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Nuclear fuel from N-waste Space expenditure justified: Narlikar
Trends
THIS UNIVERSE Prof Yash
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Nuclear fuel from N-waste Many people consider management of high-level nuclear waste as a complex issue. The fuel discharged from a nuclear power reactor contains 94 per cent uranium,1 per cent transuranic elements such as neptunium, plutonium, americium and curium and about 5 per cent fission products such as caesium-137, strontium-90 etc Transuranic elements are long lived and remain toxic for thousands of years. There is international consensus that the nuclear industry can design, construct and operate deep geological repositories to dispose of high-level waste, including transuranic elements permanently. There may be smarter solutions. A few years ago, scientists from the Bhabha Atomic Research Centre argued that we can eliminate the stigma attached to nuclear waste and nuclear energy, if we recover some of the transuranic elements, and use them as nuclear fuel. The study, authored by M. Srinivasan, K. Subba Rao, S Garg and P K Iyengar and presented at the 5th International Conference on Emerging Nuclear Energy Systems at Kalsruhe in July 1989 found that each and every isotope of transuranic elements is a more valuable nuclear fuel than the corresponding fissile isotopes of plutonium. Fission products in the used fuel arise from the splitting of uranium or transuranic elements. Most of the fission products such as caesium-137 which have half-lives of a few tens of years decay relatively rapidly. In a few hundred years, the activity of fission products such as cesium-137 will be negligible. We must keep the long-lived activity away from the biosphere for a long period because of the presence of long-lived transuranic radionuclides such as plutonium-239 (half-life 24,000 years). If we destroy transuranic elements by some means, the long-term radiation hazard will reduce substantially; the activity will be insignificant after a few hundred years. One method is to burn them efficiently in fast reactors. Keeping the active material away for a few hundred years is feasible If we irradiate uranium in light water reactors, at a power level of 1000 MWe for just over a month, every tonne of spent fuel, after a few years of cooling, will contain nearly 10 kg of plutonium, 0.5 kg of neptunium, 0.041 kg of curium and 0.14 kg of americium. These elements are not “wastes”. Scientists will be able to develop innovative recovery methods and fuel fabrication technologies to use these elements. The production rate of heavy elements in the thorium-uranium-233 cycle is a million times less than those in the uranium-238-uranium-235 cycle. This is because fuels based on uranium-238-uranium-235 cycle need only two successive neutron captures to produce heavier nuclides; the urtanium-233 fuel cycle needs 7 to 8 neutron captures. There are exotic schemes to transmute radionuclides in waste streams using novel non-fission neutron sources such as spallation targets, superconducting cyclotrons or fusion reactor blankets. For instance, Yousry Gohar from the Argonne National Laboratory suggested that 344-MW- integrated- fusion power from deuterium-tritium plasmas for 30 years with an availability factor of 0.75, can dispose of 70,000 tons of the US inventory of spent fuel generated up to 2015. The concept eliminates the need for a deep geological repository site. He claimed that show- casing the device which offers energy from the transmutation process to produce revenue, may help to enhance public acceptance of fusion energy. Ultimately, the simplicity of the process and the cost- benefit criteria will prevail. BARC study is mostly theoretical. BARC scientists have developed methods to recover heavy elements on a laboratory scale I justify referring to the 1989 Indian study now because new ways related to high level nuclear waste management are still under discussion. USA and Sweden plan to dispose of the spent fuel without reprocessing. India, France, UK and Japan will reprocess it to recover plutonium. In 1977, Jimmy Carter halted funding for reprocessing of spent fuel. USA is now considering the revival of the programme .The proposed US policy aims to reduce the number of geologic repositories in USA to one, reuse valuable parts of the used fuel to maximize the energy from uranium ore and to recycle used fuel to minimize waste. India’s atomic energy programme which Dr. Bhabha proposed in 1954 had all these elements! — K.S. Parthasarathy is former Secretary, Atomic Energy Regulatory Board
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Space expenditure justified: Narlikar Jayant Narlikar, Padama Vibhushan awardee and Emeritus Professor at the Inter-University Centre for Astronomy and Astrophysics, is the leading Indian astrophysicist internationally known for his work in cosmology, in championing models alternative to the popularly believed Big Bang model. In a brief interview with The Tribune’s Bhartesh Singh Thakur, Narlikar deliberated on the fundamental question of justification of spending big dollars on space missions in the background of equally undeniable poverty on the earth. Bhartesh: Recently, NASA’s $ 420 million Phoenix probe, which also has Canadian Space Agency’s investment of $37 million for the meteorological station, landed on Mars’s north pole successfully. As a theoretical scientist, do you consider it right to spend huge money on space missions just to find out whether microbes exist in extra-terrestrial space or not? Narlikar: Man has always been inspired by the spirit of adventure. Why climb Mt Everest? Why go sailing round the earth single-handed? What made Columbus and Vasco-de-Gama undertake long voyages? Having conquered the earth it is but natural that man turns his eyes to space. Landing on the moon, safaris to Mars, etc have to be looked at in this way in the first instance. Secondly, these exploits may have long-term advantages. Space colonies, habitats on the Moon and Mars may become realities in the future. Economic gains will follow. For example, the problem faced on the Earth may be solved by erecting huge reflectors in space collecting solar energy. Thus what may appear huge investments today may pay dividends later. Recall that the colonial nations ultimately gained by the voyages of early adventures. B: But this money could be spent on poverty alleviation programmes. N: It is fallacy to argue that if this money were not spent on space programme, it would be available to fight poverty on the earth. The money could have gone more likely into armaments, corruption etc. which have higher proximity on the political agenda.
