Radioisotope thermoelectric generator - Wikipedia, the free encyclopedia. A radioisotope thermoelectric generator (RTG, RITEG) is an electrical generator that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect.
Production, Distribution, and Applications of Californium-252 Neutron Sources R. C. Martin, J. B. Knauer, and P. A. Balo Chemical Technology Division Oak Ridge National Laboratory* Oak Ridge, TN 3783 l-6385 U.S.A. To. Nuclear Power Assessment Study–Final NUCLEAR POWER ASSESSMENT STUDY Final Report Radioisotope Power Systems Program. IAEA-TECDOC-1430 Radioisotope handling facilities and automation of radioisotope production December 2004. This contribution is designed to document the radioisotope dating data for groups of chondrites, stony achondrites, pallasites and mesosiderites, and irons. A trace radioisotope is a radioisotope that occurs naturally in trace amounts (i.e., extremely small). Generally speaking, trace radioisotopes have half-lives that are short in comparison to the age of the Earth, since.
This generator has no moving parts. RTGs have been used as power sources in satellites, space probes, and unmanned remote facilities such as a series of lighthouses built by the former Soviet Union inside the Arctic Circle. RTGs are usually the most desirable power source for unmaintained situations that need a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical. Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. History[edit]. A pellet of 2. Pu. O2 as used in the RTG for the Cassini and Galileo missions. This photo was taken after insulating the pellet under a graphite blanket for several minutes and then removing the blanket.
Cyclotron produced radionuclides: principles and practice international atomic energy agency vienna, 2008 technical reports series no. 465. Document QAS/08.262/FINAL November 2008 RADIOPHARMACEUTICALS Final text for addition to The International Pharmacopoeia (November 2008) This text was adopted at the Forty-third WHO Expert Committee on Specifications for. A radioisotope power generator must meet stringent safety criteria. Under no circumstance should it subject people to undue radiation exposure.It must also be reliable, operating for long periods of time without failure.
The pellet is glowing red hot because of the heat generated by radioactive decay (primarily О±). The initial output is 6. RTGs were developed in the US during the late 1. Mound Laboratories in Miamisburg, Ohio under contract with the United States Atomic Energy Commission. The project was led by Dr.
Bertram C. Blanke.[1]The first RTG launched into space by the United States was SNAP 3 in 1. Navy Transit 4. A spacecraft. One of the first terrestrial uses of RTGs was in 1. US Navy at uninhabited Fairway Rock in Alaska. RTGs were used at that site until 1. A common RTG application is spacecraft power supply.
Systems for Nuclear Auxiliary Power (SNAP) units were used for probes that traveled far from the Sun rendering solar panels impractical. As such, they were used with Pioneer 1. Pioneer 1. 1, Voyager 1, Voyager 2, Galileo, Ulysses, Cassini, New Horizons and the Mars Science Laboratory. RTGs were used to power the two Viking landers and for the scientific experiments left on the Moon by the crews of Apollo.
SNAP 2. 7s). Because the Apollo 1. RTG rests in the South Pacific ocean, in the vicinity of the Tonga Trench.[2] RTGs were also used for the Nimbus, Transit and LES satellites. By comparison, only a few space vehicles have been launched using full- fledged nuclear reactors: the Soviet RORSAT series and the American SNAP- 1. A. In addition to spacecraft, the Soviet Union constructed many unmanned lighthouses and navigation beacons powered by RTGs.[3] Powered by strontium- 9. Sr), they are very reliable and provide a steady source of power. Critics[who?] argue that they could cause environmental and security problems as leakage or theft of the radioactive material could pass unnoticed for years, particularly as the locations of some of these lighthouses are no longer known due to poor record keeping.
In one instance, the radioactive compartments were opened by a thief.[3] In another case, three woodsmen in Georgia came across two ceramic RTG heat sources that had been stripped of their shielding. Two of the three were later hospitalized with severe radiation burns after carrying the sources on their backs. The units were eventually recovered and isolated.[4]There are approximately 1,0.
RTGs in Russia. All of them have long exhausted their 1. They are likely no longer functional, and may be in need of dismantling. Some of them have become the prey of metal hunters, who strip the RTGs' metal casings, regardless of the risk of radioactive contamination.[5]The United States Air Force uses RTGs to power remote sensing stations for Top- ROCC and SEEK IGLOO radar systems predominantly located in Alaska.[6]In the past, small "plutonium cells" (very small 2. Pu- powered RTGs) were used in implanted heart pacemakers to ensure a very long "battery life".[7] As of 2. The design of an RTG is simple by the standards of nuclear technology: the main component is a sturdy container of a radioactive material (the fuel).
Thermocouples are placed in the walls of the container, with the outer end of each thermocouple connected to a heat sink. Radioactive decay of the fuel produces heat. It is the temperature difference between the fuel and the heat sink that allows the thermocouples to generate electricity. A thermocouple is a thermoelectric device that converts thermal energy directly into electrical energy using the Seebeck effect.
