SCIENCE & TECHNOLOGY

 Secrets of ‘deadly’ plutonium
K.S. Parthasarathy
P
lutonium (media always call it “deadly”) was the first synthetic element which Glen Seaborg and his co-workers produced in 1941 at the Berkeley Radiation Laboratory, University of California. Scientists know very well the complex nuclear properties of plutonium. What puzzles them is the fact that it has properties of a metal or a chemical compound.

Trends
No-reflection coating
T
he velvet background on a painting of Elvis looks black because it reflects so little light. But getting a surface to reflect no light at all is surprisingly difficult. Now, researchers have created a virtually reflection-free surface by coating it with filaments only a few billionths of a metre thick.

Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE 
PROF YASH PAL
When we talk on the telephone the speech travels back and forth almost instantaneously. This is true even when we speak to someone in the US. But sound waves do not seem to travel that fast. Why this difference?

 


Top










Secrets of ‘deadly’ plutonium
K.S. Parthasarathy

Plutonium (media always call it “deadly”) was the first synthetic element which Glen Seaborg and his co-workers produced in 1941 at the Berkeley Radiation Laboratory, University of California. Scientists know very well the complex nuclear properties of plutonium. What puzzles them is the fact that it has properties of a metal or a chemical compound. Physicists at Rutgers, The State University of New Jersey recently unlocked some of the secrets of plutonium (Nature, March, 29).

Unlike many metals plutonium is not magnetic; it is not a good conductor of electricity. Further, it shows greater changes in volume when subjected to small changes in temperature and pressure.

The atomic structure of an element, especially the number of valence electrons, decides its properties. Earlier theories specified that the outer orbits in an atom of any element have fixed number of valence electrons.

Rutger’s group abandoned this idea and argued that the valence electrons — those which control how atoms bond with each other — fluctuate among different orbitals in solid plutonium metal on a very short time scale.

This explains the properties that scientists observe during experiments in the laboratory.

These findings and study methods may some day help scientists create safer and more versatile nuclear materials for energy industry and medicine (EurekAlert, 2007)

Why are scientists so enthusiastic about studying plutonium? We may use plutonium to make nuclear weapons or to make fuel for nuclear power plants. People are afraid of plutonium because of its association with weapons. Whenever media refers to plutonium, it invariably uses the adjective “deadly”. Besides the media, public and even some scientists continue to believe incorrectly that plutonium is the most deadly element known. They wrongly believe that a single speck of plutonium inhaled can kill a person.

In 1993, The US Health Physics Society whose mission is to promote radiation safety published a position paper titled “What about ‘deadly plutonium’?” “The radiological hazards of plutonium are of the same types and magnitudes as those of such naturally occurring radioactive elements as radium and thorium,…the potential for public exposure to plutonium is negligible compared with thorium, which is found everywhere in soil and rock; it is three times as abundant as uranium and about as abundant as lead in the earth’s crust,” the position paper assured the reader.

Plutonium is chemically toxic. Substances such as arsenic, cyanide, caffeine have equal or greater toxicity (Uranium Information Centre, September 2006). The risks from plutonium are well known.

Once, Ralph Nader, the legendary US consumer activist claimed that plutonium is “the most toxic substance known to mankind”. Prof Bernard Cohen, University of Pittsburgh, offered to eat as much plutonium as Mr Nader would eat of caffeine, to demonstrate the folly of his severe toxicity claims! Nader did not accept the challenge!

Plutonium may enter human body through ingestion, inhalation or contamination of wounds. Gastro-intestinal tract poorly absorbs ingested plutonium. Though workers have handled tons of plutonium, cases of contamination through wounds occurred only very rarely. There has not been even a single death attributed to plutonium exposure.

When I joined the Atomic Energy Establishment Training School, Trombay, in 1963, one of the jokes going round was that if anyone utters the word “plutonium” he must wash his mouth well with water at least three times, apparently to avoid the poisoning effect of plutonium!

Plutonium is a beneficial element. Over a third of the energy produced in most nuclear power plants comes from plutonium. Plutonium produced in reactors and from dismantled nuclear weapons is a valuable energy source.

