light water reactor pros and conslight water reactor pros and cons

deuterium. [2] Heat carried iu\!}FRzm78,$Z&l*"k!OEVW2BQ CwrDN] `4QRTa=69b@P)|fB#2u8niX Very much operating experience has been accumulated and the designs and procedures have been largely optimized. After this process, the water is pumped back to the majority of all Western nuclear power plants. Usually there are also other means of controlling reactivity. Glasstone, Sesonske. basic power cycles in nuclear power plants. High burnup results in a lower mass of spent fuel discharged per unit of electricity generated, reducing spent fuel handling and transportation. Currently, only Russia, China, India, and Japan have operational breeder reactors. Pressurized water reactors (PWRs) make up the As Sellafield chief operating officer Rebecca Weston shared during the 2020 IAEA Scientific Forum, the UK is currently building Advanced Gas Reactors (AGR), which represent generation II of British gas-cooled reactors, developed from earlier generation I Magnox gas-cooled reactors. They also have the potential for enhanced safety and security compared to earlier designs. hb```a``c`e`ja`@ +s`,^n't0utHDP${xP/3I2c|"^g7U#av 0000005400 00000 n These cookies will be stored in your browser only with your consent. 0000000016 00000 n created inside the core of the reactor. Proposed Non-Light-Water Reactors Not Clearly Safer and Will Likely Take Decades to Achieve Reliable Commercial Operation. The use of ordinary water makes it necessary to do a certain amount of enrichment of the uranium fuel before the necessary criticality of the reactor can be maintained. The BWRX-300 produces no carbon during operation and has been . While ordinary water has some heavy water molecules in it, it is not enough to be important in most applications. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading,MA (1983). The energy choices we make today could make or break our ability to fight climate change. This core is surrounded by a shield of the uranium isotope U-238. Since the amount of separative work units (SWUs) is not a linear function of enrichment, it is more expensive to enrich higher enrichments. [2] It is however the first aqueous homogeneous reactor and the first reactor using enriched uranium as fuel and ordinary water as a moderator.[1]. primary system transfers the heat to the steam generator, where the <<758F2FC90BE263469D3E9017AC3F93B3>]/Prev 70177>> For instance, to produce one kilogram of uranium enriched to: But there are also operational aspects of high burnup fuels associated especially with the reliability of such fuel. 2 Brattle Square, Cambridge MA 02138, USA In both cases we use water as both our coolant and neutron moderator. Advanced nuclear technologies like the BWRX-300 are a key pillar of GE's energy transition leadership. NF Z R6'Z;TZ-9 [[( turbine and the attached electrical generator. Nuclear Energy in the 12st Century, 1st Ed. But What Is It. The major differences in the LWRs make up more than 80 percent of the worlds nuclear reactors, and more than three-quarters of the LWRs are PWRs. This differentiates it from a heavy water reactor, which uses heavy water as a neutron moderator. The removed fuel stored in the storage pool not only is highly radioactive but also continues to produce energy (referred to as decay heat). Most of the worlds existing reactors are power reactors, providing the heat needed to turn turbines that run electric-power generators. to carbon steel, can get melted into the coolant causing radioactive Experimental prototypes of both the American and German designs were built and operated from the 1960s to the 1980s, but by the early 1990s, they had resulted in no orders for commercial plants. The light-water reactor produces heat by controlled nuclear fission. the past two decades and are responsible for over 70% of non greenhouse Fission in the Context of Pressurized Water Reactors. major advantage of this reactor is that it is easy to operate because In May 1944, the first grams of enriched uranium ever produced reached criticality in the low power (LOPO) reactor at Los Alamos, which was used to estimate the critical mass of U235 to produce the atomic bomb. attribution to the author, for noncommercial purposes only. Updates? In the two types of Light Water [2] Light water can only work as a moderator in certain situations, as it absorbs too many neutrons to be used with uranium that is unenriched, so uranium enrichment is necessary to operate reactors that use light water as the moderator. Normal water that contains the hydrogen-1 isotope called 36 0 obj <>stream The heat is carried away from the reactor and is then used to generate steam. For the most common types of reactors the tubes are assembled into bundles with the tubes spaced precise distances apart. Ultimately, this fuel will be transferred to the U.S. Department of Energy for reprocessing or waste disposal or both, though a viable disposal program has not yet been established. Demand Congress invest in a clean energy future. These factors must be considered because they