（以下材料是科普材料，在正式科學雜誌上不被引用的，僅供初級知識介紹，讀者明鑒。 在具體過程，更需聽從在場的專家指導）
為什麽鈈的毒性這麽強? （http://zhidao.baidu.com/question/62473096.html
鈈 plutonium
一種化學元素。化學符號 Pu，原子序數 94 ，屬周期係ⅢB族，為錒係元素的成員和人工放射性元素。半衰期最長的同位素是鈈244。1940年美國G.T.西博格、E.M.麥克米倫、J.W.肯尼迪和A.C.沃爾用152.4厘米回旋加速器加速的16兆電子伏氘核轟擊鈾時發現鈈 238。第二年又發現鈈的最重要的同位素鈈 239。在自然界中隻找到兩種鈈同位素，一種是從氟碳鈰鑭礦中找到的微量鈈 244，它具有足夠長的半衰期，可能是地球上原始存在的。另一種是從含鈾礦物中找到的鈈239，是鈾238吸收自然界裏的中子而形成的。其他鈈同位素都是通過人工核反應合成的。已發現的有質量數232～246的鈈同位素。
鈈是銀白色金屬，熔點640℃，沸點 3234℃。在幹燥的空氣中，表麵的氧化膜起保護作用，氧化緩慢，但有水氣存在下氧化膜被破壞，容易被氧化。鈈溶於鹽酸、磷酸，但不溶於硝酸和濃硫酸，原因是發生鈍化作用。鈈的氧化態為＋3、＋4、＋5、＋6、＋7，以＋4價化合物最穩定。鈈的氯化物、硝酸鹽、硫酸鹽易溶於水，氧化物、氫氧化物、草酸鹽碳酸鹽不溶於水。鈈有劇毒，操作時應嚴密保護。
金屬鈈是銀白色的，與氧氣、水蒸氣和酸作用，但不與堿反應。它和鈾一樣用於核燃料和核武器。現在已經可以獲得成噸的鈈。
1945年，西博格比較了鎿和鈈，認為它們與鈾的性質相似，同時又與稀土元素中釤相似，在1945年發表了他編排的元素周期表，建立了與鑭係元素相同的錒係元素，把它們一起放置在元素周期表的下方，成為今天形式的元素周期表，並留下94號元素以後一係列的空位留待發現。
另外，鈈是世界上最毒的物質。一片阿斯匹林大小的鈈，足以毒死2億人，5克的鈈足以毒死人類。鈈的毒性比砒霜大4．86億倍，它的威力勝過核武器。
鈈的大規模製備是通過反應堆中的核反應進行的，由鈾238 吸收中子後生成，再用溶劑萃取和離子交換純化。鈈是易裂變的放射性元素，能用作核燃料，用於製造核武器。鈈用作快中子增殖反應堆燃料時，新形成的鈈比消耗的鈈還要多，可使鈾238轉變為鈈而加以充分利用。鈈238用於製造同位素電池，用作宇宙飛船、人造衛星、航標燈的電源。
下麵是維基上有關鈈毒性科普介紹（http://en.wikipedia.org/wiki/Plutonium）
Toxicity of Plutonium
Isotopes and compounds of plutonium are dangerous due to their radioactivity. Contamination by plutonium oxide (spontaneously oxidized plutonium) has resulted from a number of military nuclear accidents where nuclear weapons have burned.[85]
The alpha radiation plutonium emits does not penetrate the skin but can irradiate internal organs when plutonium is inhaled or ingested.[32] The skeleton, where plutonium is absorbed by the bone surface, and the liver, where it collects and becomes concentrated, are at risk.[31] Plutonium is not absorbed into the body efficiently when ingested; only 0.04% of plutonium oxide is absorbed after ingestion.[32] What plutonium is absorbed into the body is excreted very slowly, with a biological half-life of 200 years.[86] Plutonium passes only slowly through cell membranes and intestinal boundaries, so absorption by ingestion and incorporation into bone structure proceeds very slowly.[87][88]
Plutonium is more dangerous when inhaled than when ingested. The risk of lung cancer increases once the total dose equivalent of inhaled radiation exceeds 400 mSv.[89] The U.S. Department of Energy estimates that the lifetime cancer risk for inhaling 5,000 plutonium particles, each about 3 microns wide, to be 1% over the background U.S. average.[90] Ingestion or inhalation of large amounts may cause acute radiation poisoning and death; no human is known to have died because of inhaling or ingesting plutonium, and many people have measurable amounts of plutonium in their bodies.
The "hot particle" theory in which a particle of plutonium dust radiates a localized spot of lung tissue has been tested and found false – such particles are more mobile than originally thought and toxicity is not measurably increased due to particulate form.[87] However, when inhaled, plutonium can pass into the bloodstream. Once in the bloodstream, plutonium moves throughout the body and into the bones, liver, or other body organs. Plutonium that reaches body organs generally stays in the body for decades and continues to expose the surrounding tissue to radiation and thus may cause cancer. [91]
Several populations of people who have been exposed to plutonium dust (e.g. people living down-wind of Nevada test sites, Hiroshima survivors, nuclear facility workers, and "terminally ill" patients injected with Pu in 1945–46 to study Pu metabolism) have been carefully followed and analyzed.
These studies generally do not show especially high plutonium toxicity or plutonium-induced cancer results.[87] "There were about 25 workers from Los Alamos National Laboratory who inhaled a considerable amount of plutonium dust during the 1940's; according to the hot-particle theory, each of them has a 99.5% chance of being dead from lung cancer by now, but there has not been a single lung cancer among them."[92][93] Plutonium has a metallic taste.[94]
Criticality potential
Toxicity issues aside, care must be taken to avoid the accumulation of amounts of plutonium which approach critical mass, particularly because plutonium's critical mass is only a third of that of uranium-235.[7] A critical mass of plutonium emits lethal amounts of neutrons and gamma rays.[95] Plutonium in solution is more likely to form a critical mass than the solid form due to moderation by the hydrogen in water.[13]
Criticality accidents have occurred in the past, some of them with lethal consequences. Careless handling of tungsten carbide bricks around a 6.2 kg plutonium sphere resulted in a fatal dose of radiation at Los Alamos on August 21, 1945, when scientist Harry K. Daghlian, Jr. received a dose estimated to be 5.1 Sievert (510 rems) and died 28 days later.[96] Nine months later, another Los Alamos scientist, Louis Slotin, died from a similar accident involving a beryllium reflector and the same plutonium core (the so-called "demon core") that had previously claimed the life of Daghlian.[97] These incidents were fictionalized in the 1989 film Fat Man and Little Boy.
In December 1958, during a process of purifying plutonium at Los Alamos, a critical mass was formed in a mixing vessel, which resulted in the death of a crane operator named Cecil Kelley.[98] Other nuclear accidents have occurred in the Soviet Union, Japan, and many other countries.[98]
Flammability of plutonium
Metallic plutonium is a fire hazard, especially if the material is finely divided. In a moist environment, plutonium forms hydrides on its surface, which are pyrophoric and may ignite in air at room temperature. Plutonium expands up to 70% in volume as it oxidizes and thus may break its container.[99] The radioactivity of the burning material is an additional hazard. Magnesium oxide sand is probably the most effective material for extinguishing a plutonium fire. It cools the burning material, acting as a heat sink, and also blocks off oxygen. Special precautions are necessary to store or handle plutonium in any form; generally a dry inert gas atmosphere is required.[99][100][note 11]
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