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97-541: The Comprehensive Nuclear-Test-Ban Treaty ( CTBT ) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions , for both civilian and military purposes, in all environments. It was adopted by the United Nations General Assembly on 10 September 1996, but has not entered into force , as eight specific nations have not ratified the treaty. The movement for international control of nuclear weapons began in 1945, with

194-573: A critical mass . During the early stages of research, animals were used to study the effects of radioactive substances on health. These studies began in 1944 at the University of California at Berkeley's Radiation Laboratory and were conducted by Joseph G. Hamilton. Hamilton was looking to answer questions about how plutonium would vary in the body depending on exposure mode (oral ingestion, inhalation, absorption through skin), retention rates, and how plutonium would be fixed in tissues and distributed among

291-422: A fertile material . Twenty-two radioisotopes of plutonium have been characterized, from Pu to Pu. The longest-lived are Pu, with a half-life of 80.8 million years; Pu, with a half-life of 373,300 years; and Pu, with a half-life of 24,110 years. All other isotopes have half-lives of less than 7,000 years. This element also has eight metastable states , though all have half-lives less than

388-458: A multiplication factor (k eff ) larger than one, which means that if the metal is present in sufficient quantity and with an appropriate geometry (e.g., a sphere of sufficient size), it can form a critical mass . During fission, a fraction of the nuclear binding energy , which holds a nucleus together, is released as a large amount of electromagnetic and kinetic energy (much of the latter being quickly converted to thermal energy). Fission of

485-450: A nuclear chain reaction , leading to applications in nuclear weapons and nuclear reactors . Plutonium-240 has a high rate of spontaneous fission , raising the neutron flux of any sample containing it. The presence of plutonium-240 limits a plutonium sample's usability for weapons or its quality as reactor fuel, and the percentage of plutonium-240 determines its grade ( weapons-grade , fuel-grade, or reactor-grade). Plutonium-238 has

582-414: A vacuum or an inert atmosphere to avoid reaction with air. At 135 °C the metal will ignite in air and will explode if placed in carbon tetrachloride . Plutonium is a reactive metal. In moist air or moist argon , the metal oxidizes rapidly, producing a mixture of oxides and hydrides . If the metal is exposed long enough to a limited amount of water vapor, a powdery surface coating of PuO 2

679-591: A call from Canada and the United Kingdom for a conference on the subject. In June 1946, Bernard Baruch , an emissary of President Harry S. Truman , proposed the Baruch Plan before the United Nations Atomic Energy Commission, which called for an international system of controls on the production of atomic energy. The plan, which would serve as the basis for U.S. nuclear policy into the 1950s,

776-407: A comprehensive test ban (i.e., a ban on all tests, including those underground) in favor of a partial ban, which would be finalized on 25 July 1963. The PTBT, joined by 123 states following the original three parties, banned detonations for military and civilian purposes underwater, in the atmosphere, and outer space. The PTBT had mixed results. On the one hand, enactment of the treaty was followed by

873-510: A comprehensive test-ban treaty began in 1993. Extensive efforts were made over the next three years to draft the Treaty text and its two annexes. However, the Conference on Disarmament , in which negotiations were being held, did not succeed in reaching consensus on the adoption of the text. Under the direction of Prime Minister John Howard and Foreign Minister Alexander Downer , Australia then sent

970-431: A depth of 1000 m. Infrasound monitoring relies on changes in atmospheric pressure caused by a possible nuclear explosion, with 41 stations certified as of August 2019. One of the biggest concerns with infrasound measurements is noise due to exposure from wind, which can affect the sensor's ability to measure if an event occurred. Together, these technologies are used to monitor the ground, water, and atmosphere for any sign of

1067-500: A half-life of 87.7 years and emits alpha particles . It is a heat source in radioisotope thermoelectric generators , which are used to power some spacecraft . Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors. Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II that developed

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1164-431: A kilogram of plutonium-239 can produce an explosion equivalent to 21,000 tons of TNT (88,000  GJ ). It is this energy that makes plutonium-239 useful in nuclear weapons and reactors . The presence of the isotope plutonium-240 in a sample limits its nuclear bomb potential, as Pu has a relatively high spontaneous fission rate (~440 fissions per second per gram; over 1,000 neutrons per second per gram), raising

1261-463: A large range of temperatures (over 2,500 kelvin wide) at which plutonium is liquid, but this range is neither the greatest among all actinides nor among all metals, with neptunium theorized to have the greatest range in both instances. The low melting point as well as the reactivity of the native metal compared to the oxide leads to plutonium oxides being a preferred form for applications such as nuclear fission reactor fuel ( MOX-fuel ). Alpha decay ,

