Creating a photovoltaic cell from plant

My experiment is as follows, a photovoltaic cell obtained from a solution like this liquida.Demostrar becomes a photovoltaic cell,
For that we need a small container (filled with a mixture of water and grass: we will have extracted from the plant, the necessary components to make it conductive) a stick of graphite, and another of copper, ammeter and cables to connect everything to each other .

Now, we are going to begin to assemble our experiment.
First we need to make the liquid solution for this,  we have to crush grass blades with a little water, once done, observe the color of the water turns green, well, our mix here.
Then well assemble the stick of graphite with the copper foil with a 3mm separation between them, with this, will get a negative and a positive conductors.
Insert the device into the liquid solution, and we can see how the measurements vary according to the light we have. To increase the light collection electricity is higher, and vice versa.

Once done this, start the data collection, with different intensities of light with different color filters, we can even more opaque container, and also see that no energy is generated, since we are preventing light pass.

We can understand better the experiment, watching this video:

https://www.youtube.com/watch?v=56mTZDlLY-M

What is it?

There is already a Keystone pipeline that part of the oil fields of Alberta (Canada) and goes to Cushing (Oklahoma). The energy company TransCanada has submitted a proposal under the name Keystone XL posed an extension of this pipeline. The proposal would add more than 2700km of pipeline in two parts (with an estimated cost of $ 7 billion dollars). First, an “oil highway” would be built between Cushing refineries and the Gulf Coast of Texas. After a section from Alberta (Canada) would pass through eastern Montana to western North Dakota to descend on south be added. The proposed addition would bring the pipeline through Montana, South Dakota, Nebraska, Kansas, Oklahoma and Texas. The diameter of the pipes would enlarge current 76cm ​​to 91cm.

Because the pipeline would cross the border between Canada and the United States, TransCanada must acquire a permit from the Department of State for part of the project passing through American territory. However, the section of existing pipeline in Oklahoma requires no permissions, so TransCanada has already started building this section called “Project Gulf Coast.”

Cons
Let’s start with the facts that it has provided TransCanada. The following facts have been extracted directly from its “environmental impact statement”:

The enclosure of the village of tanks Steele City (Nebraska) emit regulated air pollutants.

The project crosses some 842km of rocky substrate that might contain fossils important to science.

Approximately 26km2 of altered surface may disappear due to increased erosion by water and wind.

Construction through water bodies cause a short-term increase of the total suspended solids and sediments deposited on 205 rivers and perennial streams.

Construction of the pipeline will affect a total of 740 wetlands, river systems and other exterior water courses. This includes 2.25 km2 wetland divided by 0.4 km2 of forest wetland, emergent wetland 0.45 km2 and 0.26 km2 of wetland shrubs and bushes. The wetland forest need between 20 and 50 years to recover from the damage. The recovery will take from 1-5 years for emerging and wetland shrubs and bushes.

The need for hydrostatic testing of the pipeline water cylinder, about 53 million liters in total, will be collected from surface water resources

The pipeline will affect a total of approximately 84km2 of land including 46.5 km2 of meadows, pastures and rangelands, some 11Km2 19km2 of forest land and farmland.

About 5.3 km2 upland and wetland: During construction of the pipeline several wildlife habitats are desbrozarán. 252 km of power lines create a collision hazard for waterfowl and other birds.

The project is likely to cause a reduction of habitats sensitive aquatic species and other wildlife. Impacts to cultural resources could include physical disturbance of archaeological sites and the introduction of visual and auditory elements (gas stations, for example) that would affect the environment.

PROS

The State Department estimated that the extension would create nearly 2,000 jobs during a two-year period.

The 1,664-mile pipeline extension is projected to bring in 830,000 barrels of crude oil a day.

GHG emissions from oil sands production are similar to those of oils produced in Venezuela and Nigeria. If Keystone XL is not approved, GHGs could actually increase through ‘crude shuffling.’..

