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146-413: 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. RTGs have been used as power sources in satellites , space probes , and uncrewed remote facilities such as a series of lighthouses built by

292-403: A cathode , and an electrolyte that allows ions, often positively charged hydrogen ions (protons), to move between the two sides of the fuel cell. At the anode, a catalyst causes the fuel to undergo oxidation reactions that generate ions (often positively charged hydrogen ions) and electrons. The ions move from the anode to the cathode through the electrolyte. At the same time, electrons flow from

438-499: A cogeneration power plant in hospitals, universities and large office buildings. In recognition of the fuel cell industry and America's role in fuel cell development, the United States Senate recognized October 8, 2015 as National Hydrogen and Fuel Cell Day , passing S. RES 217. The date was chosen in recognition of the atomic weight of hydrogen (1.008). Fuel cells come in many varieties; however, they all work in

584-428: A multi-mission radioisotope thermoelectric generator (MMRTG) in which the thermocouples would be made of skutterudite , a cobalt arsenide (CoAs 3 ), which can function with a smaller temperature difference than the current tellurium -based designs. This would mean that an otherwise similar RTG would generate 25% more power at the beginning of a mission and at least 50% more after seventeen years. NASA hopes to use

730-433: A "foreign object". A common route of production (whether accidental or deliberate) is neutron irradiation of Bi , the only naturally occurring isotope of bismuth . It is this accidental production that is cited as an argument against the use of lead-bismuth eutectic as a coolant in liquid metal reactors. However, if a sufficient demand for polonium-210 exists, its extraction could be worthwhile similar to how tritium

876-727: A SOFC system are less than those from a fossil fuel combustion plant. The chemical reactions for the SOFC system can be expressed as follows: SOFC systems can run on fuels other than pure hydrogen gas. However, since hydrogen is necessary for the reactions listed above, the fuel selected must contain hydrogen atoms. For the fuel cell to operate, the fuel must be converted into pure hydrogen gas. SOFCs are capable of internally reforming light hydrocarbons such as methane (natural gas), propane, and butane. These fuel cells are at an early stage of development. Challenges exist in SOFC systems due to their high operating temperatures. One such challenge

1022-471: A battery, except as hydrogen, but in some applications, such as stand-alone power plants based on discontinuous sources such as solar or wind power , they are combined with electrolyzers and storage systems to form an energy storage system. As of 2019, 90% of hydrogen was used for oil refining, chemicals and fertilizer production (where hydrogen is required for the Haber–Bosch process ), and 98% of hydrogen

1168-662: A complete, closed-loop system: Solar panels power an electrolyzer, which makes hydrogen. The hydrogen is stored in a 500-U.S.-gallon (1,900 L) tank at 200 pounds per square inch (1,400 kPa), and runs a ReliOn fuel cell to provide full electric back-up to the off-the-grid residence. Another closed system loop was unveiled in late 2011 in Hempstead, NY. Fuel cells can be used with low-quality gas from landfills or waste-water treatment plants to generate power and lower methane emissions . A 2.8 MW fuel cell plant in California

1314-449: A concentrated solution of KOH or NaOH which serves as an electrolyte. H 2 gas and O 2 gas are bubbled into the electrolyte through the porous carbon electrodes. Thus the overall reaction involves the combination of hydrogen gas and oxygen gas to form water. The cell runs continuously until the reactant's supply is exhausted. This type of cell operates efficiently in the temperature range 343–413   K (70 -140 °C) and provides

1460-416: A country or during peacetime. Riots in the wake of the 2020 George Floyd protests in numerous American cities led to increased amounts of looting, as looters took advantage of the delicate political situation and civil unrest surrounding the riots themselves. Up to 175 Target stores closed Nationwide during the disturbances. During the ongoing Kashmir conflict , looting of Kashmiris trapped between

1606-493: A durability of over 120,000 km (75,000 miles) with less than 10% degradation. In a 2017 Well-to-Wheels simulation analysis that "did not address the economics and market constraints", General Motors and its partners estimated that, for an equivalent journey, a fuel cell electric vehicle running on compressed gaseous hydrogen produced from natural gas could use about 40% less energy and emit 45% less greenhouse gasses than an internal combustion vehicle. Looting Looting

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1752-567: A factor of 1 – (1/2), which is 0.787%, per year. One example is the MHW-RTG used by the Voyager probes . In the year 2000, 23 years after production, the radioactive material inside the RTG had decreased in power by 16.6%, i.e. providing 83.4% of its initial output; starting with a capacity of 470 W, after this length of time it would have a capacity of only 392 W. A related loss of power in

1898-597: A fuel-to-electricity efficiency of 50%, considerably higher than the 37–42% efficiency of a phosphoric acid fuel cell plant. Efficiencies can be as high as 65% when the fuel cell is paired with a turbine, and 85% if heat is captured and used in a combined heat and power (CHP) system. FuelCell Energy, a Connecticut-based fuel cell manufacturer, develops and sells MCFC fuel cells. The company says that their MCFC products range from 300 kW to 2.8 MW systems that achieve 47% electrical efficiency and can utilize CHP technology to obtain higher overall efficiencies. One product,

2044-455: A further shielding against neutron radiation . As lead, which is an excellent shielding material against gamma rays and beta ray induced Bremsstrahlung , is not a good neutron shield (instead reflecting most of them), a different shielding material would have to be added in applications where neutrons are a concern. Most RTGs use Pu, which decays with a half-life of 87.7 years. RTGs using this material will therefore diminish in power output by

2190-460: A good example being during the 1967 First Invasion of Onitsha , where the victorious Nigerian troops were encircled and annihilated while looting. In other cases, for example, the Wahhabi sack of Karbala in 1801 or 1802, loot has contributed to further victories for an army. Not all looters in wartime are conquerors; the looting of Vistula Land by the retreating Imperial Russian Army in 1915

2336-422: A half-life of 87.7 years, reasonable power density of 0.57 watts per gram, and exceptionally low gamma and neutron radiation levels. Pu has the lowest shielding requirements. Only three candidate isotopes meet the last criterion (not all are listed above) and need less than 25 mm of lead shielding to block the radiation. Pu (the best of these three) needs less than 2.5 mm, and in many cases, no shielding

2482-461: A high operating temperature provides an advantage by removing the need for a precious metal catalyst like platinum, thereby reducing cost. Additionally, waste heat from SOFC systems may be captured and reused, increasing the theoretical overall efficiency to as high as 80–85%. The high operating temperature is largely due to the physical properties of the YSZ electrolyte. As temperature decreases, so does

2628-403: A higher current to be supplied. Such a design is called a fuel cell stack . The cell surface area can also be increased, to allow higher current from each cell. In the archetypical hydrogen–oxide proton-exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane (typically nafion ) contains the electrolyte solution that separates the anode and cathode sides. This