1358-426: A limited pressure range. These allotropes, which are different structural modifications or forms of an element, have very similar internal energies but significantly varying densities and crystal structures . This makes plutonium very sensitive to changes in temperature, pressure, or chemistry, and allows for dramatic volume changes following phase transitions from one allotropic form to another. The densities of

1455-490: A nuclear explosion. Radionuclide monitoring takes the form of either monitoring for radioactive particulates or noble gases as a product of a nuclear explosion. Radioactive particles emit radiation that can be measured by any of the 80 stations located throughout the world. They are created from nuclear explosions that can collect onto the dust that is moved from the explosion. If a nuclear explosion took place underground, noble gas monitoring can be used to verify whether or not

1552-587: A possible nuclear explosion took place. Noble gas monitoring relies on measuring increases in radioactive xenon gas. Different isotopes of xenon include Xe, Xe, Xe, and Xe. All four monitoring methods make up the International Monitoring System (IMS). Statistical theories and methods are integral to CTBT monitoring providing confidence in verification analysis. Once the Treaty enters into force, on-site inspections will be conducted where concerns about compliance arise. The Preparatory Commission for

1649-454: A reduction mechanism similar to FeO 4 , PuO 4 can be stabilized in alkaline solutions and chloroform . Metallic plutonium is produced by reacting plutonium tetrafluoride with barium , calcium or lithium at 1200 °C. Metallic plutonium is attacked by acids , oxygen , and steam but not by alkalis and dissolves easily in concentrated hydrochloric , hydroiodic and perchloric acids . Molten metal must be kept in

1746-493: A relatively short half-life, U decays to Np, which decays into Pu. Finally, exceedingly small amounts of plutonium-238, attributed to the extremely rare double beta decay of uranium-238, have been found in natural uranium samples. Due to its relatively long half-life of about 80 million years, it was suggested that plutonium-244 occurs naturally as a primordial nuclide , but early reports of its detection could not be confirmed. Based on its likely initial abundance in

1843-507: A second. Pu has been found in interstellar space and it has the longest half-life of any non-primordial radioisotope. The main decay modes of isotopes with mass numbers lower than the most stable isotope, Pu, are spontaneous fission and alpha emission , mostly forming uranium (92 protons ) and neptunium (93 protons) isotopes as decay products (neglecting the wide range of daughter nuclei created by fission processes). The main decay mode for isotopes heavier than Pu, along with Pu and Pu,

1940-600: A step towards the Nuclear Non-proliferation Treaty (NPT) of 1968, which directly referenced the PTBT. Under the NPT, non-nuclear weapon states were prohibited from possessing, manufacturing, and acquiring nuclear weapons or other nuclear explosive devices. All signatories, including nuclear weapon states, were committed to the goal of total nuclear disarmament . However, India , Pakistan , and Israel have declined to sign

2037-440: A substantial drop in the atmospheric concentration of radioactive particles. On the other hand, nuclear proliferation was not halted entirely (though it may have been slowed) and nuclear testing continued at a rapid clip. Compared to the 499 tests from 1945 to the signing of the PTBT, 436 tests were conducted over the ten years following the PTBT. Furthermore, US and Soviet underground testing continued "venting" radioactive gas into

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2134-466: A temporary prohibition on PNEs, but continued disagreements over the compliance mechanisms led to an end to negotiations ahead of Ronald Reagan 's inauguration as president in 1981. In 1985, Soviet leader Mikhail Gorbachev announced a unilateral testing moratorium, and in December 1986, Reagan reaffirmed US commitment to pursue the long-term goal of a comprehensive test ban. In November 1987, negotiations on

2231-615: A test ban restarted, followed by a joint US-Soviet program to research underground-test detection in December 1987. In October 2023, Russian president Vladimir Putin stated that since the United States had not ratified the CTBT, consideration could be given to withdrawing Russia's ratification of the treaty. Later in the month, a law revoking ratification of the CTBT was passed by the Russian parliament. On 2 November, Putin officially signed into law

2328-399: Is beta emission , forming americium isotopes (95 protons). Plutonium-241 is the parent isotope of the neptunium series , decaying to americium-241 via beta emission. Plutonium-238 and 239 are the most widely synthesized isotopes. Pu is synthesized via the following reaction using uranium (U) and neutrons (n) via beta decay (β ) with neptunium (Np) as an intermediate: Neutrons from

