Strontium-90

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Strontium-90
General
Name, symbol Strontium-90,90Sr
Neutrons 52
Protons 38
Nuclide data
Natural abundance syn
Half-life 28.8 years
Decay products 90Y
Decay mode Decay energy
Beta decay 0.546 MeV

Strontium-90 (90Sr) is a radioactive isotope of strontium, with a half-life of 28.8 years.

Contents

[edit] Radioactivity

Chain yield, % per fission[1]
Thermal Fast 14 MeV
232Th not fissile 7.32 ± 0.36 6.2 ± 1.5
233U 6.648 ± 0.073 6.39 ± 0.33 5.07 ± 0.80
235U 5.73 ± 0.13 5.22 ± 0.18 4.41 ± 0.18
238U not fissile 3.11 ± 0.14 3.07 ± 0.16
239Pu 2.013 ± 0.054 2.031 ± 0.057  ?
241Pu 1.510 ± 0.074 1.502 ± 0.041  ?

Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard. 90Sr undergoes β decay with decay energy of 0.546 MeV distributed to an electron, an anti-neutrino, and the yttrium isotope 90Y, which in turn undergoes β decay with half-life of 64 hours and decay energy 2.28 MeV distributed to an electron, an anti-neutrino, and 90Zr (zirconium), which is stable.[2] Note that 90Sr/Y is almost a perfectly pure beta source; the gamma photon emission from the decay of 90Y is so weak that it can normally be ignored.

[edit] Applications

90Sr finds extensive use in medicine and industry, as a radioactive source for thickness gauges and for superficial radiotherapy of some cancers. Controlled amounts of 90Sr and 89Sr can be used in treatment of bone cancer. As the radioactive decay of strontium-90 generates significant amount of heat, and is cheaper than the alternative 238Pu, it is used as a heat source in many Russian/Soviet radioisotope thermoelectric generators, usually in the form of strontium fluoride. It is also used as a radioactive tracer in medicine and agriculture.

A study of hundreds of thousands of deciduous teeth, collected by Dr. Louise Reiss and her colleagues as part of the Baby Tooth Survey, found a large increase in 90Sr levels through the 1950s and early 1960s. The study's final results showed that children born in 1963 had levels of 90Sr in their deciduous teeth that was 50 times higher than that found in children born in 1950, before the advent of large-scale atomic testing. An article with the study's initial findings was circulated to U.S. President John F. Kennedy in 1961, and helped convince him to sign the Partial Nuclear Test Ban Treaty with the United Kingdom and Soviet Union, ending the above-ground nuclear weapons testing that placed the greatest amounts of nuclear fallout into the atmosphere.[3]

[edit] Fission product

Medium-lived
fission products
Prop:
Unit:
t½
a
Yield
%
Q *
keV
βγ
*
155Eu 4.76 .0803 252 βγ
85Kr 10.76 .2180 687 βγ
113mCd 14.1 .0008 316 β
90Sr 28.9 4.505 2826 β
137Cs 30.23 6.337 1176 βγ
121mSn 43.9 .00005 390 βγ
151Sm 90 .5314 77 β


90Sr is a product of nuclear fission. It is present in significant amount in spent nuclear fuel and in radioactive waste from nuclear reactors and in nuclear fallout from nuclear tests. For thermal neutron fission as in today's nuclear power plants, the fission product yield from U-235 is 5.8%, from U-233 6.8%, but from Pu-239 only 2.1%.

[edit] Biochemistry

Together with caesium isotopes 134Cs, 137Cs, and iodine isotope 131I it was among the most important isotopes regarding health impacts after the Chernobyl disaster.

Strontium-90 is a "bone seeker" that exhibits biochemical behavior similar to calcium, the next lighter Group 2 element. After entering the organism, most often by ingestion with contaminated food or water, about 70–80% of the dose gets excreted. Virtually all remaining strontium-90 is deposited in bones and bone marrow, with the remaining 1% remaining in blood and soft tissues. Its presence in bones can cause bone cancer, cancer of nearby tissues, and leukemia. Exposure to 90Sr can be tested by a bioassay, most commonly by urinalysis.

[edit] Dispersal hazards

Accidental mixing of radioactive sources containing strontium with metal scrap can result in production of radioactive steel. Discarded radioisotope thermoelectric generators are a major source of 90Sr contamination in the area of the former Soviet Union.

[edit] In popular culture

Strontium 90 was the name of a short-lived 1977 British band with members Mike Howlett (bass, vocals), Sting (bass, vocals), Stewart Copeland (drums), and Andy Summers (guitar). The band is most notable for introducing Summers to Sting and Copeland, as this trio would go on to massive success as The Police. Also, in the 2008 GOTY Fallout 3, a consumable drink called "Nuka-Cola Quantum" is said to use this isotope of strontium to give it its signature blue glow.

[edit] References

  1. ^ http://www-nds.iaea.org/sgnucdat/c1.htm Chain Fission Yields, IAEA
  2. ^ Decay data from National Nuclear Data Center at the Brookhaven National Laboratory in the US.
  3. ^ Hevesi, Dennis. "Dr. Louise Reiss, Who Helped Ban Atomic Testing, Dies at 90", The New York Times, January 10, 2011. Accessed January 10, 2011.

[edit] External links

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