2774-603: A higher voltage. RTGs and fission reactors use very different nuclear reactions. Nuclear power reactors (including the miniaturized ones used in space) perform controlled nuclear fission in a chain reaction . The rate of the reaction can be controlled with neutron absorbing control rods , so power can be varied with demand or shut off (almost) entirely for maintenance. However, care is needed to avoid uncontrolled operation at dangerously high power levels, or even explosion or nuclear meltdown . Chain reactions do not occur in RTGs. Heat

2920-432: A hot water storage tank to smooth out the thermal heat production was a serious disadvantage in the domestic market place where space in domestic properties is at a great premium. Delta-ee consultants stated in 2013 that with 64% of global sales the fuel cell micro-combined heat and power passed the conventional systems in sales in 2012. The Japanese ENE FARM project stated that 34.213 PEMFC and 2.224 SOFC were installed in

3066-589: A hydrogen source would create less than one ounce of pollution (other than CO 2 ) for every 1,000 kW·h produced, compared to 25 pounds of pollutants generated by conventional combustion systems. Fuel Cells also produce 97% less nitrogen oxide emissions than conventional coal-fired power plants. One such pilot program is operating on Stuart Island in Washington State. There the Stuart Island Energy Initiative has built

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3212-455: A hydrogen-rich gas in the anode, eliminating the need to produce hydrogen externally. The reforming process creates CO 2 emissions. MCFC-compatible fuels include natural gas, biogas and gas produced from coal. The hydrogen in the gas reacts with carbonate ions from the electrolyte to produce water, carbon dioxide, electrons and small amounts of other chemicals. The electrons travel through an external circuit, creating electricity, and return to

3358-486: A larger number of such units have been deployed both on the ground and on the ocean floor than have been used on spacecraft, with public regulatory documents suggesting that the US had deployed at least 100–150 during the 1970s and 1980s. In the past, small "plutonium cells" (very small Pu-powered RTGs) were used in implanted heart pacemakers to ensure a very long "battery life". As of 2004, about ninety were still in use. By

3504-421: A much lower neutron emission rate for the oxide; this can be accomplished by a gas phase O 2 exchange method. Regular production batches of PuO 2 particles precipitated as a hydroxide were used to show that large production batches could be effectively O 2 -exchanged on a routine basis. High-fired PuO 2 microspheres were successfully O 2 -exchanged showing that an exchange will take place regardless of

3650-459: A potential of about 0.9   V. Alkaline anion exchange membrane fuel cell (AAEMFC) is a type of AFC which employs a solid polymer electrolyte instead of aqueous potassium hydroxide (KOH) and it is superior to aqueous AFC. Solid oxide fuel cells (SOFCs) use a solid material, most commonly a ceramic material called yttria-stabilized zirconia (YSZ), as the electrolyte . Because SOFCs are made entirely of solid materials, they are not limited to

3796-770: A power-plant-to-wheel efficiency of 22% if the hydrogen is stored as high-pressure gas, and 17% if it is stored as liquid hydrogen . Stationary fuel cells are used for commercial, industrial and residential primary and backup power generation. Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, communications centers, rural locations including research stations, and in certain military applications. A fuel cell system running on hydrogen can be compact and lightweight, and have no major moving parts. Because fuel cells have no moving parts and do not involve combustion, in ideal conditions they can achieve up to 99.9999% reliability. This equates to less than one minute of downtime in

3942-425: A requirement, as in enclosed spaces such as warehouses, and where hydrogen is considered an acceptable reactant, a [PEM fuel cell] is becoming an increasingly attractive choice [if exchanging batteries is inconvenient]". In 2013 military organizations were evaluating fuel cells to determine if they could significantly reduce the battery weight carried by soldiers. In a fuel cell vehicle the tank-to-wheel efficiency

4088-517: A significant increase in the looting of antiquities from archaeological sites in Egypt, as the government lost the ability to protect the sites. Other acts of modern looting, such as the looting and destruction of artifacts from the National Museum of Iraq by Islamic State militants, can be used as an easy way to express contempt for the concept of rules of war altogether. In the case of

4234-420: A similar effect of dispersion by physically grinding the inert matrix into a fine dust. RTGs pose a risk of radioactive contamination : if the container holding the fuel leaks, the radioactive material may contaminate the environment. For spacecraft, the main concern is that if an accident were to occur during launch or a subsequent passage of a spacecraft close to Earth, harmful material could be released into

4380-401: A six-year period. Since fuel cell electrolyzer systems do not store fuel in themselves, but rather rely on external storage units, they can be successfully applied in large-scale energy storage, rural areas being one example. There are many different types of stationary fuel cells so efficiencies vary, but most are between 40% and 60% energy efficient. However, when the fuel cell's waste heat

4526-477: A steady source of power. Most have no protection, not even fences or warning signs, and the locations of some of these facilities are no longer known due to poor record keeping. In one instance, the radioactive compartments were opened by a thief. In another case , three woodsmen in Tsalendzhikha Region, Georgia found two ceramic RTG orphan sources that had been stripped of their shielding; two of

Radioisotope thermoelectric generator - Misplaced Pages Continue

4672-467: A sudden change in a country or region's government, it can be difficult to determine what constitutes looting as opposed to a new government taking custody of the property in question. This can be especially difficult if the new government is only partially recognized at the time the property is moved, as was the case during the 2021 Taliban offensive , during which a number of artifacts and a large amount of property of former government officials who had fled

4818-411: A system or device that converts energy is measured by the ratio of the amount of useful energy put out by the system ("output energy") to the total amount of energy that is put in ("input energy") or by useful output energy as a percentage of the total input energy. In the case of fuel cells, useful output energy is measured in electrical energy produced by the system. Input energy is the energy stored in

4964-437: A welding machine. In the 1960s, Pratt & Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecraft tanks). In 1991, the first hydrogen fuel cell automobile was developed by Roger E. Billings. UTC Power was the first company to manufacture and commercialize a large, stationary fuel cell system for use as

5110-572: Is flow batteries , in which the fuel can be regenerated by recharging. Individual fuel cells produce relatively small electrical potentials, about 0.7 volts, so cells are "stacked", or placed in series, to create sufficient voltage to meet an application's requirements. In addition to electricity, fuel cells produce water vapor, heat and, depending on the fuel source, very small amounts of nitrogen dioxide and other emissions. PEMFC cells generally produce fewer nitrogen oxides than SOFC cells: they operate at lower temperatures, use hydrogen as fuel, and limit

5256-467: Is a thermoelectric device that can convert thermal energy directly into electrical energy using the Seebeck effect . It is made of two kinds of metal or semiconductor material. If they are connected to each other in a closed loop and the two junctions are at different temperatures , an electric current will flow in the loop. Typically a large number of thermocouples are connected in series to generate

5402-401: Is a pure alpha-emitter and does not emit significant gamma or X-ray radiation, the shielding requirements are as low as those for Pu. While the short half-life also reduces the time during which accidental release to the environment is a concern, polonium-210 is extremely radiotoxic if ingested and can cause significant harm even in chemically inert forms, which pass through the digestive tract as

