How does a nuclear meltdown work? (w/ Video)

From: http://www.physorg.com/

This illustration of a nuclear reactor shows water entering the core and surrounding the fuel rods (vertical red bars). When the water level decreases, the fuel rods begin to heat up and face the risk of melting. Image from video below.

(PhysOrg.com) -- When working properly, nuclear reactors produce large amounts of heat via nuclear fission reactions. The heat converts the surrounding water into steam, which turns turbines and generates electricity. But if you remove the water, you also remove the most important cooling element in a nuclear reactor and open up the possibility for nuclear meltdown.

A handful of nuclear meltdowns of varying degrees of severity have occurred since the 1950s, when researchers began building and testing nuclear reactors. The most serious instance happened in 1986 in Chernobyl, Ukraine. Plagued by design flaws and operator errors, the plant experienced fires, explosions, and radiation leakage. As a result, 30 people died of acute radiation syndrome, and thousands of cases of fatal cancers and birth defects have been reported in the following years. Today, limited access is allowed inside a 30-km (19-mile) exclusion zone surrounding the area.

By comparison, the Three Mile Island accident in Harrisburg, Pennsylvania, was much less serious. In 1979, a minor cooling system malfunction led to a series of events that caused a partial meltdown that damaged one of the reactors. However, very little radiation was released into the environment due to the surrounding primary containment vessel. Although the accident caused public concern, no deaths or adverse health effects have been officially attributed to the meltdown.

In Japan, the current nuclear crisis at the Fukushima Daiichi power plant lies somewhere in between Three Mile Island and Chernobyl, according to recent news reports. Last Friday’s 9.0-magnitude earthquake and 10-meter (33-foot) tsunami waves that traveled up to 10 km (6 miles) inland overpowered several of the plant’s safety measures. Although employees at the plant have been risking their lives to try to keep the reactors cool, the chance of a serious meltdown seems to be increasing.

Inside a reactor

Inside the core of a nuclear reactor are thousands of long, thin fuel rods made of zirconium alloy that contain uranium. When a reactor is turned on, the uranium nuclei undergo nuclear fission, splitting into lighter nuclei and producing heat and neutrons. The neutrons can create a self-sustaining chain reaction by causing nearby uranium nuclei to split, too. Fresh water flows around the fuel rods, keeping the fuel rods from overheating and also producing steam for a turbine.

But if not enough water flows into the reactor’s core, the fuel rods will boil the water away faster than it can be replaced, and the water level will decrease. Even when the reactor is turned off so nuclear reactions no longer occur, the fuel rods remain extremely radioactive and hot and need to be cooled by water for an extended period of time. Without enough water, the fuel rods get so hot that they melt. If they begin to melt the nuclear reactor core and the steel containment vessel, and release radiation into the environment, nuclear meltdown occurs.

What's happening at the Fukushima nuclear power plant. Video credit: Reuters.

Japan’s cooling problems

When the earthquake struck Japan, three of the six reactors (Reactors 4, 5, and 6) at the Fukushima power plant were already off for routine inspections. Earthquake tremors triggered the automatic shutdown of the other three reactors, Reactors 1, 2, and 3 (along with eight other nuclear reactors at other power plants). To stop the chain reaction, control rods that absorb neutrons were inserted in between the fuel rods.

But the fuel rods are still hot, since radioactive byproducts of past fission reactions continue to produce heat. When the earthquake tore down the power lines, the plant’s main cooling system stopped working. As a backup measure, diesel generators turned on to spray the fuel rods with coolant. But the tsunami that occurred shortly after the earthquake was larger than the plant’s designers had anticipated, and water flowed over the retaining wall and into the area with the generators, causing them to fail. The next backup measure for cooling the fuel rods was a battery system, but the batteries lasted only a few hours. Later, technicians brought in mobile generators and also attempted to inject seawater into the nuclear reactors, which makes them permanently unusable but could help prevent a complete meltdown

While the nuclear technicians searched for better cooling options, the water levels continued to decrease, exposing the tops of the fuel rods. Pressure also began building in some of the reactors. So far, at least three explosions have occurred in Reactors 1, 2, and 3. The explosions happened when the fuel rods began to melt and release gases that reacted with the surrounding steam, producing hydrogen. To release some pressure and prevent explosions, technicians vented some of the reactors, which also released some radioactive material into the environment. Officials have said that the pressure in Reactor 2 dropped significantly after the explosion there, suggesting that the explosion breached the steel containment structure - the reactor’s “last resort” for containing leaked radiation.

