Difference between revisions of "Nuclear Science Lab"

Nuclear Science Lab was a trial event for Texas Division C in the 2011 season. It is an event based solely on nuclear reactions and their uses. Students are expected to be able to use radiation detection equipment and have knowledge of topics such as radiation, terminology, and nuclear decay reactions. Students are allowed to bring a scientific calculator, but NOT a graphing calculator. No resource materials may be brought to the event.

Part 1

The first part consists of experimental/practical tasks relating to nuclear instrumentation and half life. Students should be prepared to construct graphs with any data they collect. Lab topics may include half-life and decay, background radiation, shielding effectiveness, and the inverse square law. Geiger-Mueller tubes/counters, radioactive sources, and shielding materials are all provided by the supervisor.

Half Life and Decay

The Half-Life of a substance is the time it takes for half of the radioactive atoms to decay. It then takes another half-life for half of the remaining amount to decay. Thus, radioactive decay is exponential:

$A = A_0 2^{-t/t_{1/2}}$

Higher half-life atoms are more stable.

Inverse Square Law

The inverse square law provides a geometrical and mathematical explanation for point source phenomena, such as light, sound, gravity, and electric fields. Radiation also obeys this principle. The essence of this law is that as the energy travels further from the source, whether it be a light bulb or a radioactive blob, the intensity of the energy decreases to remain equal over all area covered. Therefore, the intensity of the radiation is inversely proportional to the distance from the source thereof. There are, of course, some constraints to using this law. First, the point source must be able to spread its radiation in all directions equally, creating an ever-expanding circle. Secondly, this law is only useful if at least three of the values in the equation, or a way to find at least three values, are present. This will be described and expounded upon hereafter.

• The formula for this law is shown in the following image, where I represents the intensity of the radiation at distances 1 and 2 respectively (shown as I1, I2), and D represents the distance from the radiation source at points 1 and 2 respectively).

Alternatively, the equation can be expressed as such: I1 * D1^2 = I2 * D2^2 This expression is mathematically equivalent, and is simply another form that is easier to use for some scientists. As a piece of general advice, be sure to compare units before using the equation. Take the time to check if all intensities and all distances are in the same units, and if not, take the time to convert the units. Also compare the units to the question and the answer they are asking for.

Part 2

The second part consists of a written test focusing on the design and operation of nuclear power plants. Topics of the test include but are not limited to: nuclear reactions, nuclear materials, PWR and BWR technology, radiation types, nuclear fuel cycle, and nuclear fission.