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46-623: KAMINI is the world's first thorium-based experimental reactor . It is cooled and moderated by light water, fueled with uranium -233 metal produced by the thorium fuel cycle harnessed by the neighbouring FBTR reactor and produces 30 KW of thermal energy at full power. Bhabha Atomic Research Centre (BARC) set up a large infrastructure to facilitate the design and development of these advanced heavy water reactors . Things to be included range from materials technologies, critical components, reactor physics, and safety analysis. Several facilities have been set up to experiment with these reactors. The AHWR

92-433: A greater risk of nuclear proliferation versus comparable light-water reactors due to the low neutron absorption properties of heavy water, discovered in 1937 by Hans von Halban and Otto Frisch . Occasionally, when an atom of U is exposed to neutron radiation , its nucleus will capture a neutron , changing it to U . The U then rapidly undergoes two β decays — both emitting an electron and an antineutrino ,

138-439: A light-water moderator depends on the exact geometry and other design parameters of the reactor. One complication of this approach is the need for uranium enrichment facilities, which are generally expensive to build and operate. They also present a nuclear proliferation concern; the same systems used to enrich the U can also be used to produce much more "pure" weapons-grade material (90% or more U), suitable for producing

184-403: A lower neutron capture cross section than protium , this value isn't zero and thus part of the heavy water moderator will inevitably be converted to tritiated water . While tritium , a radioactive isotope of hydrogen, is also produced as a fission product in minute quantities in other reactors, tritium can more easily escape to the environment if it is also present in the cooling water, which

230-412: A nuclear weapon . This is not a trivial exercise by any means, but feasible enough that enrichment facilities present a significant nuclear proliferation risk. An alternative solution to the problem is to use a moderator that does not absorb neutrons as readily as water. In this case potentially all of the neutrons being released can be moderated and used in reactions with the U, in which case there

276-405: A built in cooling system, multiple shutdown systems and a fail-safe procedure that consist of a poison that shuts down the system in the case of a technical failure (FBR). The potential threat scientists try to avoid in reactors is the buildup of heat because nuclear energy escalates when it reacts with high temperatures, high pressures and chemical reactions. The AHWR has features that helps reduce

322-483: A chain reaction with the small isolated U nuclei in the fuel, thus precluding criticality in natural uranium. Because of this, a light-water reactor will require that the U isotope be concentrated in its uranium fuel, as enriched uranium , generally between 3% and 5% U by weight (the by-product from this process enrichment process is known as depleted uranium , and so consisting mainly of U, chemically pure). The degree of enrichment needed to achieve criticality with

368-412: A chemical (thorium is a toxic heavy metal ) and - to a lesser extent - radiological issue which would be solved at least in part by use of thorium in nuclear power plants. Unlike uranium , which actually contains 0.72% of fissile U material, thorium is composed almost only out of fertile Th which can be transmutated into fissile U using thermal neutrons . This allows

414-407: A high probability of absorbing neutrons with intermediate kinetic energy levels, a reaction known as "resonance" absorption. This is a fundamental reason for designing reactors with separate solid fuel segments, surrounded by the moderator, rather than any geometry that would give a homogeneous mix of fuel and moderator. Water makes an excellent moderator; the ordinary hydrogen or protium atoms in

460-582: A large low temperature heat sink around the reactor core. The AHWR incorporates several passive safety features. These include: Core heat removal through natural circulation; direct injection of emergency core coolant system (ECCS) water in fuel; and the availability of a large inventory of borated water in overhead gravity-driven water pool (GDWP) to facilitate sustenance of core decay heat removal. The emergency core cooling system (ECCS) injection and containment cooling can act ( SCRAM ) without invoking any active systems or operator action. The reactor physics design

506-415: A mixture of various isotopes , primarily U and a much smaller amount (about 0.72% by weight) of U . U can only be fissioned by neutrons that are relatively energetic, about 1 MeV or above. No amount of U can be made "critical" since it will tend to parasitically absorb more neutrons than it releases by the fission process. U, on the other hand, can support a self-sustained chain reaction, but due to

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552-690: A moderator roughly equals the temperature of the moderator) than in traditional designs, where the moderator normally is much hotter. The neutron cross section for fission is higher in U the lower the neutron temperature is, and thus lower temperatures in the moderator make successful interaction between neutrons and fissile material more likely. These features mean that a PHWR can use natural uranium and other fuels, and does so more efficiently than light water reactors (LWRs). CANDU type PHWRs are claimed to be able to handle fuels including reprocessed uranium or even spent nuclear fuel from "conventional" light water reactors as well as MOX fuel and there

