Tuesday, March 29, 2011

Question of the Week

Congratulations VCU!!!  The VCU Rams are in the Final Four!!!  Virginians are cheering for the "Cinderella" #11 seed Rams whom many said did not belong in the tournament.

Only two other teams with double-digit seeds have ever reached the Final Four.  Who were they?

And don't miss March Ratness on Thursday, March 31 (11 am) at the Science Museum of Virginia!!!  Four rats will play their own tournament - who do you think will win???

Friday, March 25, 2011

Question of the Week

Gas prices are on the rise again...  The world's supply of fossil fuel is limited and will eventually be exhausted.  Production is becoming more difficult and more expensive.  Many Americans are turning to renewable energy.  What exactly is renewable energy?  Can you name 5 renewable energy sources?

Answer:  Renewable energy is energy that comes from resources that are naturally replenished.  Sources of renewable energy are:  sunlight, wind, geothermal, tides, biomass, and hydroelectricity.

Wednesday, March 23, 2011

Traveling by Air in the 1940s

A recent acquisition into the collection of the Virginia Aviation Museum is this 1944 Eastern Airlines timetable which contains flight times and prices.

At the time of this publication, one way travel from Richmond cost at most $85.25 for a trip to Brownsville, Texas and the cheapest flight was $7.45 to get to Baltimore, Maryland.

Eastern Airlines began offering passenger flights out of Richmond beginning in 1932.

Wednesday, March 16, 2011

Understanding Japan’s Nuclear Crisis

This image made available from Tokyo Electric Power Co.
 via Kyodo News, shows the damaged No. 4 unit of the
Fukushima Dai-ichi nuclear complex in Okumamachi,
 northeastern Japan, on March 15, 2011.
 White smoke billows from the No. 3 unit.
Credit: AP Photo/Tokyo Electric Power Co. via Kyodo News
By Harrison Mebane
Physics graduate student
University of Illinois

In the aftermath of the devastating earthquake and tsunami in Japan, the world is watching an unfolding crisis in Japan’s Fukushima nuclear reactors. Below is an attempt to explain the science behind the crisis to the best of our knowledge. Not a nuclear expert myself, I asked my son, a Physics graduate student at the University of Illinois. Yesterday he attended a seminar on campus where professors explained what we currently know about the situation. Here’s his report.

In order to understand what's going on, you need a good image of what the reactor looks like.  Here is a good picture: http://1.bp.blogspot.com/-YCQGP12Grn0/TXwmsKea0YI/AAAAAAAAAp8/Gc3-w9VHPcI/s1600/BoilingWaterReactorDesign_3.jpg

This type of reactor is called a boiling water reactor. The reddish cylinder in the middle is the reactor core. Inside are fuel rods, which are zirconium clad tubes filled with uranium pellets. The fuel rods are surrounded with water being pumped in from outside. The water serves two purposes in this type of reactor: it is a coolant, and it slows down neutrons so that they are more easily absorbed by the uranium (it is called a moderator in this context). The problem at the Fukushima reactors occurred when power was lost. When power is lost, the reactor automatically shuts down (control rods are inserted, which stops the sustained reaction). Water has to be actively pumped into the reactor to cool it. Without power, the water circulation stops. The Fukushima reactors had multiple diesel generators on-hand, but the tsunami appears to have knocked all of them out. They had backup battery power, but it didn't last long. Once power was lost, the water in the reactor just sat there and began to boil off. The core remains hot long after the reaction has stopped because the fuel still contains a lot of radioactive material which will continue to decay. That is the main issue right now. If they could guarantee a constant safe water level in all of the reactor cores, the problem would be solved. They are currently pumping in seawater (which will ruin the reactors, but they aren't worried about that), but this is difficult because the core is under such high pressure. They need very strong pumps to get water in.

Now, the big news lately has been these explosions. To the best of anyone's knowledge, these were hydrogen explosions. It is not at all obvious where the hydrogen comes from, since it is not a decay product. It comes from the fact that steam can react with the fuel rods' zirconium cladding to create zirconium oxide (in effect, it rusts). Steam normally does not come in contact with the zirconium but it did in this case because the water level sank below the tops of the fuel rods (this is what the media means when they say the fuel rods were "exposed"). As oxygen is leached off of the steam molecules in the formation of zirconium oxide, hydrogen is produced. At some point, the pressure of the steam became dangerously high and had to be vented. It was vented out of the core and then out of the primary containment vessel (labeled in the diagram) into the secondary containment vessel. This is where the explosions occurred. Interestingly, the steel plates surrounding the secondary containment vessel are "meant" to be blown off in the case of an explosion. If they were on too tightly, an explosion might damage the primary containment vessel, and that would be bad. So that's exactly what happened in all of the explosions. You can see the steel skeleton in pictures of the exploded reactors.

