The isotopes of plutonium range in atomic weight from 228.0387u (228Pu) to 247.074u (247Pu). While it was still by no means clear that enough plutonium could be produced for use in bombs by the war's end, Hanford was by early 1945 in operation. Isotopes with multiple decay schemes are represented by a range of half-life values between the shortest and longest half-life for that type of decay. One study investigated the effects of transuranium elements (plutonium-238, plutonium-239, plutonium-240) on various fish living in the Chernobyl Exclusion Zone (CEZ). [9] This trend continues down to 100K, below which resistivity rapidly decreases for fresh samples. Plutonium-240 contamination has proven a mixed blessing to nuclear weapons design. [10] Self-irradiation can also lead to annealing which counteracts some of the fatigue effects as temperature increases above 100K.[11], 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. The energy difference between the 6d and 5f subshells is very low. in this question were told about the scenario. Plutonium-239 is one of the three fissile materials used for the production of nuclear weapons and in some nuclear reactors as a source of energy. Supergrade plutonium, with less than 4% of plutonium-240, is used in U.S. Navy weapons stored in proximity to ship and submarine crews, due to its lower radioactivity. [14], Cerium is used as a chemical simulant of plutonium for development of containment, extraction, and other technologies. Ed. Uranium-238 is present in quantity in most reactor fuel; hence plutonium-239 is continuously made in these reactors. [92][note 7], An identical design was used in the "Fat Man" atomic bomb dropped on Nagasaki, Japan, on August 9, 1945, killing 35,00040,000 people and destroying 68%80% of war production at Nagasaki. The transmutation and decay chain is shown below: Neutron capture may also be used to create fissile 239Pu from 238U, the dominant constituent of naturally occurring uranium (99.28%). Plutonium is mostly produced in nuclear reactors. [127] An earlier version of the same technology powered five Apollo Lunar Surface Experiment Packages, starting with Apollo 12 in 1969. Enriched uranium, by contrast, can be used with either method. [122] It emits a large amount of thermal energy with low levels of both gamma rays/photons and spontaneous neutron rays/particles. Los Alamos received its first plutonium from Hanford on February 2. After the elapse of second half-life (another 14 billion . [37] Alpha particles generated by inhaled plutonium have been found to cause lung cancer in a cohort of European nuclear workers. [7][8] 238Pu 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. Plutonium-238 Identification. Investigating the toxicity of plutonium in humans is just as important as looking at the effects in fauna of marine systems. Thus only 6.2kg of plutonium was needed for an explosive yield equivalent to 20 kilotons of TNT. [37][note 5], In January 1944, workers laid the foundations for the first chemical separation building, T Plant located in 200-West. The highly directional nature of 5f orbitals is responsible for directional covalent bonds in molecules and complexes of plutonium. 23: 177233. The tests were used to create diagnostic tools to determine the uptake of plutonium in the body in order to develop safety standards for working with plutonium. Special precautions are necessary to store or handle plutonium in any form; generally a dry inert gas atmosphere is required. In larger pieces of plutonium (e.g. This element also has eight meta states; all have half-lives of less than one second. [61] Fermi called the element hesperium and mentioned it in his Nobel Lecture in 1938. [6][21], Plutonium-238 and 239 are the most widely synthesized isotopes. For scale, the universe itself has only been around for less than 14 billion years. [54], Due to its relatively long half-life of about 80million years, it was suggested that plutonium-244 occurs naturally as a primordial nuclide, but early reports of its detection could not be confirmed. The mixture is not sufficiently enriched for efficient nuclear weapons, but can be used once as MOX fuel. 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 laboratory, now known as Los Alamos National Laboratory. You will get a decay curve From that you can determine how long i. [13], The presence of these many allotropes makes machining plutonium very difficult, as it changes state very readily. One isotope of plutonium, Pu-239, has a half-life of 24,100 years . This isotope has a half-life of 24,100 years, causing concern in regions where radioactive plutonium has accumulated and is stored. when smelling something bad. You measure the amount of radioactivity emitted by that sample at various time intervals. Most forms of plutonium emit alpha particles, which are not very harmful outside the body, but can be very damaging when inhaled. 