Also, a fire ignited at Reactor 4, thought to be caused by a large pile of spent fuel rods in a pond. Spent fuel rods need to be kept fully submerged in water for cooling, but the lack of water has left some of the rods partially exposed. Smoke from the fire temporarily increased radiation levels around the reactor, so preventing future fires is very important. The Fukushima plant has seven ponds of spent fuel rods from the past few decades. By some estimates, there may be as many as half a million spent fuel rods that are still radioactive and could catch fire if not kept cool.

Japanese officials have stated that radiation around the nuclear reactors has risen to the level where it would adversely affect a person’s health. Officials have implemented a 20-km (12-mile)-radius evacuation zone, and have advised people to stay indoors. The US has told its citizens living in the area to stay at least 50 miles away from the power plant. Some people have been taking prophylactic iodine as a safety measure; consuming this non-radioactive iodine before exposure to radioactive iodine can fill a person’s thyroid and hopefully prevent absorption of the radioactive variety. Fortunately, westerly winds have so far blown much of the radioactive material out to sea.

Overall, because the extreme events that caused the cooling problems are so rare and unexpected, it’s difficult to predict exactly what will happen next for Japan’s nuclear plants.

More information: via: IEEE Spectrum, The Wall Street Journal, Scientific American, and National Geographic

© 2010 PhysOrg.com

New invention can turn your plastic bags into fuel at home

by Katie Gatto
from http://www.physorg.com/

(PhysOrg.com) -- Plastic bags help you carry your groceries home, they make excellent liners for smaller-sized trash cans, and now they can help you to heat your home. A Japanese inventor has found a way to convert plastic grocery bags, bottles and caps into usable petroleum.

 

Plastic bags are, of course, made from petroleum to begin with, but it is not the same kind of petroleum that is used in fuel. In order to turn home waste into home power the machine heats up the waste plastic and traps the vapors created in a system of pipes and water chambers. Finally, the machine condenses the vapors into crude oil, that can be used for heating on the home level.


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This is not the first device of this kind. A large power plant which is located just outside of Washington, D.C., is currently testing a similar process for use on the community level. This is simply the first device of this kind that is meant for use on a single-home scale. 

The machines conversion process can turn two pounds of plastic into one quart of oil, using only one kilowatt-hour of energy. The crude oil produced can then either be used in a power generator or be further refined into gasoline, though one would need a second machine to complete the refining process and create gasoline.


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Many home users will be deterred by the initial cost, since the machine currently runs about $10,000. The developer hopes that the cost will be reduced as the demand for the device increases. The device is named the carbon-negative system and it is being sold by the Blest Corporation.

More information: http://www.blest.c … english.html

© 2010 PhysOrg.com

The Awesome Hidden Power of Dog Poop

From: http://dogblog.dogster.com/

Finally! A use for dog poop!

A way-cool invention called the Park Spark was unveiled last week in a Cambridge, Mass., dog park. The methane digester converts dog poop into energy, and that energy is now powering a gas-burning lamp at the park. Because of this, people can see where their dogs poop at night, and feed the machine, for a sort of never-ending flame. It’s kind of like an Olympic torch, only with more humble, odiferous roots.

Here’s how it works: Your dog poops. You scoop it with a specially made biodegradable bag, deposit it into a feeding tube, and turn a hand crank so methane rises to the top, and is available to be burned by whatever you connect to it. It’s that simple. You have made poop into light.