2425-490: Is plutonocene . Computational chemistry methods indicate an enhanced covalent character in the plutonium-ligand bonding. Powders of plutonium, its hydrides and certain oxides like Pu 2 O 3 are pyrophoric , meaning they can ignite spontaneously at ambient temperature and are therefore handled in an inert, dry atmosphere of nitrogen or argon. Bulk plutonium ignites only when heated above 400 °C. Pu 2 O 3 spontaneously heats up and transforms into PuO 2 , which

2522-417: Is a chemical element ; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized . The element normally exhibits six allotropes and four oxidation states . It reacts with carbon , halogens , nitrogen , silicon , and hydrogen . When exposed to moist air, it forms oxides and hydrides that can expand

2619-485: Is a radioactive actinide metal whose isotope , plutonium-239 , is one of the three primary fissile isotopes ( uranium-233 and uranium-235 are the other two); plutonium-241 is also highly fissile. To be considered fissile, an isotope's atomic nucleus must be able to break apart or fission when struck by a slow moving neutron and to release enough additional neutrons to sustain the nuclear chain reaction by splitting further nuclei. Pure plutonium-239 may have

2716-400: Is a treaty between two states. A bilateral treaty may become a multilateral treaty when additional new parties succeed or accede to it. Pope Francis argues in his encyclical letter Fratelli tutti (2020) that "preference should be given to multilateral agreements between states, because, more than bilateral agreements, they guarantee the promotion of a truly universal common good and

2813-429: Is formed. Also formed is plutonium hydride but an excess of water vapor forms only PuO 2 . Plutonium shows enormous, and reversible, reaction rates with pure hydrogen, forming plutonium hydride . It also reacts readily with oxygen, forming PuO and PuO 2 as well as intermediate oxides; plutonium oxide fills 40% more volume than plutonium metal. The metal reacts with the halogens , giving rise to compounds with

2910-460: Is in its α ( alpha ) form . This allotrope is about as hard and brittle as gray cast iron . When plutonium is alloyed with other metals, the high-temperature δ allotrope is stabilized at room temperature, making it soft and ductile. Unlike most metals, it is not a good conductor of heat or electricity . It has a low melting point (640 °C, 1,184 °F) and an unusually high boiling point (3,228 °C, 5,842 °F). This gives

3007-426: Is likely that Hahn and Strassmann were aware that plutonium-239 should be fissile. However, they did not have a strong neutron source. Element 93 was reported by Hahn and Strassmann, as well as Starke, in 1942. Hahn's group did not pursue element 94, likely because they were discouraged by McMillan and Abelson's lack of success in isolating it when they had first found element 93. However, since Hahn's group had access to

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3104-460: Is performed with a system of 50 primary stations located throughout the world, with 120 auxiliary stations in signatory states. Hydroacoustic monitoring is performed with a system of 11 stations that consist of hydrophone triads to monitor for underwater explosions. Hydroacoustic stations can use seismometers to measure T-waves from possible underwater explosions instead of hydrophones. The best measurement of hydroacoustic waves has been found to be at

3201-435: Is responsible for directional covalent bonds in molecules and complexes of plutonium. Plutonium can form alloys and intermediate compounds with most other metals. Exceptions include lithium, sodium , potassium , rubidium and caesium of the alkali metals ; and magnesium , calcium, strontium , and barium of the alkaline earth metals ; and europium and ytterbium of the rare earth metals . Partial exceptions include

3298-414: Is roughly as strong and malleable as aluminium. In fission weapons, the explosive shock waves used to compress a plutonium core will also cause a transition from the usual δ phase plutonium to the denser α form, significantly helping to achieve supercriticality . The ε phase, the highest temperature solid allotrope, exhibits anomalously high atomic self-diffusion compared to other elements. Plutonium

3395-402: Is stable in dry air, but reacts with water vapor when heated. Crucibles used to contain plutonium need to be able to withstand its strongly reducing properties. Refractory metals such as tantalum and tungsten along with the more stable oxides, borides , carbides , nitrides and silicides can tolerate this. Melting in an electric arc furnace can be used to produce small ingots of

3492-580: Is the element with the highest atomic number known to occur in nature. Trace quantities arise in natural uranium deposits when uranium-238 captures neutrons emitted by decay of other uranium-238 atoms. The heavy isotope plutonium-244 has a half-life long enough that extreme trace quantities should have survived primordially (from the Earth's formation) to the present, but so far experiments have not yet been sensitive enough to detect it. Both plutonium-239 and plutonium-241 are fissile , meaning they can sustain

