Archive for January, 2014:

Mouse Trap Reactor

Description:
The Mouse Trap Reactor is a visual representation of a chain reaction in a confined space. Useful as an analogy for an uncontrolled nuclear reaction.

scouts

Background:
The splitting of a massive nucleus into two fragments, each with a smaller mass than the original is known as nuclear fission. A typical example of nuclear fission is the splitting of a Uranium-235 nucleus. This is a reaction that is used in nuclear reactors to generate heat by which steam is produced and used to turn turbines that generate electricity. The fission of Uranium 235 begins when the Uranium 235 captures a slow moving neutron and forms an unstable “compound nucleus”. The compound nucleus quickly disintegrates into a Barium-141 nucleus, a Krypton-92 nucleus, two or three neutrons (2.5 average), and a tremendous amount of energy (~200MeV per fission).

Because the Uranium-235 fission reaction produces 2 or 3 neutrons, it is possible for it to initiate a series of subsequent fission reactions. Each neutron released can initiate another fission event, resulting in the emission of more neutrons, followed by more fission events, and so on. This is a chain reaction – one event triggers several others, which in turn trigger more events, and so on. In a nuclear power plant the chain reaction is controlled by restricting the number of neutrons available to collide with the Uranium. This is accomplished by absorbing some of the released neutrons with various materials. In an uncontrolled chain reaction (such as an atom bomb explosion) there is nothing to control the number of neutrons being released, so the rate of the chain reaction increases dramatically.

This video features ANS member, Matt Dennis, demonstrating the “Mouse Trap Reactor”. The activity, which is essentially a 3’x4’x4′ cube with clear plexiglass sides, with rows of mousetraps screwed into the bottom, covering the whole area. Ping pong balls are placed on each mousetrap after the traps are set.  You can cycle through large groups of students and give a presentation prior to allowing one lucky student to throw an additional ping pong ball into the “reactor” which starts a fast and loud chain reaction. We suggest discussing fission as the splitting of the atom and the source of power, in the form of heat, used in nuclear power plants. Depending on the audience’s age level, you can discuss the ping pong balls as neutrons that are released in fission and carry the chain reaction to other mouse traps or the fissile atoms, Uranium 235 or Plutonium 239.


Materials:

  • 100 modified mousetraps
  • 101 practice golf balls or Ping Pong balls (100 + 1 trigger ball)
  • A reaction chamber (plexiglass or acrylic)

Procedure: 

  1. Arm the mousetraps and place them in a 10 by 10 grid on the reactor base.
  2. While positioning the traps, hold them by their sides on the end opposite the trigger paddle and alternate the direction of the trigger paddle.
  3. After positioning a row of mousetraps, place a cardboard partitions around it to avoid triggering armed traps.
  4. Once the reactor is in the classroom, carefully remove the reaction chamber and load the balls onto the armed traps.
  5. Once the reactor chamber is in place, a trigger ball (representing a neutron) is dropped through a hole in the top of the reactor where it triggers the chain reaction. The whole reaction takes about 2 seconds.

Tips:

  • When moving the loaded reactor, use a cart with air-filled tires and move it gently
  • Arming the traps is tedious and requires a delicate touch
  • Once the reactor is fully set up don’t let anyone to near it; the slightest bump could set it off prematurely
  • The traps tend to get destroyed after several uses. Try to have extra traps to replace these after performing the demonstration

October 2013

ReActions_masthead_October

 

 

 

 

 

Fusion: Scientists Move Closer to Ignition

Scientists and engineers have long wanted to develop technology enabling them to utilize fusion reactions as a source of controlled power. Why? Fusion has the potential to provide very large amounts of energy. The challenge has been that attempts to harness fusion in a controlled reaction have required the input of more energy than was released during the fusion. Recent reports indicate that work at the National Ignition Facility (NIF) located at Lawrence Livermore National Laboratory (LLNL) is moving researchers forward in their quest for a self-sustaining, controlled fusion reaction.

target_capsule_ill

Researchers at NIF focus 192 laser beams, all at the same time, on a target container called a hohlraum (a German word meaning “hollow room”) about the size of a pencil eraser. The hohlraum holds a small super-cooled capsule of two hydrogen isotopes — deuterium and tritium. When the lasers are fired — in nanosecond (billionth-of-a-second) pulses – they deliver an enormous amount of energy and power. This heats and compresses the hydrogen isotopes so much that fusion takes place

Recently, the NIF completed a test which suggests that there is one significant challenge yet to overcome. That challenge? The capsule containing the deuterium and tritium breaks apart prematurely. As a result the research team is working to design an improved capsule for the hydrogen isotopes.

