Spent fuel pool
Spent fuel pools are storage pools for spent fuel from nuclear reactors. They are 40 or more feet deep, with the bottom 14 feet equipped with storage racks designed to hold fuel assemblies removed from the reactor. A reactor's pool is specially designed for the reactor in which the fuel was used and situated at the reactor site. An away-from-reactor, Independent Spent Fuel Storage Installation, such as the one located at the Morris Operation, is sometimes used. In many countries, the fuel assemblies, after being in the reactor for 3 to 6 years, are stored underwater for 10 to 20 years before being sent for reprocessing or dry cask storage; the water provides shielding from radiation. While only about 20 feet of water is needed to keep radiation levels below acceptable levels, the extra depth provides a safety margin and allows fuel assemblies to be manipulated without special shielding to protect the operators. About a quarter to a third of the total fuel load of a reactor is removed from the core every 12 to 24 months and replaced with fresh fuel.
Spent fuel rods generate intense heat and dangerous radiation. Fuel is moved from the reactor and manipulated in the pool by automated handling systems, although some manual systems are still in use; the fuel bundles fresh from the core are segregated for several months for initial cooling before being sorted into other parts of the pool to wait for final disposal. Metal racks keep the fuel in controlled positions for physical protection and for ease of tracking and rearrangement. High-density racks incorporate or other neutron-absorbing material to ensure subcriticality. Water quality is controlled to prevent the fuel or its cladding from degrading. Current regulations in the United States permit re-arranging of the spent rods so that maximum efficiency of storage can be achieved; the maximum temperature of the spent fuel bundles decreases between 2 and 4 years, less from 4 to 6 years. The fuel pool water is continuously cooled to remove the heat produced by the spent fuel assemblies. Pumps circulate water from the spent fuel pool to heat exchangers back to the spent fuel pool.
The water temperature in normal operating conditions is held below 50 °C. Radiolysis, the dissociation of molecules by radiation, is of particular concern in wet storage, as water may be split by residual radiation and hydrogen gas may accumulate increasing the risk of explosions. For this reason the air in the room of the pools, as well as the water, must be continually monitored and treated. Rather than manage the pool's inventory to minimize the possibility of continued fission activity, China is building a 200 MWt nuclear reactor to run on used fuel from nuclear power stations to generate process heat for district heating and desalination. An SFP operated as a deep pool-type reactor. Other research envisions a similar low-power reactor using spent fuel where instead of limiting the production of hydrogen by radiolysis, it is encouraged by the addition of catalysts and ion scavengers to the cooling water; this hydrogen would be removed to use as fuel. If there is a prolonged interruption of cooling due to emergency situations, the water in the spent fuel pools may boil off resulting in radioactive elements being released into the atmosphere.
In the magnitude 9 earthquake that struck the Fukushima nuclear plants in March 2011, three of the spent fuel pools were in buildings that lost the roof and were seen to be emitting water vapor. The US NRC wrongly stated that the pool at reactor 4 had boiled dry—this was denied at the time by the Japanese and found to be incorrect in subsequent inspection and data examination. According to nuclear plant safety specialists, the chances of criticality in a spent fuel pool are small avoided by the dispersal of the fuel assemblies, inclusion of a neutron absorber in the storage racks and overall by the fact that the spent fuel has too low an enrichment level to self-sustain a fission reaction, they state that if the water covering the spent fuel evaporates, there is no element to enable a chain reaction by moderating neutrons. According to Dr. Kevin Crowley of the Nuclear and Radiation Studies Board, "successful terrorist attacks on spent fuel pools, though difficult, are possible. If an attack leads to a propagating zirconium cladding fire, it could result in the release of large amounts of radioactive material."