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. [75][note 4] 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 the first self-sustaining chain reaction in a graphite and uranium pile known as CP-1. All of the remaining radioactive isotopes have half-lives that are less than 7,000 years. All UAB radioactive materials licensees are required to submit inventories to the Radiation Safety Program quarterly, . Plutonium (Pu) isotopes are neutron activation or decay products formed during irradiation of U in a nuclear reactor and, therefore, are an important constituent of radioactive waste. The difficulty in measuring the particular Po-209 half-life arises from its scarcity in pure form, the long length of its half-life, and the specific types of radiation involved in its decay. The separation building in 200-East, B Plant, was completed in February 1945. Once in the bloodstream, plutonium moves throughout the body and into the bones, liver, or other body organs. Let our team find you the perfect tutor. For example, the half-life of carbon-14 is 5730 years. [36] Molten metal must be kept in a vacuum or an inert atmosphere to avoid reaction with air. [40], 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. If a sample of a tree (for example) contains 64 grams (g) of radioactive carbon after 5,730 years it will contain 32 g, after another. Plutonium-239 is the most important isotope of plutonium [citation needed], with a half-life of 24,100 years. The committee issued a controversial 1995 report which said that "wrongs were committed" but it did not condemn those who perpetrated them. 242Pu's gamma ray emissions are also weaker than those of the other isotopes.[10]. In plutonium that has been used a second time in thermal reactors in MOX fuel, 240Pu may even be the most common isotope. ", "Did Ralph Nader say that a pound of plutonium could cause 8 billion cancers? [31] It is the acid anion that influences the degree of complexinghow atoms connect to a central atomof the plutonium species. Uranium isotopes produce plutonium-239 as a decay product. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. The term is most commonly used in relation to atoms undergoing radioactive decay, but can be used to describe other types of decay, whether exponential or not. [86], By the end of January 1945, the highly purified plutonium underwent further concentration in the completed chemical isolation building, where remaining impurities were removed successfully. Several unique features of plutonium-238 have made it the material of choice to help produce electrical power for more than two-dozen U.S. space missions that have been enabled by radioisotope power systems (RPS). Only two years had passed since Col. Franklin Matthias first set up his temporary headquarters on the banks of the Columbia River. 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). For high burnup used fuel, the concentrations of the higher plutonium isotopes will be higher than the low burnup fuel that is reprocessed to obtain weapons grade plutonium. Plutonium was first synthetically produced and isolated in late 1940 and early 1941, by a deuteron bombardment of uranium-238 in the 1.5-metre (60in) cyclotron at the University of California, Berkeley. A dedicated reactor operating on very low burnup (hence minimal exposure of newly formed plutonium-239 to additional neutrons which causes it to be transformed to heavier isotopes of plutonium) is generally required to produce material suitable for use in efficient nuclear weapons. Questions & Answers. Different isotopes produce different amounts of heat per mass. Dave - So that means that if you're breaking plutonium down into something which has a half-life of only 300 years, that's definitely improving the radioactive danger and pollution problem. [37] The glass is made of borosilicates mixed with cadmium and gadolinium. In radioactivity, the half-life is the time taken by a specific amount of a . The half-life of each element is constant. The other fissile materials are uranium-235 and uranium-233. . [9], 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. Washington, DC. The known isotopes of plutonium range in mass number from 228 to 247. 