Category: AQA Unit 5 Nuclear/ Thermal

France expands nuclear power plans despite Fukushima

BBC News Update……… http://www.bbc.co.uk/news/world-europe-13595455 People look at the construction site of the third-generation European Pressurised Water nuclear reactor (EPR) in Flamanville, north-western France, in this file picture taken in April 2011

With dwindling fossil fuel supplies, France is increasingly reliant on its nuclear power plants which now provide it with three-quarters of its electricity

In the aftermath of Japan’s nuclear crisis at Fukushima, some European nations are rethinking their atomic plans. But France, home to 58 of 143 reactors in the EU, remains nuclear energy’s champion, and plans not to retire its power stations but to expand them. Emma Jane Kirby examines why.

For many tourists visiting the tranquil north Normandy coast, the giant EPR reactor at Flamanville is little more than a lamentable industrial scar on a rather beautiful landscape.

But to the French government, Flamanville’s European Pressurised Reactor (EPR) is the embodiment of the future.

Following the disaster at Japan’s Fukushima nuclear power station – which was heavily damaged by the deadly 11 March quake and tsunami – President Nicolas Sarkozy announced there would be an audit of all nuclear facilities.

But he added firmly that France would not be rethinking its nuclear energy policy as neighbours Germany, Italy and Switzerland have.

Unlike Germany’s reversal of policy on Monday that will see it phase out the country’s 17 nuclear power stations by 2022, Mr Sarkozy said France was confident that nuclear energy was safe and it was “out of the question” to end nuclear power.

The EPR being constructed in Flamanville is marketed as the most secure power station yet.

A protester wearing a gas mask stands in front of the construction site of the third-generation European Pressurised Water nuclear reactor (EPR) in Flamanville, during an anti-nuclear demonstration, on 23 April, 2011Anti-nuclear protesters have made their thoughts about the Flamanville expansion abundantly clear. It is built by EDF, a company which is 80% owned by the French government. The system is organised into four sub-systems (current plants in operation only have two), each located in separate rooms away from the reactor building.

Simultaneous failure of the systems is regarded as almost impossible; the idea is that if an incident were to occur on one of the systems, the reactor could continue to operate safely during repairs, as at least two other systems would remain available.

In the event of a meltdown, the core would be isolated by the reactor building’s dual-wall containment which has one wall in pre-stressed concrete designed to withstand significant increases in pressure, and the second in reinforced concrete, known as the concrete shell. But many French people – including Didier Anger, an anti-nuclear campaigner and former MEP – are not convinced.

Tsunami breaching the power plant's defences (Image: TEPCO)Fukushima was heavily damaged by the 11 March quake and tsunami. “That’s just propaganda,” Mr Anger told the BBC at his home a few miles inland from Flamanville. He pointed to the strong ties between EDF and the French government and asked how we could trust the government’s word about nuclear safety when it owns such a massive stake in the company that builds the reactors? It was all, he insisted, the “same club”.

“France claims to be a democracy,” he laughed. “But in terms of the nuclear industry we are yet to prove that! “A few weeks ago, after Fukushima, the current director of our nuclear safety authority announced in front of MPs that perhaps we should stop the EPR reactor to look at any possible problems.

“A few hours later he was made to back-pedal… he was silenced… because the power of the old boys’ network is formidable in France.”

Two years ago, cracks were found in the concrete base of the reactor dome at Flamanville and welding proved to be sub-standard. Addressing those safety issues has meant the project is now at least two years behind schedule and way over budget.

This week, European nuclear watchdogs must start safety checks – or stress tests – on their nuclear facilities to make sure they could withstand an earthquake or tsunami like that at Fukushima. Although a 9m (30 ft) wave is unlikely on the North Normandy coast at Flamanville, Prof Jacques Foos, one of France’s most respected nuclear scientists, says all precautions must be taken. “The accident at Fukushima proved completely extraordinary events can happen,” he told me. “So what would happen if a giant wave did hit one of our nuclear power plants? We need to check that out. “I’m not saying we need to think about every eventuality such as what would happen if we were struck by a meteorite… but I am saying that when we build nuclear power plants now, we have to think the unthinkable.” The high-tech EPR reactor at Flamanville has been designed to withstand disasters such as a plane crash – but older reactors will not have such sophisticated security systems. Claude Birraux, an MP with President Sarkozy’s governing UMP party, has been chairing the official French parliamentary inquiry into the Fukushima accident, and hopes that the EU stress tests coupled with the separate French audit will help to reassure a nervous French public.

