Fukushima ongoing nuclear disaster

• Japan braces itself for 'once in a decade' typhoon

I was reading the above article about the once in a decade typhoon and began thinking about a conversation my son and I were having today on the phone about just how bad the Fukushima nuclear disaster is ongoing for the next 50,000 years or more for all life in the sea around Japan. IF one of the reactors had not been reprocessing nuclear weapons grade plutonium that was one of the reactors that melted down a couple of years ago it wouldn't be as bad as it is now.

Though it is true that Chernobyl is still the worst peace time nuclear disaster of all time, Fukushima in the long run is going to be much worse because of it's location and because plutonium has a 25,000 year half life. So, even 50,000 years from now the plutonium in one of the three reactors that melted down there will still be killing life in that area because being on the ocean there ISN"T presently any real way to stop it from causing more harm for 50,000 years or more into the future already. So, though it could be said that Fukushima is not the worst nuclear disaster so far it will naturally become the worst disaster over time because it will literally almost never end.

Where will you and I be 50,000 years from now? But, even with us long gone it will still be 1/2 as powerful in it's radiating action as now and 25,000 years from now it still will be as powerful a reaction as now. And because of it's location right on the ocean and in the water table on land there just isn't a viable solution to put an end to it at present that can work that would be feasible and practical long term.

Any water that is put in holding tanks there will eat through any holding tank eventually and wind up in the ocean. This is a given because Japan has No place to take the radiated water to away from Fukushima and it wouldn't likely be legal to do that in Japan even if there were such a place in Japan. So, logically all radiated water there is going to eventually wind up in the ocean sooner or later.  And this will go on at the present rate for 25,000 years and then at half that rate for another 25,000 years and then at half that rate for another 25,000 years. So, 75,000 years from now some radiation will be going into the ocean still from Fukushima.

 

Weapons-grade plutonium

Pu-239 is produced artificially in nuclear reactors when a neutron is absorbed by U-238, forming U-239, which then decays in a rapid two-step process into Pu-239. It can then be separated from the uranium in a nuclear reprocessing plant.
Weapons-grade plutonium is defined as being predominantly Pu-239, typically about 93% Pu-239.^[8] Pu-240 is produced when Pu-239 absorbs an additional neutron and fails to fission. Pu-240 and Pu-239 are not separated by reprocessing. Pu-240 has a high rate of spontaneous fission, which can cause a nuclear weapon to predetonate. To reduce the concentration of Pu-240 in the plutonium produced, weapons program plutonium production reactors (e.g. B Reactor) irradiate the uranium for a far shorter time than is normal for a nuclear power reactor. More precisely, weapons-grade plutonium is obtained from uranium irradiated to a low burnup.
This represents a fundamental difference between these two types of reactor. In a nuclear power station, high burnup is desirable. Power stations such as the obsolete British Magnox and French UNGG reactors, which were designed to produce either electricity or weapons material, were operated at low power levels with frequent fuel changes using online refuelling to produce weapons-grade plutonium. Such operation is not possible with the light water reactors most commonly used to produce electric power. In these the reactor must be shut down and the pressure vessel disassembled to gain access to the irradiated fuel.
While it has been claimed that spent LWR fuel could be reprocessed to produce plutonium that, while not weapons grade, could be used to produce a nuclear explosion (even if only one of fizzle yield),^[9] this has never been demonstrated. In particular, a 1962 test at the US Nevada National Security Site (then known as the Nevada Proving Grounds) using non-weapons-grade plutonium used plutonium produced in a Magnox reactor in the United Kingdom. The plutonium used was provided to the US under the 1958 US-UK Mutual Defence Agreement. Its isotopic composition has not been disclosed, other than the description reactor grade and it has not been disclosed which definition was used in describing the material for this test as reactor grade.^[10] The plutonium was apparently sourced from the military Magnox reactors at Calder Hall or Chapelcross. The content of plutonium-239 in material used for the 1962 test is estimated to have been at least 85%, much higher than typical spent fuel from currently operating reactors. Therefore, this test does not prove that constructing a bomb from plutonium sourced from modern spent fuel, which contains no more than 70% Pu-239, is possible.^[11]
Occasionally, low-burnup spent fuel has been produced by a commercial LWR when an incident such as a fuel cladding failure has required early refuelling. If the period of irradiation has been sufficiently short, this spent fuel could be reprocessed to produce weapons grade plutonium.

end quote from:

Weapons-grade plutonium

 

Plutonium

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This article is about the radioactive element. For other uses, see Plutonium (disambiguation).

