要15克PU-239才能保持与单个克的放射性相同的放射性（约1 ci（约1 ci）或RA-226的克37 GBQ），CS-137的一克具有大约超过一公斤PU-239的放射性。因此，可发布的大多数放射性都来自裂变产品，其激活和中子捕获产品以更小的方式贡献。

This part is basic physics and simply isn’t open to much interpretation – decades of careful measurements have shown us how many of whichfission products are formedduring sustained uranium fission. From there, the basic physics of radioactive decay can tell us what’s left after any period of decay. So if we assume the worst case – that somehow all of the fission products are going to leak into the ocean – the logical starting place is to figure out how much radioactivity is even present at this point in time.

2012年1月，能源部西北国家实验室（PNNL）使用复杂的计算机计划来计算fission product inventoryof the #1 and #3 reactors at the Fukushima Dai’ichi site – they calculated that each reactor held about 6.2 million curies (about 230 billion mega-becquerels) of radioactivity 100 days after shut-down. The amount of radioactivity present today can be calculated (albeit not easily due to the number of radionuclides present) – the amount of radioactivity present today reflects what there was nearly three years ago minus what has decayed away since the reactors shut down. After 1000 days (nearly 3 years) the amount of radioactivity is about 1% of what was present at shutdown (give or take a little) and about a tenth what was present after 100 days. Put all of this together and accounting for what was present in the spent fuel pools (the reactor in Unit 4 was empty but the spent fuel pool still contains decaying fuel rods) and it seems that the total amount of radioactivity present in all of the affected reactors and their spent fuel pools is in the vicinity of 20-30 million curies at this time.

By comparison, the National Academies of Science calculated in 1971 (in a report titledRadioactivity in the Marine Environment）太平洋拥有200多个billioncuries of natural potassium (about 0.01% of all potassium is radioactive K-40), 19 billion curies of rubidium-87, 600 million curies of dissolved uranium, 80 million curies of carbon-14, and 10 million curies of tritium (both C-14 and H-3 are formed by cosmic ray interactions in the atmosphere).

水中可能有多少放射性？

已经从1、2和3单位逃脱了相当多的放射性 - 许多挥发性和可溶性放射性核素已释放到环境中。剩余的放射性核素恰恰是因为它们要么在环境中移动不足，要么是因为它们锁定在剩余的燃料中。因此，这种放射性的很大一部分不可能发布。但是，为了争论，让我们假设有3000万个放射性象征将被释放到太平洋进入西海岸 - 水中有多少放射性？

The Pacific Ocean has avolume of about 7×1023ML或大约7×1020Liters和North Pacific拥有大约一半的数量（在过去的几年中，可能没有太多的水越过赤道）。如果我们忽略了太平洋进入其他海洋的循环，并且在赤道穿过赤道很简单 - 3000万居属于3×1020升到大约10-13curies per liter of water, or about 0.1 picocuries (pCi) per liter (1 curie is a million million pCi).Natural radioactivity（根据美国国家科学院的说法）海水中的铀和钾约为300 pci/升，因此这是水中自然放射性的一小部分。如果我们做出一个简化的假设，即所有这些溶解的放射性都是CS-137（最坏的情况），那么我们可以使用美国EPA在Federal Guidance Report #12计算花费一整年沉浸in this water would give you a radiation dose of much less than 1 mrem – a fraction of the dose you’d get from natural background radiation in a single day (natural radiation exposure from all sources – cosmic radiation, radon, internal radionuclides, and radioactivity in the rocks and soils – is slightly less than 1 mrem daily). This is as close as we can come to zero risk.

这是最坏的情况下– assuming that全部of the radioactivity in all of the reactors and spent fuel pools dissolves into the sea. Any realistic case is going to be far lower. The bottom line is that, barring an unrealistic scenario that would concentrate all of the radioactivity into a narrow stream, there simply is too little radioactivity and too much water for there to be a high dose to anyone in the US. Or to put it another way – we don’t have to evacuate California, Alaska, or Hawaii; and Caldicott’s suggestion to evacuate the entire Northern Hemisphere is without any credible scientific basis. And this also makes it very clear that – barring some bizarre oceanographic conditions – radioactivity from Fukushima is incapable of causing any impact at all on the sea life around Hawaii or Alaska let alone along California.