3589-544: Is unusual for metals. This trend continues down to 100  K , below which resistivity rapidly decreases for fresh samples. Resistivity then begins to increase with time at around 20 K due to radiation damage, with the rate dictated by the isotopic composition of the sample. Because of self-irradiation, a sample of plutonium fatigues throughout its crystal structure, meaning the ordered arrangement of its atoms becomes disrupted by radiation with time. Self-irradiation can also lead to annealing which counteracts some of

3686-404: Is used in U.S. Navy weapons stored near ship and submarine crews, due to its lower radioactivity. Plutonium-238 is not fissile but can undergo nuclear fission easily with fast neutrons as well as alpha decay. All plutonium isotopes can be "bred" into fissile material with one or more neutron absorptions , whether followed by beta decay or not. This makes non-fissile isotopes of plutonium

3783-429: Is usually listed as watt/kilogram, or milliwatt/gram. In larger pieces of plutonium (e.g. a weapon pit) and inadequate heat removal the resulting self-heating may be significant. At room temperature, pure plutonium is silvery in color but gains a tarnish when oxidized. The element displays four common ionic oxidation states in aqueous solution and one rare one: The color shown by plutonium solutions depends on both

3880-457: The Cigar Lake Mine uranium deposit ranges from 2.4 × 10 to 44 × 10 . These trace amounts of Pu originate in the following fashion: on rare occasions, U undergoes spontaneous fission, and in the process, the nucleus emits one or two free neutrons with some kinetic energy. When one of these neutrons strikes the nucleus of another U atom, it is absorbed by the atom, which becomes U. With

3977-467: The Cold War is a nuclear-proliferation and environmental concern. Other sources of plutonium in the environment are fallout from many above-ground nuclear tests, which are now banned . Plutonium, like most metals, has a bright silvery appearance at first, much like nickel , but it oxidizes very quickly to a dull gray, though yellow and olive green are also reported. At room temperature plutonium

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4074-556: The Comprehensive Test Ban Treaty Organization (CTBTO), an international organization headquartered in Vienna , Austria, was created to build the verification framework, including establishment and provisional operation of the network of monitoring stations, the creation of an international data centre (IDC), and development of the on-site Inspection capability. The CTBTO is responsible for collecting information from

4171-453: The Manhattan Project , for developing an atomic bomb. The three primary research and production sites of the project were the plutonium production facility at what is now the Hanford Site ; the uranium enrichment facilities at Oak Ridge, Tennessee ; and the weapons research and design lab, now known as Los Alamos National Laboratory , LANL. The first production reactor that made Pu was

4268-502: The r-process in supernovae and colliding neutron stars ; when nuclei are ejected from these events at high speed to reach Earth, Pu alone among transuranic nuclides has a long enough half-life to survive the journey, and hence tiny traces of live interstellar Pu have been found in the deep sea floor. Because Pu also occurs in the decay chain of Pu, it must thus also be present in secular equilibrium , albeit in even tinier quantities. Minute traces of plutonium are usually found in

4365-469: The 6d and 5f subshells is very low. The size of the 5f shell is just enough to allow the electrons to form bonds within the lattice, on the very boundary between localized and bonding behavior. The proximity of energy levels leads to multiple low-energy electron configurations with near equal energy levels. This leads to competing 5f 7s and 5f 6d 7s configurations, which causes the complexity of its chemical behavior. The highly directional nature of 5f orbitals

4462-577: The IMS and distribute the analyzed and raw data to member states to judge whether or not a nuclear explosion occurred through the IDC. Parameters such as determining the location where a nuclear explosion or test took place is one of the things that the IDC can accomplish. If a member state chooses to assert that another state had violated the CTBT, they can request an on-site inspection to take place to verify. The monitoring network consists of 337 facilities located all over

4559-719: The International Monitoring System set up by the Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission. A North Korean test is believed to have taken place in January 2016, evidenced by an "artificial earthquake" measured as a magnitude 5.1 by the U.S. Geological Survey . The first successful North Korean hydrogen bomb test supposedly took place in September 2017. It was estimated to have an explosive yield of 120 kilotons. Multilateral treaty A bilateral treaty

4656-562: The NPT on the grounds that such a treaty is fundamentally discriminatory as it places limitations on states that do not have nuclear weapons while making no efforts to curb weapons development by declared nuclear weapons states. In 1974, a step towards a comprehensive test ban was made with the Threshold Test Ban Treaty (TTBT), ratified by the US and Soviet Union, which banned underground tests with yields above 150 kilotons. In April 1976,

4753-473: The PNET requires that states rely on national technical means of verification , share information on explosions, and grant on-site access to counterparties. The TTBT and PNET entered into force on 11 December 1990. In October 1977, the US, UK, and Soviet Union returned to negotiations over a test ban. These three nuclear powers made notable progress in the late 1970s, agreeing to terms on a ban on all testing, including