It is made of two kinds of metal (or semiconductors) that can both conduct electricity. They are connected to each other in a closed loop. If the two junctions are at different temperatures, an electric current will flow in the loop. Criteria for selection of isotopes[edit]The radioactive material used in RTGs must have several characteristics: Its half- life must be long enough so that it will release energy at a relatively constant rate for a reasonable amount of time.
The amount of energy released per time (power) of a given quantity is inversely proportional to half- life. An isotope with twice the half- life and the same energy per decay will release power at half the rate per mole.
Typical half- lives for radioisotopes used in RTGs are therefore several decades, although isotopes with shorter half- lives could be used for specialized applications. For spaceflight use, the fuel must produce a large amount of power per mass and volume (density). Density and weight are not as important for terrestrial use, unless there are size restrictions. The decay energy can be calculated if the energy of radioactive radiation or the mass loss before and after radioactive decay is known. Energy release per decay is proportional to power production per mole. Alpha decays in general release about 1.
Radiation must be of a type easily absorbed and transformed into thermal radiation, preferably alpha radiation. Beta radiation can emit considerable gamma/X- ray radiation through bremsstrahlung secondary radiation production and therefore requires heavy shielding.
Isotopes must not produce significant amounts of gamma, neutron radiation or penetrating radiation in general through other decay modes or decay chain products. The first two criteria limit the number of possible fuels to fewer than 3.
Plutonium- 2. 38, curium- 2. Plutonium- 2. 38 has a half- life of 8. Pu has the lowest shielding requirements; Only three candidate isotopes meet the last criterion (not all are listed above) and need less than 2. Pu (the best of these three) needs less than 2. Pu RTG, as the casing itself is adequate. Pu has become the most widely used fuel for RTGs, in the form of plutonium(IV) oxide (Pu.
O2). Unlike the latter RTG fuels, 2. Pu must be specifically synthesized and is not abundant as a nuclear waste product. At present only Russia has maintained consistent 2. Pu production, while the USA restarted production at circa 1.
At present these are the only countries with declared production of 2. Pu in quantities useful for RTGs. Pu is produced at typically 8. Strontium- 9. 0 has been used by the Soviet Union in terrestrial RTGs. Sr decays by ОІ emission, with minor Оі emission. While its half life of 2.
Pu, it also has a lower decay energy with a power density of 0. Because the energy output is lower it reaches lower temperatures than 2. Pu, which results in lower RTG efficiency. Sr is a high yield waste product of nuclear fission and is available in large quantities at a low price.[1. Some prototype RTGs, first built in 1. US Atomic Energy Commission, have used polonium- 2. This isotope provides phenomenal power density (pure 2.
Po emits 1. 40 W/g) because of its high decay rate, but has limited use because of its very short half- life of 1. A half- gram sample of 2. Po reaches temperatures of over 5. В°C (9. 00 В°F).[1. Americium- 2. 41 is a potential candidate isotope with a longer half- life than 2. Pu: 2. 41. Am has a half- life of 4.
However, the power density of 2. Am is only 1/4 that of 2.
Pu, and 2. 41. Am produces more penetrating radiation through decay chain products than 2. Pu and needs more shielding.
Even so, its shielding requirements in an RTG are the second lowest of all possible isotopes: only 2. Pu requires less. With a current global shortage[1. Pu, 2. 41. Am is being studied as RTG fuel by ESA.[1. An advantage over 2. Pu is that it is produced as nuclear waste and is nearly isotopically pure.
Prototype designs of 2. Am RTGs expect 2- 2.
We/kg for 5- 5. 0 We RTGs design, putting 2. Am RTGs at parity with 2. Pu RTGs within that power range.[1. Life span[edit]9. Sr- powered Soviet RTGs in dilapidated condition.
Most RTGs use 2. 38. Pu, which decays with a half- life of 8. RTGs using this material will therefore diminish in power output by a factor of 1в€’0. One example is the RTG used by the Voyager probes.
In the year 2. 00. RTG had decreased in power by 1. W, after this length of time it would have a capacity of only 3. W. A related loss of power in the Voyager RTGs is the degrading properties of the bi- metallic thermocouples used to convert thermal energy into electrical energy; the RTGs were working at about 6. By the beginning of 2. Voyager RTGs had dropped to 3.
W for Voyager 1 and to 3. W for Voyager 2.[1. Efficiency[edit]RTGs use thermocouples to convert heat from the radioactive material into electricity. Thermocouples, though very reliable and long- lasting, are very inefficient; efficiencies above 1.
RTGs have efficiencies between 3–7%. Thermoelectric materials in space missions to date have included silicon–germanium alloys, lead telluride and tellurides of antimony, germanium and silver (TAGS). Studies have been done on improving efficiency by using other technologies to generate electricity from heat.
Achieving higher efficiency would mean less radioactive fuel is needed to produce the same amount of power, and therefore a lighter overall weight for the generator. This is a critically important factor in spaceflight launch cost considerations.