The United States needs to move deliberately toward alternative sources of energy, and the federal government must take the lead by supporting emerging technologies and providing dollars for research. But the U.S. and the world remain oil dependent. While that must change, such massive shifts in energy mix take time. In the meantime, the world benefits from oil produced by friendly, democratic nations such as Canada, which reduces its dependence on unstable regimes in the Middle East…

 

 

http://www.isfoundation.com/es/news/detengamos-el-oleoducto-keystone-xl

http://alternativeenergy.procon.org/view.answers.php?questionID=001628

http://www.latinpost.com/articles/8522/20140308/keystone-xl-pipeline-project-pros-cons-facts-recent-poll-shows.htm

http://www.realclearenergy.org/2011/11/10/pros_amp_cons_of_the_keystone_xl_pipeline_242960.html

Georgetown University (Washington DC), President Barack Obama delivered one of the most anticipated speeches in recent months in which he announced the National Plan on Climate Change. In it he presented his vision of the measures his government will take to prepare the country for the effects of climate change and the need to combine these efforts with other countries around the world to combat this serious problem.

According to data provided by the White House, the 2012 was the year with more extreme temperatures in the United States, a third of the population lived for over a hundred days to an average of 37.5 degrees and weather derivatives disaster effect emissions cost the nation 100,000 million.

Given these data and on the mission, expressed in many occasions, “leaving a better world for our children and grandchildren,” Obama has presented the main points of a plan that has the support of the political class, or the environmentalists, but the basis for fighting the problem affecting harshly United States in recent years.

President Obama’s Climate Action Plan focuses on:

– Regulating Greenhouse Gas Emissions
– Energy Efficiency
– Renewable Energy
– Natural Gas
– Leading by Example
– Climate Resilience
– International Climate Change Leadership

The project includes setting first limits on polluting industry and promotion, through financial assistance and other facilities to operate on public land, the production of wind and solar energy.

According to the White House , this action plan should allow the United States to fulfill the commitments made by the President in the climate summit in Copenhagen in 2009 , to 2020 to reduce emissions of greenhouse gas by 17 percent , compared with 2005 levels .

Obama argued that Americans ” are already paying the price of inaction ” , describing 2012 as the warmest year in history , which ended up affecting agricultural crops in the Midwest .

“The question is whether we have the courage to act before it is too late and how they respond will have a profound impact on the world we will leave to our children and grandchildren,” said Obama , who highlighted the afternoon heat today in Washington to underscore its new environmental plan. “As president, as a parent and as an American , I’m here to tell you that we have to act,” he said.

Obama said he had asked the EPA to develop rules to regulate carbon emissions from power plants that burn coal and are responsible for 40 % of the carbon dioxide pollution .

” Power plants still emit unlimited amounts of carbon dioxide free air quantities. That’s not right , is not safe and must stop,” the president claimed .

The president also said the controversial Keystone XL pipeline project between Canada and the United States may only be approved if its implementation requires not increase emissions of greenhouse gases .

“Our national interest is maintained only if the project does not significantly exacerbates the problem of carbon pollution ,” Obama said in a speech at Georgetown University .

Obama’s plan basically skirt the obstacles found earlier proposals to regulate power plants in Congress, where his Republican opponents have opposed the measure , arguing it would be too costly or doubt about the scientific evidence behind climate change .

” We do not have time for a meeting of the Association of the Flat Earth ” joked the president.
Obama proposed 8,000 million in loan guarantees to support investments in new technologies in extraction of fossil resources and energy efficiency, and asked “strengthen” U.S. production of natural gas to get ” clean and safe ” energy in the medium term.

The new White House plan also provides for the granting of permits for renewable energy projects , solar or wind to produce enough electricity to more than six million people by 2020.

The federal government itself increase by 20 % the total energy consumed by renewable sources in the next seven years , Obama promised .

But the president acknowledged that despite these efforts , the planet will continue to warm “for a while ” and announced provisions to protect U.S. territory from the effects of rising sea levels and storms. “It will take time for carbon emissions stabilize,” he said.

The Secretary of State , John Kerry , a senator who led several unsuccessful efforts to reduce greenhouse gas emissions , stressed that the plan demonstrates the seriousness of the U.S. in the climate issue and called on other countries to do more.

” The decisive action at home empowers us to make further progress at the international level on a shared challenge,” Kerry said during a visit to Kuwait, a major producer of crude.

Obama pledged to withdraw support to the construction Sites of coal burning power plants and promote global free trade in technologies that help reduce pollution.

” If we get that agreement can establish a sustainable future for this generation ,” he said .

Reduction in CO2 Emission

United States announced first limits on emissions of carbon dioxide (CO2) of new power plants that run on gas and coal in order to combat climate change.