India set up its first plutonium plant on January 22, 1965. Plutonium will play an important role in India’s three-stage nuclear power programme.

India is one among the handful of countries that has mastered all aspects of plutonium technology. We must not allow unfounded fear of technology to come in the way of progress.

Top

Trends
No-reflection coating

The velvet background on a painting of Elvis looks black because it reflects so little light. But getting a surface to reflect no light at all is surprisingly difficult. Now, researchers have created a virtually reflection-free surface by coating it with filaments only a few billionths of a metre thick.

Improved anti-reflective surfaces might have many uses. For example, they could eliminate light-wasting reflections in fiber-optic telecommunications, or the surfaces could brighten low-power light-emitting diode (LED) lamps.

Applied to a clear surface, the coating would make a lens absorb more light, increasing its transparency. On an opaque surface, the filaments would make a silicon solar cell, for example, almost perfectly absorbing.

The coating creates “really a new class of materials,” says E. Fred Schubert, a member of the research team at Rensselaer Polytechnic Institute in Troy, N.Y.

Asteroids are solar powered

Sunlight can cause asteroids to spin more quickly, scientists said on Wednesday, showing a new just how dynamic a place our solar system can be.

International teams of scientists studying two asteroids, one about a mile wide and the other about 375 feet wide, confirmed a previously unproven theory that sunlight can affect the rotation of asteroids because they tend to be irregularly shaped and not perfectly round.

Stephen Lowry of Queen’s University Belfast in Northern Ireland said the findings boost the understanding of the physical properties and dynamics of asteroids — chunks of metal and rock rattling around in space.

This is important as asteroids are leftovers from the formation of the solar system, along with comets, and so by studying them we gain insights into what the solar system was like some 4.5 billion years ago,” Lowry said by e-mail.

Map search by camera phones

Lost in Seattle with nothing but a camera phone? Just snap a picture of a nearby building, send off the photo to a database and soon you’ll get back a map and information about where you are.

The new web service is one of over 40 new technologies and ideas displayed by Microsoft Corp. at its research department’s annual TechFest fair.

Microsoft Research TechFest is the world’s largest software maker’s chance to show off the talent of its 750 global researchers, who are working on problems ranging from how to use sensors in medical science to how to view high-definition pictures through a web browser.

The technologies and products on display are at various stages of development. Some are ready to be incorporated into existing products, while others are years away from finding the right application to utilise the technology. —Reuters

Top

THIS UNIVERSE 
PROF YASH PAL

When we talk on the telephone the speech travels back and forth almost instantaneously. This is true even when we speak to someone in the US. But sound waves do not seem to travel that fast. Why this difference?

When we use the telephone, we produce sound that travels to the nearby mouthpiece. The microphone converts the sound vibrations into electrical variations. What goes over the wire is the electrical signal. The instrument of the receiver converts the electrical signal into sound. The electrical signal travels almost with the velocity of light, which is 300,000 kilometres per second. To travel to America and back would take about 1/8 of a second. That is almost instantaneous as far as human perception is concerned.

Sound waves move through compression and decompression of the material medium in which they travel. Sound is a mechanical wave that is necessarily much slower than an electromagnetic wave, which does not require a medium to travel. The electrical signal in wires also moves extremely fast because electrons being conveyers of this signal also travel very fast. In microwave transmission lines electromagnetic waves travel as if they are going through a pipe. The household TV cable is an example of that. Such cables crisscross large distances on land and under the oceans. These days one also uses optical fiber cables and satellites to convey signals over long distances. For optical communication the signal is converted to digitally modulated light beam that travels at the speed of light through thin fibers of glass. When we take the satellite route we have to go up to the satellite 36,000 kilometres above the earth and the same distance back down to a ground station from where the normal telephone network takes over. Because of this reason it is often found that when we happen to get a satellite channel there is a delay of about a quarter second each way and about half a second between your asking a question off a friend in America and hearing his reply. After a while people learn to live with this inconvenience.

Top


HOME PAGE