How amazing is that? The Park Spark is able to convert something that was not worthy of the bottom of your shoe into energy that can light up your night. And it prevents the greenhouse gas, methane, from doing environmental damage. The infographic below shows the contrast between scooping the poop, and making it into energy:

According to Fast Company, the Park Spark team can also envision dog poop being used to power portable tea stands, and popcorn (poopcorn?) stands. But it will never power large projects like lighting up an entire block. Poop is grand, but apparently it has its limitations.

The Park Spark in Cambridge wasn’t an underground number, but a couple of large yellow tanks above ground. Check it out below.

It’s brilliant to have a big, above-ground demo like this for people (like me) who would find it harder to imagine how dog doo can light up your life if the setup were below ground.

I hope the idea catches on, and that within a few years, any dog-filled park that doesn’t have a Park Spark will look like it’s stuck in the Dark Ages.

By: Maria Goodavage

Atlantis Unveils The World’s Largest Tidal Turbine – The AK1000™

From: http://www.atlantisresourcescorporation.com/

Atlantis Resources Corporation (“Atlantis”), one of the world’s leading developers of electricity-generating tidal current turbines, unveiled the largest and most powerful tidal power turbine ever built, the AK1000™, yesterday at Invergordon, Scotland. The AK1000™ is due for installation at a dedicated berth at the European Marine Energy Centre (“EMEC”), located in Orkney, Scotland later this summer. Dignitaries, utilities and technology partners from around the world attended the unveiling of the flagship turbine at the Isleburn Engineering facility, taking the only opportunity to view the turbine before it is installed on the seabed and connected to the grid at EMEC. Despatching 1MW of predictable power at a water velocity of 2.65m/s, the AK1000™ is capable of generating enough electricity for over 1000 homes. It is designed for harsh weather and rough, open ocean environments such as those found off the Scottish coast. The turbine incorporates cutting edge technology from suppliers across the globe, has an 18 meter rotor diameter, weighs 1300 tonnes and stands at a height of 22.5 meters. The giant turbine is expected to be environmentally benign due to a low rotation speed whilst in operation and will deliver predictable, sustainable power to the local Orkney grid. CEO of Atlantis, Timothy Cornelius, said: “The unveiling and installation of the AK1000™ is an important milestone, not only for Atlantis, but for the marine power industry in the United Kingdom. It represents the culmination of 10 years of hard work, dedication and belief from all our partners, staff, directors and shareholders. The AK1000™ is capable of unlocking the economic potential of the marine energy industry in Scotland and will greatly boost Scotland’s renewable generation capacity in the years to come.” “ Today is not just about our technology, it is about the emergence of tidal power as a viable asset class that will require the development of local supply chains employing local people to deliver sustainable energy to the local grid. The AK1000™ takes the industry one step closer to commercial scale tidal power projects.” The AK1000™ nacelle was fabricated by Soil Marine Dynamics in Newcastle in England and the gravity base structure and system assembly was completed by Isleburn Engineering, a member of the Aberdeen based Global Energy Group. Steel for the turbine came from Corus’ Scunthorpe facility. “The AK1000™ development program has injected over £5M to date into UK Plc’s renewable energy sector and has provided employment across a broad range of sectors including design, engineering, fabrication and project management. We are at the start of a new industrial boom, akin to the development of the North Sea oil & gas fields. If we receive the same support from all levels of government that the oil & gas industry received to make the North Sea the success that it is, then the future is very bright for marine power and even brighter for Scotland”

5 Companies Making Fuel From Algae Now

Ubiquitous and easy to grow, algae has long been a promising biomass-to-fuel candidate in the eyes of researchers. Now algae is a burgeoning sector in biofuels with several high-profile start-ups, including Craig Venter’s Synthetic Genomics, and the interest of big-time investors like Bill Gates and ExxonMobil. Of course, hurdles still exist to make a competitive fuel. Algal biofuels still cost too much to produce—over $8 a gallon (pdf), according to the DOE. Furthermore, most existing strains do not yield oil in the quantities needed to quickly scale up to commercial production of biofuels. Companies also need to worry about contaminating local ecosystems and the amount of water needed to grow cultures in large batches. Despite these challenges inroads—and actual fuel—are being made in the nascent field. Here are 5 projects leading the pack today.