Power plants and coal gas are responsible for a third of the emissions of greenhouse gases in the United States.

Under this proposal, future plants to natural gas will have to limit emissions of carbon dioxide (CO2) to 453 kilos per megawatt-hour, and 499 kilos per megawatt-hour for smaller units.

As for new coal-fired power plants, they can not exceed 499 kilos per megawatt-hour with the ability to opt out means stricter limits, but spread over several years.

Currently the most modern coal-fired plants produce about 800 kilos per megawatt-hour, according to the industry.

An army of megawatts

In addition, Obama announced that federal agencies are working on a new target -100 MW renewable power to be installed by the year 2020 all residential buildings subsidized by the administration (six million households). The Climate Change Plan Obama is also set in the army of the United States Department of Defense is the largest energy consumer in the United States, has been located, says the Obama-Plan to implement 3,000 MW of energy renewables in its military facilities by 2025.

The automobile industry

Additional Plan announces that after 2018, and in collaboration with industry and other key industry players, the Administration “develop”-from 2018 – consumption patterns for heavy road transport still demanding in order to further reduce the fuel consumption per unit. Finally, the Obama Administration is committed to supporting the implementation of patterns also for renewable fuels and investing in research and development in next generation biofuels. According to the Environmental Protection Agency (U.S. EPA), in 2011 (latest data available) the electricity sector was the main cause of emissions of greenhouse gases (GHG) in the country (33% of total); transport was the second (28%).

…And saving
Meanwhile, the Obama plan aims to double energy efficiency by 2030 (relative to that recorded in 2010). In autumn 2013 , was put into operation a plan , and plans to put a program in place to finance subsidies efficiency investments in rural communities valued at $ 250 million . Among the achievements already made , the Obama Plan cites the Better Buildings Initiative , launched in 2011 with the aim of helping industrial and commercial buildings to be 20 % more efficient in 2020: “So far , says the Plan- more 120 organizations have joined to it. ” They have also been driven projects on energy efficiency in the home . Projects under the plan , have already benefited more than one million homes , ” many families are saving over $ 400 on your heating bills and air conditioning in the first year.” The Obama Plan announces the expansion of multifamily housing plan on a long horizon : 2020 .

But as I always say, not all that glitters is gold here so here I leave a link, which will help you to understand the reality that can hide or not this ambitious plan. (http://www.climatecentral.org/news/qa-breaking-down-key-features-of-obamas-climate-plan-16154)

 

Sources

http://www.whitehouse.gov/sites/default/files/image/president27sclimateactionplan.pdf

http://www.energias-renovables.com/articulo/obama-el-clima-de-opinion-y-el-20130626

http://www.programapaiseficienciaenergetica.cl/energia/eeuu-limitara-emisiones-de-co2-de-nuevas-centrales-electricas/

http://www.climatecentral.org/news/qa-breaking-down-key-features-of-obamas-climate-plan-16154

 

During the visit to Boston MOS, I found many things that caught my attention, but above allthe part that came to understand was the best of Energy, because it is a subject on which we have expanded a lot in class. In this section of the museum, you could live in person, the process of obtaining energy from different sources.

Above all, this space focused on solar energy, wind, etc., ie, renewable energy.
We had the opportunity to experiment with different devices, and thus, 100% understand how they worked. What called my attention, was how well they were exposed to different experiments, especially wind turbine and solar panels.

When I get home I left wanting to know more about this exhibition of Energized , so here I started to check that they were engaged , despite having been in the MOS , needed to expand my knowledge of this exhibition , and as they say is based on “Exploring renewable Energy” . But what is it? Okay, now try to explain the four major processes that are explained in this exhibition .

Concentrated Solar Power

What Is It?

Concentrated solar power (CSP) focuses sunlight onto a small area and uses the resulting heat to make electricity. Mirrors or lenses concentrate the scattered light from the Sun into a focal point, heating up a fluid by hundreds of degrees. The heat is used to make steam, which moves a turbine and generates electrical power.

 

Why Does It Matter?

Sunlight is the Earth’s most abundant energy resource, but it disperses so much that little energy is available at any given spot. By focusing the Sun’s light onto a focused area using parabolic troughs, dishes, or even huge towers, the energy is concentrated and used more effectively to make electricity.
One of the drawbacks of CSP is the large amount of space that is needed to collect a useful amount of solar energy. But in places such as deserts with open, sunny spaces, concentrating solar technologies can generate utility-scale power at relatively low cost.