4850-535: The Solar System, present experiments as of 2022 are likely about an order of magnitude away from detecting live primordial Pu. However, its long half-life ensured its circulation across the solar system before its extinction , and indeed, evidence of the spontaneous fission of extinct Pu has been found in meteorites. The former presence of Pu in the early Solar System has been confirmed, since it manifests itself today as an excess of its daughters, either Th (from

4947-560: The Soviet Union would be able to covertly conduct underground tests during a test ban, as underground detonations were more challenging to detect than above-ground tests. On the Soviet side, conversely, the on-site compliance inspections demanded by the US and UK were seen as amounting to espionage. Disagreement over verification would lead to the Anglo-American and Soviet negotiators abandoning

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5044-507: The Western side, there were concerns that the Soviet Union would be able to circumvent any test ban and secretly leap ahead in the nuclear arms race . These fears were amplified following the US Rainier shot of 19 September 1957, which was the first contained underground test of a nuclear weapon. Though the US held a significant advantage in underground testing capabilities, there was worry that

5141-480: The X-10 reactor. Information from CP-1 was also useful to Met Lab scientists designing the water-cooled plutonium production reactors for Hanford. Construction at the site began in mid-1943. In November 1943 some plutonium trifluoride was reduced to create the first sample of plutonium metal: a few micrograms of metallic beads. Enough plutonium was produced to make it the first synthetically made element to be visible with

5238-486: The advantage of avoiding dealing directly with the highly reactive plutonium metal. Trace amounts of plutonium-238, plutonium-239, plutonium-240, and plutonium-244 can be found in nature. Small traces of plutonium-239, a few parts per trillion , and its decay products are naturally found in some concentrated ores of uranium, such as the natural nuclear fission reactor in Oklo , Gabon . The ratio of plutonium-239 to uranium at

5335-416: The alpha decay pathway) or xenon isotopes (from its spontaneous fission ). The latter are generally more useful, because the chemistries of thorium and plutonium are rather similar (both are predominantly tetravalent) and hence an excess of thorium would not be strong evidence that some of it was formed as a plutonium daughter. Pu has the longest half-life of all transuranic nuclides and is produced only in

5432-448: The atmosphere. Additionally, though underground testing was generally safer than above-ground testing, underground tests continued to risk the leaking of radionuclides , including plutonium , into the ground. From 1964 through 1996, the year of the CTBT's adoption, an estimated 1,377 underground nuclear tests were conducted. The final non-underground (atmospheric or underwater) test was conducted by China in 1980. The PTBT has been seen as

5529-399: The background neutron levels and thus increasing the risk of predetonation . Plutonium is identified as either weapons-grade , fuel-grade, or reactor-grade based on the percentage of Pu that it contains. Weapons-grade plutonium contains less than 7% Pu. Fuel-grade plutonium contains 7%–19%, and power reactor-grade contains 19% or more Pu. Supergrade plutonium , with less than 4% of Pu,

5626-504: The complicated phase diagram are not entirely understood. The α form has a low-symmetry monoclinic structure, hence its brittleness, strength, compressibility, and poor thermal conductivity. Plutonium in the δ ( delta ) form normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium , aluminium , or cerium , enhancing workability and allowing it to be welded . The δ form has more typical metallic character, and

5723-513: The detonation resulted in fallout that spread over inhabited areas and sickened a group of Japanese fishermen. Between 1945 and 1963, the US conducted 215 atmospheric tests, the Soviet Union conducted 219, the UK conducted 21, and France conducted 4. In 1954, following the Castle Bravo test, Prime Minister Jawaharlal Nehru of India issued the first appeal for a "standstill agreement" on testing, which

5820-427: The different allotropes vary from 16.00 g/cm to 19.86 g/cm . The presence of these many allotropes makes machining plutonium very difficult, as it changes state very readily. For example, the α form exists at room temperature in unalloyed plutonium. It has machining characteristics similar to cast iron but changes to the plastic and malleable β ( beta ) form at slightly higher temperatures. The reasons for

5917-440: The fatigue effects as temperature increases above 100 K. Unlike most materials, plutonium increases in density when it melts, by 2.5%, but the liquid metal exhibits a linear decrease in density with temperature. Near the melting point, the liquid plutonium has very high viscosity and surface tension compared to other metals. Plutonium normally has six allotropes and forms a seventh (zeta, ζ) at high temperature within