After the September 11, 2001 attacks the Nuclear Regulatory Commission required American nuclear plants "to protect with high assurance" against specific threats involving certain numbers and capabilities of assailants. Plants were required to "enhance the number of security officers" and to improve "access controls to the facilities". Deep geological repository Dry cask storage Lists of nuclear disasters and radioactive incidents Nuclear fuel cycle Radioactive waste Spent nuclear fuel shipping cask Radiological Terrorism: Sabotage of Spent Fuel Pool Storage of Spent Nuclear Fuel U. S. Nuclear Regulatory Commission An example diagram of a Spent Fuel Pool Indian Point Energy Center "Geek Answers: Does nuclear waste glow?" BY GRAHAM TEMPLETON 07.17.2014 at Geek.com
A reservoir is, most an enlarged natural or artificial lake, pond or impoundment created using a dam or lock to store water. Reservoirs can be created in a number of ways, including controlling a watercourse that drains an existing body of water, interrupting a watercourse to form an embayment within it, through excavation, or building any number of retaining walls or levees. Defined as a storage space for fluids, reservoirs may hold gasses, including hydrocarbons. Tank reservoirs elevated, or buried tanks. Tank reservoirs for water are called cisterns. Most underground reservoirs are used to store liquids, principally either water or petroleum, below ground. Reservoir is most an enlarged natural or artificial lake. A dam constructed in a valley relies on the natural topography to provide most of the basin of the reservoir. Dams are located at a narrow part of a valley downstream of a natural basin; the valley sides act as natural walls, with the dam located at the narrowest practical point to provide strength and the lowest cost of construction.
In many reservoir construction projects, people have to be moved and re-housed, historical artifacts moved or rare environments relocated. Examples include the temples of Abu Simbel, the relocation of the village of Capel Celyn during the construction of Llyn Celyn, the relocation of Borgo San Pietro of Petrella Salto during the construction of Lake Salto. Construction of a reservoir in a valley will need the river to be diverted during part of the build through a temporary tunnel or by-pass channel. In hilly regions, reservoirs are constructed by enlarging existing lakes. Sometimes in such reservoirs, the new top water level exceeds the watershed height on one or more of the feeder streams such as at Llyn Clywedog in Mid Wales. In such cases additional side dams are required to contain the reservoir. Where the topography is poorly suited to a single large reservoir, a number of smaller reservoirs may be constructed in a chain, as in the River Taff valley where the Llwyn-on, Cantref and Beacons Reservoirs form a chain up the valley.
Coastal reservoirs are fresh water storage reservoirs located on the sea coast near the river mouth to store the flood water of a river. As the land based reservoir construction is fraught with substantial land submergence, coastal reservoir is preferred economically and technically since it does not use scarce land area. Many coastal reservoirs were constructed in Europe. Saemanguem in South Korea, Marina Barrage in Singapore and Plover Cove in China, etc are few existing coastal reservoirs. Where water is pumped or siphoned from a river of variable quality or size, bank-side reservoirs may be built to store the water; such reservoirs are formed by excavation and by building a complete encircling bund or embankment, which may exceed 6 km in circumference. Both the floor of the reservoir and the bund must have an impermeable lining or core: these were made of puddled clay, but this has been superseded by the modern use of rolled clay; the water stored in such reservoirs may stay there for several months, during which time normal biological processes may reduce many contaminants and eliminate any turbidity.
The use of bank-side reservoirs allows water abstraction to be stopped for some time, when the river is unacceptably polluted or when flow conditions are low due to drought. The London water supply system is one example of the use of bank-side storage: the water is taken from the River Thames and River Lee. Service reservoirs store treated potable water close to the point of distribution. Many service reservoirs are constructed as water towers as elevated structures on concrete pillars where the landscape is flat. Other service reservoirs can be entirely underground in more hilly or mountainous country. In the United Kingdom, Thames Water has many underground reservoirs, sometimes called cisterns, built in the 1800s, most of which are lined with brick. A good example is the Honor Oak Reservoir in London, constructed between 1901 and 1909; when it was completed it was said to be the largest brick built underground reservoir in the world and it is still one of the largest in Europe. This reservoir now forms part of the southern extension of the Thames Water Ring Main.