By Jeremy Jacquot

1. Algenol Biofuels

The Project /// $850 million committed to build algae farm that sells ethanol fuel for $3 per gallon

The Location /// Sonoran Desert (Mexico)

The Technology /// The company’s goal is to produce fuel directly from the algae without killing or harvesting the creatures, allowing for a shorter turnaround time to make fuel. The company claims its process lets it make around 6000 gallons per acre per year.

To Market /// Production is expected to begin by the end of 2010. Algenol intends to produce 1 billion gallons annually by 2012. They say their production costs will be around 85 cents per gallon.

2. Solix Biofuels

The Project /// A demonstration facility that could produce up to 3000 gallons of algal biofuels per acre per year by the end of 2009

The Location /// Coyote Gulch, Colo.

The Technology /// Solix uses specialized photo-bioreactors in which batches of microalgal cultures are grown in large, closed-growth chambers under controlled light and temperature conditions. The company claims its closed systems can produce up to seven times as much biomass as open-pond systems. Once the cultures are fully grown, their oil is extracted through the use of chemical solvents like benzene or ether. The solvents are mixed into the chambers to separate the oil from the algae, and it is then collected from the surface. Solix is also collaborating with the Los Alamos National Laboratory to use its acoustic-focusing technology to concentrate algal cells into a dense mixture by blasting them with sound waves. Oil can then be extracted from the mixture by squeezing it out; this makes the extraction process much easier and cheaper, obviating the need for chemical solvents.

To Market /// Tentatively by the winter of 2009.

3. Sapphire Energy

The Project /// A 300-acre integrated algal biorefinery

The Location /// Southern New Mexico

The Technology /// Sapphire’s focus is on “green crude," a liquid that has the same composition as crude oil, and is therefore compatible with existing refineries. The company has already shown that its fuel can be used in cars and even jets. Sapphire has a 100-acre pilot facility near Las Cruces, N.M.

To Market /// The plan is to make 1 million gallons of diesel and jet fuel per year by 2011, 100 million by 2018, and 1 billion gallons per year by 2025. There are no figures as of yet for the now-running 300-acre facility.

4. Solazyme

The Project /// Along with Sustainable Oils (camelina-based biofuel) and Honeywell subsidiary UOP (biodiesel), Solazyme plans to supply 400,000 gallons of fuel to the Air Force and 190,000 gallons to the U.S. Navy 1500 gallons of jet fuel for the U.S. Navy by 2010.

The Location /// South San Francisco

The Technology /// Solazyme engineers designer algal cultures using DNA from different strains to maximize oil production and size and grows them in large fermentation vessels before harvesting their oil. It first tested its jet fuel in late 2008.

To Market /// Solazyme claims that it is on track to produce over 20,000 gallons of fuel for the Navy by 2010. The company hopes to bring the cost of its fuel down to $60 to $80 per barrel within next two to three years.

5. Seambiotic

The Project /// 5-hectare commercial plant

The Location /// Israel

The Technology /// Seambiotic grows microalgal cultures in open ponds using flue gases like carbon dioxide and nitrogen from a nearby coal plant as feedstocks. Its 1000-square-meter facility produces roughly 23,000 grams of algae per day—three tons of algal biomass would yield around 100 to 200 gallons of biofuel. It recently formed a partnership with NASA to optimize the growth rates of its microalgae.

To Market /// Up and running since 2003, Seambiotic set up a pilot plant in 2005. Seambiotic expects its commercial plant to be ready by late 2009.

