Transcript Nuclear

Nuclear energy

Review: Elements and Isotopes

What are elements defined by?

 What are isotopes?

 What is the difference between a stable and a radioactive isotope?


 experience radioactive decay (the loss of alpha or beta particles over time)  Result: atoms of one element physically change into another element.

– Eg Carbon-14 decays to Nitrogen-14 by loss of negative beta particles  Radioactive half life= the amount of time it takes for 50% of the radioactive isotope in a substance to decay.


Plutonium-239 has a half-life of 24,000 years. How much of a 4 gram sample will remain after 96,000 years?


1g b.








Dating with radioactive isotopes  Carbon-14 can be used to estimate the age of plant and animal remains

Geological dating with Uranium

 Uranium-238 is a very common radioisotope that decays to a stable isotope of lead  It has a half life of 4.5 billion years

The discovery of radioactive atoms

1896 uranium radiation observed  1898 radiation consists of high energy particles  1919 N nuclei hit with alpha particles turned into O  1938 First fission reaction

Nuclear rxns vs combustion


   Atoms do not change; are rearranged Mass of reactants = mass of products Energy is released as heat when bonds break


  Nucleic changes result in element transformations Small of amount of matter releases large amounts of energy…less mass in products

Types of nuclear reactions

 Fission  Fusion


 Nuclear power plants use U-235, a radioactive isotope of uranium.

– Mining – Enrichment  Fuel assembly

Nuclear power plant




Math Practice

After 100 million years, only 1/32 of the original amount of a particular radioactive waste will remain. The half-life of this radioactive waste is how many million years?

a. 10 b. 20 c. 30 d. 40 e. 50 2.

You have 180g of a radioactive substance. It has a half life of 265 yrs. After 1,325 yrs, what mass remains?

Nuclear waste

  Low level – Radioactive solids, liquids, or gases that give off small amounts of ionizing radiation – Sources include power plants, hospitals, research labs, and industries – Low Level Radioactive Waste Policy Act 1980 & 1985  All states must be responsible for disposal of non defense related waste produced w/in their borders.

High level – Radioactive solids, liquids, or gases that initially give off large amounts of ionizing radiation – Sources include anything that was inside the reactor core (metals, water, gases, spent fuel)

Nuclear Waste Policy Act 1982

    Stated that there must be a permanent site for storing high level waste by 1998 – That was not met; postponed to 2010 at earliest 1987 Congress identified Yucca Mountain in Nevada as the best potential site In 2002 it was officially approved by Congress Rescinded by Obama in 2009


 Scientists disagree about the best methods for long-term storage of high level radioactive waste: – Bury it deep underground.

– Shoot it into space.

– Bury it in the Antarctic ice sheet.

– Bury it in the deep-ocean floor that is geologically stable.

– Change it into harmless or less harmful isotopes.

The risks of nuclear energy

     Meltdown Acute radiation syndrome Daily radiation for workers (carcinogenic over time) Radiation into groundwater from stored waste Small scale persistent radiation to nearby communities

Radiation and health

 We are exposed to natural (background radiation) and artificial radiation every day – 300 millirems per year from space/the atmosphere, the soil (radon), foods we eat (radioactive potassium) – 60 millirems from manmade radiation (radiowaves, hospitals, industries, housing materials, microwaves, cell phones, tobacco, television, smoke detectors, etc.)

Figure 16-19