5548-538: Is almost equal parts Cs-135 and Cs-137, plus significant amounts of stable Cs-133 and, in "young" spent fuel, short lived Cs-134. If isotope separation , a costly and time-consuming process, is to be avoided, this has to be factored in, too. While historically RTGs have been rather small, there is in theory nothing preventing RTGs from reaching into the Megawatt thermal range of power. However, for such applications actinides are less suitable than lighter radioisotopes as

5694-406: Is commonly used as strontium titanate in RTGs, which increases molar mass by about a factor of 2. Furthermore, depending on the source, isotopic purity may not be obtainable. Plutonium extracted from spent nuclear fuel has a low share of Pu-238, so plutonium-238 for use in RTGs is usually purpose-made by neutron irradiation of neptunium-237 , further raising costs. Caesium in fission products

5840-454: Is economically recovered from the heavy water moderator in CANDUs . Americium-241 is a candidate isotope with much greater availability than Pu. Although Am has a half-life of 432 years, which is about five times longer than that of Pu and could hypothetically power a device for centuries, missions with more than 10 years were not the subject of the research until 2019. The power density of Am

5986-498: Is either the result of direct orders, despite to Russia's claims to the contrary, or due to Russian soldiers not being issued with adequate food and other resources by their commanders. The term "looting" is also sometimes used to refer to antiquities being removed from countries by unauthorized people, either domestic people breaking the law seeking monetary gain or foreign nations, which are usually more interested in prestige or previously, "scientific discovery". An example might be

Radioisotope thermoelectric generator - Misplaced Pages Continue

6132-486: Is funded, the goal would be to set up automation and scale-up processes in order to produce an average of 1.5 kg (3.3 lb) per year by 2025. Strontium-90 has been used by the Soviet Union in terrestrial RTGs. Sr decays by β emission, with minor γ emission. While its half life of 28.8 years is much shorter than that of Pu, it also has a lower decay energy with a power density of 0.46 watts per gram. Because

6278-651: Is greater than 45% at low loads and shows average values of about 36% when a driving cycle like the NEDC ( New European Driving Cycle ) is used as test procedure. The comparable NEDC value for a Diesel vehicle is 22%. In 2008 Honda released a demonstration fuel cell electric vehicle (the Honda FCX Clarity ) with fuel stack claiming a 60% tank-to-wheel efficiency. It is also important to take losses due to fuel production, transportation, and storage into account. Fuel cell vehicles running on compressed hydrogen may have

6424-462: Is most likely that they melted through the glacier and were pulverized, whereupon the Pu–Zr alloy fuel oxidized soil particles that are moving in a plume under the glacier. Many Beta-M RTGs produced by the Soviet Union to power lighthouses and beacons have become orphaned sources of radiation. Several of these units have been illegally dismantled for scrap metal (resulting in the complete exposure of

6570-544: Is needed in a 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 (PuO 2 ). However, plutonium(IV) oxide containing a natural abundance of oxygen emits neutrons at the rate of roughly 2.3 × 10  n/sec/g of plutonium-238. This emission rate is relatively high compared to the neutron emission rate of plutonium-238 metal. The metal containing no light element impurities emits roughly 2.8 × 10  n/sec/g of plutonium-238. These neutrons are produced by

6716-421: Is only one-fourth that of Pu, and Am produces more penetrating radiation through decay chain products than Pu and needs more shielding. Its shielding requirements in a RTG are the third lowest: only Pu and Po require less. With a current global shortage of Pu, Am is being studied as RTG fuel by ESA and in 2019, UK's National Nuclear Laboratory announced the generation of usable electricity. An advantage over Pu

6862-482: Is produced by steam methane reforming , which emits carbon dioxide. The overall efficiency (electricity to hydrogen and back to electricity) of such plants (known as round-trip efficiency ), using pure hydrogen and pure oxygen can be "from 35 up to 50 percent", depending on gas density and other conditions. The electrolyzer/fuel cell system can store indefinite quantities of hydrogen, and is therefore suited for long-term storage. Solid-oxide fuel cells produce heat from

7008-504: Is produced through spontaneous radioactive decay at a non-adjustable and steadily decreasing rate that depends only on the amount of fuel isotope and its half-life. In an RTG, heat generation cannot be varied with demand or shut off when not needed and it is not possible to save more energy for later by reducing the power consumption. Therefore, auxiliary power supplies (such as rechargeable batteries) may be needed to meet peak demand, and adequate cooling must be provided at all times including

7154-472: Is prohibited by international law , and constitutes a war crime . During a disaster, police and military forces are sometimes unable to prevent looting when they are overwhelmed by humanitarian or combat concerns, or they cannot be summoned because of damaged communications infrastructure. Especially during natural disasters, many civilians may find themselves forced to take what does not belong to them in order to survive. How to respond to that and where

7300-589: Is referred to as the heart of the PEMFC and is usually made of a proton-exchange membrane sandwiched between two catalyst -coated carbon papers . Platinum and/or similar types of noble metals are usually used as the catalyst for PEMFC, and these can be contaminated by carbon monoxide , necessitating a relatively pure hydrogen fuel. The electrolyte could be a polymer membrane . Phosphoric acid fuel cells (PAFCs) were first designed and introduced in 1961 by G. V. Elmore and H. A. Tanner . In these cells, phosphoric acid

7446-438: Is said to be the largest of the type. Small-scale (sub-5kWhr) fuel cells are being developed for use in residential off-grid deployment. Combined heat and power (CHP) fuel cell systems, including micro combined heat and power (MicroCHP) systems are used to generate both electricity and heat for homes (see home fuel cell ), office building and factories. The system generates constant electric power (selling excess power back to

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7592-441: 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

7738-514: Is spacecraft power supply. Several generations of RTG design have been used for probes that traveled far from the Sun, rendering solar panels impractical. As such, they have been used for Pioneer 10 and 11 ; Voyager 1 and 2 ; Galileo ; Ulysses ; Cassini ; New Horizons ; and are planned for the Dragonfly mission to Titan . RTGs were also used instead of solar panels to power

7884-416: Is that it is produced as nuclear waste and is nearly isotopically pure. Prototype designs of Am RTGs expect 2–2.2 W e /kg for 5–50 W e RTGs design but practical testing shows that only 1.3–1.9 W e can be achieved. Americium-241 is currently used in small quantities in household smoke detectors and thus its handling and properties are well-established. However, it decays to neptunium-237 ,

8030-796: Is the Lia radiological accident in Georgia , December 2001. Strontium-90 RTG cores were dumped behind, unlabeled and improperly dismanteled, near the Soviet-built Enguri Dam . Three villagers from the nearby village of Lia were unknowingly exposed to it and injured; one of them died in May 2004 from the injuries sustained. The International Atomic Energy Agency led recovery operations and organized medical care. Two remaining RTG cores are yet to be found as of 2022. There have been several known accidents involving RTG-powered spacecraft: One RTG,