Environmentalist group Greenpeace activists are suspended next to protest banner on one of the cooling towers of the nuclear plant of Belleville-sur-Loire, central France, in March 2007Critics say businesses are scared off by the EPR reactor

“There will be a review made by the safety authorities and if one nuclear power plant is not able to answer to those questions (set by the EU), it can maybe be shut down,” he said. “Maybe.”

Nuclear technology is one of France’s major exports. Three years ago, France struck a deal with the UK to build four new EPR reactors in Britain but in December 2009 it lost a $40bn (£24bn) reactor deal with Abu Dhabi amid recriminations that it was too costly.

President Sarkozy insisted that the deal was lost because its high safety standards drove up the cost. Professor Jacques Foos hopes that in a post-Fukushima world its “safety first” EPR reactors will bring in more business for France. “We will see a boost in sales now,” he said confidently. “Because who would baulk at paying for safety these days? You can’t have a reactor these days that’s thought of as being too safe.” A boost in sales should result in a boost in jobs but that’s not an argument that holds much sway with anti-nuclear campaigner Didier Anger. Building on a second EPR reactor on the Normandy coast at Penly begins next year but Mr Anger doubts it will boost employment.

“In Flamanville, we thought the EPR would bring a lot of employment… but 50% of the workers are from Poland or Romania, or at least not from here,” he complained. He pointed to the high 9.7% unemployment rate in the Cherbourg area and asked me why I thought the jobless total was so high. “It’s because a lot of businesses are scared off by the EPR reactor,” said Mr Anger. “They think what if there was an accident? The exclusion zone would be 20km [12 miles] or more. That’s no good for business… so they don’t set up here.”

Nuclear landscape? But if France is to make more sales with the EPR reactor, who will the new customers be when most of Europe appears to be pulling out of the nuclear energy game and mothballing their old reactors? Could nuclear technology be sold to countries which simply aren’t ready to deal with the potential risks?

Chernobyl's Number Four Reactor - 20 April 2011Memories of the disaster at Chernobyl linger in France quarter of a century later. MP Claude Birraux insists that France will only sell nuclear technology to responsible countries. “There are three rules: safety, safety and safety, whatever the cost,” he said. “You need to have regulation, legislation and you need an independent safety authority… otherwise no… you can’t have it.”

France began developing its civilian nuclear programme as a response to oil shortages in the 1970s. With dwindling fossil fuel supplies, the country is increasingly reliant on its nuclear power plants which now provide it with three-quarters of its electricity.

Nuclear energy, said Claude Birraux, was essential for “French independence”. With 58 nuclear reactors already in operation here, sites like Flamanville look likely to be part of the French landscape for many years to come.

Permanent link to this article: https://animatedscience.co.uk/2011/france-expands-nuclear-power-plans-despite-fukushima

UK’s atomic clock ‘is world’s most accurate’

This is an article from BBC Science, really useful for how we work out units!

By Jason Palmer Science and technology reporter, BBC News, Teddington

Caesium clock at NPL (NPL)An atomic clock at the UK’s National Physical Laboratory (NPL) has the best long-term accuracy of any in the world, research has found.

Studies of the clock’s performance, to be published in the journal Metrologia, show it is nearly twice as accurate as previously thought.

The clock would lose or gain less than a second in some 138 million years.

The UK is among the handful of nations providing a “standard second” that keeps the world on time.

However, the international race for higher accuracy is always on, meaning the record may not stand for long.

The NPL’s CsF2 clock is a “caesium fountain” atomic clock, in which the “ticking” is provided by the measurement of the energy required to change a property of caesium atoms known as “spin”.