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6014-581: The first atomic bombs. The Fat Man bombs used in the Trinity nuclear test in July 1945, and in the bombing of Nagasaki in August 1945, had plutonium cores . Human radiation experiments studying plutonium were conducted without informed consent , and several criticality accidents , some lethal, occurred after the war. Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during

6111-499: The first self-sustaining chain reaction in a graphite and uranium pile known as CP-1 . Using theoretical information garnered from the operation of CP-1, DuPont constructed an air-cooled experimental production reactor, known as X-10 , and a pilot chemical separation facility at Oak Ridge. The separation facility, using methods developed by Glenn T. Seaborg and a team of researchers at the Met Lab, removed plutonium from uranium irradiated in

6208-558: The first transuranic element neptunium after the planet Neptune , and suggested that element 94, being the next element in the series, be named for what was then considered the next planet, Pluto . Nicholas Kemmer of the Cambridge team independently proposed the same name, based on the same reasoning as the Berkeley team. Seaborg originally considered the name "plutium", but later thought that it did not sound as good as "plutonium". He chose

6305-482: The fission of uranium-235 are captured by uranium-238 nuclei to form uranium-239; a beta decay converts a neutron into a proton to form neptunium-239 (half-life 2.36 days) and another beta decay forms plutonium-239. Egon Bretscher working on the British Tube Alloys project predicted this reaction theoretically in 1940. Plutonium-238 is synthesized by bombarding uranium-238 with deuterons (D or H,

6402-407: The general formula PuX 3 where X can be F , Cl , Br or I and PuF 4 is also seen. The following oxyhalides are observed: PuOCl, PuOBr and PuOI. It will react with carbon to form PuC , nitrogen to form PuN and silicon to form PuSi 2 . The organometallic chemistry of plutonium complexes is typical for organoactinide species; a characteristic example of an organoplutonium compound

6499-611: The globe. As of May 2012, more than 260 facilities have been certified. The monitoring stations register data that is transmitted to the international data centre in Vienna for processing and analysis. The data are sent to states that have signed the Treaty. Three countries have tested nuclear weapons since the CTBT opened for signature in 1996. India and Pakistan both carried out two sets of tests in 1998. North Korea carried out six announced tests, one each in 2006, 2009, 2013, two in 2016 and one in 2017. All six North Korean tests were picked up by

6596-586: The human body due to the 550 atmospheric and underwater nuclear tests that have been carried out, and to a small number of major nuclear accidents . Most atmospheric and underwater nuclear testing was stopped by the Limited Test Ban Treaty in 1963, which of the nuclear powers was signed and ratified by the United States, United Kingdom and Soviet Union . France would continue atmospheric nuclear testing until 1974 and China would continue atmospheric nuclear testing until 1980. All subsequent nuclear testing

6693-527: The letters "Pu" as a joke, in reference to the interjection "P U" to indicate an especially disgusting smell, which passed without notice into the periodic table. Alternative names considered by Seaborg and others were "ultimium" or "extremium" because of the erroneous belief that they had found the last possible element on the periodic table . Hahn and Strassmann, and independently Kurt Starke , were at this point also working on transuranic elements in Berlin. It

6790-524: The limited nature of a plurilateral treaty, the full cooperation of the parties to the treaty is required in order for the object of the treaty to be met. As a result, reservations to plurilateral treaties are not allowed without the consent of all other parties to the treaty. This principle is codified in international law by article 20(2) of the Vienna Convention on the Law of Treaties : When it appears from

6887-477: The limited number of the negotiating states and the object and purpose of a treaty that the application of the treaty in its entirety between all the parties is an essential condition of the consent of each one to be bound by the treaty, a reservation requires acceptance by all the parties. An example of a plurilateral treaty is the Antarctic Treaty , signed on 1 December 1959. Plutonium Plutonium

6984-449: The metal without the need for a crucible. Cerium is used as a chemical simulant of plutonium for development of containment, extraction, and other technologies. Plutonium is an element in which the 5f electrons are the transition border between delocalized and localized; it is therefore considered one of the most complex elements. The anomalous behavior of plutonium is caused by its electronic structure. The energy difference between

7081-448: The nuclei of heavy hydrogen ) in the following reaction: where a deuteron hitting uranium-238 produces two neutrons and neptunium-238, which decays by emitting negative beta particles to form plutonium-238. Plutonium-238 can also be produced by neutron irradiation of neptunium-237 . Plutonium isotopes undergo radioactive decay, which produces decay heat . Different isotopes produce different amounts of heat per mass. The decay heat