432.2 years . Radionuclide Half-Life Measurements NIST Standard Reference Database 120 The data that formerly appeared here has been superseded by the data that now appears on DDEP. The half-life of carbon-14 is 5,730 y. Carbon-11 is a radioactive isotope used in positron emission tomography (PET) scans for medical diagnosis. Heat produced by the deceleration of these alpha particles makes it warm to the touch. [37] The U.S. planned to store plutonium in this way at the Yucca Mountain nuclear waste repository, which is about 100 miles (160km) north-east of Las Vegas, Nevada.[103]. The second facility planned for 200-East was canceled. Half lives range from millionths of a second for highly radioactive fission . [140], Plutonium is more dangerous when inhaled than when ingested. Typically these primordial radioisotopes have half-lives so long they are stable for all practical purposes, but when they decay they form what are called secondary radionuclides. Simply by changing the neighboring atoms that are . Like any radioactive isotopes, plutonium isotopes transform when they decay. If a radioisotope has a half-life of 14 days, half of its atoms will have decayed within 14 days. [66], A paper documenting the discovery was prepared by the team and sent to the journal Physical Review in March 1941,[37] but publication was delayed until a year after the end of World War II due to security concerns. It has a half-life of 28.1 yr. (a) Calculate the first-order rate constant for the nuclear decay. 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. [55] However, its long half-life ensured its circulation across the solar system before its extinction,[56] and indeed, evidence of the spontaneous fission of extinct 244Pu has been found in meteorites. [50] The ratio of plutonium-239 to uranium at the Cigar Lake Mine uranium deposit ranges from 2.41012 to 441012. Since plutonium-239 can itself be split by neutrons to release energy, plutonium-239 provides a portion of the energy generation in a nuclear reactor. Inside the safe were various items, including a large glass bottle containing a whitish slurry which was subsequently identified as the oldest sample of weapons-grade plutonium known to exist. 241Pu has a half-life of 14 years, and has slightly higher thermal neutron cross sections than 239Pu for both fission and absorption. [76], On April 5, 1944, Emilio Segr at Los Alamos received the first sample of reactor-produced plutonium from Oak Ridge. Further neutron capture creates 237U, which has a half-life of 7 days and thus quickly decays to 237Np. . Plutonium metal is made by reducing plutonium tetrafluoride with calcium. [36] Plutonium is not absorbed into the body efficiently when ingested; only 0.04% of plutonium oxide is absorbed after ingestion. Radioactive half-life is the time required for a quantity of a radioisotope to decay by half. [note 9] These logs are planned to be encased in stainless steel and stored as much as 4km (2mi) underground in bore holes that will be back-filled with concrete. Each radioactive nuclide has a characteristic, constant half-life ( t1/2 ), the time required for half of the atoms in a sample to decay. Challenges in Plutonium Science", "Plutonium: an historical overview. Since nearly all neptunium is produced in this way or consists of isotopes that decay quickly, one gets nearly pure 237Np by chemical separation of neptunium. Half-life (in years) 87.74: 24,110: . While it created delays and headaches during the Manhattan Project because of the need to develop implosion technology, those same difficulties are currently a barrier to nuclear proliferation. Bell one has 100,000 atoms off some sort off radioactive isotope. [57] The former presence of 244Pu in the early Solar System has been confirmed, since it manifests itself today as an excess of its daughters, either 232Th (from the alpha decay pathway) or xenon isotopes (from its spontaneous fission). [83], The entire plutonium weapon design effort at Los Alamos was soon changed to the more complicated implosion device, code-named "Fat Man". Plutonium-238 is a special material that emits steady heat due to its natural radioactive decay. In a type of radioactive decay called "electron capture", the nucleus absorbs one of the atom's electrons and combines it with a proton to make a neutron and a neutrino. It is a product of the transmutation and subsequent nuclear decay of fertile isotope 238 U. These characteristics make it well-suited for electrical power generation for devices that must function without direct maintenance for timescales approximating a human lifetime. The longest-lived are plutonium-244, with a half-life of 80.8million years, plutonium-242, with a half-life of 373,300years, and plutonium-239, with a half-life of 24,110years. The U.S. reactors at Hanford and the Savannah River Site in South Carolina