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Trends Georgia Tech researchers think the SnoMote — a small robot designed like a snowmobile — will be able to deal with the nasty weather and with slippery terrain that constantly cracks and shifts. They envision dozens of SnoMotes roving Antarctica’s vast expanses to add to data already collected by satellites and a handful of weather stations and sensors. Ayanna Howard, an associate professor at Georgia Tech in Atlanta, has worked for two years under a NASA grant to perfect the 2-foot-long robots. — AP Shrimps can see beyond rainbow
A giant shrimp living on Australia’s Great Barrier Reef can see a world beyond the rainbow that is invisible to other animals, scientists said
on Wednesday. Mantis shrimps, dubbed “thumb splitters” by divers because of their vicious claws, have the most complex eyes in the animal kingdom, capable of seeing colours from the ultraviolet to the infrared, as well as detecting other subtle variations in light. They view the world in up to 12 primary colours — four times as many as humans — and can measure six different kinds of light polarization, Swiss and Australian researchers reported. Polarization is the direction of oscillation in light waves. Just why Gonodactylus smithii needs this level of rarefied vision is unclear, although the researchers suspect it is to do with food and sex. —Reuters Monkey with robotic arm
“They are using a motorised prosthetic arm to reach out, grab and bring the food back to their face,” said Andrew Schwartz of the University of Pittsburgh School of Medicine, whose study will appear in an upcoming issue of the journal Nature. Schwartz said the technology behind this feat may lead to brain-powered prosthetic limbs for people with spinal cord injuries or disabling diseases that make such simple
tasks impossible. The monkey guides the robot arm the same way it does its natural limbs, through brain signals.—
Reuters
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THIS UNIVERSE This phenomenon has a beautiful origin. We all know that the sun is very hot even on its surface. The atoms on the surface are highly ionised. Most of the atoms being those of hydrogen leads to a plasma consisting largely of protons and electrons. Due to the high temperature, helped by turbulent electromagnetic fields, the sun emits a mixture of protons, some nuclei of a few other atoms and electrons. This mixture travels out into space at speeds of a few hundred kilometres per second. Such an emission, known as the solar wind, is believed to be a common feature of all stars. Unlike light this represents physical transport of solar material. Now think of what can happen when this swarm of charged particles approaches the earth. The first obstruction it encounters is the earth’s magnetic field, much earlier than its atmosphere. You know what happens when a wire carrying current interacts with a magnetic field? It is subjected to a force that is normal to the direction of both, the electric current and the magnetic field (Remember that each moving charged particle, positive or negative, is like a current). Earth’s magnetic field is almost like that of a bar magnet with its poles quite near to the geographic poles of the earth. At low latitude the magnetic field is almost parallel to the earth surface. As a result, the charged particles are bent away from the earth. On the other hand, near the magnetic poles the particles are travelling parallel to the magnetic field. Hence, they do not suffer much deflection and can sneak into the upper atmosphere. It is here that a visible drama is enacted. Charged particles plowing through the thin air ionise its atoms to various levels and de-excitation of these atoms produces multicoloured light at various levels of the upper levels of the atmosphere. Changing density and spread of the incoming streams of protons and electrons produce dancing sheets of colour. This is the magnificent spectacle of Aurora. Why does a membrane form on milk when it is left exposed to the air, but not when the vessel is covered? I suspect you are talking of warm milk. When milk is heated, the cream globules along with casein, being lighter, come to the top. In an open pot, there is more cooling from the top because of evaporation and increased radiation. When hot, the cream is almost a liquid. If the water begins to evaporate, the globules of cream and casein coalesce. As they cool, the cream begins to get thicker and begins to look like a membrane. When the pot is covered, evaporation from the surface is dramatically reduced. The cream and casein globules remain separated by watery milk that inhibits the formation of the membrane. But, I suspect even in this case you will get a layer of “malai”, the membrane you talk about. So, there. Now everyone can have a go at it.
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Robotic rovers have patrolled deep space and the deepest seas, but scientists are still struggling to create drones that can overcome the multiple challenges of exploring Antarctica.
Using only its brainpower, a monkey can direct a robotic arm to pluck a marshmallow from a skewer and stuff it into its mouth, researchers said
on Wednesday.