What’s Next?

Because the Sun’s energy is intermittent, maximum sunlight can be captured for only a few hours each day even in the sunniest locations. Some of the newest installations use molten salt that can store heat for hours or even days, allowing solar power plants to continue generating electricity during the night or during times of cloudy weather.

 

Photovoltaic Energy

What Is It?
Photovoltaics, also called solar panels or PV, transform sunlight into electricity. Photovoltaic cells are made from materials called semiconductors. The most common semiconductor used in solar cells is silicon, which is found in sand and is abundant in the Earth’s crust. When sunlight strikes the surface of the cell, some of the light particles are absorbed by the semiconducting material, causing negative electric charges to flow across the surface of the cell. The cell is designed so that the charges will uniformly flow in one direction and can be used to do electrical work.

Why Does It Matter?
Because solar panels are self-contained systems, they can be used in remote locations away from the electric grid, or they can be grid-connected. Solar panels are often used on roadways or on space satellites. Although photovoltaic panels are most commonly installed on building rooftops, they can also be integrated into the buildings as roofs, windows, curtain walls, and even parking canopies. Solar farms are increasingly being used for utility-scale production as well, although they require a large amount of space to collect utility-scale amounts of solar energy.

What’s Next?
Because silicon is also used in circuit boards and must be chemically treated (“doped”) to be a semiconductor, current photovoltaic technology is significantly more expensive than fossil fuels or many other renewable methods. New thin-film and “string ribbon” materials require far less silicon to do the same job as older cells. New generations of photovoltaics made from plastics and inks may soon make solar panels much cheaper or as easy to fabricate as printing a letter!

Wind Power
What Is It?
People have been using wind power to accomplish tasks for centuries. Wind turbines convert the energy of moving air into electricity. The wind spins the turbine’s curved blades, creating torque that turns a geartrain and drives a generator. The generated electric current can be stored in batteries or sent via transmission lines into the electric grid. Huge, utility scale turbines and wind farms power whole cities or neighborhoods, while smaller residential-scale machines can power an individual home or building.

Why Does It Matter?
Since 2000, the total installed electric capacity from wind turbines exploded from 2,000 to 37,000 megawatts (as of March 2011). All of these turbines have been installed on land, but the U.S. Department of Energy estimates that the country’s coasts are windy enough to meet the nation’s power needs many times over. Cape Wind in Massachusetts will be America’s first offshore wind farm, and a project called Deepwater Wind in Block Island, Rhode Island, will test a “jacketed design” (similar to deepwater oil rigs) that allow turbines to be sited up to 20 miles offshore.
Since June 2011, the Museum of Science has drawn 100% of its electricity from green energy. Renewable Energy Certificates (RECs) from wind energy facilities across the U.S. match all of the Museum’s electricity usage.

What’s Next?
One of the biggest challenges of wind power is that the wind is variable. Wind power systems are often connected to the electric utility grid to share clean energy across a large region; the utility provides electricity when the wind isn’t blowing. Wind power can also generate electricity at remote sites off the grid or can charge batteries — such as those in plug-in electric vehicles — for later use.

Geothermal Energy

What Is It?
Geothermal electric systems generate electric power using heat from within the Earth. Engineers drill a mile or more into the Earth’s crust, tapping into underground reservoirs where hot rocks and water are heated by magma deep beneath the surface. Geothermal power is sometimes called hydrothermal generation, because the energy comes from hot water. The hot steam pushes a turbine to spin a generator, generating clean electricity.

Why Does It Matter?
Because the Earth’s core is so hot, the potential for geothermal energy is tremendous. However, geothermal reservoirs (“hot spots”) are most common where the plates that make up the Earth’s crust intersect. Although the United States is the world leader in total geothermal power production, all of its geothermal power is concentrated in just four western states. A single site north of San Francisco called “The Geysers” accounts for over half of all U.S. geothermal electricity. Small nations that are located on plate boundaries, such as Iceland and the Phillipines, generate large portions of their electricity from geothermal power.