The top of the reservoir is now used by the Aquarius Golf Club. Service reservoirs perform several functions, including ensuring sufficient head of water in the water distribution system and providing water capacity to out peak demand from consumers, enabling the treatment plant to run at optimum efficiency. Large service reservoirs can be managed to reduce the cost of pumping, by refilling the reservoir at times of day when energy costs are low. Circa 3 000 BC, the craters of extinct volcanoes in Arabia were used as reservoirs by farmers for their irrigation water. Dry climate and water scarcity in India led to early development of stepwells and water resource management techniques, including the building of a reservoir at Girnar in 3000 BC. Artificial lakes dating to the 5th century BC have been found in ancient Greece; the artificial Bhojsagar lake in present-day Madhya Pradesh state of India, constructed in the 11th century, covered 650 square kilometres. In Sri Lanka large reservoirs were created by ancient Sinhalese kings in order to save the water for irrigation.
The famous Sri Lankan king Pa
A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling, rolling, or hammering; such processes are needed in the production of many material goods, including flour, paper and many metal products. These watermills may comprise gristmills, paper mills, textile mills, trip hammering mills, rolling mills, wire drawing mills. One major way to classify watermills is by wheel orientation, one powered by a vertical waterwheel through a gear mechanism, the other equipped with a horizontal waterwheel without such a mechanism; the former type can be further divided, depending on where the water hits the wheel paddles, into undershot, overshot and pitchback waterwheel mills. Another way to classify water mills is by an essential trait about their location: tide mills use the movement of the tide. According to Terry S. Reynolds and R. J. Forbes, the water wheel may have originated from the ancient Near East in the 3rd century BC for use in moving millstones and small-scale grain grinding.
Reynolds suggests that the first water wheels were norias and, by the 2nd century BC, evolved into the vertical watermill in Syria and Asia Minor, from where it spread to ancient Greece and the Roman Empire. S. Avitsur supports a Near-Eastern origin for the watermill. Engineers in the Hellenistic world used the two main components of watermills, the waterwheel and toothed gearing, along with the Roman Empire, operated undershot and breastshot waterwheel mills. Early evidence of a water-driven wheel is the Perachora wheel, in Greece. An early written reference is in the technical treatises Pneumatica and Parasceuastica of the Greek engineer Philo of Byzantium; the British historian of technology M. J. T. Lewis has shown that those portions of Philo of Byzantium's mechanical treatise which describe water wheels and which have been regarded as Arabic interpolations date back to the Greek 3rd-century BC original; the sakia gear is fully developed, attested in a 2nd-century BC Hellenistic wall painting in Ptolemaic Egypt.
Lewis assigns the date of the invention of the horizontal-wheeled mill to the Greek colony of Byzantium in the first half of the 3rd century BC, that of the vertical-wheeled mill to Ptolemaic Alexandria around 240 BC. The Greek geographer Strabon reports in his Geography a water-powered grain-mill to have existed near the palace of king Mithradates VI Eupator at Cabira, Asia Minor, before 71 BC; the Roman engineer Vitruvius has the first technical description of a watermill, dated to 40/10 BC. He seems to indicate the existence of water-powered kneading machines; the Greek epigrammatist Antipater of Thessalonica tells of an advanced overshot wheel mill around 20 BC/10 AD. He praised for its use in grinding grain and the reduction of human labour: Hold back your hand from the mill, you grinding girls. For Demeter has imposed the labours of your hands on the nymphs, who leaping down upon the topmost part of the wheel, rotate its axle. If we learn to feast toil-free on the fruits of the earth, we taste again the golden age.
The Roman encyclopedist Pliny mentions in his Naturalis Historia of around 70 AD water-powered trip hammers operating in the greater part of Italy. There is evidence of a fulling mill in 73/4 AD in Roman Syria. Another Roman author Ausonius mentions a lot of watermills in the walley of Rhine and its tributaries in the 4th century, it is that a water-powered stamp mill was used at Dolaucothi to crush gold-bearing quartz, with a possible date of the late 1st century to the early 2nd century. The stamps were operated as a batch of four working against a large conglomerate block, now known as Carreg Pumpsaint. Similar anvil stones have been found at other Roman mines across Europe in Spain and Portugal; the 1st-century AD multiple mill complex of Barbegal in southern France has been described as "the greatest known concentration of mechanical power in the ancient world". It featured 16 overshot waterwheels to power an equal number of flour mills; the capacity of the mills has been estimated at 4.5 tons of flour per day, sufficient to supply enough bread for the 12,500 inhabitants occupying the town of Arelate at that time.