By international definition, it is the electromagnetic waves required to accomplish this “spin flip” that are measured; when 9,192,631,770 peaks and troughs of these waves go by, one standard second passes.

Matching colours

Inside the clock, caesium atoms are gathered into bunches of 100 million or so, and passed through a cavity where they are exposed to these electromagnetic waves.

The colour, or frequency, is adjusted until the spins are seen to flip – then the researchers know the waves are at the right frequency to define the second.

The NPL-CsF2 clock provides an “atomic pendulum” against which the UK’s and the world’s clocks can be compared, ensuring they are all ticking at the same time.

That correction is done at the International Bureau of Weights and Measures (BIPM) in the outskirts of Paris, which collates definitions of seconds from six “primary frequency standards” – CsF2 in the UK, two in France, and one each in the US, Germany and Japan.

For those six high-precision atomic pendulums, absolute accuracy is a tireless pursuit.

At the last count in 2010, the UK’s atomic clock was on a par with the best of them in terms of long-term accuracy: to about one part in 2,500,000,000,000,000.

What time is it, exactly?

World clock

  • The international time standard is maintained by a network of over 300 clocks worldwide
  • These are sent by satellite and averaged at BIPM, a measurement institute in France
  • But the “tick” of any one of them could drift out of accuracy, so BIPM corrects the average using six “primary frequency standards” in Europe, the US and Japan
  • Their corrected result, “International Atomic Time”, is occasionally compared with the time-honoured measure of time by astronomical means
  • Occasionally a “leap second” is added or subtracted to correct any discrepancy

But the measurements carried out by the NPL’s Krzysztof Szymaniec and colleagues at Pennsylvania State University in the US have nearly doubled the accuracy.

The second’s strictest definition requires that the measurements are made in conditions that Dr Szymaniec said were impossible actually to achieve in the laboratory.

“The frequency we measure is not necessarily the one prescribed by the definition of a second, which requires that all the external fields and ‘perturbations’ would be removed,” he explained to BBC News.

“In many cases we can’t remove these perturbations; but we can measure them precisely, we can assess them, and introduce corrections for them.”

The team’s latest work addressed the errors in the measurement brought about by the “microwave cavity” that the atoms pass through (the waves used to flip spins are not so far in frequency from the ones that flip water molecules in food, heating them in a microwave oven).

A fuller understanding of how the waves are distributed within it boosted the measurement’s accuracy, as did a more detailed treatment of what happens to the measurement when the millions of caesium atoms collide.

Without touching a thing, the team boosted the known accuracy of the machine to one part in 4,300,000,000,000,000.

But as Dr Szymaniec said, the achievement is not just about international bragging rights; better standards lead to better technology.

“Nowadays definitions for electrical units are based on accurate frequency measurements, so it’s vital for the UK as an economy to maintain a set of standards, a set of procedures, that underpin technical development,” he said.

“The fact that we can develop the most accurate standard has quite measurable economic implications.”

Permanent link to this article: https://animatedscience.co.uk/2011/uks-atomic-clock-is-worlds-most-accurate

Exam Past Papers Unit 5 & 5D

Here is a zipped file structure to download to your PC. It contains all the exam questions from AQA for Unit 5 from 2002 to 2010. Remember this includes the legacy or old spec papers from 2002-8 which are very similar.

Turning Points Exam Papers 2002_10

Permanent link to this article: https://animatedscience.co.uk/2011/exam-past-papers-unit-5-5d

The Electron a “charged particle”

The story of cathode rays begins in 1855. In that year, Heinrich Geissler invented the mercury vacuum pump. With the pump he could remove almost all of the air from a sealed glass tube.  Geissler’s friend Julius Plucker used the pump to evacuate a special kind of tube. Inside the tube were two electrodes. Plucker attached one electrode, called the anode, to the positive terminal of a battery. He attached the other electrode, the cathode, to the negative terminal. He noticed that the glass near the cathode glowed with greenish light. When Plucker held a magnet near the tube, the glowing spot moved.  Plucker’s student, Johann Wilhelm Hittorf, put solid objects inside the tube between the cathode and the glow. The objects cast shadows. Hittorf concluded that the cathode was emitting something that travelled in straight lines, like light rays. The German physicist Eugen Goldstein named them “cathode rays.”