What’s Next?
Current geothermal installations have been limited to places where water is easily accessed. Engineered geothermal systems (EGS) are created by drilling into hot, dry rocks and injecting cold water under pressure. As the pressure builds, the rocks fracture and the liquids are heated by the surrounding rock. A recent study by MIT estimated that engineered geothermal systems could meet the world’s electricity needs for thousands of years.

 

Hydroelectric Power
What Is It?
Hydropower is electricity produced by moving water, and is used so widely in the U.S. that it generates more electricity than any other renewable source. Rushing water from a river or waterfall is channeled through pipes, spinning a turbine to drive a generator. Because the flow of water is relatively constant, except in times of drought, hydropower can deliver large amounts of continuous electricity over long periods of time.
Why Does It Matter?
Hydropower requires strong currents to produce significant amounts of electricity. Much of the hydropower in the United States is generated in the Pacific Northwest. Although hydropower is a renewable and inexhaustible electricity source, it does carry some associated environmental concerns. Building large dams can negatively impact local ecosystems and interfere with fish migration patterns. Technologies such as fish ladders can help reduce the environmental impacts of hydropower, but additional installations in the United States are unlikely to be large.
What’s Next?
Other forms of hydropower can be used to produce electricity from moving water. Tide power and wave power provide new ways to create electricity from the oceans. Tidal barrages have been in existence for decades, but they are often expensive and pose similar environmental concerns to dams. Newer methods may produce cheaper electricity with less environmental impact. The Aguçadoura Wave Farm in Portugal, built by Pelamis, is the world’s first utility-scale wave farm. It features snakelike turbines with a series of hydraulic rams. A second installation is planned off the coast of Scotland.

 

 

http://legacy.mos.org/energized/index.php

http://www.mos.org/

Pandora’s Promise is a 2013 documentary film about the nuclear power debate, directed by Robert Stone. Its central argument is that nuclear power, which still faces historical opposition from environmentalists, is a relatively safe and clean energy source which can help mitigate the serious problem of anthropogenic global warming. The title is derived from the ancient Greek myth of Pandora, who released numerous evils into the world, yet as the movie’s tagline recalls: “At the bottom of the box she found hope.”

The movie features several notable individuals, some of whom were once vehemently opposed to nuclear power but who now speak in favor of it, including Stewart Brand, Gwyneth Cravens, Mark Lynas, Richard Rhodes and Michael Shellenberger.

Anti-nuclear advocate Helen Caldicott is questioned and along with Harvey Wasserman appears briefly at the beginning. Historic clips of Jane Fonda, Ralph Nader and Amory Lovins speaking are used.

Richard Branson is credited as an executive producer, as are Paul and Jody Allen, whose production company, Vulcan Productions, helped provide financial support. A total of $1.2 million (US) was raised to finance the film, “particularly through Impact Partners, which provides documentary financing from individual investors. Mr. Stone said the money came mainly from wealthy “tech heads” who have worked in Silicon Valley.”

Here’s how the film Pandora’s Promise propagated nuclear power myths:

1. Claimed Nuclear Energy Is Cheaper Than Renewable Energy

The enormous cost of building nuclear power plants is a key inhibiting factor for the energy source. Despite receiving immensely greater subsidies than renewable energy from the beginning of its development, nuclear energy is still not competitive with fossil fuels in the U.S., and new wind energy is estimated to be less expensive than new nuclear generation. Yet the Breakthrough Institute’s Michael Shellenberger asserted that nuclear power is “a much more economical alternative to very expensive solar panels or very expensive wind turbines that require backup power.” He also dismissed renewable energy and energy efficiency, one of the cheapest ways to address climate change, as a “religion.”

Renewable energy prices have actually been dropping while the costs of nuclear are on the rise—as nuclear power has scaled up in France and the U.S., so have the costs of power plant construction. Meanwhile, solar prices have dropped 99 percent in the last quarter century, and solar and wind energies are predicted to be cost-competitive with fossil fuels—without the use of subsidies—by 2025.

2. Blamed Environmentalists For Preventing Nuclear Deployment

Pandora’s Promise focused on opposition to nuclear power from some in the environmental movement. In the film, author Mark Lynas even compared anti-nuclear activists to global warming deniers. However, this narrative paints a misleading picture: the lack of nuclear expansion in the U.S. comes down to a simple case of economics. Currently, nuclear power cannot compete with gas-fired power. As the libertarian Cato Institute’s Jerry Taylor explained that there’s “zero evidence” that environmental opposition is preventing new nuclear power plants, a myth that he said has been purported by nuclear advocates who “like to dodge the cost estimates.”