Closing thoughts

There’s no doubt that enough radiation can be harmful, but the World Health Organization has concluded that Fukushima will not produce any widespread health effects in Japan (or anywhere else) – just as Chernobyl failed to do nearly three decades ago. And it seems that as more time goes by without the predicted massive environmental and health effects they’ve predicted, the doom-sayers become increasingly strident as though shouting ever-more dire predictions at increasing volume will somehow compensate for the fact that their predictions have come to naught.

尽管有所有的修辞学未来几年可能没有杀死。在这一点上，科学是世界科学界的判断（专门从事辐射及其健康影响的人）的判断。可悲的是，反核运动在试图利用2011年的悲剧来激发毫无根据的恐惧方面仍然保持一致。我不确定艾默生会属于哪个类别，但是即使事实继续反对它们，我也必须承认它们的一致性。

帖子愚蠢的一致性appears onScienceWonk, FAS’s blog for opinions from guest experts and leaders.

Posted onNov.06, 2013inBasic Science,Fukushima,福岛,Health,Junk Science,Nuclear energy,公共安全,辐射,辐射健康效应,风险,ScienceWonk Blogby

再次闯入

Don-QuixoteI’d been planning on waiting a little longer before returning to the topics of Fukushima and radiation health effects, but a particularly egregiously bad New York Times op-ed piece deserves some attention. So once more into the breach.

在10月30日纽约时报, pediatrician and anti-nuclear activist Helen Caldicott used the nuclear reactor accident in Fukushima as an opportunity to express her concerns about nuclear energy – a calling she has followed since the Three Mile Island reactor accident. Unfortunately, Caldicott included a number of errors in her editorial that are sufficiently serious as to invalidate her conclusions. I’d like to take an opportunity to take a look at these mistakes and to explain the science behind them.

In the first paragraph of her article, Caldicott states that “the mass of scientific and medical literature…amply demonstrates that ionizing radiation is a potent carcinogen and that no dose is low enough not to induce cancer.”

To the contrary, even the most conservative hypothesis (linear no-threshold) holds that low doses of radiation pose very little threat of cancer. Using a slope factor of 5% added risk of cancer fatality per 1 Sv (100 rem) of exposure, the risk of developing cancer from 1 rem of radiation is about 0.05% (5 chances in 10,000). This risk is far lower than the risk of developing cancer as a habitual smoker, from working with a number of solvents (e.g. benzene), working with a number of laboratory chemicals, and so forth. Epidemiologists have noted no increase in cancer rates among people living in areas with high levels of natural background radiation, as well as among the lowest-dose groups of atomic bomb survivors (in fact, people living in the states with the highest levels of natural radiation have lower cancer rates than do those who live in the lowest-dose rate states). Not only that, butage-adjusted cancer rates have dropped steadily(with the exception of smoking-related cancers) over the last century, in spite of dramatic increases in medical radiation exposure. In the words of respected radiation biologist Antone Brooks, these observations show us that “if (low levels of) radiation cause cancer it’s not a heavy hitter.” The bottom line is that, if even the lowest doses of radiation can cause cancer (which has not yet been shown to be either correct or incorrect), radiation is a weak carcinogen – not the “potent carcinogen” that Caldicott would have us believe.

In the second paragraph of her article, Caldicott states that “Large areas of the world are becoming contaminated by long-lived nuclear elements secondary to catastrophic meltdowns: 40% of Europe from Chernobyl, and much of Japan.”