8176-403: Is the act of stealing, or the taking of goods by force, typically in the midst of a military, political, or other social crisis, such as war , natural disasters (where law and civil enforcement are temporarily ineffective), or rioting . The proceeds of all these activities can be described as booty , loot , plunder , spoils , or pillage. During modern-day armed conflicts , looting

8322-594: Is the cells' short life span. The high-temperature and carbonate electrolyte lead to corrosion of the anode and cathode. These factors accelerate the degradation of MCFC components, decreasing the durability and cell life. Researchers are addressing this problem by exploring corrosion-resistant materials for components as well as fuel cell designs that may increase cell life without decreasing performance. MCFCs hold several advantages over other fuel cell technologies, including their resistance to impurities. They are not prone to "carbon coking", which refers to carbon build-up on

8468-534: Is the potential for carbon dust to build up on the anode, which slows down the internal reforming process. Research to address this "carbon coking" issue at the University of Pennsylvania has shown that the use of copper-based cermet (heat-resistant materials made of ceramic and metal) can reduce coking and the loss of performance. Another disadvantage of SOFC systems is the long start-up, making SOFCs less useful for mobile applications. Despite these disadvantages,

8614-406: Is unlikely as SrTiO 3 passes through the digestive tract of humans or other animals unchanged, but the animal or human who ingested it would still receive a significant radiation dose to the sensitive intestinal lining during passage. Mechanical degradation of "pebbles" or larger objects into fine dust is more likely and could disperse the material over a wider area, however this would also reduce

8760-506: Is used as a non-conductive electrolyte to pass protons from the anode to the cathode and to force electrons to travel from anode to cathode through an external electrical circuit. These cells commonly work in temperatures of 150 to 200 °C. This high temperature will cause heat and energy loss if the heat is not removed and used properly. This heat can be used to produce steam for air conditioning systems or any other thermal energy-consuming system. Using this heat in cogeneration can enhance

8906-436: Is used to heat a building in a cogeneration system this efficiency can increase to 85%. This is significantly more efficient than traditional coal power plants, which are only about one third energy efficient. Assuming production at scale, fuel cells could save 20–40% on energy costs when used in cogeneration systems. Fuel cells are also much cleaner than traditional power generation; a fuel cell power plant using natural gas as

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9052-693: Is used, the CO 2 is released when methane from natural gas is combined with steam, in a process called steam methane reforming , to produce the hydrogen. This can take place in a different location to the fuel cell, potentially allowing the hydrogen fuel cell to be used indoors—for example, in forklifts. The different components of a PEMFC are The materials used for different parts of the fuel cells differ by type. The bipolar plates may be made of different types of materials, such as, metal, coated metal, graphite , flexible graphite, C–C composite , carbon – polymer composites etc. The membrane electrode assembly (MEA)

9198-623: The Electrochemical Society journal Interface in 2008, wrote, "While fuel cells are efficient relative to combustion engines, they are not as efficient as batteries, primarily due to the inefficiency of the oxygen reduction reaction (and ... the oxygen evolution reaction, should the hydrogen be formed by electrolysis of water). ... [T]hey make the most sense for operation disconnected from the grid, or when fuel can be provided continuously. For applications that require frequent and relatively rapid start-ups ... where zero emissions are

9344-636: The Gulf War , Saddam Hussein 's soldiers caused significant damage to both Kuwaiti and Saudi infrastructure. They also stole from private companies and homes. In April 2003, looters broke into the National Museum of Iraq, and thousands of artefacts remain missing. Syrian conservation sites and museums were looted during the Syrian Civil War , with items being sold on the international black market . Reports from 2012 suggested that

9490-604: The Indian and Pakistani militarized zones is common and widespread. In 2022, international observers accused Russia of engaging in large scale looting during the Russo-Ukrainian War , reporting the widespread looting of everything from food to industrial equipment. Despite the publication of numerous photos and videos by Ukrainian journalists and civilians, numerous Russian commanders have denied these claims. International observers have theorized that this looting

9636-579: The National Inventors Hall of Fame in 2013. Jordan and Birden worked on an Army Signal Corps contract (R-65-8- 998 11-SC-03-91) beginning on 1 January 1957, to conduct research on radioactive materials and thermocouples suitable for the direct conversion of heat to electrical energy using polonium-210 as the heat source. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg, Ohio , under contract with

9782-573: The SNAP-19C , was lost near the top of Nanda Devi mountain in India in 1965 when it was stored in a rock formation near the top of the mountain in the face of a snowstorm before it could be installed to power a CIA remote automated station collecting telemetry from the Chinese rocket testing facility. The seven capsules were carried down the mountain onto a glacier by an avalanche and never recovered. It

9928-461: The Soviet Arctic coast by the late 1980s. Many different types of RTGs (including Beta-M type) were built in the Soviet Union for a wide variety of purposes. The lighthouses were not maintained for many years after the dissolution of the Soviet Union in 1991 . Some of the RTG units disappeared during this time—either by looting or by the natural forces of ice/storm/sea. In 1996, a project

10074-528: The Soviet Union inside the Arctic Circle . Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. The expense of RTGs tends to limit their use to niche applications in rare or special situations. The RTG was invented in 1954 by Mound Laboratories scientists Kenneth (Ken) C. Jordan (1921–2008) and John Birden (1918–2011). They were inducted into

10220-625: The Sr-90 source), fallen into the ocean, or have defective shielding due to poor design or physical damage. The US Department of Defense cooperative threat reduction program has expressed concern that material from the Beta-M RTGs can be used by terrorists to construct a dirty bomb . However, the Strontium titanate perovskite used is resistant to all likely forms of environmental degradation and cannot melt or dissolve in water. Bioaccumulation

10366-761: The United States Atomic Energy Commission . The project was led by Dr. Bertram C. Blanke. The first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238 metal, aboard the Navy Transit 4A spacecraft . One of the first terrestrial uses of RTGs was in 1966 by the US Navy at uninhabited Fairway Rock in Alaska. RTGs were used at that site until 1995. A common RTG application

10512-500: The critical mass is orders of magnitude below the mass needed to produce such amounts of power. As Sr-90, Cs-137 and other lighter radionuclides cannot maintain a nuclear chain reaction under any circumstances, RTGs of arbitrary size and power could be assembled from them if enough material can be produced. In general, however, potential applications for such large-scale RTGs are more the domain of small modular reactors , microreactors or non-nuclear power sources. Plutonium-238 has

10658-774: The early modern period and reaching its peak in the New Imperialism era, European colonial powers frequently looted areas they captured during military campaigns against non-European states. In the 1930s, and even more so during the Second World War , Nazi Germany engaged in large-scale and organized looting of art and property , particularly in Nazi-occupied Poland . Looting, combined with poor military discipline , has occasionally been an army's downfall since troops who have dispersed to ransack an area may become vulnerable to counter-attack,