can lead to a decrease in operational reliability. core heats water, but does not boil it. In either case, after flowing through the turbines, the steam turns back into water in the condenser. The four leading SMR designs are: mPower Reactor by Charlotte, NC-headquartered . with pellets of substances such as hafnium or cadmium that are In general, LWR's are divided into two categories: Pressurized water reactors (PWR) - are characterized by the high-pressure primary circuit (to keep the water in a liquid state) Introduction @F3> * J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1. Nuclear Engineering and Design (1996) . PWRs are very stable and is easier to operate as long as there is power being provided. endstream endobj 12 0 obj <> endobj 13 0 obj <> endobj 14 0 obj <>/Font<>/ProcSet[/PDF/Text]>> endobj 15 0 obj <> endobj 16 0 obj <> endobj 17 0 obj <> endobj 18 0 obj <>stream A light water reactor uses normal water as the moderator that cools the reactor and produces the steam that powers the turbines Light water reactors require uranium to be enriched from 2.5-3.5% for the reaction to be contained in a nuclear reactor *Heavy water reactors Used in Canada Uses "heavy water" l_ v(M responsible for removing excess heat from the steam, which allows the The uranium oxide is dried before inserting into the tubes to try to eliminate moisture in the ceramic fuel that can lead to corrosion and hydrogen embrittlement. The main concerns associated with high burnup of fuels are: Strategic management and decision-making regarding the middle part of nuclear fuel cycles is a very specific problem of power engineering. The industry's multimillion-dollar PR campaign has resulted in only two new Westinghouse AP1000 light-water reactors (in the foreground of the photo above), which are still under construction in Georgia with a price tag of $14 billion eachdouble their estimated costand taking more than twice their estimated completion time. Utilities schedule maintenance and reload during the spring and fall, when electricity demand is lowest and the electrical grid usually has reserve capacity. 1, water is pumped under high pressure to the reactor core where it The power grid makes modern life possiblebut its also holding us back. [1] Although the Light water reactors (LWR's) come in two distinct flavours, the PWR ( pressurised water reactor) and the BWR ( boiling water reactor ). touch or mix, so there is no chance for contamination. Tell Congress we need electric vehicle infrastructure nationwide. Addison-Wesley Pub. The control rods are partially removed from the core to allow a chain reaction to occur. Although this is its major fuel, the uranium 238 atoms also contribute to the fission process by converting to plutonium 239; about one-half of which is consumed in the reactor. The water in the secondary loop enters the steam generator at a pressure and temperature slightly below that required to initiate boiling. less power is being produced as the heat increases. This technology does not contribute to air pollution, except during the mining and processing of uranium ore. Breeder reactors use a small core, which is important to sustain chain reactions. Besides, they do not even need moderators for slowing down neutrons, as they use fast neutrons. [3] In addition, the For example, last fall the Department of Energy (DOE) gave both TerraPower and X-Energy, developer of a high-temperature, gas-cooled pebble-bed reactor, $80 million grants to begin operating first-of-a-kind commercial units by 2027, most likely at the Columbia Generating Station site in Washington. The longer residence in the reactor requires a higher corrosion resistance. In fact, according to the UCS report, sodium-cooled fast reactors such as the Natrium would likely be less uranium-efficient. They would not reduce the amount of waste that requires long-term isolation in a geologic repository. ;z-L~gtq{p( Report Finds That Advanced Nuclear Reactor Designs Are No Better Than Current Reactorsand Some Are Worse. In the PWR, water at high pressure and temperature removes heat from the core and is transported to a steam generator. because all of our regulation is based on light water reactors. The Light Water Reactor Sustainability (LWRS) Program is working on It powers communities in 28 U.S. states and contributes to many non-electric applications, ranging from the medical field to space exploration. Climate change is one of the most devastating problems humanity has ever facedand the clock is running out. is heated by the energy generated by the fission of atoms. Light-water reactors are refueled by removing the reactor headafter lowering and unlatching the safety rods in the case of a PWR. The nuclear reactions take place Light water can be used as a moderator in certain reactors, mainly pressurized water reactors and boiling water reactors. We are a 501(c)(3) nonprofit organization. The saturated steam that exits the core region is transported through a series of separators and dryers located within the reactor vessel that promote a superheated state. material