Uses of Radiation

Useful Radioisotopes Found in Spent Nuclear Fuel

Isotope Radiation Half Life Uses
Cs-137 alpha, beta 30 years studying soil erosion, calibration of detecting devices
Cs-135 alpha, beta 2.0 million years potential use in ion propulsion engines
Sr-90 beta 28 years atomic batteries, SNAP power source, medical radionuclides
Am-241 alpha 458 years smoke detectors
Am-243 alpha 7,950 years No know domestic use
Tc-99 beta, gamma 210,000 years bone imaging, medical tracers
Pu-239 alpha 24,390 years fuel for fast breeder reactors
Pu-240 alpha 6,580 years No know domestic use
Np-237 alpha 2.2 million years possible reactor fuel or military use


The above list is based on the following chart of predominate radionucluides present in uranium decay.


Image courtesy of world-nuclear.org

Atomic Batteries and Betavoltaics

The idea of atomic batteries has been around for over 100 years. They seek to use charged particles released from radioactive materials to generate a current. In the past these batteries have been used in space missions as well as military applications. New developments that hope to decrease their size will allow them to be used in implanted medical devices and low voltage electrical devices.

Atomic batteries offer a lifespan relative to the half-life of the radioactive material being used, meaning that they can provide power for decades before they need to be replaced. The most common type of atomic battery uses betavoltaics. This means that a semiconductor material is used to absorb beta decay and generate a current.

Semiconductor materials are unfortunately decayed by beta particles. As a result the batteries donít last as long as they could. A team at the University of Missouri have designed an atomic battery that uses a liquid semiconductor, which allows it to degrade slower. Another design to solve this problem mixed the radioactive material with a phosphor (light-giving substance) and surround it with a transparent material. The semiconductor is replaced by a photoelectric surface of silicon. The radiation never passes beyond the transparent material and the light is collected and converted into electricity.

Cornell University has developed an atomic battery that uses a piezoelectric cantilever to produce electricity. Beta decay charges the cantilever which is then attracted to a positively charged thin film. When they touch, the two cantilevers receive equal charges and repel each other. The movement repeats and creates an electric charge.



Image courtesy of Cornell News

Semiconductors

The following background information on semiconductors has been included because of their direct use in atomic/nuclear batteries. Semiconductors are a ubiquitous part of modern society. They are the heart that keeps the pulse of technology pumping as they are found in microprocessor chips and transistors.



Image courtesy of The Free Dictionaries Project

Anything that is computerized or uses radio waves depends on the utilization of semiconductors. Semiconductors are mostly composed of silicon or some sort of crystalline inorganic solid (Group 4A has 4 valence electrons which offers an ease of uniformity when crystallizing). This causes them to partially be considered resistors as they modify the permeability of electricity between objects. To determine the magnitude of conductibility, materials with different periodic properties are used. One particular property that is of importance when considering material usage is the variance in electron mobility. Because of material consistency in a semiconductor, the range of electricity that is allowed to pass through is made controllable. This control allows for the alteration of operationsí speed, temperature, and power of electronic devices.



Image courtesy of CalFinder Residential Solar Power Site

In reference to atomic batteries, two main types of semiconductors are deliberated upon: silicon and germanium, silicon being the more common of the two. Silicon is easier to obtain and more popularly shipped and manufactured around the world. Silicon in solar panels last, on average, up 20 years. If this is an accurate analogous for the durability of silicon as semiconductors this would prove that it lasts longer and is the most widely accepted choice. Silicon is also easier to process and experiences less leakage than most materials commonly used in semiconductors. In terms of price, Silicon comes in as the cheapest material across all grades. Regular grade silicon costs $0.50 per gram.



Image courtesy of Periodic Table - Silicon

Germanium is an avid competitor in the conductive world. It is similar to silicon in that they are periodic group neighbors. However, its availability is not as highly ranked as that of silicon seeing as germanium is the fiftieth most commonly found element and silicon is the second most abundant element in the Earthís crust.





 



#3 Cesium is not of vast economic importance.
  http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=5609&mesg_id=20141

Applications of Caesium-137 in Soil Erosion and Sedimentation Studies
  http://people.exeter.ac.uk/yszhang/caesium/welcome.htm

Betavoltaics
  http://everything2.com/title/Betavoltaics

Commercial Purposes of Strontium-90
  http://www.hps.org/publicinformation/ate/q219.html

Electron mobility in semiconductors
  http://adsabs.harvard.edu/abs/1983PhRvB..28.4535N

Germanium
  http://periodic.lanl.gov/32.shtml

How Semiconductors Work
  http://www.howstuffworks.com/diode.htm

How Semiconductors Work
  http://www.essortment.com/electronics-questions-semiconductors-work-29388.html

How long do solar panels last?
  http://scitizen.com/future-energies/how-long-do-solar-panels-last-_a-14-2897.html

List of Radioactive Elements
  http://www.buzzle.com/articles/list-of-radioactive-elements.html

Medical Uses
  http://www.chem.duke.edu/~jds/cruise_chem/nuclear/medical.html

Neptunium
  http://www.worldlingo.com/ma/enwiki/en/Neptunium

Nuclear battery keeps going, and going ...
  http://www.msnbc.msn.com/id/7843868/ns/technology_and_science-science/

Physics of Uranium and Nuclear Energy
  http://www.world-nuclear.org/education/phys.htm

Physics of Uranium and Nuclear Energy
  http://www.world-nuclear.org/education/phys.htm

Plutonium-239
  http://www.ausetute.com.au/nuclesum.html

Science: New Atomic Battery
  http://www.time.com/time/magazine/article/0,9171,723820,00.html

Silicon
  http://www.speclab.com/elements/silicon.htm

Smoke Detectors and Americium-241
  http://www.chem.duke.edu/~jds/cruise_chem/nuclear/smoke.html

Technitium-99
  http://www.ausetute.com.au/nuclesum.html

The Atomic Battery
  http://www.technologyreview.com/Infotech/14548/?a=f

Tiny 'nuclear batteries' unveiled
  http://news.bbc.co.uk/2/hi/technology/8297934.stm

Tiny atomic battery developed at Cornell could run for decades unattended, powering sensors or machines
  http://www.news.cornell.edu/releases/Oct02/cantilever.ws.html

Uses of Cesium-137
  http://www.ehow.com/list_7263688_uses-cesium_137.html

What is Betavoltaics?
  http://www.wisegeek.com/what-is-betavoltaics.htm




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