10804-511: The ionic conductivity of YSZ. Therefore, to obtain the optimum performance of the fuel cell, a high operating temperature is required. According to their website, Ceres Power , a UK SOFC fuel cell manufacturer, has developed a method of reducing the operating temperature of their SOFC system to 500–600 degrees Celsius. They replaced the commonly used YSZ electrolyte with a CGO (cerium gadolinium oxide) electrolyte. The lower operating temperature allows them to use stainless steel instead of ceramic as

10950-428: The waste heat produced by the primary power cycle - whether fuel cell, nuclear fission or combustion - is captured and put to use, increasing the efficiency of the system to up to 85–90%. The theoretical maximum efficiency of any type of power generation system is never reached in practice, and it does not consider other steps in power generation, such as production, transportation and storage of fuel and conversion of

11096-454: The ASRG uses a Stirling power device that runs on radioisotope (see Stirling radioisotope generator ) The radioactive material used in RTGs must have several characteristics: The first two criteria limit the number of possible fuels to fewer than thirty atomic isotopes within the entire table of nuclides . Plutonium-238 , curium-244 , strontium-90 , and most recently americium-241 are

11242-557: The BES-5 Buk ( БЭС-5 ) reactor was a fast reactor which used thermocouples based on semiconductors to convert heat directly into electricity *** not really an RTG, the SNAP-10A used enriched uranium fuel, zirconium hydride as a moderator, liquid sodium potassium alloy coolant, and was activated or deactivated with beryllium reflectors Reactor heat fed a thermoelectric conversion system for electrical production. **** not really an RTG,

11388-672: The Bacon fuel cell after its inventor, has been used in NASA space programs since the mid-1960s to generate power for satellites and space capsules . Since then, fuel cells have been used in many other applications. Fuel cells are used for primary and backup power for commercial, industrial and residential buildings and in remote or inaccessible areas. They are also used to power fuel cell vehicles , including forklifts, automobiles, buses, trains, boats, motorcycles, and submarines. There are many types of fuel cells, but they all consist of an anode ,

11534-581: The Center for Space Nuclear Research (CSNR) in 2013 for studies of feasibility. However the essentials are unmodified. RTG have been proposed for use on realistic interstellar precursor missions and interstellar probes . An example of this is the Innovative Interstellar Explorer (2003–current) proposal from NASA. An RTG using Am was proposed for this type of mission in 2002. This could support mission extensions up to 1000 years on

11680-494: The DFC-ERG, is combined with a gas turbine and, according to the company, it achieves an electrical efficiency of 65%. The electric storage fuel cell is a conventional battery chargeable by electric power input, using the conventional electro-chemical effect. However, the battery further includes hydrogen (and oxygen) inputs for alternatively charging the battery chemically. Glossary of terms in table: The energy efficiency of

11826-410: The RTGs was estimated at 1 in 10. The launch was successful and Cassini–Huygens reached Saturn . To minimize the risk of the radioactive material being released, the fuel is stored in individual modular units with their own heat shielding. They are surrounded by a layer of iridium metal and encased in high-strength graphite blocks. These two materials are corrosion- and heat-resistant. Surrounding

11972-517: 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 67% of their total original capacity instead of the expected 83.4%. By the beginning of 2001, the power generated by the Voyager RTGs had dropped to 315 W for Voyager 1 and to 319 W for Voyager 2 . By 2022, these numbers had dropped to around 220 W. NASA has developed

12118-408: The alpha decay from the radioisotope is also used in alpha-neutron reactions with a suitable element such as beryllium . This way a long-lived neutron source is produced. Because the system is working with a criticality close to but less than 1, i.e. K eff < 1, a subcritical multiplication is achieved which increases the neutron background and produces energy from fission reactions. Although

12264-493: The anode that results in reduced performance by slowing down the internal fuel reforming process. Therefore, carbon-rich fuels like gases made from coal are compatible with the system. The United States Department of Energy claims that coal, itself, might even be a fuel option in the future, assuming the system can be made resistant to impurities such as sulfur and particulates that result from converting coal into hydrogen. MCFCs also have relatively high efficiencies. They can reach

12410-478: The anode to the cathode through an external circuit, producing direct current electricity. At the cathode, another catalyst causes ions, electrons, and oxygen to react, forming water and possibly other products. Fuel cells are classified by the type of electrolyte they use and by the difference in start-up time ranging from 1 second for proton-exchange membrane fuel cells (PEM fuel cells, or PEMFC) to 10 minutes for solid oxide fuel cells (SOFC). A related technology

12556-423: The anode to the cathode), as is the case in all other types of fuel cells. Oxygen gas is fed through the cathode, where it absorbs electrons to create oxygen ions. The oxygen ions then travel through the electrolyte to react with hydrogen gas at the anode. The reaction at the anode produces electricity and water as by-products. Carbon dioxide may also be a by-product depending on the fuel, but the carbon emissions from

12702-545: The antiquities were being traded for weapons by the various combatants. Both customary international law and international treaties prohibit pillage in armed conflict . The Lieber Code , the Brussels Declaration (1874), and the Oxford Manual have recognized the prohibition against pillage. The Hague Conventions of 1899 and 1907 ( modified in 1954 ) obliges military forces not only to avoid

12848-567: The atmosphere; therefore their use in spacecraft and elsewhere has attracted controversy. However, this event is not considered likely with current RTG cask designs. For instance, the environmental impact study for the Cassini–Huygens probe launched in 1997 estimated the probability of contamination accidents at various stages in the mission. The probability of an accident occurring which caused radioactive release from one or more of its three RTGs (or from its 129 radioisotope heater units ) during

12994-522: The bones it can significantly damage the bone marrow , a rapidly dividing tissue), it is usually not employed in pure form in RTGs. The most common form is the perovskite strontium titanate (SrTiO 3 ) which is chemically nigh-inert and has a high melting point. While its Mohs hardness of 5.5 has made it ill-suited as a diamond simulant , it is of sufficient hardness to withstand some forms of accidental release from its shielding without too fine dispersal of dust. The downside to using SrTiO 3 instead of

13140-548: The cathode. There, oxygen from the air and carbon dioxide recycled from the anode react with the electrons to form carbonate ions that replenish the electrolyte, completing the circuit. The chemical reactions for an MCFC system can be expressed as follows: As with SOFCs, MCFC disadvantages include slow start-up times because of their high operating temperature. This makes MCFC systems not suitable for mobile applications, and this technology will most likely be used for stationary fuel cell purposes. The main challenge of MCFC technology

13286-513: The celebration of victory. In the wake of the Napoleonic Wars and particularly after World War II , norms against wartime plunder became widely accepted. In the upper ranks, the proud exhibition of the loot plundered formed an integral part of the typical Roman triumph , and Genghis Khan was not unusual in proclaiming that the greatest happiness was "to vanquish your enemies... to rob them of their wealth". In ancient times, looting