Now, one major concern at this point is the spent fuel ponds. You can see one of these in the image; it is the pool of water just to the right of the core containing rectangular slabs. These slabs are spent fuel. The spent fuel is put in this pool to cool off after most of its uranium-235 has reacted. It stays hot for a long time, though, so it is kept in the pool until it is cool enough to move to a secure location. After the explosions, you can see that the spent fuel pond is exposed to the outside. That's fine as long as there is water in there to absorb/block radiation. The fear is that either a) the water will boil off, or b) the pools were damaged in the explosions (or the fire a couple days ago) and could be leaking. The more worrisome scenario is situation b. If the water level drops enough, the spent fuel will no longer be cooled effectively, and it may begin to melt. If it gets hot enough to ignite, the fire would send large amounts of radiation into the air. That is what happened at Chernobyl, though at Chernobyl the core itself caught fire, so it was much worse. It is unclear how secure the spent fuel ponds are at this point.

During the last two days there have been significant radiation spikes which have forced personnel to leave temporarily. During these spikes, the radiation was high enough to cause radiation poisoning in an hour or two. Nobody knows the source of the radiation. There has been some speculation that it was due to a leak in the suppression pool, which is the torus below the primary containment structure in the picture. This torus is full of water and is meant to relieve pressure in the primary containment vessel if it gets too high (maybe when they released pressure into the secondary containment structure, the suppression pool wasn't taking enough pressure away, or maybe they just wanted to vent off the hydrogen). At this point the suppression pool has been in contact with radioactive material, so a leak in it would result in possible leakage into the environment. Again, this is just speculation at this point, and it is unclear how much, if any, leakage has occurred.

Tuesday, March 15, 2011

Question of the Week

In the wake of the devastating earthquake in Japan, tsunamis are on people's minds.  How much do you know about them? 

Take this brief tsunami quiz and find out:

1.  Name 4 geologic events that might cause a tsunami.

2.  Tsunamis are also called wave trains because they are a series of waves, not just one wave.  How far apart in time can they be?

3.  In deep ocean water, how fast can a tsunami travel?

4.  Suppose you are in a boat in the middle of the ocean and a tsunami approaches.  What would happen?

5.  What happens when the tsunami approaches land?

6.  Has Virginia ever experienced a devastating tsunami?

1.  Tsunamis may be caused by earthquakes, landslides, volcanic eruptions or a meteor impact in the ocean.
2.  Tsunami waves can be as far as one hour apart.
3.  In deep ocean water, tsunamis can travel as fast as 500 miles per hour (800 kilometers per hour), as fast as a commercial jet.
4.  Not much.  In the open ocean, tsunamis are often less than a foot tall.  You probably wouldn't notice its passage.
5.  As a tsunami approaches land, the depth of the water decreases causing the bottom of the wave to slow while the top continues at the same speed.  The sea then begins to rise, either as a giant wave or as a rapidly rising tide.
6.  Yes, a meteor struck at the current mouth of the Chesapeake Bay about 35 million years ago, causing a huge tsunami which may have flowed over the Blue Ridge Mountains.

Monday, March 7, 2011

Question of the Week

On this day in 1876, Alexander Graham Bell received a patent for the telephone from the US Patent Office.  On March 10, three days after receiving the patent, he successfully transmitted the famous first words.

What famous sentence was transmitted?

Answer:  "Mr. Watson, come here, I want to see you."

Now, you may ask, who was Mr. Watson?  Thomas Watson was an experienced electrical designer and mechanic.  While Bell had the "germ of a great invention," he realized he did not have the equipment nor the expertise to make a working model.  A chance meeting at a machine shop changed all that.  There he met Watson and hired him as his assistant.  On that historic day, March 10, 1876, Mr. Watson heard the words loud and clear through the liquid transmitter now known as the telephone.  Just think how far we have come since then...

Wednesday, March 2, 2011

Question of the Week

The word "nerd" is a fairly recent addition to the English language and is now quite common in everyday speech.

When and where was the first recorded usage of the word?

(Hint:  Today is Dr. Seuss's birthday...)

Answer:  Dr. Seuss holds the honor of first printed usage of the word "nerd."  It appeared in the book If I Ran the Zoo, written in 1950.