"38"^^ . "Strontium-90 (90Sr) is a radioactive isotope of strontium, with a half life of 28.8 years. Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard. 90Sr undergoes \u03B2\u2212 decay with decay energy of 0.546 MeV to an electron and the yttrium isotope 90Y, which in turn undergoes \u03B2\u2212 decay with half life of 64 hours and decay energy 2.28 MeV for beta particles to an electron and 90Zr (zirconium), which is stable. 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. 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. It is obtained during nuclear reprocessing of spent nuclear fuel. 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%. 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 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. Exposition to 90Sr can be tested by a bioassay, most commonly by urinalysis. Stronti\u00F9m-90 -- keyi jenereit mikroweiv en blow-off bodi. 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."@en . . "#7F7"@en . . "9.0885888E8"^^ . "Strontium-90 (90Sr) is a radioactive isotope of strontium, with a half life of 28.8 years. Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard. 90Sr undergoes \u03B2\u2212 decay with decay energy of 0.546 MeV to an electron and the yttrium isotope 90Y, which in turn undergoes \u03B2\u2212 decay with half life of 64 hours and decay energy 2.28 MeV for beta particles to an electron and 90Zr (zirconium), which is stable. 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."@en . . . "0.546"^^ . "isotopes of yttrium#90"@en . . . . "Stronti\u00F9m-90"@en . . . . "Y"@en . "90"^^ . "52"^^ . . "Sr"@en . "90"^^ .