Monthly Archives: May 2014

Three Nuclear Accidents – An infographic.

Following on from last weeks post the Infographic below details three major nuclear accidents and the outcomes.  Graphic courtesy of LiveScience.
chernobyl nuclear disaster infographic
Source:LiveScience

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The Chernobyl Nuclear Plant Disaster

28 years ago in the early morning hours of April 26, 1986, the Chernobyl nuclear power plant in Ukraine (formerly part of the Soviet Union) exploded, creating what has been described as the worst nuclear disaster the world has ever seen.

 
Chernobyl is located about 81 miles (130 km) north of the city of Kiev in Ukraine, and about 12 miles (20 km) south of the border with Belarus.  The four reactors at the Chernobyl Nuclear Power Plant were designed and built during the 1970s and 1980s. A manmade reservoir, roughly 8.5 square miles (22 sq. km) in size and fed by the Pripyat River, was created to provide cooling water for the reactor.

On 26 April 1986, at 01:23, reactor four suffered a catastrophic power increase, leading to explosions in its core. This dispersed large quantities of radioactive fuel and core materials into the atmosphere and ignited the combustible graphite moderator. The burning graphite moderator increased the emission of radioactive particles, carried by the smoke, as the reactor had not been encased by any kind of hard containment vessel. The accident occurred during an experiment scheduled to test a potential safety emergency core cooling feature, which took place during a normal shutdown procedure.
In most nuclear reactors, where water is used as a coolant and to moderate the reactivity of the nuclear core, as the core heats up and produces more steam, the increase in steam bubbles or “voids” in the water reduces the reactivity in the nuclear core. This is an important safety feature found in most reactors built in the United States and other Western nations.
 
But not in the RBMK-1000, which used graphite to moderate the core’s reactivity and to keep a continuous nuclear reaction occurring in the core. As the nuclear core heated and produced more steam bubbles, the core became more reactive, not less, creating a positive-feedback loop that engineers refer to as a “positive-void coefficient.”
Basically, when extremely hot nuclear fuel rods were lowered into cooling water, an immense amount of steam was created, which — because of the RBMK reactors’ design flaws — created more reactivity in the nuclear core of reactor number 4. The resultant power surge caused an immense explosion that detached the 1,000-ton plate covering the reactor core, releasing radiation into the atmosphere and cutting off the flow of coolant into the reactor.
A few seconds later, a second explosion of even greater power than the first blew the reactor building apart and spewed burning graphite and other parts of the reactor core around the plant, starting a number of intense fires around the damaged reactor and reactor number 3, which was still operating at the time of the explosions.
The explosions killed two plant workers, who were the first of several workers to die within hours of the accident. For the next several days, as emergency crews tried desperately to contain the fires and radiation leaks, the death toll climbed as plant workers succumbed to acute radiation sickness.

Most of the radiation released from the failed nuclear reactor was from iodine-131, cesium-134 and cesium-137. Iodine-131 has a relatively short half-life of eight days, according to UNSCEAR, but is rapidly ingested through the air and tends to localize in the thyroid gland. Cesium isotopes have longer half-lives (cesium-137 has a half-life of 30 years) and are a concern for years after their release into the environment. 

On April 27, the residents of Pripyat were evacuated — about 36 hours after the accident had occurred. By that time, many were already complaining about vomiting, headaches and other signs of radiation sickness. Officials eventually closed off an 18-mile (30 km) area around the plant; residents were told they would be able to return after a few days, so many left their personal belongings and valuables behind.

Abandoned Pripyat

During the construction of the sarcophagus, a scientific team re-entered the reactor as part of an investigation dubbed “Complex Expedition”, to locate and contain nuclear fuel in a way that could not lead to another explosion. These scientists manually collected cold fuel rods, but great heat was still emanating from the core. Rates of radiation in different parts of the building were monitored by drilling holes into the reactor and inserting long metal detector tubes. The scientists were exposed to high levels of radiation and radioactive dust.

After six months of investigation, in December 1986, they discovered with the help of a remote camera an intensely radioactive mass in the basement of Unit Four, more than two metres wide and weighing hundreds of tons, which they called “the elephant’s foot” for its wrinkled appearance. The mass was composed of sand, glass and a large amount of nuclear fuel that had escaped from the reactor. The concrete beneath the reactor was steaming hot, and was breached by solidified lava and spectacular unknown crystalline forms termed chernobylite. It was concluded that there was no further risk of explosion.

Contamination from the Chernobyl accident was scattered irregularly depending on weather conditions, much of it deposited on mountainous regions such as the Alps, the Welsh mountains and the Scottish Highlands, where adiabatic cooling caused radioactive rainfall.

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Magnesium

Magnesium has the atomic number 12 and is an alkaline earth metal with the symbol Mg. It is a common element, the eighth-most-abundant element in the Earth’s crust and ninth in the known universe as a whole. Magnesium is the fourth-most-common element in the Earth as a whole (behind iron, oxygen and silicon), making up 13% of the planet’s mass and a large fraction of the planet’s mantle.