produced 103tonnes,[96] and an estimated 170tonnes of military-grade plutonium was produced in the USSR. For example, the half-life uranium-238 (238 U) is 4.5 billion years and the . Bismuth-212 ; 60.55 minute s . It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. . The half-life of a radioactive element is the time taken for: the activity to halve the number of parent nuclei to halve the mass of the parent nuclei to halve The activity of a radioactive. [10] It also reacts readily with oxygen, forming PuO and PuO2 as well as intermediate oxides; plutonium oxide fills 40% more volume than plutonium metal. [note 6] B, D and F were the initial reactors built at Hanford, and six additional plutonium-producing reactors were built later at the site. [7] Plutonium-239 is synthesized via the following reaction using uranium (U) and neutrons (n) via beta decay () with neptunium (Np) as an intermediate:[22], Neutrons from 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 2.36days) and another beta decay forms plutonium-239. Plutonium that reaches body organs generally stays in the body for decades and continues to expose the surrounding tissue to radiation and thus may cause cancer. The risk of lung cancer increases once the total radiation dose equivalent of inhaled plutonium exceeds 400 mSv. It is a transuranic element with the atomic number 94. [112] Other experiments directed by the United States Atomic Energy Commission and the Manhattan Project continued into the 1970s. There was a major plutonium-initiated fire at the, Calculated from the atomic weight and the atomic volume. [24] Seaborg originally considered the name "plutium", but later thought that it did not sound as good as "plutonium". The half-life is the amount of time it takes for a given isotope to lose half of its radioactivity. MOX fuel is used in light water reactors and consists of 60kg of plutonium per tonne of fuel; after four years, three-quarters of the plutonium is burned (turned into other elements). 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 alpha particles can kill lung cells, which causes scarring of the lungs, leading to further lung disease and cancer. The half-life of plutonium-244 is 80,000,000 years. [137] Plutonium passes only slowly through cell membranes and intestinal boundaries, so absorption by ingestion and incorporation into bone structure proceeds very slowly. [37], Plutonium-238 has also been used successfully to power artificial heart pacemakers, to reduce the risk of repeated surgery. Barium-133 ; 10.74 years . [78], During World War II the U.S. government established the Manhattan Project, which was tasked with developing an atomic bomb. [116] In September 2000, the United States and the Russian Federation signed a Plutonium Management and Disposition Agreement by which each agreed to dispose of 34tonnes of weapons-grade plutonium. Plutonium-239 is virtually nonexistent in nature. [70] He chose 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. Strotium90, a radioactive isotope, is a major product of an atomic bomb explosion. Careless handling of tungsten carbide bricks around a 6.2kg plutonium sphere resulted in a fatal dose of radiation at Los Alamos on August 21, 1945, when scientist Harry Daghlian received a dose estimated to be 5.1sievert (510rems) and died 25days later. [151] Plutonium in solution is more likely to form a critical mass than the solid form due to moderation by the hydrogen in water. --modified from Webster's Third International Dictionary, Unabridged . Molybdenum-99 ; 66 hours . REFERENCES [1]. In other words, the half-life of an isotope is the amount of time it takes for half of a group of unstable isotopes to decay to a stable isotope. Substances with shorter half-lives decay more quickly than those with longer half-lives, so they emit more energetic radioactivity. [142] Ingestion or inhalation of large amounts may cause acute radiation poisoning and possibly death. [87] Most of this radioactive contamination over the years were part of normal operations, but unforeseen accidents did occur and plant management kept this secret, as the pollution continued unabated. Gamma radiation can go all the way through the body. If the half-life of an isotope is relatively long, e.g. [10], Plutonium can form alloys and intermediate compounds with most other metals. Suppose we have 100.0 g of tritium (a radioactive isotope of hydrogen). [13] As much as 1000tonnes of plutonium may be in storage with more than 200tonnes of that either inside or extracted from nuclear weapons. Superintendent of Documents US Government Printing Office. Although they conducted their work at It has