The English scientist William Crookes thought cathode rays were streams of molecules that had picked up a negative electric charge. Crookes knew from the laws of electricity and magnetism that a charged particle in a magnetic field would move in a circle. Since a magnetic field caused cathode rays to move in a circle, Crookes reasoned, they must be made of charged particles.

If cathode rays were streams of charged particles, an electric field also should have deflected their path. The German physicist Heinrich Hertz tested this hypothesis. He set a cathode ray tube between two metal plates. One plate was positively charged and the other was negatively charged. Negatively charged molecules should have been attracted to the positive plate. When Hertz connected his tube to the battery, the cathode rays kept going in a straight line. Hertz concluded that the cathode rays were a new kind of electromagnetic wave.  Hertz’s student, Philipp Lenard, designed a cathode ray tube with a thin foil at one end. The cathode rays went right through the foil. Since molecules of gas could not go through the foil, Lenard knew that cathode rays could not be charged molecules. He agreed with his teacher that they must be electromagnetic waves.

Then Jean-Baptiste Perrin conducted a very simple but very clever experiment. He accelerated a beam of electrons in a glass tube. You can see at the start of my video how the spot on the glass tube is the impact of the electrons causing fluorescent on paint on the inside of the tube. He then setup a magnetic field at 90 degrees to the beam using coils of wire (Helmholz coils). As you increase the current flow inside the coils the field becomes stronger causing the beam to curve according to Flemings LH rule of FBI. Now as the beam is directed down to a collector which is connected to a gold leaf electroscope the leaf rises. This shows us that the beam is in fact charged. Further experiments show the charge is also negative. This is evidence that cathode rays are in not part of the EM Spectrum.

Permanent link to this article: https://animatedscience.co.uk/2011/the-electron-a-charged-particle

The Hydrogen Bomb…Teller–Ulam

File:Teller-Ulam device 3D.svg

This is part of a great Wikipedia Article, read more here….

The Teller–Ulam design is the nuclear weapon design concept used in most of the world’s nuclear weapons.  It is colloquially referred to as “the secret of the hydrogen bomb” because it employs hydrogen fusion to generate neutrons. However, in most applications the bulk of its destructive energy comes from uranium fission, not hydrogen fusion. It is named for its two chief contributors, Edward Teller and Stanisław Ulam, who developed it in 1951 for the United States. It was first used in multi-megaton-range thermonuclear weapons. As it is also the most efficient design concept for small nuclear weapons, today virtually all the nuclear weapons deployed by the five major nuclear-armed nations use the Teller–Ulam design.

Its essential features, which officially remained secret for nearly three decades, are:

  1. separation of stages into a triggering “primary” explosive and a much more powerful “secondary” explosive.
  2. compression of the secondary by X-rays coming from nuclear fission in the primary, a process called the “radiation implosion” of the secondary.
  3. heating of the secondary, after cold compression, by a second fission explosion inside the secondary.

The radiation implosion mechanism is a heat engine exploiting the temperature difference between the hot radiation channel, surrounding the secondary, and the relatively cool interior of the secondary. This temperature difference is briefly maintained by a massive heat barrier called the “pusher”. The pusher is also an implosion tamper, increasing and prolonging the compression of the secondary, and, if made of uranium, which it usually is, it undergoes fission by capturing the neutrons produced by fusion. In most Teller–Ulam weapons, fission of the pusher dominates the explosion and produces radioactive fission product fallout.

The first test of this principle was the “Ivy Mikenuclear test in 1952, conducted by the United States. In the Soviet Union, the design was known as Andrei Sakharov‘s “Third Idea“, first tested in 1955. Similar devices were developed by the United Kingdom, China, and France, though no specific code names are known for their designs

Permanent link to this article: https://animatedscience.co.uk/2010/the-hydrogen-bomb-teller%e2%80%93ulam

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