598-422: A much larger share of the original material to be used without the need for fast breeder reactors and while producing orders of magnitude less minor actinides . However, as thorium itself is not fissile, it has to be "bred" first to obtain a fissile material, which can then be used in the same reactor that "bred" the U or chemically separated for use in a separate "burner" reactor. The proposed design of

644-509: A pressure of 7 MPa , heat is then removed. The main focus with this model is to get the total power and a coarse spatial power distribution within the core to be within certain degree of accuracy. The reactor design incorporates advanced technologies, together with several proven positive features of Indian pressurised heavy water reactors (PHWRs). These features include pressure tube type design, low pressure moderator, on-power refueling, diverse fast acting shut-down systems, and availability of

690-508: A suitable moderator due to overlooking impurities and thus made unsuccessful attempts using heavy water (which they correctly identified as an excellent moderator). The Soviet nuclear program likewise used graphite as a moderator and ultimately developed the graphite moderated RBMK as a reactor capable of producing both large amounts of electric power and weapons grade plutonium without the need for heavy water or - at least according to initial design specifications - uranium enrichment . Pu

736-434: Is enough U in natural uranium to sustain criticality. One such moderator is heavy water , or deuterium-oxide. Although it reacts dynamically with the neutrons in a fashion similar to light water (albeit with less energy transfer on average, given that heavy hydrogen, or deuterium , is about twice the mass of hydrogen), it already has the extra neutron that light water would normally tend to absorb. The use of heavy water as

782-420: Is a fissile material suitable for use in nuclear weapons . As a result, if the fuel of a heavy-water reactor is changed frequently, significant amounts of weapons-grade plutonium can be chemically extracted from the irradiated natural uranium fuel by nuclear reprocessing . In addition, the use of heavy water as a moderator results in the production of small amounts of tritium when the deuterium nuclei in

828-493: Is a stub . You can help Misplaced Pages by expanding it . This article about an Indian building or structure is a stub . You can help Misplaced Pages by expanding it . Pressurised heavy water reactor A pressurized heavy-water reactor ( PHWR ) is a nuclear reactor that uses heavy water ( deuterium oxide D 2 O) as its coolant and neutron moderator . PHWRs frequently use natural uranium as fuel, but sometimes also use very low enriched uranium . The heavy water coolant

874-459: Is a large tank of water on top of the primary containment vessel, called the gravity-driven water pool (GDWP). This reservoir is designed to perform several passive safety functions . The overall design of the AHWR is to utilize large amounts of thorium and the thorium cycle . The AHWR is much like that of the pressurized heavy water reactor (PHWR), in that they share similarities in the concept of

920-426: Is a pressure tube type of heavy water reactor. The Government of India , Department of Atomic Energy (DAE), is fully funding the future development, the current development, and the design of the advanced heavy water reactor. The new version of advanced heavy water reactors will be equipped with more general safety requirements. India is the base for these reactors due to India's large thorium reserves; therefore, it

966-486: Is an innovation in renewable energy safety as it will limit the use of fissile uranium-235 to breeding fissile uranium-233 from fertile thorium-232. The extraction of nuclear energy from the 90th element thorium is said to have more energy than the world's oil, coal, and uranium combined. The AHWR has safety features that distinguish it from conventional lightwater nuclear reactors. Some of these features consist of: strong safety systems, reduction of heat from core through

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1012-404: Is kept under pressure to avoid boiling, allowing it to reach higher temperature (mostly) without forming steam bubbles, exactly as for a pressurized water reactor (PWR). While heavy water is very expensive to isolate from ordinary water (often referred to as light water in contrast to heavy water ), its low absorption of neutrons greatly increases the neutron economy of the reactor, avoiding

1058-569: Is more geared for continual use and operation of the AHWR. Thorium is three times more abundant in the Earth's crust than uranium, though less abundant in terms of economically viable to extract proven reserves, with India holding the largest proven reserves of any country. A lot of thorium is also contained in the tailings of mines that extract rare earth elements from monazite which usually contains both rare earth elements and thorium. As long as demand for thorium remains low, these tailings present

1104-453: Is normally accomplished by use of an on-power refuelling system. The increased rate of fuel movement through the reactor also results in higher volumes of spent fuel than in LWRs employing enriched uranium. Since unenriched uranium fuel accumulates a lower density of fission products than enriched uranium fuel, however, it generates less heat, allowing more compact storage. While deuterium has

