Month: August 2016

What went wrong with Fukushima?

What went wrong with Fukushima?

What went wrong with Fukushima?

08/04/16

“What exactly took place with the fukushima reactor?”

 

Many people still remember the events of March 11th, 2011. On that day, an earthquake and a tsunami both with an insurmountable amount of force hit Japan, causing truly catastrophic damage. What was particularly hit were the Nuclear reactors in Fukushima, causing a great dispersal of radiation into the surrounding region

Let’s start with the basics. The reactors in Fukushima use both plutonium and uranium as fuel. These atoms are so large that they can easily become unstable. If a neutron hits them then they are likely to collapse. When fission occurs, these atoms release at least two neutrons, which  cause a butterfly effect know as a chain reaction if those neutrons hit more atoms, causing much energy to be created which ends up as heat. Fukushima use water as a coolant to form steam, which passes through a moisture separator to power a large turbine to create electrical energy.

Usually, reactors have a shutdown safety feature, in which a control rod slams into the fission reactor, stopping the fission process. However, since the isotopes are still in the process of decaying, so the “decay heat” needs to be removed so a meltdown does not ensue. Usually, this is accomplished by a cooling pump. However, this cooling pump often requires energy, so it usually takes it from the grid or two backup diesel generators.

Since radiation is still being generated, a three-layer security system is often put into place. This protection system includes fuel cadding (which uses a thin layer of a zirconium alloy to surround the fuel rod), the reactor vessel (a thick steel vessel that contains the fuel rods and a high-pressure coolant) and the containment structure (a thick shell of reinforced concrete). And since pressure from the water reactor often rises with the water temperature level, the vessel has safety valves that are designed to vent pressure (usually in the form of steam or radioactive water).

What happened in Fukushima went as follows; The earthquake caused massive tremors, which caused the fail-safety features to activate. However, the connection to the grid was knocked out by the earthquakes, and the tidal waves destroyed the diesel engines. This in turn caused a heat buildup, which in turn lead to a complete meltdown for three of the reactors.

Whatever has happened, the people lost in Fukushima will always be in our hearts, and we must strive constantly to make sure that such a calamity does not happen again. After reading, this, try to find a way to help the victims of Fukushima

Magnetic field polarity

Magnetic field polarity

Magnetic field polarity

08/03/16

“Why do scientists describe magnets as having a north and south pole?”

 

Magnets are very interesting pieces of the physical universe. They seem to be able to attract and repel objects with a completely invisible field. However, why is it that one side of a magnetic field can attract objects and the other side repel, and how can we describe the direction of this physical field?

When studying magnetism, scientists and engineers have decided to describe the flow of magnetic field in terms of polarity. All magnets have  are fundamentally dipolar, which means that one side is like the “positive” charge on an electron, while another is like a “negative” charge. Similar to electrons, opposite polarities attract and like ones repel. However, instead of being called positive and negative, these sides of a magnet are called the north and south poles respectively, almost like how the earth has a north and south pole (speaking of which, the earth’s magnetic poles are actually opposite of the geographic poles, but that is a topic for another time). For specifying the direction, Physicists have constructed the system so that the magnetic field will point from the north pole to the south.

Eddy current braking

Eddy current braking

Eddy current braking

08/02/16

“How can we apply the theory of eddy currents to transportation?”

What separates scientists and engineers is very simple, scientists discover new phenomena about the natural universe, while engineers take this knowledge and apply it to accomplish something useful. For example, scientists might discover that a specific current forms when conductors had a changing magnetic flux is applied to it, and name it something like eddy current. Now, how could an engineer take a phenomena like this and make it do something productive for humanity?

Well, let’s think about it like an engineer. We know that this current occurs because of an external magnetic field. Furthermore, we know that when current interacts with an external magnetic field, a perpendicular force is formed on the medium of the current. So let’s go further and think about we can do with this force. Well, a force can oppose motion, so how about we take this physical phenomena and apply it to an area that involves motion, namely transportation.

Let’s suppose that we have wheels made out of a conductive material, and that these wheels are moving at a certain RPM. If we take a magnet, and put the wheels in between both poles, then the constantly moving wheels will experience a constantly changing magnetic flux since parts of the conductor will always be moving into and out of the field. This will in turn generate an eddy current, which will produce a force that opposes the motion of the wheel, which in turn will cause it to slow down and brake. Engineers have termed this mechanism eddy current braking. Eddy current are so popular that they are used in many different cases, whether it be recreational gym equipment or high speed electric trains!

Hallback array

Hallback array

Hallback array

08/01/16

“How can we create a one-sided magnet?

We have a problem. Suppose that we want to create a magnet, but with one very simple yet very difficult constraint, we want the magnetic field to be only present on one side.
Now that we have decided on the requirements, let’s use our engineering abilities to bring this idea into reality. Our main problem is that magnets fields are usually symmetric on both sides because the polarity of the entire material points in the same direction. Now, how can we get around this physical phenomena to acheive our goals? Well, luckily for us, there is another facet of magnets that could be quite cordial to our goal if applied correctly. If two magnetic fields interact with eachother and go in oppossite direction, then there would be a cancellation of force. Now, what if instead of having one continuous material with each part having the same magnetic direction, we were to fasten discrete blocks together, with each the polarity of each block being 90 degrees perpendicular to the block before it? With this method, the magnetic fields on one side of the blocks would cancel out while the fields on the opposite side would super-combine, giving us a nearly one sided magnet if the this pattern repeats. Scientist and Engineers have termed this type of arrangement a hallbach array. Believe it or not, you probably see hallbach arrays everytime time in the morning, as hallbach arrays are what what makes refridgerator magnets work!