3. Whitewashed The Issue Of Nuclear Waste

Although nuclear power has potential to become a major power source, it comes with baggage. The U.S. has accumulated more than 70,000 metric tons of spent nuclear fuel, and continues to accumulate 2,200 tons per year, yet CNN’s documentary made light of this waste—Lynas claimed that nuclear waste is “not an environmental issue.”

The Associated Press reported that the nation “has no place to permanently store the material, which stays dangerous for tens of thousands of years.” Most of this waste currently “sits in water-filled cooling pools like those at the Fukushima Dai-ichi” at the power plants themselves, some of which “contain four times the amount of spent fuel that they were designed to handle.”

The film also failed to mention leaks that currently challenge the upstate New York power plant, Indian Point. According to the Union of Concerned Scientists, the plant experiences consistent leaks during refueling, though the Nuclear Regulatory Commission did not act on this. The scientists called the status quo of nuclear waste cleanup “untenable,” yet CNN’s documentary barely glossed over this ongoing issue.

But not everything that glitters is gold, so I will encourage that you read this other article, published on the Guardian Newspaper. (http://www.theguardian.com/environment/damian-carrington-blog/2013/nov/08/pandoras-promise-pro-nuclear-movie-climate-change)

 

 

 

The MIT Nuclear Research Reactor (MITR) serves the research purposes of the Massachussets Institute of Technology. It is a tank-type 6 MW reactor that is moderated and cooled by light water and usesheavy water as a reflector. It is the second largest university based researchreactor in the US (after the University of MIssouri Research Center) and has been in operation since 1958.It is the fourth-oldest operating reactor in the country.

 

The MIT Nuclear Reactor Laboratory (MIT-NRL) is an interdepartmental center that operates a high performance 6 MW research reactor known as the MITR-II. It is the second largest university research reactor in the U.S. and the only one located on the campus of a major research university. During its long and distinguished history, the NRL has supported educational training and cutting-edge research in the areas of nuclear fission engineering, material science, radiation effects in biology and medicine, neutron physics, geochemistry, and environmental studies.

It is the only university research facility in the U.S. where students can be directly involved in the development and implementation of nuclear engineering experimental programs with neutron flux levels comparable to power reactors. The MITR-II is an indispensable resource for developing the workforce for the future of nuclear power.

The MITR-II is equipped with experimental facilities available to users both within and outside MIT. NRL staff also provide technical assistance for research projects for high school students, undergraduate and graduate students, university researchers and faculty members, and national laboratory users.

THE REACTOR

The MITR-II, the major experimental facility of the NRL, is a heavy-water reflected, light-water cooled and moderated nuclear reactor that utilizes flat, plate-type, finned, aluminum-clad fuel elements. The average core power density is about 70 kW per liter. The maximum fast and thermal neutron flux available to experimenters are 1.2×10¹⁴ and 6×10¹³neutrons/cm²-s, respectively. Experimental facilities available at the MIT research reactor include two medical irradiation rooms, beam ports, automatic transfer facilities (pneumatic tubes), and graphite-reflector irradiation facilities. In addition, several in-core experimental facilities(ICSAs) are available. It generally operates 24/7, except for planned outages for maintenance. The MITR-II encompasses a number of inherent (i.e., passive) safety features, including negative reactivity temperature coefficients of both the fuel and moderator; a negative void coefficient of reactivity; the location of the core within two concentric tanks; the use of anti-siphon valves to isolate the core from the effect of breaks in the coolant piping; a core-tank design that promotes natural circulation in the event of a loss-of-flow accident; and the presence of a full containment. These features make it an exceptionally safe facility.

USES

The MITR research program encompasses most aspects of neutron science and engineering including nuclear medicine. Some of these activities are:

Boron neutron capture therapy
Radiation synovectomy
Neutron activation analysis for the identification of trace elements and isotope ratios in geological specimens
Fission engineering
Materials testing
Training
Neutron transmutation doping of silicon

The MITR is one of only six facilities in the world to be engaged in patient trials for the use of boron neutron capture therapy (BNCT) to treat both brain tumors and skin cancer. The MITR fission converter beam is the first to be designed for BNCT.