1150-540: Is ongoing research into the ability of CANDU type reactors to operate exclusively on such fuels in a commercial setting. (More on that in the article on the CANDU reactor itself) Pressurised heavy-water reactors do have some drawbacks. Heavy water generally costs hundreds of dollars per kilogram, though this is a trade-off against reduced fuel costs. The reduced energy content of natural uranium as compared to enriched uranium necessitates more frequent replacement of fuel; this

1196-605: Is primed for high burn up with thorium -based fuel (BARC, 2013). Recycled thorium that is recovered from the reactor is then sent back, and plutonium is stored to be later used for a fast breeder reactor . The fuel for AHWR would be manufactured by the Advanced Fuel Fabrication Facility , which is under the direction of Bhabha Atomic Research Centre (BARC) Tarapur. AFFF is currently working on PFBR fuel rod production. AFFF has been associated with fuel rod fabrication for other research purposes in

1242-432: Is the bulk of natural uranium is also fissionable with fast neutrons.) This requires the use of a neutron moderator , which absorbs virtually all of the neutrons' kinetic energy , slowing them down to the point that they reach thermal equilibrium with surrounding material. It has been found beneficial to the neutron economy to physically separate the neutron energy moderation process from the uranium fuel itself, as U has

1288-530: Is the case in those PHWRs which use heavy water both as moderator and as coolant. Some CANDU reactors separate out the tritium from their heavy water inventory at regular intervals and sell it at a profit, however. While with typical CANDU derived fuel bundles, the reactor design has a slightly positive Void coefficient of reactivity, the Argentina designed CARA fuel bundles used in Atucha I , are capable of

1334-498: Is the world's only thorium-based experimental reactor . KAMINI was the first and is currently the only reactor in the world designed specifically to use uranium-233 fuel. Use of the large thorium reserves to produce nuclear fuel is a key strategy of India's nuclear energy program . 12°33′30″N 80°10′30″E  /  12.55833°N 80.17500°E  / 12.55833; 80.17500 This article about nuclear power and nuclear reactors for power generation

1380-532: Is tuned to maximise the use of thorium based fuel, by achieving a slightly negative void coefficient . Fulfilling these requirements has been possible through the use of PuO 2 -ThO 2 MOX, and ThO 2 -UO 2 MOX in different pins of the same fuel cluster, and the use of a heterogeneous moderator consisting of amorphous carbon (in the fuel bundles) and heavy water in 80–20% volume ratio. The core configuration lends itself to considerable flexibility and several feasible solutions, including those not requiring

1426-540: The AHWR is that of a heavy-water-moderated nuclear power reactor that will be the next generation of the PHWR type. It is being developed at Bhabha Atomic Research Centre (BARC), in Mumbai, India and aims to meet the objectives of using thorium fuel cycles for commercial power generation. The AHWR is a vertical pressure tube type reactor cooled by boiling light water under natural circulation. A unique feature of this design

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1472-565: The PHWR family. The key to maintaining a nuclear chain reaction within a nuclear reactor is to use, on average, exactly one of the neutrons released from each nuclear fission event to stimulate another nuclear fission event (in another fissionable nucleus). With careful design of the reactor's geometry, and careful control of the substances present so as to influence the reactivity , a self-sustaining chain reaction or " criticality " can be achieved and maintained. Natural uranium consists of

1518-513: The first one transmuting the U into Np , and the second one transmuting the Np into Pu . Although this process takes place with natural uranium using other moderators such as ultra-pure graphite or beryllium, heavy water is by far the best. The Manhattan Project ultimately used graphite moderated reactors to produce plutonium, while the German wartime nuclear project wrongfully dismissed graphite as

1564-403: The heavy water absorb neutrons, a very inefficient reaction. Tritium is essential for the production of boosted fission weapons , which in turn enable the easier production of thermonuclear weapons , including neutron bombs . This process is currently expected to provide (at least partially) tritium for ITER . The proliferation risk of heavy-water reactors was demonstrated when India produced

1610-486: The involvement of uranium-235 reactors and the poor structures of the facilities they were in. Since then, International Atomic nuclear Association has stepped up protocols in nuclear facilities in order to prevent these accidents from occurring again. One of the top security measures for a meltdown is containment of radioactivity from escaping the reactor. The Defence in Depth is a method used in nuclear facilities to acquire