than is required for them to go prompt critical". back into water in the condenser. rights, including commercial rights, are reserved to the author. The remaining assemblies are then shifted within the core, and finally fresh assemblies are loaded into the empty positions. Light-water reactors (LWRs) are power reactors that are cooled and moderated with ordinary water. Breeder reactors use highly enriched fuels, which pose the danger of critical accidents. primary and secondary loops are separate, water can never be There are two basic types: the pressurized-water reactor (PWR) and the boiling-water reactor (BWR). The framework includes metrics such as fuel efficiency, spent fuel toxicity . In the German system, the helium passes through interstices in the bed of the spherical fuel elements, whereas in the American system, it passes through holes in the graphite prisms that align along the axis of the core region in the reactor vessel. It is mandatory to procure user consent prior to running these cookies on your website. Learn more. Let us have a look at the pros and cons of breeder reactors. 0000001124 00000 n The reactor vessel is filled to the top with water, and, since the core is near the bottom of the vessel, the water acts as a shield for the operators. [3] The purpose of this experiment was to determine the feasibility of a nuclear reactor using light water as a moderator and coolant, and cladded solid uranium as fuel. In light water reactors, there exists a thick-walled pressure vessel that contains the nuclear fuel and the moderator and coolant water circulates among the fuel rods to slow neutrons and carry away thermal energy. Help strengthen scientific integrity at federal agencies. in the nuclear reactor core, where the nuclear fuel components are Light-water reactors (LWRs) are power reactors that are cooled and moderated with ordinary water. The Office of Nuclear Energy within the U.S. Department of Energy (DOE) focuses its research primarily on maintaining the existing fleet of reactors . products to circulate throughout the loop. Sign up to receive the latest and greatest articles from our site automatically each week (give or take)right to your inbox. Deployment of advanced SMRs can help drive economic growth. Committee on Future Nuclear Power, Economic Simplified Boiling Water Reactor (ESBWR), "Federation of American Scientists - Early reactor", "ORNL - An Account of Oak Ridge National Laboratory's Thirteen Nuclear Reactors", "ORNL - History of the X10 Graphite Reactor", "INEL - MTR handbook Appendix F (historical backgroup)", "DOE oral history presentation program - Interview of LITR operator transcript", "Tech Guru's PlanFight Climate Change with Nuclear Power", "European Nuclear Society - Light water reactor", Light Water Reactor Sustainability (LWRS) Program, https://en.wikipedia.org/w/index.php?title=Light-water_reactor&oldid=1098042862, This page was last edited on 13 July 2022, at 23:16. A benefit (crucial aspect for some operators) is that loading the high burnup assemblies in the periphery reduces the. The light-water reactor uses uranium 235 as a fuel, enriched to approximately 3 percent. It also calls on Congress to require the DOE to convene an independent commission to review the technical merits of all proposed non-light-water reactors and only approve projects with a high likelihood of commercialization that are clearly safer and more secure than the current fleet. Both standard light-water designs are fueled with uranium dioxide pellets in zirconium alloy cladding (see above Fuel types). This heat converts water in the exchanges into steam, which is used to drive a turbine and generate electricity. 0000003783 00000 n This website uses cookies to improve your experience while you navigate through the website. PWR fuel bundles are about 4 meters in length. [8] Along with the SECURE reactor,[9] it relied on passive measures, not requiring operator actions or external energy supplies, to provide safe operation. After sufficient impacts, the velocity of the neutron will be comparable to the thermal velocities of the nuclei; this neutron is then called a thermal neutron. Light water is simply ordinary water that does not contain large amounts of deuterium, making it distinct from heavy water. core of the reactor contains less fissile material, decreasing the Physics of Nuclear Kinetics. cool water that is flowing through the tubes in the condenser is In nuclear fission reactors, the neutrons must be slowed down to ensure an effective fission chain reaction occurs. protium. 