Plutonium
94Pu
Sm ↑ Pu ↓ (Uqh) neptunium ← plutonium → americium
Plutonium in the periodic table
Appearance
silvery white, tarnishing to dark gray in air
General properties
Name, symbol, number	plutonium, Pu, 94
Pronunciation	/pluːˈtoʊniəm/ ploo-TOH-nee-əm
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(244)
Electron configuration	[Rn] 5f6 7s2 2, 8, 18, 32, 24, 8, 2
History
Naming	after minor planet Pluto, itself a newly coined name
Discovery	Glenn T. Seaborg, Arthur Wahl, Joseph W. Kennedy, Edwin McMillan (1940–1)
Physical properties
Phase	solid
Density (near r.t.)	19.816 g·cm−3
Liquid density at m.p.	16.63 g·cm−3
Melting point	912.5 K, 639.4 °C, 1182.9 °F
Boiling point	3505 K, 3228 °C, 5842 °F
Heat of fusion	2.82 kJ·mol−1
Heat of vaporization	333.5 kJ·mol−1
Molar heat capacity	35.5 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1756 1953 2198 2511 2926 3499
Atomic properties
Oxidation states	8, 7, 6, 5, 4, 3, 2, 1 (amphoteric oxide)
Electronegativity	1.28 (Pauling scale)
Ionization energies	1st: 584.7 kJ·mol−1
Atomic radius	159 pm
Covalent radius	187±1 pm
Miscellanea
Crystal structure	monoclinic
Magnetic ordering	paramagnetic[1]
Electrical resistivity	(0 °C) 1.460 µΩ·m
Thermal conductivity	6.74 W·m−1·K−1
Thermal expansion	(25 °C) 46.7 µm·m−1·K−1
Speed of sound	2260 m·s−1
Young's modulus	96 GPa
Shear modulus	43 GPa
Poisson ratio	0.21
CAS registry number	7440-07-5
Most stable isotopes
Main article: Isotopes of plutonium
iso NA half-life DM DE (MeV) DP 238Pu trace 87.74 y SF 204.66[2]  — α 5.5 234U 239Pu 100% 2.41 × 104 y SF 207.06  — α 5.157 235U 240Pu trace 6.5 × 103 y SF 205.66  — α 5.256 236U 241Pu syn 14 y β− 0.02078 241Am SF 210.83  — 242Pu trace 3.73 × 105 y SF 209.47  — α 4.984 238U 244Pu trace 8.08 × 107 y α 4.666 240U SF  —
v t e · ref

Plutonium is a transuranic radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon and hydrogen. When exposed to moist air, it forms oxides and hydrides that expand the sample up to 70% in volume, which in turn flake off as a powder that can spontaneously ignite. It is radioactive and can accumulate in the bones. These properties make the handling of plutonium dangerous.
Plutonium is the heaviest primordial element by virtue of its most stable isotope, plutonium-244, whose half-life of about 80 million years is just long enough for the element to be found in trace quantities in nature.^[3] Plutonium is mostly a byproduct of nuclear reactions in reactors where some of the neutrons released by the fission process convert uranium-238 nuclei into plutonium.^[4]
Both plutonium-239 and plutonium-241 are fissile, meaning that they can sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors. Plutonium-240 exhibits a high rate of spontaneous fission, raising the neutron flux of any sample containing it. The presence of plutonium-240 limits a sample's usability for weapons or reactor fuel, and determines its grade.
Plutonium-238 has a half-life of 88 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors.
A team led by Glenn T. Seaborg and Edwin McMillan at the University of California, Berkeley laboratory first synthesized plutonium in 1940 by bombarding uranium-238 with deuterons. Trace amounts of plutonium were subsequently discovered in nature. Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II, which developed the first atomic bombs. The first nuclear test, "Trinity" (July 1945), and the second atomic bomb used to destroy a city (Nagasaki, Japan, in August 1945), "Fat Man", both had cores of plutonium-239. Human radiation experiments studying plutonium were conducted without informed consent, and several criticality accidents, some lethal, occurred during and after the war. Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during the Cold War is a nuclear-proliferation and environmental concern. Other sources of plutonium in the environment are fallout from numerous above-ground nuclear tests (now banned).