The free element (metal) is not found naturally on Earth, as it is highly reactive (though once produced, it is coated in a thin layer of oxide (see passivation), which partly masks this reactivity). The free metal burns with a characteristic brilliant-white light, making it a useful ingredient in flares. You probably remember burning Magnesium Ribbon in school.  Some of the light that burning magnesium produces is in the ultraviolet range. Just as ultraviolet light will burn your skin, it will also burn the retinas of your eyes if they are not protected, hence not looking directly at the light or using suitable safety eyewear.



Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength.

Magnesium has many uses, but most of us are familiar with aluminium-magnesium alloys, which are often found in cell phones and other electronic gadgets that must be strong yet light weight. Gardeners and tropical fish hobbyists are also very familiar with magnesium, since plants need it to grow (a magnesium deficiency is indicated by yellow leaves).  Animals need small amounts of magnesium to support proper bodily functions too.

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What is a Rotary Evaporator?

A rotary evaporator is a device used in laboratories for the efficient and gentle removal of solvents from samples by evaporation. Scientists often talk about a sample being evaporated under reduced pressure – ie in a rotary evaporator.

Rotary evaporators are also used in molecular cooking for the preparation of distillates and extracts.

 


The main components of a rotary evaporator are:

  1. A motor unit that rotates the evaporation flask or vial containing the user’s sample.
  2. A vapour duct that is the axis for sample rotation, and is a vacuum-tight conduit for the vapour being drawn off of the sample.
  3. A vacuum system, to substantially reduce the pressure within the evaporator system.
  4. A heated fluid bath (generally water) to heat the sample.
  5. A condenser with either a coil passing coolant, or a “cold finger” into which coolant mixtures such as dry ice and acetone are placed.
  6. A condensate-collecting flask at the bottom of the condenser, to catch the distilling solvent after it re-condenses.
  7. A mechanical or motorised mechanism to quickly lift the evaporation flask from the heating bath.

The vacuum system used with rotary evaporators can be as simple as a water aspirator with a trap immersed in a cold bath (for non-toxic solvents), or as complex as a regulated mechanical vacuum pump with refrigerated trap.

Glassware used in the vapour stream and condenser can be simple or complex, depending upon the goals of the evaporation, and any propensities the dissolved compounds might give to the mixture (e.g., to foam or “bump”).

Commercial instruments are available that include the basic features, and various traps are manufactured to insert between the evaporation flask and the vapour duct. Modern equipment often adds features such as digital control of vacuum such as the KNF SC950 unit shown below, digital display of temperature and rotational speed, and vapour temperature sensing.

Users of rotary evaporators must take precautions to avoid contact with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. Under these circumstances, the winding action of the rotating parts can draw the users into the apparatus resulting in breakage of glassware, burns, and chemical exposure. Extra caution must also be applied to operations with air reactive materials, especially when under vacuum. A leak can draw air into the apparatus and a violent reaction can occur.  Care must also be taken to avoid implosions resulting from use of glassware that contains flaws, such as star-cracks. Explosions may occur from concentrating unstable impurities during evaporation.


What would it be like… if you could just disappear from the daily lab routine? As easily and quickly as liquid escapes from the rotary evaporator? This is the fantasy in the IKA image video above.

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The World Cup is fast approaching…..the science of the football

The early forms of football played in England, sometimes referred to as “mob football”, would be played between neighbouring towns and villages, involving an unlimited number of players on opposing teams who would clash en masse, struggling to move an item, such as inflated animal’s bladder to particular geographical points, such as their opponents’ church, with play taking place in the open space between neighbouring parishes.

The 2014 FIFA World Cup will be the 20th FIFA World Cup, that is scheduled to take place in Brazil from 12 June to 13 July 2014.

The first balls were made of natural materials, such as an inflated pig bladder, later put inside a leather cover, which has given rise to the United States slang-term “pigskin”. Modern balls are designed by teams of engineers to exacting specifications, with rubber or plastic bladders, and often with plastic covers. Various leagues and games use different balls.

The precise shape and construction of footballs is typically specified as part of the rules and regulations.

Most modern footballs are stitched from 32 panels of waterproofed leather or plastic: 12 regular pentagons and 20 regular hexagons. The 32-panel configuration is the spherical polyhedron corresponding to the truncated icosahedron; it is spherical because the faces bulge from the pressure of the air inside.

The first 32-panel ball was marketed by Select in the 1950s in Denmark. This configuration became common throughout Continental Europe in the 1960s, and was publicised worldwide by the Adidas Telstar, the official ball of the 1970 World Cup.

A truncated icosahedron (left) compared with a football


The familiar 32-panel football design is sometimes referenced to describe the truncated icosahedron Archimedean solid, carbon buckyballs (as below) or the root structure of geodesic domes.

Buckminsterfullerene C60


There are a number of different types of football balls depending on the match and turf including: training footballs, match footballs, professional match footballs, beach footballs, street footballs, indoor footballs, turf balls, futsal footballs and mini/skills footballs.

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