Americium-241 ( 241 Am) is an americium isotope. Like all isotopes of americium, it's radioactive. 241 Am is the most common americium isotope. This is the most common american isotope in nuclear waste. The Americium-241 has a half-life of 432.2 years. These are commonly found in ionization type smoke detectors. This is a potential fuel for long-term radioisotope thermoelectric generators (RTGs). Parent nuclides generally are? - from 241 Pu, EC from 241 Cm and? from 245 Bk. 241 Am is fissile and the critical mass of naked balls is 57.6 to 75.6 kilograms and the diameter of a 19-21 cm sphere. Americium-241 has a specific activity of 3.43 Ci/g (curies per gram or 126.9 gigabequerels (GBq) per gram). It is commonly found in the form of americium-241 dioxide ( 241 Amo 2 ). This isotope also has one meta state; 241m Am, with excitation energy 2,2 MeV, and half beam 1,23? s. Its presence in plutonium is determined by the original concentration of plutonium-241 and the age of the sample. Due to the low penetration of alpha radiation, the americium-241 only poses a health risk when ingested or inhaled. Plutonium samples containing plutonium-241 contained a buildup of 241 Am. Removal of americium-241 chemistry from reprocessed plutonium (eg during plutonium hole rework) may be necessary in some cases.
Video Americium-241
Nucleosynthesis
Americium-241 has been produced in small quantities in nuclear reactors for decades, and many kilos of 241 Am has accumulated now. However, since it was first offered for sale in 1962, the price, about US $ 1,500 per gram 241 Am, remains virtually unchanged due to the very complicated procedure of separation.
Americium-241 tidak disintesis langsung dari uranium - bahan reaktor yang paling umum - tetapi dari isotop plutonium 239 Pu. Yang terakhir perlu diproduksi pertama, sesuai dengan proses nuklir berikut:
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Pengambilan second neutron oleh 239 Pu (recover yang disebut (n,?)), Diikuti oleh - decay, menghasilkan 241 Am:
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The plutonium present in spent fuel contains about 12% of the 241 Pu. Since the conversion to 241 Am, 241 Pu can be extracted and can be used to produce further 241 Am. However, the process is somewhat slow: half of the original amount of 241 Pu decays to 241 Am after about 14 years, and 241 Am reaches maximum after 70 years.
Diperoleh 241 Am dapat digunakan untuk menghasilkan isotop amerisium berat dengan menangkap neutron lebih lanjut di dalam reaktor nuklir. Dalam reaktor air ringan (LWR), 79% dari 241 Am mengkonversi ke 242 Am dan 10% ke isomer nuklirnya 242m Am:
- 79%: Ãâ
Maps Americium-241
Decay
Americium-241 decays primarily through alpha decay, with weak gamma-ray side-effects. The? -decay is displayed as follows:
Energy? -decay is 5.486 MeV for 85% of the time (which is widely accepted for standard? -tekay energy), 5.443 MeV for 13% of the time, and 5.388 MeV for the remaining 2%. Energy? -ray is 59,5409 keV for most, with a small amount of other energy like 13.9 keV, 17.8 keV and 26.4 keV.
The second most common type of decay for the americium-241 is the decay of the group, with a branched ratio of less than 7.4ÃÆ'â ⬠"10 -16 . Also shown as follows:
The most common (most rare) decay types experienced by the americium-241 are spontaneous fission, with a branched ratio of 4ÃÆ'â ⬠"10 -12 and occurring 1.2 times per gram per second 241 Am. It's written like that (star sign shows excited core):
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Detektor asap tipe-ionisasi
Americium-241 is the only synthetic isotope that has found its way to households, where the most common type of smoke detector (ionisation type) uses 241 Amo 2 (americium- 241 dioxide) as a source of ionizing radiation. This isotope is preferable to 226 Ra as 241 Am emits 5 times more alpha particles and also emits relatively little harmful gamma radiation. With a half-life of 432.2 years, the americium in smoke detectors decreased and covered about 3% of neptunium after 19 years, and about 5% after 32 years. The number of americium in a typical new smoke detector is 0.29 micrograms (about one-diminishes the weight of sand grains) with the activity of 1 microcurie/37 kilobequerels (1.0? Ci/37 kBq). Some old industrial smoke detectors (especially from Pyrotronics Corporation) can load up to 80 ° C. The amount of 241 Am decreases slowly as it decays into neptunium-237 different transuranic elements with a longer half-life ( about 2.14 million years). The alpha particles emitted through the ionization chamber, the space filled with air between the two electrodes, allowing small, constant electric currents to pass between the capacitor plates due to the radiation that ionizes the intermediate air space. Any smoke that enters the space block/absorbs some alpha particles from free passes and reduces ionization and therefore causes a decrease in current. The alarm circuit detects this current decline and as a result, triggers a piezoelectric buzzer to sound. Compared to alternative optical smoke detectors, ionisation smoke detectors are cheaper and can detect particles that are too small to produce significant light scattering. However, this is more prone to false alarms.