A similar mill complex existed on the Janiculum hill, whose supply of flour for Rome's population was judged by emperor Aurelian important enough to be included in the Aurelian walls in the late 3rd century. A breastshot wheel mill dating to the late 2nd century AD was excavated at Les Martres-de-Veyre, France; the 3rd-century AD Hierapolis water-powered stone sawmill is the earliest known machine to incorporate a crank and connecting rod mechanism. Further sawmills powered by crank and connecting rod mechanisms, are archaeologically attested for the 6th-century water-powered stone sawmills at Gerasa and Ephesus. Literary references to water-powered marble saws in what is now Germany can be found in Ausonius 4th-century poem Mosella, they seem to be indicated about the same time by the Christian saint Gregory of Nyssa from Anatolia, demonstrating a diversified use of water-power in many parts of the Roman Empire. The earliest turbine mill was
Tide pools or rock pools are shallow pools of seawater that form on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide. Many tide pools are habitats of adaptable animals that have engaged the attention of naturalists and marine biologists, as well as philosophical essayists: John Steinbeck wrote in The Log from the Sea of Cortez, "It is advisable to look from the tide pool to the stars and back to the tide pool." Tidal pools exist in the intertidal zones. These zones are submerged by the sea at high tides and during storms, may receive spray from wave action. At other times the rocks may undergo other extreme conditions, baking in the sun or exposed to cold winds. Few organisms can survive such harsh conditions. Lichens and barnacles live in this region. In this zone, different barnacle species live at tightly constrained elevations. Tidal conditions determine the exact height of an assemblage relative to sea level; the intertidal zone is periodically exposed to sun and wind, which desiccate barnacles, which need to be well adapted to water loss.
Their calcite shells are impermeable, they possess two plates which they slide across their mouth opening when not feeding. These plates protect against predation; the high tide zone is flooded during each high tide. Organisms must survive wave action and exposure to the sun; this zone is predominantly inhabited by seaweed and invertebrates, such as sea anemones, chitons, green algae, mussels. Marine algae provide shelter for hermit crabs; the same waves and currents that make life in the high tide zone difficult bring food to filter feeders and other intertidal organisms. Called the lower littoral zone; this area is submerged and is exposed only during unusually low tide. It teems with life and has much more marine vegetation seaweeds. There is greater biodiversity. Organisms in this zone do not have to be as well adapted to drying temperature extremes. Low tide zone organisms include abalone, brown seaweed, crabs, green algae, isopods, limpets and sometimes small vertebrates such as fish; these creatures can grow to larger sizes because there is more available energy and better water coverage: the water is shallow enough to allow more sunlight for photosynthetic activity, the salinity is at normal levels.
This area is relatively protected from large predators because of the wave action and shallow water. Tide pools provide a home for hardy organisms such as starfish and clams. Inhabitants must be able to deal with a changing environment — fluctuations in water temperature and oxygen content. Hazards include strong currents, exposure to midday sun and predators. Waves can draw them out to sea. Gulls drop sea urchins to break them open. Starfish are eaten by gulls themselves. Black bears sometimes feast on intertidal creatures at low tide. Although tide pool organisms must avoid getting washed away into the ocean, drying up in the sun, or getting eaten, they depend on the tide pool's constant changes for food; the sea anemone Anthopleura elegantissima reproduces clones of itself through a process of longitudinal fission, in which the animal splits into two parts along its length. The sea anemone Anthopleura sola engages in territorial fights; the white tentacles, which contain stinging cells, are for fighting.
The sea anemones sting each other until one moves. Some species of starfish can regenerate lost arms. Most species must retain an intact central part of the body to be able to regenerate, but a few can regrow from a single ray; the regeneration of these stars is possible. Sea palms look similar to palm trees, they live in the middle to upper intertidal zones in areas with greater wave action. High wave action may increase nutrient availability and moves the blades of the thallus, allowing more sunlight to reach the organism so that it can photosynthesize. In addition, the constant wave action removes competitors, such as the mussel species Mytilus californianus. Recent studies have shown that Postelsia grows in greater numbers when such competition exists — a control group with no competition produced fewer offspring than an experimental group with mussels. Alternatively, the mussels may prevent the growth of competing algae such as Corallina or Halosaccion, allowing Postelsia to grow after wave action removes the mussels.
