viernes, 7 de octubre de 2011
lunes, 29 de agosto de 2011
Los residuos sólidos finos provenientes del área de explotación pueden dar lugar a una elevación de la capa de sedimentos en los ríos de la zona. Algunos de los impactos reconocidos nos introducen en uno de los riesgos y amenazas de daño más significativos: El Agua, principal insumo de todo proyecto minero, es a la vez el recurso natural más escaso.El uso d
Diques y lagunas de oxidación mal construidas, mal mantenidas, con inadecuado manejo, almacenamiento y transporte de insumos (como combustibles, lubricantes, reactivos químicos y residuos líquidos) conducen a la contaminación de las aguas de superficie.
Los vientos impactan transportando el material particulado sobre los glaciares, sentenciando anticipadamente su paulatina pero segura agonía. La actividad minera genera, movimientos de tierra y polvos que se depositarán directamente sobre los glaciares, con lo cual se producirá un aumento de la temperatura de los mismos y su consecuente derretimiento.
En algunos lugares de Chile, Bolivia y Perú, los desvíos se efectúan cerca de fronteras internacionales, produciendo serios conflictos transfronterizos.
El agotamiento del agua asociado a la apertura de futuras minas a tajo abierto, inevitablemente reduce el nivel local y a veces regional del agua. Esto puede causar la sequía de los afluentes y reducir el nivel del agua en pozos vecinos. Esto último aumenta los costos de bombeo de agua ha
La reducción de vertientes y riachuelos puede afectar el uso de agua para el ganado y la vida silvestre nativa, así como los usos domésticos y municipales. El agotamiento se detiene cuando lo hace la minería, pero los niveles de agua podrían requerir de muchos años para volver a su estado original (o casi original).
lunes, 6 de junio de 2011
TOKYO — Japan declared states of emergency for five nuclear reactors at two power plants after the units lost cooling ability in the aftermath of Friday's powerful earthquake. Thousands of residents were evacuated as workers struggled to get the reactors under control to
Less than a year ago, a drilling rig exploded off the coast of the United States, kill
ing 11 workers and pouring 4 million barrels of oil into the Gulf of Mexico. No natural disaster cau
sed this tragedy. It was entirely man-made. President Obama halted deep-water drilling but lifted the moratorium less than six months later. On Friday, while fielding questions about Japan's nuclear reactors, he proudly noted that his administration, under new, stricter rules, had "approved more than 35 new offshore drilling permits."
That's how we deal with tragedies in the oil business. Accidents happen. People die. Pollution spreads. We don't abandon oil. We study what went wrong, try to fix it, and move on.
Contrast this with the panic over Japan's reactors. For 40 years, they've quietly done their work. Three days ago, they were hit almost simultaneously by Japan's worst earthquake and one of its worst tsunamis. Not one reactor container has failed. The only employee who has died at a Japanese nuclear facility since the quake was killed by a crane. Despite this, voices are rising in Europe and the United States to abandon nuclear power. Industry analysts predict that the Japan scare, like Chernobyl, will freeze plant construction.
Let's cool this panic before it becomes a political meltdown.
Early reports said four Japanese plants were in trouble. Now it appears only two were disabled. Early reports said three employees had radiation sickness. Now we're hearing only one is sick, and even in that case, the radiation dose appears relatively low. Two reactor buildings exploded, but these were explosions of excess hydrogen, not nuclear fuel, and neither of them ruptured the inner containers that encase the reactor cores. Some radiation has leaked, but according to measurements outside the plants,the amount so far is modest. Any leak
is bad, and the area of contamination, even at low rates, will probably spread. Japan needs our sympathy and our help. But let's not exaggerate the crisis.
In advanced countries like Japan and the United States, nuclear plants are built to standards no drilling rig can touch. If a sensor, cable, or power source fails, another sensor, cable, or power source is available. Containers of steel or concrete envelop the reactors to prevent massive radiation leaks. Chernobyl didn't have such a container. Three Mile Island did. That's why Three Mile Island produced no uncontrolled leakage or injuries.
Japan's plants were designed to withstand quakes and tsunamis, but not a combination of this magnitude. At the affected facilities, the quake knocked out the primary cooling systems, and the tsunami wiped out the backup diesel generators. Then a valve malfunction thwarted efforts to pump water into one of the reactors. Everything that could go wrong did.
Despite this, the reactor containers have held firm. The explosions around them have blown outward, relieving pressure, as designed. Meanwhile, plant operators, deprived of their primary and secondary power sources for cooling the cores, have tapped batteries and deployed alternate generators. To relieve pressure, they've released vapor. And in some cases, they've pumped seawater and boric acid into the reactors, destroying them to protect th
e public. Cooling systems are back online at two previously impaired reactors, and a backup pump has averted cooling problems at a third plant.
The reactor where the crisis began, Fukushima Daiichi Unit 1, is one of Japan's oldest. It was two weeks from its 40-year expiration date when the quake hit. Similar plants in the United States have been upgraded to ensure that in the event of power failure, water can still be pumped in to cool them.
And nuclear plants are indisputably getting safer. Since 1990, worker radiation exposure and automatic reactor shutdowns worldwide havedeclined by a factor of three. According to an analysis last year by the Nuclear Energy Agency of the Organization for Economic Co-operation and Development, plants being constructed by today's standards are 1,600 times safer than early nuclear plants, in terms of the predicted frequency of a large radiation leak. Even if a reactor core is damaged, as in Japan, the NEA report notes that today, "the probability of a release to the environment is about ten times less than that of core damage," thanks to improvements in fuel, circuits, and containment.
If Japan, the United States, or Europe retreats from nuclear power in the face of the current panic, the most likely alternative energy source is fossil fuel. And by any measure, fossil fuel is more dangerous. The sole fatal nuclear power accident of the last 40 years, Chernobyl, directly killed 31 people. By comparison, Switzerland's Paul Scherrer Institutecalculates that from 1969 to 2000, more than 20,000 people died in severe accidents in the oil supply chain. More than 15,000 people died in severe accidents in the coal supply chain—11,000 in China alone. The rate of direct fatalities per unit of energy production is 18 times worse for oil than it is for nuclear power.
Even if you count all the deaths plausibly related to Chernobyl—9,000 to 33,000 over a 70-year period—that number is dwarfed by the death rate from burning fossil fuels. The OECD's 2008 Environmental Outlook calculates that fine-particle outdoor air pollution caused nearly 1 million premature deaths in the year 2000, and 30 percent of this was energy-related. You'd need 500 Chernobyls to match that level of annual carnage. But outside Chernobyl, we've had zero fatal nuclear power accidents.
That doesn't mean we can ignore what has happened in Japan. Precisely because nuclear accidents are so rare, we have to study them intensely. Each one tells us what to fix in the next generation of power plants. The most obvious mistake in Japan was parking the diesel generators in an area low enough to be flooded by a quake-driven tsunami. The batteries that backed up the generators weren't adequate, either. They lasted only eight hours, and power outage fallback plans at U.S. reactors are even shorter. Moreover, this is the second time an advanced nuclear facility has had to vent radioactive vapor (Three Mile Island was the first). Maybe it's time to require filtration systems that scrub the vaporbefore it's released.
Sen. Joe Lieberman of Connecticut says we should "put the brakes" on nuclear power plant construction until we figure out what went wrong in Japan. Rep. Ed Markey of Massachusetts wants a moratorium on new reactors in "seismically active areas" while we study the problem. That's fine. But let's not block construction indefinitely while we go on mindlessly pumping oil. Because nuclear energy, for all its risks, is safer.