13432-462: The cell substrate, which reduces cost and start-up time of the system. Molten carbonate fuel cells (MCFCs) require a high operating temperature, 650 °C (1,200 °F), similar to SOFCs . MCFCs use lithium potassium carbonate salt as an electrolyte, and this salt liquefies at high temperatures, allowing for the movement of charge within the cell – in this case, negative carbonate ions. Like SOFCs, MCFCs are capable of converting fossil fuel to

13578-496: The chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. The first fuel cells were invented by Sir William Grove in 1838. The first commercial use of fuel cells came almost a century later following the invention of the hydrogen–oxygen fuel cell by Francis Thomas Bacon in 1932. The alkaline fuel cell , also known as

13724-513: The country fell into the hands of the Taliban before they were recognized as the legitimate government of Afghanistan by other countries. Further looting and burning of civilian homes and villages has been defended by the Taliban as within their right as the legitimate government of Afghanistan. Looting can also be common in cases where civil unrest is contained largely within the borders of

13870-474: The defeated populations, which were often enslaved . Women and children might become absorbed into the victorious country's population, as concubines , eunuchs and slaves. In other pre-modern societies, objects made of precious metals were the preferred target of war looting, largely because of their ease of portability. In many cases, looting offered an opportunity to obtain treasures and works of art that otherwise would not have been obtainable. Beginning in

14016-399: The design on the next New Frontiers mission. Radioactive materials contained in RTGs are dangerous and can even be used for malicious purposes. They are not useful for a genuine nuclear weapon , but still can serve in a " dirty bomb ". The Soviet Union constructed many uncrewed lighthouses and navigation beacons powered by RTGs using strontium-90 (Sr). They are very reliable and provide

14162-616: The desired strontium titanate plus carbon dioxide . If desired, the strontium titanate product can then be formed into a ceramic-like aggregate via sintering . Some prototype RTGs, first built in 1958 by the US Atomic Energy Commission, have used polonium-210 . This isotope provides phenomenal power density (pure Po emits 140 W /g) because of its high decay rate , but has limited use because of its very short half-life of 138 days. A half-gram sample of Po reaches temperatures of over 500 °C (900 °F). As Po

14308-730: The destruction of enemy property but also to provide for its protection. Article 8 of the Statute of the International Criminal Court provides that in international warfare, "pillaging a town or place, even when taken by assault", is a war crime . In the aftermath of World War II , a number of war criminals were prosecuted for pillage. The International Criminal Tribunal for the Former Yugoslavia (1993–2017) brought several prosecutions for pillage. The Fourth Geneva Convention of 1949 explicitly prohibits

14454-606: The development of his first crude fuel cells. He used a combination of sheet iron, copper, and porcelain plates, and a solution of sulphate of copper and dilute acid. In a letter to the same publication written in December 1838 but published in June 1839, German physicist Christian Friedrich Schönbein discussed the first crude fuel cell that he had invented. His letter discussed the current generated from hydrogen and oxygen dissolved in water. Grove later sketched his design, in 1842, in

14600-549: The diffusion of nitrogen into the anode via the proton exchange membrane, which forms NOx. The energy efficiency of a fuel cell is generally between 40 and 60%; however, if waste heat is captured in a cogeneration scheme, efficiencies of up to 85% can be obtained. The first references to hydrogen fuel cells appeared in 1838. In a letter dated October 1838 but published in the December 1838 edition of The London and Edinburgh Philosophical Magazine and Journal of Science , Welsh physicist and barrister Sir William Grove wrote about

14746-404: The efficiency of phosphoric acid fuel cells from 40 to 50% to about 80%. Since the proton production rate on the anode is small, platinum is used as a catalyst to increase this ionization rate. A key disadvantage of these cells is the use of an acidic electrolyte. This increases the corrosion or oxidation of components exposed to phosphoric acid. Solid acid fuel cells (SAFCs) are characterized by

14892-447: The electricity into mechanical power. However, this calculation allows the comparison of different types of power generation. The theoretical maximum efficiency of a fuel cell approaches 100%, while the theoretical maximum efficiency of internal combustion engines is approximately 58%. Values are given from 40% for acidic, 50% for molten carbonate, to 60% for alkaline, solid oxide and PEM fuel cells. Fuel cells cannot store energy like

15038-413: The end of 2007, the number was reported to be down to just nine. The Mound Laboratory Cardiac Pacemaker program began on 1 June 1966, in conjunction with NUMEC. When it was recognized that the heat source would not remain intact during cremation, the program was cancelled in 1972 because there was no way to completely ensure that the units would not be cremated with their users' bodies. The design of an RTG

15184-472: The energy output is lower it reaches lower temperatures than Pu, which results in lower RTG efficiency. Sr has a high fission product yield in the fission of both U and Pu and is thus available in large quantities at a relatively low price if extracted from spent nuclear fuel . As Sr is a very reactive alkaline earth metal and a so-called "bone seeker" that accumulates in bone-tissue due to its chemical similarity to calcium (once in

15330-438: The first 3.5 minutes following launch was estimated at 1 in 1,400; the chances of a release later in the ascent into orbit were 1 in 476; after that the likelihood of an accidental release fell off sharply to less than 1 in a million. If an accident which had the potential to cause contamination occurred during the launch phases (such as the spacecraft failing to reach orbit), the probability of contamination actually being caused by

15476-442: The flat plane configuration of other types of fuel cells and are often designed as rolled tubes. They require high operating temperatures (800–1000 °C) and can be run on a variety of fuels including natural gas. SOFCs are unique because negatively charged oxygen ions travel from the cathode (positive side of the fuel cell) to the anode (negative side of the fuel cell) instead of protons travelling vice versa (i.e., from

15622-463: The fuel. According to the U.S. Department of Energy, fuel cells are generally between 40 and 60% energy efficient. This is higher than some other systems for energy generation. For example, the internal combustion engine of a car can be about 43% energy efficient. Steam power plants usually achieve efficiencies of 30-40% while combined cycle gas turbine and steam plants can achieve efficiencies above 60%. In combined heat and power (CHP) systems,

15768-549: The graphite blocks is an aeroshell, designed to protect the entire assembly against the heat of reentering the Earth's atmosphere. The plutonium fuel is also stored in a ceramic form that is heat-resistant, minimising the risk of vaporization and aerosolization. The ceramic is also highly insoluble . The plutonium-238 used in these RTGs has a half-life of 87.74 years, in contrast to the 24,110 year half-life of plutonium-239 used in nuclear weapons and reactors . A consequence of

15914-506: The grid when it is not consumed), and at the same time produces hot air and water from the waste heat . As the result CHP systems have the potential to save primary energy as they can make use of waste heat which is generally rejected by thermal energy conversion systems. A typical capacity range of home fuel cell is 1–3 kW el , 4–8 kW th . CHP systems linked to absorption chillers use their waste heat for refrigeration . The waste heat from fuel cells can be diverted during