Intertidal fish List of British Isles rockpool life Rocky shore Tidal swimming pools in Britain
A waterway is any navigable body of water. Broad distinctions are useful to avoid ambiguity, disambiguation will be of varying importance depending on the nuance of the equivalent word in other languages. A first distinction is necessary between maritime shipping routes and waterways used by inland water craft. Maritime shipping routes cross oceans and seas, some lakes, where navigability is assumed, no engineering is required, except to provide the draft for deep-sea shipping to approach seaports, or to provide a short cut across an isthmus. Dredged channels in the sea are not described as waterways. There is an exception to this initial distinction for legal purposes, see under international waters. Where seaports are located inland, they are approached through a waterway that could be termed "inland" but in practice is referred to as a "maritime waterway"; the term "inland waterway" refers to navigable rivers and canals designed to be used by inland waterway craft only, implicitly of much smaller dimensions than seagoing ships.
In order for a waterway to be navigable, it must meet several criteria: it must be deep enough to accommodate vessels loading to the design draft. Vessels using waterways vary from small animal-drawn barges to immense ocean tankers and ocean liners, such as cruise ships; the European Conference of Ministers of Transport established in 1953 a classification of waterways, expanded to take into account the development of push-towing. Europe is a continent with a great variety of waterway characteristics, which makes this classification valuable to appreciate the different classes of waterway. There is a remarkable variety of waterway characteristics in many countries of Asia, but there has not been any equivalent international drive for uniformity; this classification is provided by the UN Economic Commission for Europe, Inland Transport Committee, Working Party on Inland Water Transport. A low resolution version of that map is shown here. Media related to Waterways at Wikimedia Commons Blue Book on European inland waterways - access to the Blue Book database.
The objective of the “Blue Book” is to establish an inventory of existing and envisaged standards and parameters of "E-waterways" and ports in Europe and to show, on an internationally comparable basis, the current inland navigation infrastructure parameters prescribed on the Agreement on Main Inland Waterways of International Importance Waterscape - Britain's official guide to canals and lakes
Melt ponds are pools of open water that form on sea ice in the warmer months of spring and summer. The ponds are found on glacial ice and ice shelves. Ponds of melted water can develop under the ice. Melt ponds are darker than the surrounding ice, their distribution and size is variable, they absorb solar radiation rather than reflecting it as ice does and, have a significant influence on Earth's radiation balance. This differential, which had not been scientifically investigated until has a large effect on the rate of ice melting and the extent of ice cover. Melt ponds can melt through to the ocean's surface. Seawater entering the pond increases the melt rate because the salty water of the ocean is warmer than the fresh water of the pond; the increase in salinity depresses the water's freezing point. Water from melt ponds over land surface can run into crevasses or moulins – tubes leading under ice sheets or glaciers – turning into meltwater; the water may reach the underlying rock. The effect is an increase in the rate of ice flow to the oceans, as the fluid behaves like a lubricant in the basal sliding of glaciers.
The effects of melt ponds are diverse. Research by Ted Scambos, of the National Snow and Ice Data Center, has supported the melt water fracturing theory that suggests the melting process associated with melt ponds has a substantial effect on ice shelf disintegration. Seasonal melt ponded and penetrating under glaciers shows seasonal acceleration and deceleration of ice flows affecting whole icesheets. Accumulated changes by ponding on ice sheets appear in the earthquake record of Greenland and other glaciers: "Quakes ranged from six to 15 per year from 1993 to 2002 jumped to 20 in 2003, 23 in 2004, 32 in the first 10 months of 2005." Ponding in the extreme is lakes and lakes in association with glaciers are examined in the particular case of the Missoula Floods. Moulin Glacier ice accumulation Antarctic ice pack Arctic ice pack
Vernal pools called vernal ponds or ephemeral pools, are seasonal pools of water that provide habitat for distinctive plants and animals. They are considered to be a distinctive type of wetland devoid of fish, thus allow the safe development of natal amphibian and insect species unable to withstand competition or predation by fish. Certain tropical fish lineages have however adapted to this habitat specifically. During most years, a vernal pool basin will experience inundation from local surface runoff, followed by desiccation from evapotranspiration; these conditions are associated with Mediterranean climate. Most pools are dry for at least part of the year, fill with the winter rains or snow melt; some pools may remain at least filled with water over the course of a year or more, but all vernal pools dry up periodically. A key time during vernal pool development between the flooding and evaporation phases is the flowering of native species, which attracts pollinators and influences seed distribution patterns.