The researchers are encouraged by the results so far, but have a significant challenge to overcome before they achieve ignition.

***

Fusion – a nuclear reaction in which two atoms fuse and form a new kind of atom in which the two original atoms are combined.

Ignition – a point at which the fusion reaction produces more energy than is needed to initiate it

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Explore these resources for more information about the National Ignition Facility.

What is NIF?

https://lasers.llnl.gov/about/nif/about.php

https://lasers.llnl.gov/about/nif/

http://en.wikipedia.org/wiki/National_Ignition_Facility 

Recent news releases from NIF

http://lasers.llnl.gov/newsroom/press_releases

Access a gallery with interesting videos from NIF  https://lasers.llnl.gov/multimedia/video_gallery/

The seven wonders of NIF

https://lasers.llnl.gov/about/nif/seven_wonders.php

Inertial Confinement Fusion: How to Make a Star

https://lasers.llnl.gov/programs/nic/icf

More related images

http://www.aps.org/about/physics-images/archive/nif-target.cfm

Other places to read about the NIF milestone

http://www.bbc.co.uk/news/science-environment-24429621

http://www.foxnews.com/science/2013/10/08/massive-laser-brings-us-one-step-closer-to-mastering-fusion/

Video of Countdown to a Laser Shot

http://www.youtube.com/watch?v=CgdSVt6vHV0

Video: NIF as Featured on BBC

http://www.youtube.com/watch?v=DyB7Ho_W9RE


Ion Engine Sets Record for Test Duration

An advanced engine design from NASA completed 48,000 hours of operation – that’s five and one-half years — making it the longest test duration for any space propulsion system demonstration. The test was voluntarily ended even though the thruster was still operational because the test had exceeded requirements for anticipated space missions.

Photo: NASA

Photo: NASA

This type of propulsion system would reduce the amount of fuel that would be required for space missions, allowing increased science payload without huge increases in the overall size of the vehicle.

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Read more about the engine test from NASA

http://www.nasa.gov/home/hqnews/2013/jun/HQ_13-193_Ion_Thruster_Record.html#.Umbgq1Onn2l

About the xenon ion engine

http://io9.com/nasa-shows-off-a-prototype-of-its-new-xenon-ion-engine-510277963

Article about how another ion engine may enable long trips in space with less time

http://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html#.UmbixVOnn2k

Article about potential for “quick trips” to Mars using fusion engines

http://www.space.com/23084-mars-exploration-nuclear-fusion-rocket.html


Increasing Oil Content of Plant Leaves

Scientists at Brookhaven National Laboratory have identified the genes required to enhance oil production and accumulation in plant leaves. By managing the expression of these genes, researchers were able to increase oil content in leaves. Knowledge and application of this technique will make it possible to increase the energy content of plant-based foods and renewable biofuel.

Photo: Brookhaven National Laboratory Overexpressing the gene for PDAT, an enzyme involved in oil production, caused plant leaves to accumulate large amounts of oil in large globules (left). When scientists also added a gene for olesin, a protein known to encapsulate oil droplets, clusters of smaller, more stable droplets formed (right).

Photo: Brookhaven National Laboratory
Overexpressing the gene for PDAT, an enzyme
involved in oil production, caused plant leaves to
accumulate large amounts of oil in large
globules (left). When scientists also added a
gene for olesin, a protein known to encapsulate
oil droplets, clusters of smaller, more stable
droplets formed (right).

Studies were done using laboratory plants. Researchers hope the strategy can be transferred to crop plants which are used to feed livestock or generate renewable energy, increasing energy content and nutritional value.