0000004889 00000 n The Power Grid Is a Top Climate Solution. The high-temperature gas-cooled reactor (HTGR), as mentioned above in Fuel types, is fueled by a mixture of graphite and fuel-bearing microspheres. [2] Lastly, By continuing, you accept our use of cookies. Do You Know Which African American Inventor Created Which Product? There are several safety benefits that come from using light water as a moderator. The steam-water mixture leaves In the PWR design a soluble neutron absorber, usually boric acid, is added to the reactor coolant allowing the complete extraction of the control rods during stationary power operation ensuring an even power and flux distribution over the entire core. developing the currently operating facilities to operate beyond the There are two basic types: the pressurized-water reactor (PWR) and the boiling-water reactor (BWR). After the discoveries of fission, moderation and of the theoretical possibility of a nuclear chain reaction, early experimental results rapidly showed that natural uranium could only undergo a sustained chain reaction using graphite or heavy water as a moderator. In the PWR, water at high pressure and temperature removes heat from the core and is transported to a steam generator. 0000000816 00000 n Generally, the fuel bundles consist of fuel rods bundled 14x14 to 17x17. Cant breed new fuel susceptible to uranium shortage. This process of slowing neutrons down is known as moderation, and the material that slows down these neutrons is known as a neutron moderator. steam to condense. The simplest of these light water reactors is the boiling water reactor. water is kept under high pressure,allowing it to be heated to higher temperatures without boiling,like in pressurised water reactor. Some studies show that soon, even with the present enrichment limit (5 wt %), fuel burnup could be extended near to 70 MWd/kg. [4] In light water reactors, there exists a thick-walled pressure vessel that contains the nuclear fuel and the moderator and coolant water circulates among the fuel rods to slow neutrons and carry away thermal energy.[4]. Williams. In boiling water reactors, the fuel is similar to PWR fuel except that the bundles are "canned"; that is, there is a thin tube surrounding each bundle. Since it reuses fuel, the expenses for mining, and processing of uranium ore are minimized. Light-water reactors (LWRs) are power reactors that are cooled and moderated with ordinary water. 24," August 2012, p. 28. Higher burnup fuels require higher initial enrichment to sustain reactivity. Some developers promise that they can demonstrate, license and deploy their non-light-water reactors on a commercial scale as early as the end of this decade, enabling them to address the climate crisis in the near term. It requires liquefied sodium or potassium metal as a coolant, as water would slow down the neutrons. This is primarily done to prevent local density variations from affecting neutronics and thermal hydraulics of the nuclear core on a global scale. FA bow can increase control rods drop time due to friction between control rod and bowed guide tubes. January 1993. This capability is known as a negative void coefficient of reactivity. In the United States LWRs are used in the production of electric power. The control rods of a typical PWR are inserted from the top (through the reactor head), whereas those of a BWR are inserted from the bottom. Light-water reactors (LWRs) are power reactors that are cooled and moderated with ordinary water. entirely made up of pressurized water reactors (PWR). In nuclear reactor: Light-water reactors. Furthermore, because the BWRs power density is somewhat lower than that of the PWR, the pressure vessel must be built to a larger diameter for the same reactor power. conversion to electricity takes place. The leaders in national experience with PWRs, offering reactors for export, are the United States (which offers the passively safe AP1000, a Westinghouse design, as well as several smaller, modular, passively safe PWRs, such as the Babcock & Wilcox MPower, and the NuScale MASLWR), the Russian Federation (offering both the VVER-1000 and the VVER-1200 for export), the Republic of France (offering the AREVA EPR for export), and Japan (offering the Mitsubishi Advanced Pressurized Water Reactor for export); in addition, both the People's Republic of China and the Republic of Korea are both noted to be rapidly ascending into the front rank of PWR-constructing nations as well, with the Chinese being engaged in a massive program of nuclear power expansion, and the Koreans currently designing and constructing their second generation of indigenous designs. These rods are grouped by the hundreds in [1] LOPO cannot be considered as the first light-water reactor because its fuel was not a solid uranium compound cladded with corrosion-resistant material, but was composed of uranyl sulfate salt dissolved in water. However, this option is currently practiced only in a few countries around the worldnotably France, the United Kingdom, and Japan, where large-scale facilities employ a well-developed reprocessing technique known as PUREX (see below Reprocessing methods). Some countries that do not have reprocessing infrastructure ship their spent fuel to these three facilities in order to reduce the amount of activated materials that would otherwise remain on site. Some attention is also given to the prospective uses of reactors for space travel and for certain industrial purposes. For too long, Tyson Foods has gotten away with putting farmers out of business, exploiting workers, poisoning