Manufacturing process
The americium-making process used in the switch on the ionization-type smoke detector begins with americium dioxide. Amo 2 is mixed thoroughly with gold, formed into briquettes, and fused with pressure and heat at more than 1470 ° F (800 ° C). Silver support and gold front cover (or gold or palladium alloy) are applied to briquettes and sealed with hot forging. The briquettes are then processed through several cold rolling stages to achieve the desired radiation thickness and level of emission. The final thickness is about 0.008 inches (0.2 mm), with a gold cover representing about one percent of the thickness. The resulting foil strip, which is about 0.8 inches (20 mm) wide, is cut into 39 inch (1 meter) long sections. The sources were perforated from the foil strip. Each dish, about 0.2 inches (5 mm) in diameter, is mounted on a metal cradle, usually made of aluminum. Holders are housing, which is the majority of what is seen on the button. A thin rim on the cradle is rolled down to completely seal the cut edges around the disc.
Radionuclides
Since 241 Am has approximately the same half-life as 238 Pu (432.2 years vs. 87 years), has been proposed as active radioisotope thermoelectric generator, for use in spacecraft. Although the americium-241 produces less heat and electricity than plutonium-238 (the power yield is 114.7 mW/g for 241 Am vs. 390 mW/g for 238 Pu ). and although its radiation poses a greater threat to humans due to gamma and neutron emissions, it has the advantage for long-term missions with significantly longer half-life and the European Space Agency working on RTGs based on the american-241 for its space probe, global plutonium-238 and easy access to the 241 americs in Europe from nuclear waste reprocessing.
Its protective requirements in the RTG are the second lowest of all possible isotopes: less 238 Pu. The advantage over 238 Pu is that it is produced as nuclear waste and almost pure isotope. Design prototype 241 Am RTG expects 2-2.2 W e /kg for design RTG 5-50Ã, W e , puts 241 Am RTG in parity with 238 Pu RTGs in that power range.
Neutron Source
Oksida 241 Am yang ditekan dengan berilium dapat menjadi sumber neutron yang sangat efisien, karena mereka memancarkan partikel alfa selama peluruhan radioaktif:
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Di sini amerisium bertindak sebagai sumber alfa, dan berilium menghasilkan neutron karena penampangnya yang besar untuk reaksi nuklir (?, N):
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The most widespread use of neutron sources 241 AmBe is a neutron probe - a tool used to measure the amount of water present in the soil, as well as the humidity/density for quality control in road construction. 241 Neutron sources are also used in well logging applications, as well as in neutron radiography, tomography and other radio-chemical inquiries.
Production of other elements
Americium-241 is sometimes used as a starting material for the production of transuranic elements and other transactinides - for example, firing neutrons 241 Am generates 242 Am:
From there, 82.7% of 242 Am decays to 242 Cm and 17.3% becomes 242 Pu:
82.7% ->
17.3% ->
Dalam reactor nuklir, 242 Am juga naik-dikonversi oleh penangkapan neutron that 243 Am dan 244 Am, yang diubah oleh? -dua untuk 244 Cm:
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Irradiation 241 Am by 12 C or 22 Ne ion produces isotope 253 Ice (einsteinium) or 263 Db (dubnium), respectively. Furthermore, the buffered element ( 243 Bk isotope) was first deliberately produced and identified by bombarding 241 Am with alpha particles, in 1949, by the same Berkeley group, using a cyclotron The same 60-inch that has been used for many previous experiments. Similarly, nobelium was produced at the Joint Institute for Nuclear Research, Dubna, Russia, in 1965 in several reactions, one of which included irradiation of 243 Am with 15 N. In addition , one of the synthesis reactions to lawrencium, was discovered by scientists at Berkeley and Dubna, including bombing 243 Am with 18 O.
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