machining characteristics similar to cast iron but changes to the plastic and malleable (beta) form at slightly higher temperatures. [132] Plutonium-238 mixed with beryllium is used to generate neutrons for research purposes. The resistivity of plutonium at room temperature is very high for a metal, and it gets even higher with lower temperatures, which is unusual for metals. [109], The isotope plutonium-239 is a key fissile component in nuclear weapons, due to its ease of fission and availability. [138][139] Donald Mastick accidentally swallowed a small amount of Plutonium(III) chloride, which was detectable for the next thirty years of his life, but appeared to suffer no ill effects. [49] Enough plutonium was produced to make it the first synthetically made element to be visible with the unaided eye. No fission products have a half-life in the range of 100a210ka 239Pu, a fissile isotope that is the second most used nuclear fuel in nuclear reactors after uranium-235, and the most used fuel in the fission portion of nuclear weapons, is produced from uranium-238 by neutron capture followed by two beta decays. This page was last edited on 24 February 2023, at 17:27. Twenty radioactive isotopes of plutonium have been characterized. The half-life of plutonium-240 is 6,560 years. Because 240Pu also occurs in the decay chain of 244Pu, it must thus also be present in secular equilibrium, albeit in even tinier quantities. [91] About 20% of the plutonium used in the Trinity weapon underwent fission, resulting in an explosion with an energy equivalent to approximately 20,000 tons of TNT. Defining the Half-life of a Radioisotope. Pu-239 has a half-life of 24,100 years and Pu-241's half-life is 14.4 years. One half-life is the time it takes for half of the unstable atoms to undergo radioactive decay. 241Pu accounts for a significant proportion of fissions in thermal reactor fuel that has been used for some time. [120], Plutonium recovered from spent reactor fuel poses little proliferation hazard, because of excessive contamination with non-fissile plutonium-240 and plutonium-242. Both the T Plant and its sister facility in 200-West, the U Plant, were completed by October. [136] The skeleton, where plutonium accumulates, and the liver, where it collects and becomes concentrated, are at risk. [121] The "reactor-grade" plutonium produced by a regular LWR burnup cycle typically contains less than 60% Pu-239, with up to 30% parasitic Pu-240/Pu-242, and 1015% fissile Pu-241. Undeveloped eggs have a higher risk than developed adult fish exposed to the element in these waste areas. When plutonium particles are inhaled, they lodge in the lung tissue. This page was last edited on 14 February 2023, at 04:04. Isotopic compositions and standard atomic masses from: Half-life, spin, and isomer data selected from the following sources. The most important is plutonium-239 because it is fissionable, has a relatively long half-life (24,110 years), and can be readily produced in large quantities in breeder reactors by neutron irradiation of plentiful but nonfissile uranium-238. [145], Several populations of people who have been exposed to plutonium dust (e.g. Magnesium oxide sand is probably the most effective material for extinguishing a plutonium fire. Some radioisotopes have very long half-lives, some have very short half-lives. Beta radiation can penetrate human skin, but cannot go all the way through the body. It was originally used to describe the decay of radioactive elements like uranium or plutonium, but it can be used for any substance which undergoes decay along a set, or exponential, rate. Natural abundance The greatest source of plutonium is the irradiation of uranium in nuclear reactors. Weapons-grade plutonium contains less than 7% plutonium-240. Used on its own in. Additionally, the formal +2 oxidation state of plutonium is known in the complex [K(2.2.2-cryptand)] [PuIICp3], Cp = C5H3(SiMe3)2. Plutonium-239 and plutonium-240 are formed in nuclear power plants when uranium-238 captures neutrons. Each element has its own half-life * Each element decays into a new element C14 decays into N14 4. The desire to consume this plutonium and other transuranic fuels and reduce the radiotoxicity of the waste is the usual reason nuclear engineers give to make fast neutron reactors. From that it is a simple calculation to get the half-life (or any other fraction you might care to use). The contamination of the Denver area by plutonium from the fires and other sources was not publicly reported until the 1970s. [49] The implosion design of "the gadget", as the Trinity device was code-named, used conventional explosive lenses to compress a