Researchers found that disabling the gene for an enzyme known as PDAT had no effect on oil production in seeds, but it dramatically decreased oil production in leaves. But, overexpressing the gene for PDAT resulted in a 60-fold increase in oil production in leaves.

In further experiments, the researchers overexpressed a gene that caused extra production of a protein which kept the oil droplets from fusing together. When the two genes were both overexpressed, there was a 160-fold increase in oil production.

By using radio-labeled carbon (C-14), researchers were able to decipher the biochemical mechanism for increased oil production.

One researcher noted that leaves produced with overexpression of PDAT would provide almost twice the oil yield, by weight, that can be obtained from canola seeds, one of the widely used crops for food and biodiesel  production.

More research will be required to apply the techniques to bioenergy or food crops. Work is now being done to explore the effect of gene overexpression in biomass crops such as sugarcane.

Read more…


Pioneers in Nuclear Field: Hahn, Meitner, and Strassman

Among the pioneers in nuclear science is a trio of people who first realized that the uranium atom could be split by bombarding it with neutrons. The trio? Otto Hahn, Lise Meitner, and Fritz Strassman were those pioneers.Early in his career, Hahn isolated radioactive thorium. Lise Meitner was just the second woman to receive a doctorate in science from the University of Vienna in 1905. Eventually, the team of Meitner and Hahn worked with Strassman. They were deeply involved in studies of the products resulting from neutron bombardment of uranium.Read more about their work and how World War II impacted their lives and work at

http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/hahn-meitner-strassman.aspx

http://ansnuclearcafe.org/2012/02/14/lise-meitners-fantastic-explanation-nuclear-fission/


Research Activity for Your Students

Constructing a Time Line of Developments in Nuclear Science

Objectives

Learn about the early development of atomic and nuclear science

Develop teamwork by sharing information

Tools
Use standard library resources such as an encyclopedia, specialized science encyclopedia, or reference materials. A computer and internet access will provide quicker access to many resources.  Read More…


What is the Higgs?

The link below will take you to a simplified explanation of what the Higgs boson is. Black and white drawings lead you step-by-step to an improved understanding of the Higgs.

http://www.nytimes.com/interactive/2013/10/08/science/the-higgs-boson.html?ref=science#/?g=true&higgs1_slice=0

Constructing a Time Line of Developments in Nuclear Science

Objectives

  • Learn about the early development of atomic and nuclear science
  • Develop teamwork by sharing information

Tools
Use standard library resources such as an encyclopedia, specialized science encyclopedia, or reference materials. A computer and internet access will provide quicker access to many resources.
Directions

The people, places and things in the list below have played a role in the development of our understanding of the structure of matter or in the growth and application of nuclear science and technology.

Research the names and events listed, looking for:

  • the time (range of years) during which the person lived or the event occurred
  • the major contribution to nuclear science and technology (theory or application) made by the person or event
  • the year in which the contribution or discovery was made (if available)
  • useful information about what this discovery or contribution has done to improve our understanding of the world, to improve health, to enhance quality of life, etc.

After everyone has completed the research, the class should share the information and arrange people and events on a time line.

  •  Atoms for Peace Speech
  • BORAX III
  • Antoine Henri Becquerel
  • Frederick Joliot
  • Herman Blumgart
  • Irene Joliot-Curie
  • Niels Bohr
  • Martin Klaproth
  • James Chadwick
  • Lise Meitner
  • Marie & Pierre Curie
  • Dmitri Mendeleev
  • Higgs Boson
  • CERN
  • John Dalton
  • USS Nautilus
  • Democritus
  • Ida Noddack
  • Dresden-1
  • Uncertainty Principle
  • Albert Einstein
  • Theory of Relativity
  • Enrico Fermi
  • Wilhelm Roentgen
  • Otto Frisch
  • Ernest Rutherford
  • Hans Geiger
  • Glenn Seaborg
  • Maria Goeppert-Mayer
  • Shippingport
  • Otto Hahn
  • Fritz Strassman
  • Werner K. Heisenberg
  • Dr. Rosalyn Yalow
  • Peter W. Higgs
  • Francois Englert

 


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