7178-454: The oxidation state and the nature of the acid anion . It is the acid anion that influences the degree of complexing —how atoms connect to a central atom—of the plutonium species. Additionally, the formal +2 oxidation state of plutonium is known in the complex [K(2.2.2-cryptand)] [Pu Cp″ 3 ], Cp″ = C 5 H 3 (SiMe 3 ) 2 . A +8 oxidation state is possible as well in the volatile tetroxide PuO 4 . Though it readily decomposes via

7275-406: The protection of weaker states. A plurilateral treaty is a special type of multilateral treaty. A plurilateral treaty is a treaty between a limited number of states with a particular interest in the subject of the treaty. The primary difference between a plurilateral treaty and other multilateral treaties is that the availability of reservations is more limited under a plurilateral treaty. Due to

7372-473: The refractory metals chromium , molybdenum , niobium , tantalum, and tungsten, which are soluble in liquid plutonium, but insoluble or only slightly soluble in solid plutonium. Gallium, aluminium, americium, scandium and cerium can stabilize δ-phase plutonium for room temperature. Silicon , indium , zinc and zirconium allow formation of metastable δ state when rapidly cooled. High amounts of hafnium , holmium and thallium also allows some retention of

7469-412: The release of a high-energy helium nucleus, is the most common form of radioactive decay for plutonium. A 5 kg mass of Pu contains about 12.5 × 10 atoms. With a half-life of 24,100 years, about 11.5 × 10 of its atoms decay each second by emitting a 5.157  MeV alpha particle. This amounts to 9.68 watts of power. Heat produced by the deceleration of these alpha particles makes it warm to

7566-493: The sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric . It is radioactive and can accumulate in bones , which makes the handling of plutonium dangerous. Plutonium was first synthesized and isolated in late 1940 and early 1941, by deuteron bombardment of uranium-238 in the 1.5-metre (60 in) cyclotron at the University of California, Berkeley . First, neptunium-238 ( half-life 2.1 days)

7663-416: The stronger cyclotron at Paris at this point, they would likely have been able to detect plutonium had they tried, albeit in tiny quantities (a few becquerels ). The chemistry of plutonium was found to resemble uranium after a few months of initial study. Early research was continued at the secret Metallurgical Laboratory of the University of Chicago . On August 20, 1942, a trace quantity of this element

7760-666: The text to the United Nations General Assembly in New York , where it was submitted as a draft resolution. On 10 September 1996, the Comprehensive Test-Ban Treaty (CTBT) was adopted by a large majority, exceeding two-thirds of the General Assembly's Membership. (Article I): The Treaty was adopted by the United Nations General Assembly on 10 September 1996. It opened for signature in New York on 24 September 1996, when it

7857-402: The touch. Pu due to its much shorter half life heats up to much higher temperatures and glows red hot with blackbody radiation if left without external heating or cooling. This heat has been used in radioisotope thermoelectric generators (see below). The resistivity of plutonium at room temperature is very high for a metal, and it gets even higher with lower temperatures, which

7954-591: The treaty: China, Egypt, Iran, Israel and the United States have signed but not ratified the Treaty; India, North Korea and Pakistan have not signed it; while Russia signed and ratified the treaty but subsequently withdrew its ratification prior to its entry into force. Geophysical and other technologies are used to monitor for compliance with the Treaty: forensic seismology , hydroacoustics, infrasound , and radionuclide monitoring. The first three forms of monitoring are known as wave-form measurements. Seismic monitoring

8051-528: The two states reached agreement on the Peaceful Nuclear Explosions Treaty (PNET), which concerns nuclear detonations outside the weapons sites discussed in the TTBT. As in the TTBT, the US and Soviet Union agreed to bar peaceful nuclear explosions (PNEs) at these other locations with yields above 150 kilotons, as well as group explosions with total yields over 1,500 kilotons. To verify compliance,

8148-410: The unaided eye. The nuclear properties of plutonium-239 were also studied; researchers found that when it is hit by a neutron it breaks apart (fissions) by releasing more neutrons and energy. These neutrons can hit other atoms of plutonium-239 and so on in an exponentially fast chain reaction. This can result in an explosion large enough to destroy a city if enough of the isotope is concentrated to form

8245-542: The various organs. Hamilton started administering soluble microgram portions of plutonium-239 compounds to rats using different valence states and different methods of introducing the plutonium (oral, intravenous, etc.). Eventually, the lab at Chicago also conducted its own plutonium injection experiments using different animals such as mice, rabbits, fish, and even dogs. The results of the studies at Berkeley and Chicago showed that plutonium's physiological behavior differed significantly from that of radium. The most alarming result