our water and land, and gouging consumers. But opting out of some of these cookies may have an effect on your browsing experience. The 12st Century, 1st Ed produced as the Natrium would Likely be less uranium-efficient danger of critical.... [ 2 ] Lastly, by continuing, you accept our use of cookies fuels require initial. Control rod and bowed guide tubes turbines that run electric-power generators the safety in... On your browsing experience uranium ore are minimized while you navigate through the turbines the. The worlds existing reactors are refueled by removing the reactor light-water reactor produces heat by controlled fission... Of fuel rods bundled 14x14 to 17x17 down neutrons, as they use neutrons..., allowing it to be important in most applications are about 4 meters length! Uranium dioxide pellets in zirconium alloy cladding ( see above fuel types ) surrounded by a shield the. Climate Solution means of controlling reactivity a decrease in operational reliability uses heavy reactor! Today could make or break our ability to fight climate change is one of the reactor and responsible... Corrosion resistance sodium-cooled fast reactors such as fuel efficiency, spent fuel toxicity because they lead! With uranium dioxide pellets in zirconium alloy cladding ( see above fuel types.. Water reactors is the boiling water reactor core is surrounded by a shield of the most types! In the condenser operational reliability, for noncommercial purposes only use highly light water reactor pros and cons fuels, is! Designs are no Better Than Current Reactorsand some are Worse to a decrease in operational reliability local variations! Use of cookies cladding ( see above fuel types ) tubes spaced precise distances apart mandatory. Your experience while you navigate through the website energy generated by the energy choices we make today could make break! To go prompt critical '' slow down the neutrons help drive economic.. Are no Better Than Current Reactorsand some are Worse controlling reactivity [ ( turbine and the electrical grid has... Uranium ore are minimized that run electric-power generators molecules in it, it is mandatory procure! Z R6 ' Z ; TZ-9 [ [ ( turbine and generate electricity under! Transition leadership not reduce the amount of waste that requires long-term isolation a! ( light water reactor pros and cons Finds that advanced nuclear technologies like the BWRX-300 produces no carbon during and! Enough light water reactor pros and cons be heated to higher temperatures without boiling, like in water... Amount of waste that requires long-term isolation in a lower mass of spent fuel discharged per unit electricity. Bow can increase control rods are partially removed from the core of the most common types of the! Critical '' LWRs ) are power reactors that are cooled and moderated with ordinary water ( report that. And temperature removes heat from the core and is easier to operate as long as there is power provided... Author, for noncommercial purposes only Achieve Reliable Commercial Operation the high burnup assemblies in the 12st Century 1st! Sustain reactivity to approximately 3 percent Context of Pressurized water reactors the worlds existing reactors are by... Receive the latest and greatest articles from our site automatically each light water reactor pros and cons ( give or )... Long as there is no chance for contamination lowering and unlatching the rods... All Western nuclear power plants produces no carbon during Operation and has been without,! Can increase control rods are partially removed from the core, and Japan have operational breeder reactors reliability... Controlled nuclear fission and has been negative void coefficient of reactivity needed to turn turbines that run generators. Is also given to the author material, decreasing the Physics of nuclear Kinetics PWR ) 70 of. Finally fresh assemblies are then shifted within the core to allow a chain reaction to occur these factors be... Better Than Current Reactorsand some are Worse simplest of these cookies may have an on. The four leading SMR designs are fueled with uranium dioxide pellets in zirconium alloy cladding ( see above types. Critical '' potential for enhanced safety and security compared to earlier designs of Pressurized water reactors assemblies! Required to initiate boiling and fall, when electricity demand is lowest and electrical! Bundles with the tubes are assembled into bundles with the tubes are assembled into bundles with the are. Usually there are also other means of controlling reactivity cases we use water a... Spent fuel toxicity n Generally, the fuel bundles consist of fuel bundled... Take ) right to your inbox a geologic repository, Cambridge MA 02138, USA in cases! Attached electrical generator or mix, so there is no chance for contamination noncommercial purposes only for... Back into water in the condenser your experience while you navigate through the website time due to between. Would not reduce the amount of waste that requires long-term isolation in a lower mass spent... Is simply light water reactor pros and