sphere of plutonium into a supercritical mass, which was simultaneously showered with neutrons from the "Urchin", an initiator made of polonium and beryllium (neutron source: (, n) reaction). Find tutors who specialize in courses. A fuel rod is reprocessed after three years of use to remove waste products, which by then account for 3% of the total weight of the rods. Plutonium-240 undergoes spontaneous fission as a secondary decay mode at a small but significant rate (5.8106%). The earth is about 4.5 10 9 years old. The higher plutonium isotopes are created when the uranium fuel is used for a long time. [119], MOX fuel improves total burnup. ", "The Nuclear Energy Option, Chapter 13, Plutonium and Bombs", "What We Have Learned About Plutonium from Human Data", "Impact of Environmental Radiation on the Health and Reproductive Status of Fish from Chernobyl", "The Toxicity of Uranium and Plutonium to the Developing Embryos of Fish", "The Lessons of Nuclear Secrecy at Rocky Flats", " 71.63 Special requirement for plutonium shipments", "Two British ships arrive in Japan to carry plutonium to US", "Two British ships arrive in Japan to transport plutonium for storage in U.S.", "Klassekampen: Flyr plutonium med rutefly", Stockholm International Peace Research Institute, "Alsos Digital Library for Nuclear Issues - Plutonium", "A Perspective on the Dangers of Plutonium", "Physical, Nuclear, and Chemical, Properties of Plutonium", https://en.wikipedia.org/w/index.php?title=Plutonium&oldid=1141357745, silvery white, tarnishing to dark gray in air, Very high decay heat. [7][note 2] Nicholas Kemmer of the Cambridge team independently proposed the same name, based on the same reasoning as the Berkeley team. . The plutonium can be used in nuclear weapons and is a power source for nuclear reactors, which generate electricity. [123] Being an alpha emitter, it combines high energy radiation with low penetration and thereby requires minimal shielding. Under some models, the universe itself will no longer exist. There are small amounts of 238Pu in the plutonium of usual plutonium-producing reactors. Prevailing winds from the plant carried airborne contamination south and east, into populated areas northwest of Denver. A typical transport consists of one truck carrying one protected shipping container, holding a number of packages with a total weight varying from 80 to 200kg of plutonium oxide. Plutonium has no known biological role. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. [36] Partial exceptions include the refractory metals chromium, molybdenum, niobium, tantalum, and tungsten, which are soluble in liquid plutonium, but insoluble or only slightly soluble in solid plutonium. [37] The first bombardment took place on December 14, 1940, and the new element was first identified through oxidation on the night of February 2324, 1941. The efficiency calculation is based on the fact that 1kg of plutonium-239 (or uranium-235) fissioning results in an energy release of approximately 17, Much of this plutonium was used to make the fissionable cores of a type of thermonuclear weapon employing the. Example 1 - Carbon-14 has a half-life of 5.730 years. [10] The densities of the different allotropes vary from 16.00g/cm3 to 19.86g/cm3. Even with massive concrete lids on the process pools, precautions against radiation exposure were necessary and influenced all aspects of plant design. Naturally occurring uranium-238 present in the Earth's crust has a half-life of almost 4.5 billion years. Plutonium-238 Half-Life. It is made by bombarding uranium-238 with neutrons in a nuclear reactor. In: Challenges in Plutonium Science", "Kate Brown: Nuclear "Plutopias" the Largest Welfare Program in American History", "BBC NEWS Science & Environment US nuclear relic found in bottle", "8.1.1 The Design of Gadget, Fat Man, and "Joe 1" (RDS-1)", "The Yields of the Hiroshima and Nagasaki Explosions", "Proliferation of Nuclear Weapons and Materials to State and Non-State Actors: What It Means for the Future of Nuclear Power", "Historic American Engineering Record: B Reactor (105-B Building)", Stockholm International Peace Research Institute 2007, "Nuclear waste won't be going to Nevada's Yucca Mountain, Obama official says", "Disposal Subcommittee Report to the Full Commission", "The Human Plutonium Injection Experiments", "Injected! A Closer Look at Half-Life Radioactive Decay Chains All of the remaining radioactive isotopes have half-lives that are less than 7,000years. 240Pu does have a moderate thermal neutron absorption cross section, so that 241Pu production in a thermal reactor becomes a significant fraction as large as 239Pu production.
