Strontium-90 is a radionuclide. It is one of the best long-lived high-energy beta particle emitters known. A beta particle is a subatomic particle ejected from the nucleus. They are comparable to electrons and have a charge of -1. They were discovered by Henri Becquerel (1852-1908) and in 1900 he showed they were identical to electrons. While the beta particle itself isn't radioactive their energy expressed in the form of speed can harm cells. They can break chemical bonds and form ions. Beta particles are released if a nucleus has too many neutrons for the protons; it is believed they break down into a proton, an electron and an antineutrino. The proton stays in the nucleus while the electron and the antineutrino are ejected with a great deal of energy. Since the proton count has changed the atom of strontium-90 has been converted to an unstable atom of yttrium-90. Since yttrium-90 is unstable it decays into a stable atom of zirconium. If not all the extra energy was ejected with the beta particle and antineutrino then the nucleus would also release a gamma photon. If strontium-90 was to do this it would be more dangerous but the excess energy is already released.
The human body also mistakes strontium for calcium due to their similar atomic radii (Ca-180pm, Sr-215.1pm) and similar chemical behaviour and the body uses this for the bones and teeth. If this is Sr-90 that is used then the body is concentrating a beta particle emitter and this can cause various bone disorders and diseases. So much Sr-90 was released in nuclear tests in the 50s and 60s that the American Department of Defence developed a unit so people could see the health limits. One Strontium Unit is equal to a picocurie from Sr-90 per gramme of Calcium in the skeleton. The US National Academy of Sciences believes that the maximum safe level of Sr-90 is 100 Strontium Units. This unit was initially known as the Sunshine Unit until public ridicule brought its disuse.
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Uses
This uses the Peltier-Seebeck Effect, which is the conversion of heat differences to an electric voltage. The thermocouples are made of two different conducting metals or semiconductors. They are connected to each other in a closed loop. Electrons will flow from the conductor where the electrons are at the highest energy level to where they are lower. Since electrons are crossing the gaps two opposing voltages have been set up but because the electrons cross the junction at the same rate the two voltages cancel each other out. Since there is no overall voltage there is no current flow.
If the energy levels of each conductor were to change at different rates when there is the same change in temperature then the energy levels of each conductor would be different. This means that more electrons would cross from one junction than at the other this would create a larger voltage at one junction than the other therefore a current will start flowing.
Many RTGs using Strontium-90 were built by the Soviet Union and they now pose environmental problems due to leakage or they pose security problems as theft of low-level nuclear materials could go unnoticed. Some of these RTGs can no longer be found due to poor record keeping in the Soviet Union.
RTGs however are safer than Nuclear Power Stations as no chain reactions take place; therefore nuclear meltdown isn't a possibility. The radioactive decay that takes place in RTGs cannot cause other particles to decay as well so nuclear fission does not occur.
Cathode Ray Tubes is where the majority of strontium (70%) that is produced is used. They are used in the glass in colour televisions and in computer monitors. They are designed to absorb harmful X-rays that are being emitted while allowing the useful wavelengths through.
Zinc refining requires some strontium.
Strontium is also used in fluorescent glass, phosphorescent paint, greases, sugar beet refining and in some toothpastes.
Health & Safety
Pure strontium reacts vigorously in air and if finely powdered can spontaneously combust at room temperature, so it is considered a fire hazard. The only way to keep it pure is to store it under kerosene; otherwise it will react with oxygen in air and form a strontium oxide surface. This surface is a yellowish colour.
People are most likely to encounter strontium by drinking or eating it. The highest concentrations of strontium in food are in grains, leafy vegetables and dairy products. High concentrations of strontium aren't generally dangerous but there have been cases where people have suffered allergic reactions to strontium. Strontium poses the biggest danger to children as it can disrupt bone development. This can only occur if the strontium is in the thousands in the part per million range. And strontium concentration in food or drink is not this high.
Radioactive strontium (Sr-90) poses a more serious threat to health. It was released during nuclear tests in the 50s and 60s and at when a lot is absorbed by the body it may cause anaemia and oxygen shortages and bone disorders and with extreme concentrations can result in cancer if the strontium damages the genetic material in cells. Radioactive strontium-90 will eventually decay to a stable isotope of zirconium. This will take time as it has a half-life of 28.78 years.
3D Model Of Strontium Atoms
Solid strontium has a cubic crystal close-packed structure that is face centred. Three allotropic crystalline forms of the metal exist with transition points at 235°C and 540°C.
Bibliography
This is a website designed by the Mineral Information Institute, it doesn't have any obvious agenda such as trying to persuade you to buy the minerals rather it seems to be an academic institution's site.
This website seems to be an individual's attempt to show the origins of the names of elements and I think it is a reliable site.
This website is a mineralogical database.
This is a Biography of Thomas Hope by WP Doyle and it is on The University of Edinburgh's website
This is the Minerals of Scotland website
This site has the periodic table and details of the elements. It is one of the first sites found on Google and it does advertise its products on the side. I don't think that this compromises the information obtained here and makes it unreliable, just less detailed.
This site has only a definition of Angstroms
This site briefly explains Beta Decay but it isn't very detailed.
This site is about Beta Particles by the US Environmental Protection Agency, it probably has no bias.
This site isa trying to sell its product but it does occassionally give some information.
This site is by the US Environmental protection Agency about Strontium and particularly Sr-90.
An individual has put up the periodic table as well as some figures.
The periodic table most of these contadict on the price of strontium.
A US government article about Strontium.
seems to be a library of biographies which has a definition of the "strontium unit".
AN individual's work which contains a list of refractive indicies but the author isn't too sure of some of them so neither am I.
This tells us what optical dispersion actually is.
A site explaining what RTGs are and how they work it seems to be quite reliable since it agrees with
This site should be quite reliable.
This is a definition of the Peltier-Seebeck Effect
This site provides information about the allotropes of Strontium.
[23] Pocket Guide to Minerals, Andrew Clark, Hamlyn,1979
[24] Science Encyclopedia,Kingfisher,1995
This article is a sample intended to persuade people to but the complete version but that is to reason to have incomplete or inaccurate figures in it.
Seemingly thorough and reliable and with no bias.
A compilation from a vaerity of sources.
This is a biography of Henri Becquerel on the Nobel Prize website.
Advertises ceramic magnets but also provides information about the process of manufacturing.
Explains which elements give what colours in fireworks.