这是一个很难解析的声明，因为这是一个模糊的陈述。如果通过“受污染”，Caldicott意味着存在原本不会存在的放射性核素，那么她是错误的 - 实际上，您可以在几乎欧洲，亚洲和北美几乎每平方英里都发现跨越人工放射性核素的痕迹她声称的40％。但是，这意味着我们可以检测到土壤中这些核素的痕量水平 - 这样做也可以从1940年代到1960年代的大气核武器测试中找到痕迹。就此而言，我们可以从铅油的时代开始几乎在整个世界上发现铅污染。但是，铅污染也更加深入 - 科学家发现，格陵兰冰川的铅痕迹可以追溯到罗马帝国。但是，没有人会从古罗马人的污染中引起铅中毒，就像从CS-137和SR-90的微小痕迹中没有人会发现北半球的CS-137和SR-90的射线疾病（或癌症）。但是，卡尔迪科特无法真正评论一个事实，即人工核能已经污染了近70年的世界，因为这会破坏她的说法，即福岛和切尔诺贝利的放射性污染正在造成欧洲和日本的死亡和破坏。

在第三段中，卡尔迪科特指出，“ 2009年纽约科学学院的一份报告“ Chernobyl”估计，近一百万次已经死于这场灾难。在日本，1000万人居住在高度污染的地点。”

Caldicott is correct that the NYAS reported over a million deaths from Chernobyl. However, this report itself was highly criticized for being scientifically implausible – the NYAS is a respected organization, but in this case their conclusions are at odds with the reality noted on the ground by the World Health Organization. Specifically, the WHO concluded that in the first 20 years, fewer than 100 people could be shown to have died from radiation sickness and radiation-induced cancers and they further concluded that, even using the worst-case LNT model, fewer than 10,000 would eventually succumb from radiation-induced cancer as a result of this accident. This is not a trivial number – but it is less than 1% of the one million deaths the NYAS claims. And in fact the actual number is likely to be far lower, as physicianMichael Repacholi noted in an interview与BBC。实际上，即使是世界卫生组织的国际癌症研究机构也承认：“吸烟将在同一人群中造成数千倍的癌症。”即使切尔诺贝利和福岛受到的污染足以引起最终的健康问题，我们也可以通过将注意力戒烟（或为此，对童年的疫苗接种）来对公众做更多的好处，而不是花费数千亿美元清洁up contamination that doesn’t seem to be causing any harm.

In the fourth paragraph of her piece, Caldicott notes that “Children are 10 to 20 times more radiosensitive than adults, and fetuses thousands of times more so; women are more sensitive than men.”

To the contrary – the National Academies of Science published asweeping 2006 reportthat summarizes the state of the world’s knowledge on the “Health Risks from Exposure to Low Levels of Ionizing Radiation” in which they conclude that children are between 2-3 times as sensitive to radiation as are adults – more sensitive as adults, but a far cry from Caldicott’s claim.

The reproductive effects of radiation are also well-known – fetal radiation exposures of less than 5 rem are incapable of causing birth defects according to our best science, and the疾病控制中心flatly states that exposure to even higher radiation doses is not a cause for alarm under most circumstances. This conclusion, by the way, is based on studies of hundreds of thousands of women who were exposed to radiation from medical procedures as well as during the atomic bombings in Japan – it is based on a tremendous amount of hard evidence.

This claim of Caldicott’s, by the way, is particularly egregious and has the potential to do vast harm if it’s taken seriously. Consider – in the aftermath of the Chernobyl accident it is estimated that over 100,000 women had abortions unnecessarily because they received poor medical advice from physicians who, like Caldicott, simply didn’t understand the science behind fetal radiation exposure. There are estimates that as many as a quarter million such abortions took place in the Soviet Union, although these numbers can’t be confirmed.