16060-438: The interstellar probe, because the power output would decline more slowly over the long term than plutonium. Other isotopes for RTG were also examined in the study, looking at traits such as watt/gram, half-life, and decay products. An interstellar probe proposal from 1999 suggested using three advanced radioisotope power sources (ARPS). The RTG electricity can be used for powering scientific instruments and communication to Earth on

16206-462: The ions are reunited with the electrons and the two react with a third chemical, usually oxygen, to create water or carbon dioxide. Design features in a fuel cell include: A typical fuel cell produces a voltage from 0.6 to 0.7 V at a full-rated load. Voltage decreases as current increases, due to several factors: To deliver the desired amount of energy, the fuel cells can be combined in series to yield higher voltage , and in parallel to allow

16352-476: The line between unnecessary "looting" and necessary " scavenging " lies are often dilemmas for governments. In other cases, looting may be tolerated or even encouraged by governments for political or other reasons, including religious, social or economic ones. Looting by a victorious army during war has been a common practice throughout recorded history. Foot soldiers viewed plunder as a way to supplement an often-meagre income and transferred wealth became part of

16498-400: The load. At the anode a catalyst ionizes the fuel, turning the fuel into a positively charged ion and a negatively charged electron. The electrolyte is a substance specifically designed so ions can pass through it, but the electrons cannot. The freed electrons travel through a wire creating an electric current. The ions travel through the electrolyte to the cathode. Once reaching the cathode,

16644-564: The looting of civilian property during wartime. Theoretically, to prevent such looting, unclaimed property is moved to the custody of the Custodian of Enemy Property , to be handled until returned to its owners. Despite international prohibitions against the practice of looting, the ease with which it can be done means that it remains relatively common, particularly during outbreaks of civil unrest during which rules of war may not yet apply. The 2011 Egyptian Revolution , for example, caused

16790-609: The membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water. In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel , methanol ( see: direct-methanol fuel cells and indirect methanol fuel cells ) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water. When hydrogen

16936-472: The most chemically mobile among the actinides. Curium-250 is the isotope with the lowest atomic number that primarily decays by spontaneous fission, a process that releases many times more energy than alpha decay. Compared to plutonium-238, curium-250 provides about a quarter of the power density, but 95 times the half-life (~8300 years vs. ~87 years). As it is a neutron emitter (weaker than californium-252 but not entirely negligible) some applications require

17082-594: The most often cited candidate isotopes, but 43 more isotopes out of approximately 1,300 were considered at the beginning in the 1950s. The table below does not necessarily give power densities for the pure material but for a chemically inert form. For actinides this is of little concern as their oxides are usually inert enough (and can be transformed into ceramics further increasing their stability), but for alkali metals and alkaline earth metals like caesium or strontium respectively, relatively complex (and heavy) chemical compounds have to be used. For example, strontium

17228-527: The native metal is that its production requires energy. It also reduces power density, as the TiO 3 part of the material does not produce any decay heat. Starting from the oxide or the native metal, one pathway to obtaining SrTiO 3 is to let it transform to strontium hydroxide in aqueous solution, which absorbs carbon dioxide from air to become less soluble strontium carbonate . Reaction of strontium carbonate with titanium dioxide at high temperature produces

17374-505: The number of fissions produced in the RTG is very small (making their gamma radiation negligible), because each fission reaction releases over 30 times more energy than each alpha decay (200  MeV compared to 6 MeV), up to a 10% energy gain is attainable, which translates into a reduction of the Pu needed per mission. The idea was proposed to NASA in 2012 for the yearly NASA NSPIRE competition, which translated to Idaho National Laboratory at

17520-490: The original fuel cell design by using a sulphonated polystyrene ion-exchange membrane as the electrolyte. Three years later another GE chemist, Leonard Niedrach, devised a way of depositing platinum onto the membrane, which served as a catalyst for the necessary hydrogen oxidation and oxygen reduction reactions. This became known as the "Grubb-Niedrach fuel cell". GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini . This

17666-441: The other three isotopes discussed in this section, Pu must be specifically synthesized and is not abundant as a nuclear waste product. At present only Russia has maintained high-volume production, while in the US, no more than 50 g (1.8 oz) were produced in total between 2013 and 2018. The US agencies involved desire to begin the production of the material at a rate of 300 to 400 grams (11 to 14 oz) per year. If this plan

17812-769: The period 2012–2014, 30,000 units on LNG and 6,000 on LPG . Four fuel cell electric vehicles have been introduced for commercial lease and sale: the Honda Clarity , Toyota Mirai , Hyundai ix35 FCEV , and the Hyundai Nexo . By year-end 2019, about 18,000 FCEVs had been leased or sold worldwide. Fuel cell electric vehicles feature an average range of 505 km (314 mi) between refuelings and can be refueled in about 5 minutes. The U.S. Department of Energy's Fuel Cell Technology Program states that, as of 2011, fuel cells achieved 53–59% efficiency at one-quarter power and 42–53% vehicle efficiency at full power, and

17958-486: The pre-launch and early flight phases of a space mission. While spectacular failures like a nuclear meltdown or explosion are impossible with an RTG, there is still a risk of radioactive contamination if the rocket explodes, the device reenters the atmosphere and disintegrates, terrestrial RTGs are damaged by storms or seasonal ice, or are vandalized. Due to the shortage of plutonium-238, a new kind of RTG assisted by subcritical reactions has been proposed. In this kind of RTG,

18104-576: The previous heat treatment history of the PuO 2 . This lowering of the neutron emission rate of PuO 2 containing normal oxygen by a factor of five was discovered during the cardiac pacemaker research at Mound Laboratory in 1966, due in part to the Mound Laboratory's experience with production of stable isotopes beginning in 1960. For production of the large heat sources the shielding required would have been prohibitive without this process. Unlike

18250-455: The probes. One mission proposed using the electricity to power ion engines , calling this method radioisotope electric propulsion (REP). A power enhancement for radioisotope heat sources based on a self-induced electrostatic field has been proposed. According to the authors, enhancements of 5-10% could be attainable using beta sources. A typical RTG is powered by radioactive decay and features electricity from thermoelectric conversion, but for

18396-498: The recombination of the oxygen and hydrogen. The ceramic can run as hot as 800 °C (1,470 °F). This heat can be captured and used to heat water in a micro combined heat and power (m-CHP) application. When the heat is captured, total efficiency can reach 80–90% at the unit, but does not consider production and distribution losses. CHP units are being developed today for the European home market. Professor Jeremy P. Meyers, in

18542-593: The removal of the contents of Egyptian tombs that were transported to museums across the West . As part of World War II reparations , Soviet forces systematically plundered the Soviet occupation zone of Germany, including the Recovered Territories , which later transferred to Poland. The Soviets sent valuable industrial equipment, infrastructure and whole factories to the Soviet Union. Many factories in

18688-422: The risk of any single exposure event resulting in a high dose. Fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen ) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain

18834-501: The risk of radioactive contamination. Transforming the radioactive material into an inert form reduces the danger of theft by people unaware of the radiation hazard (such as happened in the Goiânia accident in an abandoned Cs-137 source where the caesium was present in easily water-soluble caesium chloride form). However, a sufficiently chemically skilled malicious actor could extract a volatile species from inert material and/or achieve

18980-646: The sake of knowledge, some systems with some variations on that concept are included here. Known spacecraft/nuclear power systems and their fate. Systems face a variety of fates, for example, Apollo's SNAP-27 were left on the Moon. Some other spacecraft also have small radioisotope heaters, for example each of the Mars Exploration Rovers have a 1 watt radioisotope heater. Spacecraft use different amounts of material, for example MSL Curiosity has 4.8 kg of plutonium-238 dioxide . ** not really an RTG,

19126-405: The same general manner. They are made up of three adjacent segments: the anode , the electrolyte , and the cathode . Two chemical reactions occur at the interfaces of the three different segments. The net result of the two reactions is that fuel is consumed, water or carbon dioxide is created, and an electric current is created, which can be used to power electrical devices, normally referred to as

19272-514: The same journal. The fuel cell he made used similar materials to today's phosphoric acid fuel cell . In 1932, English engineer Francis Thomas Bacon successfully developed a 5 kW stationary fuel cell. NASA used the alkaline fuel cell (AFC), also known as the Bacon fuel cell after its inventor, from the mid-1960s. In 1955, W. Thomas Grubb, a chemist working for the General Electric Company (GE), further modified

19418-438: The same, plutonium-238 is around 275 times more toxic by weight than plutonium-239. The alpha radiation emitted by either isotope will not penetrate the skin, but it can irradiate internal organs if plutonium is inhaled or ingested. Particularly at risk is the skeleton , the surface of which is likely to absorb the isotope, and the liver , where the isotope will collect and become concentrated. A case of RTG-related irradiation

19564-409: The shorter half-life is that plutonium-238 is about 275 times more radioactive than plutonium-239 (i.e. 17.3 curies (640  GBq )/ g compared to 0.063 curies (2.3 GBq)/g). For instance, 3.6  kg of plutonium-238 undergoes the same number of radioactive decays per second as 1 tonne of plutonium-239. Since the morbidity of the two isotopes in terms of absorbed radioactivity is almost exactly

19710-596: The solar-powered option, as used in prior generations of rovers . 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-10A . In addition to spacecraft, the Soviet Union built 1,007 RTGs to power uncrewed lighthouses and navigation beacons on

19856-406: The spontaneous fission of plutonium-238. The difference in the emission rates of the metal and the oxide is due mainly to the alpha, neutron reaction with the oxygen-18 and oxygen-17 present in the oxide. The normal amount of oxygen-18 present in the natural form is 0.204% while that of oxygen-17 is 0.037%. The reduction of the oxygen-17 and oxygen-18 present in the plutonium dioxide will result in

20002-764: The summer directly into the ground providing further cooling while the waste heat during winter can be pumped directly into the building. The University of Minnesota owns the patent rights to this type of system. Co-generation systems can reach 85% efficiency (40–60% electric and the remainder as thermal). Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHP products worldwide and can provide combined efficiencies close to 90%. Molten carbonate (MCFC) and solid-oxide fuel cells (SOFC) are also used for combined heat and power generation and have electrical energy efficiencies around 60%. Disadvantages of co-generation systems include slow ramping up and down rates, high cost and short lifetime. Also their need to have

20148-463: The thousands of hours. The alkaline fuel cell (AFC) or hydrogen-oxygen fuel cell was designed and first demonstrated publicly by Francis Thomas Bacon in 1959. It was used as a primary source of electrical energy in the Apollo space program. The cell consists of two porous carbon electrodes impregnated with a suitable catalyst such as Pt, Ag, CoO, etc. The space between the two electrodes is filled with

20294-588: The two Viking landers, and for the scientific experiments left on the Moon by the crews of Apollo 12 through 17 (SNAP 27s). Because the Apollo 13 Moon landing was aborted, its RTG rests in the South Pacific Ocean , in the vicinity of the Tonga Trench . The Curiosity and Perseverance Mars rover designs selected RTGs to allow greater flexibility in landing sites and longer lifespan than

20440-579: The use of a solid acid material as the electrolyte. At low temperatures, solid acids have an ordered molecular structure like most salts. At warmer temperatures (between 140 and 150   °C for CsHSO 4 ), some solid acids undergo a phase transition to become highly disordered "superprotonic" structures, which increases conductivity by several orders of magnitude. The first proof-of-concept SAFCs were developed in 2000 using cesium hydrogen sulfate (CsHSO 4 ). Current SAFC systems use cesium dihydrogen phosphate (CsH 2 PO 4 ) and have demonstrated lifetimes in

20586-496: The woodsmen were later hospitalized with severe radiation burns after carrying the sources on their backs. The units were eventually recovered and isolated. There are approximately 1,000 such RTGs in Russia, all of which have long since exceeded their designed operational lives of ten years. Most of these RTGs likely no longer function, and may need to be dismantled. Some of their metal casings have been stripped by metal hunters, despite

20732-591: Was among the factors sapping the loyalty of Poles to Russia . Local civilians can also take advantage of a breakdown of order to loot public and private property, as took place at the Iraq Museum in the course of the Iraq War in 2003. Lev Nikolayevich Tolstoy 's novel War and Peace describes widespread looting by Moscow 's citizens before Napoleon 's troops entered the city in 1812, along with looting by French troops elsewhere. In 1990 and 1991, during

20878-600: Was begun by Russian and international supporters to decommission the RTGs in the lighthouses, and by 2021, all RTGs had been removed. As of 1992, the United States Air Force also used RTGs to power remotely-located Arctic equipment, and the US government has used hundreds of such units to power remote stations globally. Sensing stations for Top-ROCC and SEEK IGLOO radar systems, predominantly located in Alaska , use RTGs. The units use strontium-90 , and

21024-540: Was called a solid polymer electrolyte fuel cell ( SPEFC ) in the early 1970s, before the proton-exchange mechanism was well understood. (Notice that the synonyms polymer electrolyte membrane and proton-exchange mechanism result in the same acronym .) On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what are commonly referred to as multi-facilitated proton membranes. The protons are conducted through

21170-566: Was sometimes prohibited due to religious concerns. For example, King Clovis I of the Franks, forbade his soldiers to loot when they campaigned near St Martin 's shrine in Tours, for fear of offending the saint. Moses, Joshua and Samuel at various points ordered the Israelites not to take loot from their enemies due to God's commandment. In warfare in ancient times, the spoils of war included

21316-408: Was the first commercial use of a fuel cell. In 1959, a team led by Harry Ihrig built a 15 kW fuel cell tractor for Allis-Chalmers , which was demonstrated across the U.S. at state fairs. This system used potassium hydroxide as the electrolyte and compressed hydrogen and oxygen as the reactants. Later in 1959, Bacon and his colleagues demonstrated a practical five-kilowatt unit capable of powering

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