Contents

• 1 Characteristics
  • 1.1 Physical properties
  • 1.2 Allotropes
  • 1.3 Nuclear fission
  • 1.4 Isotopes and synthesis
  • 1.5 Decay heat and fission properties
  • 1.6 Compounds and chemistry
    • 1.6.1 Electronic structure
  • 1.7 Alloys
  • 1.8 Occurrence
• 2 History
  • 2.1 Discovery
  • 2.2 Early research
  • 2.3 Production during the Manhattan Project
  • 2.4 Trinity and Fat Man atomic bombs
  • 2.5 Cold War use and waste
  • 2.6 Medical experimentation
• 3 Applications
  • 3.1 Explosives
  • 3.2 Mixed oxide fuel
  • 3.3 Power and heat source
• 4 Precautions
  • 4.1 Toxicity
  • 4.2 Criticality potential
  • 4.3 Flammability
• 5 Transportation
  • 5.1 Air
• 6 See also
• 7 Notes
  • 7.1 Footnotes
  • 7.2 Citations
• 8 References
• 9 External links

Characteristics

Physical properties

Plutonium, like most metals, has a bright silvery appearance at first, much like nickel, but it oxidizes very quickly to a dull gray, although yellow and olive green are also reported.^[5][6] At room temperature plutonium is in its α form (alpha). This, the most common structural form of the element (allotrope), is about as hard and brittle as grey cast iron unless it is alloyed with other metals to make it soft and ductile. Unlike most metals, it is not a good conductor of heat or electricity. It has a low melting point (640 °C) and an unusually high boiling point (3,228 °C).^[5]
Alpha decay, the release of a high-energy helium nucleus, is the most common form of radioactive decay for plutonium.^[7] A 5 kg mass of ²³⁹Pu contains about 12.5×10²⁴ atoms. With a half-life of 24,100 years, about 11.5×10¹² of its atoms decay each second by emitting a 5.157 MeV alpha particle. This amounts to 9.68 watts of power. Heat produced by the deceleration of these alpha particles makes it warm to the touch.^[8][9]
Resistivity is a measure of how strongly a material opposes the flow of electric current. The resistivity of plutonium at room temperature is very high for a metal, and it gets even higher with lower temperatures, which is unusual for metals.^[10] This trend continues down to 100 K, below which resistivity rapidly decreases for fresh samples.^[10] Resistivity then begins to increase with time at around 20 K due to radiation damage, with the rate dictated by the isotopic composition of the sample.^[10]
Because of self-irradiation, a sample of plutonium fatigues throughout its crystal structure, meaning the ordered arrangement of its atoms becomes disrupted by radiation with time.^[11] Self-irradiation can also lead to annealing which counteracts some of the fatigue effects as temperature increases above 100 K.^[12]
Unlike most materials, plutonium increases in density when it melts, by 2.5%, but the liquid metal exhibits a linear decrease in density with temperature.^[10] Near the melting point, the liquid plutonium has also very high viscosity and surface tension as compared to other metals.^[11]

Allotropes

Main article: Allotropes of plutonium

Plutonium has six allotropes at ambient pressure: alpha (α), beta (β), gamma (γ), delta (δ), delta prime (δ'), & epsilon (ε)^[13]

Plutonium normally has six allotropes and forms a seventh (zeta, ζ) at high temperature within a limited pressure range.^[13] These allotropes, which are different structural modifications or forms of an element, have very similar internal energies but significantly varying densities and crystal structures. This makes plutonium very sensitive to changes in temperature, pressure, or chemistry, and allows for dramatic volume changes following phase transitions from one allotropic form to another.^[11] The densities of the different allotropes vary from 16.00 g/cm³ to 19.86 g/cm³.^[14]
The presence of these many allotropes makes machining plutonium very difficult, as it changes state very readily. For example, the α form exists at room temperature in unalloyed plutonium. It has machining characteristics similar to cast iron but changes to the plastic and malleable β form (beta) at slightly higher temperatures.^[15] The reasons for the complicated phase diagram are not entirely understood. The α form has a low-symmetry monoclinic structure, hence its brittleness, strength, compressibility, and poor thermal conductivity.^[13]
Plutonium in the δ form normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium, aluminium, or cerium, enhancing workability and allowing it to be welded.^[15] The delta form has more typical metallic character, and is roughly as strong and malleable as aluminium.^[13] In fission weapons, the explosive shock waves used to compress a plutonium core will also cause a transition from the usual delta phase plutonium to the denser alpha form, significantly helping to achieve supercriticality.^[16] The ε phase, the highest temperature solid allotrope, exhibits anomalously high atomic self-diffusion compared to other elements.<sup>[11]

end quote from wikipedia under the heading: Plutonium</sup>