1656-401: The low natural abundance of U, natural uranium cannot achieve criticality by itself. The trick to achieving criticality using only natural or low enriched uranium, for which there is no "bare" critical mass , is to slow down the emitted neutrons (without absorbing them) to the point where enough of them may cause further nuclear fission in the small amount of U which is available. ( U which

1702-483: The moderator is the key to the PHWR (pressurized heavy water reactor) system, enabling the use of natural uranium as the fuel (in the form of ceramic UO 2 ), which means that it can be operated without expensive uranium enrichment facilities. The mechanical arrangement of the PHWR, which places most of the moderator at lower temperatures, is particularly efficient because the resulting thermal neutrons have lower energies ( neutron temperature after successive passes through

1748-473: The most effective practice of radioactive containment. The AWHR has acquired the Defense in Depth process which is used in reactors adopting provisions and required equipment in order to retain the radioactivity within the core. The Defense in Depth method establishes procedures that must be followed in order to reduce human error incidents and machine malfunctions. The procedures are the following: The AWHR

1794-411: The need for enriched fuel . The high cost of the heavy water is offset by the lowered cost of using natural uranium and/or alternative fuel cycles . As of the beginning of 2001, 31 PHWRs were in operation, having a total capacity of 16.5 GW(e), representing roughly 7.76% by number and 4.7% by generating capacity of all current operating reactors. CANDU and IPHWR are the most common type of reactors in

1840-496: The past. AFFF is the only nuclear fuel production facility in the world which has dealt with uranium, plutonium and thorium. The Indian Government announced in 2013 it would build an AHWR of 300 MWe with its location to be decided. As of 2017, the design was in the final stages of validation. Past nuclear meltdowns such as Chernobyl disaster and Fukushima nuclear accident have made the improvement of construction and maintenance of facilities to be crucial. These accidents were with

1886-483: The preferred negative coefficient. While prior to India's development of nuclear weapons (see below), the ability to use natural uranium (and thus forego the need for uranium enrichment which is a dual use technology) was seen as hindering nuclear proliferation, this opinion has changed drastically in light of the ability of several countries to build atomic bombs out of plutonium, which can easily be produced in heavy water reactors. Heavy-water reactors may thus pose

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1932-635: The pressure tubes and calandria tubes, but the tubes' orientation in the AHWR is vertical , unlike that of the PHWR. The AHWR's core is 3.5 m long and has 513 lattice locations in a square pitch of 225 mm. The core is radially divided into three burn up regions. The burn up decreases as it moves toward the external surface of the core. Fuel is occupied by 452 lattice locations and the remaining 37 locations are occupied by shutdown system-1. This consists of 37 shut-off rods, 24 locations are for reactive control devices which are consisted of 8 absorber rods, 8 shim rods, and 8 regulating rods. By boiling light water at

1978-688: The probability of this occurrence through: negative reactivity coefficients, low power density, low excess reactivity in the core and proper selection of material attributes built in. Ring 2: (Th, U)MOX/3.75 Ring 3: (Th, Pu)MOX/ 4.0 (Lower half) 2.5 (Upper half) Passive : Isolation Condenser in Gravity Driven Water Pool KAMINI KAMINI (Kalpakkam Mini reactor) is a research reactor at Indira Gandhi Center for Atomic Research in Kalpakkam , India . It achieved criticality on October 29, 1996. It

2024-402: The use of amorphous carbon based reflectors, are possible without any changes in reactor structure. The AHWR at standard is set to be a closed nuclear fuel cycle because this will lead to reduction in radio-toxicity. Because of this, the AHWR has alternate fuel options, given it has diverse fuel cycles. It can do closed types and once-through types of fuel cycles. The overall aspect of the AHWR

2070-415: The water molecules are very close in mass to a single neutron, and so their collisions result in a very efficient transfer of momentum, similar conceptually to the collision of two billiard balls. However, as well as being a good moderator, ordinary water is also quite effective at absorbing neutrons. And so using ordinary water as a moderator will easily absorb so many neutrons that too few are left to sustain

2116-506: Was designed and built jointly by the Bhabha Atomic Research Centre (BARC) and Indira Gandhi Centre for Atomic Research (IGCAR). it produces 30 kW of thermal energy at full power. KAMINI is cooled and moderated by light water, uses a beryllium oxide neutron reflector, and is fueled with uranium-233 metal produced by the thorium fuel cycle harnessed by the neighbouring FBTR reactor. As of 2006 , it

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