Americium-241

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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

Nukleosintesis

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:

${\ displaystyle \ mathrm {^ {238} _ {\ 92} U \ {\ xrightarrow {(n, \ gamma)}} \ _ {\ 92} ^ {239 } U \ {\ xrightarrow [{23.5 \ min}] {\ beta ^ {-}}} \ _ {\ 93} ^ {239} Np \ {\ xrightarrow [{2.3565 \ d}] {\ beta ^ {- }}} \ _ {\ 94} ^ {239} Pu}}  ÂÂ$

Pengambilan dua neutron oleh ²³⁹ Pu (reaksi yang disebut (n ,?)), diikuti oleh--decay, menghasilkan ²⁴¹ Am:

${\ displaystyle \ mathrm {^ {239} _ {\ 94} Pu \ {\ xrightarrow {2 ~ (n, \ gamma)}} \ _ {\ 94} ^ {241} Pu \ {\ xrightarrow [{14.35 \ yr}] {\ beta ^ {-}}} \ _ {\ 95} ^ {241} Am}}  ÂÂ$

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.

Generated ²⁴¹ Am can be used to produce heavy ammeter isotopes by further capture neutrons within the nuclear reactor. In the light water reactor (LWR), 79% of the ²⁴¹ Am converts to ²⁴² Am and 10% to its nuclear isomer ^242m

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<                 n                 ,                 ? )                                                           Ã,                           Ã,              95                                       242                                 A           m                   {\ displaystyle \ mathrm {^ {241} _ {\ 95} Am \ {\ xrightarrow {(n, \ gamma)}} \ _ {\ 95 } ^ {242} Am}}  Â

Maps Americium-241

Decay

Americium-241 decays primarily through alpha decay, with weak gamma-ray side-effects. The? -decay is displayed as follows:

$            {\displaystyle                   {}_{              \text{Â}              95            }^{              241                                        }          \mathrm{A}          \mathrm{m}          \text{Â}                      \stackrel{                \mathrm{432,2}                \mathrm{y}              }{?}                    {\text{Â}}_{              \text{Â}              93            }^{              237            }          \mathrm{N}          \mathrm{p}          \text{Â}                    {\text{Â}}_{              2            }^{              4            }          {?}^{              2                          }                    ?          \text{Â}          \mathrm{59,5409}          \text{Â}          \mathrm{k}          \mathrm{e}          \mathrm{V}              }        \{\backslash \; displaystyle\; \backslash \; mathrm\; \{^\; \{241\; \backslash !\; \backslash ,\}\; \_\; \{\backslash \; 95\}\; Am\; \backslash \; \{\backslash \; overset\; \{432.2y\}\; \{\backslash \; longrightarrow\}\}\; \backslash \; \_\; \{\backslash \; 93\; \}\; ^\; \{237\}\; Np\; ~\; ~\; \_\; \{2\}\; ^\; \{4\}\; \backslash \; alpha\; ^\; \{2\; \}\; \backslash \; gamma\; ~\; 59.5409\; ~\; keV\}\}\;  ÂÂ$

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:

${\ displaystyle \ mathrm {^ {241 \! \,} _ {\ 95} Am \ longrightarrow _ {\ 81} ^ {207} Tl _ {14} ^ {34} Si}}  ÂÂ$

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):

${\ displaystyle \ mathrm {^ {241} _ {\ 95} Am \ longrightarrow ~ _ {\ 95} ^ {241} Am ^ {*} \ longrightarrow 3_ {0 } ^ {1} n ~ ~ fisi ~ produk ~ energi ~ (\ gamma)}}  ÂÂ$

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Aplikasi

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:

$            {\displaystyle                   {}_{              \text{Â}              95            }^{              241                                        }          \mathrm{A}          \mathrm{m}          \text{Â}                      \stackrel{                \mathrm{432,2}                \mathrm{y}              }{?}                    {\text{Â}}_{              \text{Â}              93            }^{              237            }          \mathrm{N}          \mathrm{p}          \text{Â}                    {\text{Â}}_{              2            }^{              4            }          {?}^{              2                          }                    \text{Â}          ?          \text{Â}          \mathrm{59,5}          \text{Â}          \mathrm{k}          \mathrm{e}          \mathrm{V}              }        \{\backslash \; displaystyle\; \backslash \; mathrm\; \{^\; \{241\; \backslash !\; \backslash ,\}\; \_\; \{\backslash \; 95\}\; Am\; \backslash \; \{\backslash \; overset\; \{432.2y\}\; \{\backslash \; longrightarrow\}\}\; \backslash \; \_\; \{\backslash \; 93\; \}\; ^\; \{237\}\; Np\; \backslash \; \backslash \; \_\; \{2\}\; ^\; \{4\}\; \backslash \; alpha\; ^\; \{2\; \}\; \backslash \; \backslash \; gamma\; ~\; 59.5\; ~\; keV\}\}\;  ÂÂ$

Di sini amerisium bertindak sebagai sumber alfa, dan berilium menghasilkan neutron karena penampangnya yang besar untuk reaksi nuklir (?, N):

${\ textstyle \ mathrm {^ {9} _ {4} Menjadi \ \ _ {2} ^ {4} \ alpha ^ {2 } \ longrightarrow \ _ { \ 6} ^ {12} C \ \ _ {0} ^ {1} n \ \ \ gamma}}  ÂÂ$

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:

${\ displaystyle \ mathrm {^ {241} _ {\ 95} Am \ {\ xrightarrow {(n, \ gamma)}} \ _ {\ 95} ^ {242 } Am}}  ÂÂ$

From there, 82.7% of ²⁴² Am decays to ²⁴² Cm and 17.3% becomes ²⁴² Pu:

82,7% -> ${\ displaystyle \ mathrm {^ {241} _ {\ 95} Am \ {\ xrightarrow {(n, \ gamma)}} \ _ {\ 95} ^ {242 } Am \ {\ xrightarrow [{16.02 \ h}] {\ beta ^ {-}}} \ _ {\ 96} ^ {242} Cm}}  ÂÂ$

17,3% -> $            {\displaystyle                   {}_{              \text{Â}              95            }^{              241            }          \mathrm{A}          \mathrm{m}          \text{Â}                      \stackrel{                (                \mathrm{n}                ,                ?                )              \;             }{->}                    {\text{Â}}_{              \text{Â}              95            }^{              242            }          \mathrm{A}          \mathrm{m}          \text{Â}                      \underset{                                  \mathrm{16,02}                  \text{Â}                  \mathrm{h}                              \;                               {?}^{                                      }              \;             }{\overset{}{->}}                    {\text{Â}}_{              \text{Â}      Â}^{}}$

Source of the article : Wikipedia