Air-fuelled Battery Could Last Up to 10 Times Longer

Diagram of the STAIR (St Andrews Air) cell. Oxygen drawn from the air reacts within the porous carbon to release the electrical charge in this lithium-air battery. A new type of air-fuelled battery could give up to ten times the energy storage of designs currently available. This step-change in capacity could pave the way for a new generation of electric cars, mobile phones and laptops. The research work, funded by the Engineering and Physical Sciences Research Council (EPSRC), is being led by researchers at the University of St Andrews with partners at Strathclyde and Newcastle. The new design has the potential to improve the performance of portable electronic products and give a major boost to the renewable energy industry. The batteries will enable a constant electrical output from sources such as wind or solar, which stop generating when the weather changes or night falls. An early demonstration model of the STAIR (St Andrews air) cell. Improved capacity is thanks to the addition of a component that uses oxygen drawn from the air during discharge, replacing one chemical constituent used in rechargeable batteries today. Not having to carry the chemicals around in the battery offers more energy for the same size battery. Reducing the size and weight of batteries with the necessary charge capacity has been a long-running battle for developers of electric cars. The STAIR (St Andrews Air) cell should be cheaper than today’s rechargeables too. The new component is made of porous carbon, which is far less expensive than the lithium cobalt oxide it replaces. This four-year research project, which reaches its halfway mark in July, builds on the discovery at the university that the carbon component’s interaction with air can be repeated, creating a cycle of charge and discharge. Subsequent work has more than tripled the capacity to store charge in the STAIR cell. Principal investigator on the project, Professor Peter Bruce of the Chemistry Department at the University of St Andrews, says: “Our target is to get a five to ten fold increase in storage capacity, which is beyond the horizon of current lithium batteries. Our results so far are very encouraging and have far exceeded our expectations.” Cells used in the laboratory to investigate the lithium-air cell. “The key is to use oxygen in the air as a re-agent, rather than carry the necessary chemicals around inside the battery,” says Bruce. The oxygen, which will be drawn in through a surface of the battery exposed to air, reacts within the pores of the carbon to discharge the battery. “Not only is this part of the process free, the carbon component is much cheaper than current technology,” says Bruce. He estimates that it will be at least five years before the STAIR cell is commercially available. The project is focused on understanding more about how the chemical reaction of the battery works and investigating how to improve it. The research team is also working towards making a STAIR cell prototype suited, in the first instance, for small applications, such as mobile phones or MP3 players. Notes for Editors The four-year research project “An O2 Electrode for a Rechargeable Lithium Battery” began on 1 July 2007 and is scheduled to end on 30 June 2011. It has received EPSRC funding of £1,579,137. Rechargeable lithium batteries are currently comprised of a graphite negative electrode, an organic electrolyte and lithium cobalt oxide as the positive electrode. Lithium is removed from the layered intercalation compound (lithium cobalt oxide) on charging and re-inserted on discharge. Energy storage is limited by the lithium cobalt oxide electrode (0.5 Li/Co, 130 mAhg-1). The University of St Andrews design replaces the lithium cobalt oxide electrode with a porous carbon electrode and allows Li+ and e- in the cell to react with oxygen from the air. Initial results from the project found a capacity to weight ratio of 1,000 milli-amp / hours per gram of carbon (mA/hours/g), while recent work has obtained results of up to 4,000 mA/hours/g. Although the two designs work very differently, this equates to an eight-fold increase compared to a standard cobalt oxide battery found in a mobile phone. The application to renewable energy could help get round the problems of intermittent supply. By discharging batteries to provide electricity and recharging them when the wind blows or sun shines, renewables become a much more viable option. The Engineering and Physical Sciences Research Council (EPSRC) is the UK’s main agency for funding research in engineering and the physical sciences. The EPSRC invests around £740 million a year in research and postgraduate training, to help the nation handle the next generation of technological change. The areas covered range from information technology to structural engineering, and mathematics to materials science. This research forms the basis for future economic development in the UK and improvements for everyone’s health, lifestyle and culture. EPSRC also actively promotes public awareness of science and engineering. EPSRC works alongside other Research Councils with responsibility for other areas of research. The Research Councils work collectively on issues of common concern via Research Councils UK. Website address for more information on EPSRC: For more information contact: The University of St Andrews visit: www.st-andrews.ac.uk Professor Peter Bruce FRS, tel: 01334 463 825, e-mail: p.g.bruce@st-andrews.ac.uk Three images are available from the EPSRC Press Office (contact: Matthew.Thompson@epsrc.ac.uk, tel: 01793 4514)