但是，即使在这个国家，我们也看到了今天的错误信息导致问题 - 在我担任辐射安全官员期间，我被要求计算近100次胎儿辐射剂量估计值 - 主要是在严重交通事故后接受X射线的孕妇，并且许多妇女正在认真考虑在医生的建议下进行治疗堕胎。当我进行剂量计算时，没有一个单身女人的婴儿收到足够的辐射来引起问题。而且它不止于此 - 我们还有父母拒绝为孩子扫描CT扫描，更喜欢探索性手术及其随之而来的风险，而不是X射线手术的风险。最重要的是，这种想法 - 孩子和发育的婴儿对辐射非常敏感 - 可能会导致父母选择不必要的堕胎，并使孩子处于危险之中；通过拥护这些观点，Caldicott正在违反她“首先不伤害”的希波克拉底宣誓，她应该承担此任务。

最后，在她的长篇小说的最后一段中，卡尔迪科特声称“生殖器官的辐射会诱导精子和卵中的遗传突变，从而增加了糖尿病，囊性纤维化，血质体病，以及其他成千上万的遗传疾病的发生率。隐性突变最多需要20代。”

我能说的是，卡尔迪科特决定大声疾呼。事实是，医学或科学文献中没有一种情况，其中先天缺陷或遗传疾病与概念前辐射暴露有关。这不是我的结论 - 这是罗伯特·布伦特（Robert Brent）博士的结论，他对这个话题的了解比世界上的任何人都了解。鸡蛋和精子可能会受到损害，但布伦特博士指出，有一个“生物过滤器”可防止细胞损坏的细胞形成婴儿。另一条推理支持布伦特的主张 - 与自然辐射水平较低的区域相比，天然辐射水平较高的地区也没有增加出生缺陷。卡尔迪科特（Caldicott）的说法，低辐射暴露造成长期遗传损害根本不受科学或医学文献或所进行的任何观察结果的支持。

卡尔迪科特（Caldicott）声称辐射也是造成许多遗传疾病的原因同样的怀疑。世界首要的辐射科学组织（International Council on Radiation Protection, the联合国原子辐射委员会, and theNational Council on Radiation Protection and Measurements）所有人都同意，如果辐射有助于多因素疾病，那么这种影响确实非常弱 - 可能太弱了，无法与这些疾病的自然来源区分开。具体而言，Unscear计算得出的是，如果概念前辐射暴露会导致这些问题 - 将每一代人的种群暴露于1 REM的辐射1 REM可能会导致每代每一百万分娩每百万分娩和15例隐性遗传疾病造成100例遗传疾病遗传疾病（ICRP计算出类似但速度较低）。这远低于整个人群遗传疾病的背景发生率。哦 - Unscear还确定“预计多因素疾病对诱导的突变的反应要比孟德尔疾病的响应较少，因此疾病频率的预期增加非常小” - 与ICRP一致的陈述。换句话说，卡尔迪科特的主张与专门从事放射健康效应的最受尊敬的科学组织的最佳作品背道而驰。

With respect to the length of time required for genetic effects – if any – to manifest themselves, I honestly don’t know where Caldicott pulled the number of 20 generations from. This is a number I haven’t seen anywhere in the scientific literature, nowhere in any of the genetics classes I took in grad school, and nothing I ever calculated or saw calculated. As near as I can tell, she is either repeating something she heard somewhere or she made the number up to impress the reader.

结论

最重要的是，与科学或医学事实相比，Caldicott的社论更多地基于煽动性。福岛的事故很糟糕，但与引起自然灾害相比，这显得苍白。事故的后遗症已经足够糟糕了 - 成千上万的家庭流离失所，成千上万的日本人被撤离家园，以及他们所遭受的压力，焦虑和沮丧。TEPCO和日本政府将不得不花费数十亿美元来拆除该工厂，并需要数十亿美元清理受污染的地区 - 在许多情况下，清理地方并不是因为它们对生活和健康构成真正的风险，而是因为污染水平超过了任意水平等级。事情足够糟糕，而卡尔迪科特（Caldicott）试图通过提出与科学或医学现实无关的索赔来得分廉价的积分，只是为了提高她的反核议程。她的文章无助于推动辩论 - 它只能利用日本的悲剧来激怒公众的恐惧。

帖子再次闯入appears onScienceWonk, FAS’s blog for opinions from guest experts and leaders.