 

http://web.mit.edu/nrl/

On March 11, 2011  occurred in Fukushima one of the worst nuclear accidents in history after  Chernobyl accident. A 8.9 magnitude earthquake hit the northwest coast of Japan and a subsequent tsunami severely affected Dahiichi Fukushima nuclear plant on the northeast coast of Japan.

Construction of the Fukushima nuclear plants

Fukushima plants are called “Boiling Water Reactors” ( boiling water reactors or boiling ) or BWR onwards ( for short) . The nuclear fuel heats the water , the water boils and creates steam ,then the steam is carried to turbines that create electricity , after that the steam is cooled and condensed to water and such water is forwarded to be heated again by the fuel nuclear. The reactor operates at about 250 ° C 285 ° C. The nuclear fuel is uranium oxide. The uranium oxide is a ceramic with a high melting point, about 3000 ° C 2800 ° C. The fuel pellets are manufactured in or called pellets (cylinders 1 cm high and 1 cm in diameter). These pieces are put into a long tube made of Zircaloy (a zirconium alloy) with a melting point of 2200 ° C to support a temperture of 1200 ° C (due to autocatalytic water oxidation), and are tightly sealed. This tube is called fuel rod. These fuel rods are joined, of which several hundred make the reactor core. The solid fuel pellet (a ceramic oxide matrix) is the first barrier that keeps many produced radioactive products of the fission process. Zircaloy casing is the second  barrier to the release of separating radioactive fuel from the rest of the reactor. The core is placed in a “pressure vessel”. The pressure vessel is a thick steel vessel which operates at a pressure about 7MPa (~ 1000 psi), and is designed to withstand high pressures which may occur during an accident. The pressure vessel is the third barrier to the release of radioactive material. The entire first coating of the nuclear reactor – the pressure vessel, piping, pumps and reserves coolant (water) is housed in a containment structure. This structure is the fourth barrier. The containment structure is sealed, a very thick metal structure made of concrete. This containment is designed, built and tested for one function: To contain, indefinitely, a complete core melting. For that task, and a thick layer of concrete is poured around the containment structure and is called as secondary containment. (second ground). Both the main containment structure and the secondary are housed in the reactor building. This building is an outer shell that “supposedly” keeps the weather out, but nothing inside. (this is the part that was damaged in the explosion, but more on that later).

Principles of nuclear reactions

The uranium fuel generates heat by nuclear fission (induced). Uranium atoms are split into lighter atoms (fission occurs). That generates more heat with neutrons (one of the parts that form an atom). When the neutron hits another uranium atom can split, generating more neutrons and so on. That’s what is called nuclear chain reaction. Normally operating at full capacity, the number of neutrons in the nucleus is stable (remains the same).

It is worth mentioning at this point that the nuclear fuel will “never” cause a nuclear explosion the type of ‘nuclear bomb’. In Chernobyl, the explosion was caused by excessive pressure buildup, hydrogen explosion and rupture of all structures, ejecting molten core material into the environment. Note that Chernobyl had no containment structure as a barrier. Why that did not happen or will happen in Japan, will be discussed below.

To control the nuclear chain reaction, the reactor operators use the so-called “control rods”. These bars are made of neutron absorbing boron. During normal operation in a BWR, the control rods are used to maintain the chain reaction in a critical condition. The control rods are also used to reduce reactor power from 100% to about 7% (residual heat). The residual heat is caused by the decomposition / degradation of the fission products.

The deterioration of the radiation is a process in which the fission products are themselves stabilized by emitting energy in the form of small particles (alpha, beta, gamma, neutron, etc. …). There are a multitude of fission products which are produced in the reactor, including cesium and iodine. This residual heat decreases with time after the reactor shut down and has to be removed / extracted by the cooling systems to prevent overheating of the fuel rods and failure of the same as a barrier to radiation. Maintaining enough cooling to remove the residual heat from the reactor is the main challenge in the affected reactors in an accident like Japan.

What happened at Fukushima

The following is a summary of the essential facts. The earthquake that hit Japan was 5 times more powerful than the worst earthquake for which the nuclear plant could withstand (when it was built), (the Richter scale works logarithmically, the difference between 8.2 that the plant can withstand and 8.9 hit Japan is 5 times higher, not 0.7). When the earthquake hit, the nuclear reactors all went off automatically.A few seconds after the earthquake started, the control rods had been inserted into the core and the chain reaction stopped.At this point, the cooling system has to take all the residual heat. This heat is about 7% of the heat that arises when operating under normal conditions.