Ice that burns could be a green fossil fuel

by Michael Marshall

Natural gas locked up in water crystals could be a source of enormous amounts of energy – and if a new technology delivers what scientists are claiming, then it could even be emissions-free too.

To the naked eye, clathrate hydrate looks like regular ice. However, while it is made up partly of water, the water molecules are organised into "cages", which trap individual molecules of methane inside them.

Compared to other fossil fuels, methane – also known as natural gas – releases less carbon dioxide per unit of energy generated. Nevertheless, burning it still releases carbon dioxide and thus drives climate change.

However, according to research presented this week at the national meeting of the American Chemical Society, a new method of extracting the methane could effectively make it a carbon-neutral fossil fuel.

'Bridging fuel'

Due to their physical structure, clathrate hydrate cages "prefer" to have carbon dioxide at their cores, so if carbon dioxide is pumped into the hydrate, it spontaneously takes the methane's place. As a result, it should be possible to simultaneously extract methane and store carbon dioxide.

"Methane from hydrate could be a bridging fuel, to lead towards more renewable energies," says Tim Collett of the United States Geological Survey.

According to the results in Collett's presentation, the exchange process has been shown to work in the lab. Pumping carbon dioxide into rock cores containing hydrate successfully released the methane, and stored the carbon dioxide.

The US Department of Energy is now working with the oil company ConocoPhillips on a field trial in Alaska (pdf), to test whether the technique can be scaled up.

Rival technology

Previous attempts to obtain methane by heating up the hydrate were not effective, but pumping fluids out of the hydrate to release the pressure does release the methane. To be put into commercial practice, it is likely that the carbon storage method will need to outcompete this depressurisation technique.

Deborah Hutchinson of the USGS says that the technique "could make it possible to sequester CO₂."

Natural gas normally contains a percentage of CO₂, which under industry regulations must be pumped back into the gas wells when it is extracted.

"The first CO₂ to be utilised in this [new] methodology would be the CO₂ 'cleaned' from raw natural gas produced in nearby wells," says Hutchinson. In other words, the CO₂ sequestered in the extraction of methane in ice will most likely be the stuff separated from conventional gas reservoirs.

Globally, there are thought to be from 10¹⁵ to 10¹⁷ cubic metres of methane stored in hydrates – a vast store, large quantities of which should be recoverable.

'Limited sequestration'

Much of it is in sediments just below the sea floor, or trapped under permafrost. Some of the best-studied reservoirs are in Alaska, and beneath the Gulf of Mexico and the Sea of Japan.

The deposits on the North Slope of Alaska are among the richest. A 2008 USGS study showed that there are 2.4 trillion cubic metres (85 trillion cubic feet) of methane in hydrate form, which could be recovered using existing technology.

The US, Canada, Japan and Korea are all looking into clathrate hydrates as a possible energy source.

"A lot of countries are getting very serious about this," says Ray Boswell of the US National Energy Technology Laboratory. "Something that used to be more hype than reality is becoming something people are seriously talking about."

Bahman Tohidi of Heriot-Watt University's Institute of Petroleum Engineering says the Alaska trial is "a step in the right direction", but that the potential for sequestering carbon would be limited by the remote locations of the hydrate reservoirs. "You're talking about long distance CO₂ transport," he says.

Neil Crumpton of UK environmental campaign group Friends of the Earth is sceptical. "It's a technology we think is best avoided. The US should be focusing its efforts on concentrated solar power in its southwestern deserts."