Some authorities restrict the definition of vernal pools to exclude seasonal wetlands that have defined inlet and outlet channels. The justification is that such seasonal wetlands tend to be qualitatively different from isolated vernal pools. Secondly, flow patterns increase the periodic scouring and silting effect of flows through or into the wetland. Thirdly, longer distance inflow and outflow make for less endemic populations and plants. Low dissolved mineral concentrations of smaller vernal pool basins may be characterized as oligotrophic, poorly buffered with rapid pH shifts due to carbon dioxide uptake during photosynthesis. Vernal pools are so called because they are though not at their maximum depth in the spring. There are many local names for such pools, depending upon the part of the world. Vernal pools may form in forests, but they are more associated with grasslands and rocky plains or basins. While many vernal pools are only a few meters in width and prairie potholes are much larger, but still are otherwise similar in many respects, with high water in wet periods, followed by dry conditions.
Some exclude desert playas from the definition of vernal pools because their larger closed drainage basins in areas with high evaporation rates produce higher concentrations of dissolved minerals, with salinity and alkalinity favoring different species. Playas may be inundated less than vernal pools, inundation coincides with colder weather unfavorable for plant growth. Despite being dry at times, vernal pools teem with life; the most obvious inhabitants are various species of breeding toads. Some salamanders utilize vernal pools for reproduction, but the adults may visit the pool only briefly. Other notable inhabitants are Daphnia and fairy shrimp, the latter used as an indicator species to decisively define a vernal pool. Other indicator species, at least in New England, are the wood frog, the spadefoot toad, some species of mole salamanders. Certain plant species are associated with vernal pools, although the particular species depend upon the ecological region; the flora of South African vernal pools, for example, are different from those of Californian vernal pools, they have characteristic Anostraca, such as various Branchipodopsis species.
In some northern areas, tadpole shrimp are more common. Vernal pools harbor a distinct assemblage of flora and fauna that, in some cases, aren't found anywhere else on the planet. Despite this fact, about 90% of vernal pool ecosystems in California have been destroyed. Disturbingly, much of this destruction has occurred in recent years, with about 13% of remaining vernal pools being lost in the short interval from 1995-2005; the major threats to vernal pool habitats in the Central Valley are agriculture, changes in hydrology, climate change, improperly managed grazing by livestock. Vernal pools are prime habitats to be targeted for restoration work due to their value as hotpots of biodiversity as well as recent history of extensive destruction and degradation. However, there have been varying rates of success attributed to various restoration efforts. A number of hypotheses exists as to why: Hypothesis 1: Constructed pools are too deep. Hypothesis 2: Edges of constructed pools narrower than natural ones.
Hypothesis 3: Constructed pools have steeper slopes than natural ones. Results: Research suggest that the last two details are crucial in determining the habitat value of man-made vernal pools. In general, most constructed pools did not have wide enough edges. There has been a fair amount of controversy surrounding the practice of mitigation, the destruction of protected or endangered species and habitats, such as vernal pools, on the condition that whatever entity is destroying the habitat will undertake the construction of a replacement habitat to "mitigate" their impacts; this concept is difficult to apply to vernal pools, which represent a tremendous habitat value- but are difficult to replicate using construction methods. Thus, it has been controversial to apply mitigation strategies to vernal pool systems due to the obvious risks inherent in trying to reconstruct this kind of habitat. Although, some agencies are now requiring two replacements for every vernal pool, destroyed, in order to compensate for the low quality of man-made habitat.
Vernal pools can form anywhere that a depres