The earthquake destroyed the external power source of the nuclear reactor. One of the challenging accident for a nuclear power plant, and it is referred to as a “loss of external power.” The reactor and its support systems are designed to handle such accidents including backup power systems to keep the coolant pumps working. Moreover, as the powerhouse it has been turned off, and can not produce more electricity itself. During the first hour, one of the multiple sets of diesel generators began operation and provided the needed electricity. But later came the Tsumani (a rarer and larger than anticipated tsunami) and flooded the diesel generators, causing them to stop functioning. (fail).

The absence of a containment wall suitable for other tsunamis of 38 meters that are characteristic in the region allowed the tsunami (15 meters in the central and up to 40.5 in other areas) penetrated without opposition. The presence of numerous critical systems in flood prone areas facilitated a cascade of technological failures occur, culminating in the complete loss of control over the plant and its reactors. The first technical failures were recorded the same day the earthquake, Friday, March 11, with stop of  the cooling systems of two reactors and four emergency generators.

As a result of these incidents, there were evidences of a partial core melt in reactors 1, 2 and 3. Subsequently, hydrogen explosions occurred that destroyed the upper cladding of buildings housing reactors 1,3 and 4 and a blast that damaged the holding tank into the reactor 2. Multiple fires also occurred in reactor 4. In addition, spent fuel rods, stored in the spent fuel pools of units 1-4 began to overheat when the levels of these pools went down. The reactor 3 employed an especially dangerous fuel called “MOX”, formed from a mixture of uranium more plutonium.

Fear of radiation leaks prompted authorities to evacuate a radius of twenty kilometers around the plant, then this radius extending to thirty and then forty. The plant workers suffered radiation exposure on several occasions and were temporarily evacuated on several occasions.

On Monday 11 April Nuclear Security Agency and Insdustrisl (NISA) raised the severity level of the incident 7 for reactors 1, 2 and 3, the maximum on the INES scale and reached the same level of Chernobyl 1986. Given the magnitude of the incident, the authorities immediately declared a “state of nuclear emergency”, carrying out urgent measures to mitigate the effects of the accident. Thus, the resident population was evacuated in adjacent areas (with a progressive increase in the security perimeter) or the armed forces were mobilized to control the situation.

During the days were taking new decisions, like injecting sea water and boric acid in any of the reactors, provide potassium iodide to the population or shift flights of civil aviation environment of the affected plant. The measures taken, both aimed at controlling the nuclear accident as focused on ensuring the stability of the Japanese financial system, were supported by agencies such as the World Health Organization or the International Monetary Fund.

In June 2011, it was confirmed that the three active reactors at the time of the disaster had suffered a meltdown.

After the failure of the cooling systems of the reactors at the nuclear plant, controlled releases of radioactive gases to the outside were made to reduce the pressure in the containment. An undetermined amount of radioactive particles released to the outside.

On Sunday March 27 was detected in the water inside the facility a radiation level a hundred thousand times higher than normal, possibly from a leak of reactor number 2. These radiation levels hampered the work of the operators. Also the levels of radioactive iodine in seawater near the plant were 1,850 times higher than that set legal limits. Plutonium was also detected outside the reactor, possibly from reactor number 3, the only one working with that element.A few days after the accident, radioactive iodine detected in tap water in Tokyo, as well as high levels of radioactivity in milk produced in the vicinity of the plant. A week after the accident in California could detect radioactive particles from Japan, who had crossed the Pacific Ocean. Some days after radioactive iodine was detected in Finland, although in both cases ruled that the levels of radiation detected were dangerous.

On Wednesday April 27 was detected in Spain and in other European countries according to the Council for Nuclear Safety, an increase of iodine and cesium in the air coming from the Fukushima accident. The Nuclear Safety Council stated that there was no danger to health. The Japanese government acknowledged that nuclear power can not again be operational and will be dismantled after the accident has been controlled.

 

Accidente de la central nuclear de Fukushima: Una explicacion simple

http://energia-nuclear.net/accidentes-nucleares/fukushima.html

http://www.world-nuclear.org/info/Safety-and-Security/Safety-of-Plants/Fukushima-Accident/