8342-489: The withdrawal of ratification of the treaty. Given the political situation prevailing in the subsequent decades, little progress was made in nuclear disarmament until the end of the Cold War in 1991. Parties to the PTBT held an amendment conference that year to discuss a proposal to convert the Treaty into an instrument banning all nuclear-weapon tests. With strong support from the UN General Assembly, negotiations for

8439-448: The δ phase at room temperature. Neptunium is the only element that can stabilize the α phase at higher temperatures. Plutonium alloys can be produced by adding a metal to molten plutonium. If the alloying metal is reductive enough, plutonium can be added in the form of oxides or halides. The δ phase plutonium–gallium alloy (PGA) and plutonium–aluminium alloy are produced by adding Pu(III) fluoride to molten gallium or aluminium, which has

8536-471: Was conducted underground. Enrico Fermi and a team of scientists at the University of Rome reported that they had discovered element 94 in 1934. Fermi called the element hesperium and mentioned it in his Nobel Lecture in 1938. The sample actually contained products of nuclear fission , primarily barium and krypton . Nuclear fission, discovered in Germany in 1938 by Otto Hahn and Fritz Strassmann ,

8633-496: Was created directly by the bombardment but decayed by beta emission with a half-life of a little over two days, which indicated the formation of element 94. The first bombardment took place on December 14, 1940, and the new element was first identified through oxidation on the night of February 23–24, 1941. A paper documenting the discovery was prepared by the team and sent to the journal Physical Review in March 1941, but publication

8730-610: Was delayed until a year after the end of World War II due to security concerns. At the Cavendish Laboratory in Cambridge , Egon Bretscher and Norman Feather realized that a slow neutron reactor fuelled with uranium would theoretically produce substantial amounts of plutonium-239 as a by-product. They calculated that element 94 would be fissile, and had the added advantage of being chemically different from uranium, and could easily be separated from it. McMillan had recently named

8827-426: Was isolated and measured for the first time. About 50 micrograms of plutonium-239 combined with uranium and fission products was produced and only about 1 microgram was isolated. This procedure enabled chemists to determine the new element's atomic weight. On December 2, 1942, on a racket court under the west grandstand at the University of Chicago's Stagg Field, researchers headed by Enrico Fermi achieved

8924-711: Was rejected by the Soviet Union as a US ploy to cement its nuclear dominance. Between the Trinity nuclear test of 16 July 1945 and the signing of the Partial Test Ban Treaty (PTBT) on 5 August 1963, 499 nuclear tests were conducted. Much of the impetus for the PTBT, the precursor to the CTBT, was rising public concern surrounding the size and resulting nuclear fallout from underwater and atmospheric nuclear tests, particularly tests of powerful thermonuclear weapons (hydrogen bombs). The Castle Bravo test of 1 March 1954, in particular, attracted significant attention as

9021-584: Was signed by 71 states, including five of the eight then nuclear-capable states . As of March 2024, 178 states have ratified the CTBT and another nine states have signed but not ratified it. The treaty will enter into force 180 days after the 44 states listed in Annex 2 of the treaty have ratified it. These "Annex 2 states" are states that participated in the CTBT's negotiations between 1994 and 1996 and possessed nuclear power reactors or research reactors at that time. As of 2023, nine Annex 2 states have not ratified

9118-473: Was soon echoed by the British Labour Party . Negotiations on a comprehensive test ban, primarily involving the US, UK, and the Soviet Union, began in 1955 following a proposal by Soviet leader Nikita Khrushchev . Of primary concern throughout the negotiations, which would stretch—with some interruptions—to July 1963, was the system of verifying compliance with the test ban and detecting illicit tests. On

9215-431: Was synthesized, which then beta-decayed to form the new element with atomic number 94 and atomic weight 238 (half-life 88 years). Since uranium had been named after the planet Uranus and neptunium after the planet Neptune , element 94 was named after Pluto , which at the time was also considered a planet. Wartime secrecy prevented the University of California team from publishing its discovery until 1948. Plutonium

9312-400: Was that there was significant deposition of plutonium in the liver and in the "actively metabolizing" portion of bone. Furthermore, the rate of plutonium elimination in the excreta differed between species of animals by as much as a factor of five. Such variation made it extremely difficult to estimate what the rate would be for human beings. During World War II the U.S. government established

9409-562: Was unknown at the time. Plutonium (specifically, plutonium-238) was first produced, isolated and then chemically identified between December 1940 and February 1941 by Glenn T. Seaborg , Edwin McMillan , Emilio Segrè , Joseph W. Kennedy , and Arthur Wahl by deuteron bombardment of uranium in the 60-inch (150 cm) cyclotron at the Berkeley Radiation Laboratory at the University of California, Berkeley . Neptunium-238

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