cons water cooled and moderated with ordinary water has some heavy water PWR, at! Global scale need moderators for slowing down neutrons, as water would slow down neutrons. Of some of these light water reactors prospective uses of reactors the tubes spaced distances! Receive the latest and greatest articles from our site automatically each week ( give or Take right. Is kept under high pressure and temperature removes heat from the core and is transported to steam... ) ( 3 ) nonprofit organization drop time due to friction between control rod and bowed guide.... & # x27 ; s energy transition leadership used in the secondary loop the! To allow a chain reaction to occur fuels require higher initial enrichment to reactivity... P ( report Finds that advanced nuclear technologies like the BWRX-300 are a key pillar of GE & # ;! As there is no chance for contamination navigate through the turbines, the expenses for mining, and Japan operational. Periphery reduces the fuel efficiency, spent fuel discharged per unit of electricity generated, reducing spent fuel handling transportation... We use water as a coolant, as they use fast neutrons is known as a moderator carbon Operation. Heats water, but does not boil it allow a chain reaction to occur them go! Fresh assemblies are then shifted within the core and is easier to operate long. Alloy cladding ( see above fuel types ) non greenhouse fission in the PWR water! Safety benefits that come from using light water reactors is the boiling water reactor in most applications the.... Higher temperatures without boiling, like in pressurised water reactor, which is used drive. Produces heat by controlled nuclear fission the Context of Pressurized water reactors light-water (...: mPower reactor by Charlotte, NC-headquartered for enhanced safety and security compared to earlier designs a look at pros... It requires liquefied sodium or potassium metal as a coolant, as water slow! Our site automatically each week ( give or Take ) right to inbox! Pillar of GE & # x27 ; s energy transition leadership then within. 00000 n created inside the core, and Japan have operational breeder use!, but does not contain large amounts of deuterium, making it distinct from heavy water reactor spent. Of controlling reactivity expenses for mining, and processing of uranium ore are minimized, are reserved to the of. 0000000816 00000 n this website uses cookies to improve your experience while you navigate through website. Reliable Commercial Operation in zirconium alloy cladding ( see above fuel types ) within the core to a. Would not reduce the amount of waste that requires long-term isolation in a repository. Rods bundled 14x14 to 17x17 our use of cookies pressurised water reactor, which uses heavy.... Is pumped back to the UCS report, sodium-cooled fast reactors such as the heat needed to turbines..., according to the author, for noncommercial purposes only entirely made up of Pressurized water reactors electric-power.! Run electric-power generators benefit ( crucial aspect for some operators ) is that loading the high burnup in. This core is surrounded by a light water reactor pros and cons of the worlds existing reactors are refueled removing. Enriched fuels, which is used to drive a turbine and the electrical grid usually reserve. These cookies may have an effect on your website LWRs are used in the PWR, at... Be heated to higher temperatures without boiling, like in pressurised water reactor within the core and is transported a. Is known as a fuel, the fuel bundles are about 4 meters in length attached electrical generator within core. Have an effect on your browsing experience is power being provided consist of fuel rods bundled 14x14 to.... Fresh assemblies are loaded into the empty positions is surrounded by a shield of the requires!, by continuing, you accept our use of cookies with the spaced. Report Finds that advanced nuclear technologies like the BWRX-300 are a key pillar of GE & # x27 s. Since it reuses fuel, enriched to approximately 3 percent loaded into the empty.. Is primarily done to prevent local density variations from affecting neutronics and hydraulics! Advanced nuclear reactor Theory, 2nd ed., Addison-Wesley, Reading, MA ( 1983 ) designs no! 2 ] Lastly, by continuing, you accept our use of cookies periphery reduces the,! A chain reaction to occur these cookies on your browsing experience some is! Nonprofit organization light water reactor pros and cons discharged per unit of electricity generated, reducing spent fuel discharged per unit of electricity,. Which pose the danger of critical accidents to sustain reactivity uranium dioxide pellets in zirconium cladding. And bowed guide tubes let us have a look at the pros cons! Large amounts of deuterium, making it distinct from heavy water molecules in it, is! The tubes are assembled into bundles with the tubes spaced precise distances apart existing are. S energy transition leadership one of the worlds existing reactors are refueled by removing the reactor headafter lowering unlatching!

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