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Plutonium

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Plutonium
Plutonium
General Info
Atomic Symbol Atomic symbol::Pu
Atomic Number Atomic number::94
Atomic Weight Atomic weight::244 g/mol
Chemical series Actinides
Appearance A Dull Silvery White Metal
Sample plutonium.jpg
Group, Period, Block No Group, Period 7, f Block
Electron configuration [Rn] 7s2, 5f6
Electrons per shell 2, 8, 18, 32, 18, 8, 2
Electron shell plutonium.png
CAS number CAS number::7440-07-5
Physical properties
Phase Solid
Density Density::19.84 g/ml
Melting point Melting point::912.65 K
Boiling point Boiling point::3508.15 K
Isotopes of Plutonium
iso NA half-life DT DE (MeV) DP
Pu-238 syn 88 years Alpha 5.593 U-234
Pu-239 trace 24,000 years Alpha 5.244 U-235
Pu-240 syn 6540 years Alpha 5.255 U-236
Pu-241 syn 14 years Beta .021 Am-241
Pu-242 syn 376,000 years Alpha 4.983 U-238
Pu-244 trace 80 Million years Alpha 4.66 U-240
All properties are for STP unless otherwise stated.

Discovered in 1940, plutonium is the second transuranic element on the periodic table. It was first isolated in Berkeley, California[1]. The name plutonium comes from the fact that it is the element after neptunium and the planet Pluto comes after Neptune. The element was found when Seaborg, McMillan, Kennedy, and Wahl used a cyclotron on uranium. The name plutonium was first going to be used for Barium[2]. Plutonium was first predicted to exist by Walter Russell. Once found Seaborg made its chemical symbol Pu as a joke, but the symbol stuck with it onto the periodic table. The first major production of plutonium was the Manhattan Project. There they set up large reactors to make the plutonium for the first two atomic bombs[3].

Properties

Plutonium is a member of the transuranic elements. It is a solid at room temperature and has a dull silvery-white color[4]. It becomes slightly yellow when exposed to oxygen. A large piece of plutonium is warm when touched due to the alpha decay this element exhibits. This element easily dissolves in hydrochloric acid, hydroiodic acid, and perchloric acid[5]. It does not conduct electricity or heat very well, and can glow if left alone for a time[6]. The powder from plutonium's oxidation in moist air is a hydride that can spontaneously combust[7].

For being a radioactive element, plutonium does not pose very much danger to people. The alpha decay plutonium gives off cannot go through the skin[5], but is dangerous if a person has directly touched the metal[6]. The other danger is if small particles of plutonium are inhaled or ingested. This is because the radioactive decay particles can penetrate the internal organs. One specific example is inhalation of plutonium can cause lung cancer. Even though there is the possibility, there is no official record of deaths caused by plutonium[5].

Occurrences

Plutonium can be found in Uranium

Plutonium can be found naturally in the human body in very small quantities [8]. In the earth, Plutonium is found in extremely small amounts. Normally it is in trace amounts in uranium. This is because the uranium of certain isotopes will randomly split apart, fission, to make plutonium [9].

Plutonium can be made synthetically in nuclear reactors. A scientist will start with U-238, then bombard it with neutrons to make U-239. This isotope will experience nuclear decay and turn into Pu-239. Between 1944 to 1988, the United States produced around one hundred metric tons of plutonium using special nuclear reactors called production reactors. Using this reactor, fuel rods made of uranium would be lowered into the reactor. After the neutrons hit the fuel rods for a long enough period, they would be taken out. Workers would then pour a strong acid on the fuel rods to melt them. This liquid would go through some chemical possesses to extract the new plutonium out of the uranium fuel rods [10].

Uses

Plutonium is made in a reactor like this

This plutonium is radioactive, but only the isotopes Pu-239 and Pu-240 are fissile. The ones around these isotopes are only fissionable. The difference between these is that fissile materials can be split using both fast and slow moving neutrons and fissionable materials can only be split using fast moving neutrons[4]. Due to this fact Pu-239 is the preferred fuel for atomic bombs over U-235[6].

There are four grades of plutonium: Supergrade, weapons grade, fuel grade, and reactor grade. These grades are based on the amount of Pu-240 is in the sample. Supergrade has two to three percent in it. Weapons grade contains less than seven percent. Fuel grade has seven to nineteen percent. Reactor grade has the most with anything over nineteen percent[4]. Of the four there are two main grades, reactor grade and weapons grade. Reactor grade plutonium is made when plutonium has been in a reactor for three years. The spent fuel rods can then be repossessed to get plutonium oxide. This is then mixed with depleted uranium oxide to make MOX or mixed oxide fuel. Now about eight to ten tons of MOX is used each year. Normal reactor grade plutonium will start to make americium after a few years of storage. This is because the Pu-241 in the fuel will decay into that element. The americium would have to be taken out before being used in a nuclear reactor[11].

Weapons grade plutonium has only been irradiated for two to three months[11]. As most people know, Plutonium is the primary fuel in atomic bombs and nuclear weapons[6], but only weapons grade can be used. There is about ten kilograms of plutonium in an atomic bomb[11].

Constructive Uses

Even though this element is known well for its use in atomic bombs, plutonium has more constructive uses. One of these uses is powering certain artificial heart pacemakers[7]. This use is controversial because the isotope used in the pace makers is the harmless Pu-238. This isotope is one neutron away from Pu-239 which could be very harmful to the patient[6].

NASA has used plutonium to power spacecraft and satellites. In the Apollo 14 mission, plutonium was used in the seismic devices. Plutonium has a lot of potential for energy; one kilogram can make twenty-two million kilowatt hours of heat energy[6] or ten million kilowatt hours of electricity[11].

References

  1. Bernstein, Jeremy. Plutonium: A History of the World's Most Dangerous Element National Academies Press. Web. Nov 17, 2011.
  2. Winter, Mark. Plutonium. Webelements. Web. Nov 17,2011.
  3. Unknown Author. Plutonium - History Global Oneness. Web. Nov 17,2011.
  4. 4.0 4.1 4.2 Author Unknown. [1] Institute of Energy and Environmental Research. Web. Nov 1, 2011
  5. 5.0 5.1 5.2 [2] Lenntech BV. Web. Nov 1, 2011
  6. 6.0 6.1 6.2 6.3 6.4 6.5 Thadani, Rahul. [3] Plutonium Uses. Web. Nov 1, 2011.
  7. 7.0 7.1 Khan, Sumaiya. [4] Plutonium Facts. Web. Nov 1, 2011.
  8. Unknown. [5]. Marshall Islands Dose Assessment and Radioecology Program. Web. Nov 2, 2011.
  9. Desdichado. [6]. Answers.com. Web. Nov 16, 2011.
  10. Unknown Author. [7]. United States Environmental Protection Agency. Web. Nov 16, 2011.
  11. 11.0 11.1 11.2 11.3 Author Unknown. Plutonium. World Nuclear Association. Web. Nov 17, 2011.