1 Nuclear Energy Chapter 16

Atoms and Radioactivity All common forms of matter are composed of atoms. All atoms are composed of: 1) Protons (found in the nucleus) 2) Neutrons (found in the nucleus) 3) Electrons (found orbiting the nucleus) 2

Isotopes Elements that have the same number of protons and electrons but Different numbers of neutrons 3 1 proton and 1 electron  1 proton and 1 electron and 1 neutron  1 proton and 1 electron and 2 neutrons 

Atoms and Radioactivity Radioactive - Nuclei of certain atoms are unstable and spontaneously decompose and release particles and energy. Radioactive Half-Life - Time it takes for half the radioactive material to spontaneously decompose.

What is released by radiation? 3 Things: Alpha Particles Beta Particles Gamma Rays 5

16.2 Reactions and Reactors Nuclear Fission – A reactions in which the nucleus of a large atom is split into smaller nuclei 6

7 – Nuclear Chain Reaction - Splitting nuclei release neutrons, which themselves strike more nuclei, in turn releasing even more neutrons.

8 The Nature of Nuclear Energy Only certain kinds of atoms are suitable for development of a nuclear chain reaction. – The two most common are uranium-235 and Plutonium-239.  Requires certain quantity of nuclear fuel (critical mass).

9 Nuclear Fission Reactors Nuclear Reactor - Device that permits a controlled fission chain reaction. – Nucleus of U-235 atom struck by slowly moving neutron from another atom.  Nucleus split into smaller particles.  More neutrons released.  Strike more atoms.

10 Nuclear Fission Reactors Control Rods - Made of a non-fissionable material (boron, graphite) that are lowered into reactor to absorb neutrons. – Withdrawn to increase rate of fission.

11 Workings of A Nuclear Reactor Nuclear reactor serves same function as fossil-fuel boiler: produces heat - converts water to steam - turns a turbine - generating electricity. Breeder Reactors - Nuclear fission reactor that forms a new supply of radioactive isotopes during operation. (i.e., U 238 turns into Pu 239 )

12 Boiling Water Reactor

13 Nuclear Power Plants in North America

Radioactive Waste High Level Radioactive Waste: – At this time, no country has a permanent storage solution for the disposal of high- level radioactive waste.  Politics of disposal are as crucial as disposal method.  Most experts feel the best solution is to bury waste in a stable geologic formation.

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16 Low-Level Radioactive Waste Includes cooling water from nuclear reactors, material from decommissioned reactors, protective clothing, and like materials. – Prior to 1970, U.S. alone placed 90,000 barrels of low-level radioactive waste on the ocean floor.  Moratorium in 1970, banned in 1983.

17 Low - Level Waste Currently, U.S. produces about 800,000 cubic meters of low-level radioactive waste annually. – Presently buried in various scattered disposal sites.  Political limbo.

18 Low-Level Radioactive Waste Sites

19 Reactor Safety Three Mile Island - Pennsylvania – March 28, Partial Core Melt-Down.  Pump and valve malfunction.  Operator error compounded problem.  Crippled reactor was de-fueled in 1990 at a cost of about $1 billion.  Placed in monitored storage until its companion reactor reaches the end of its useful life.

20 Reactor Safety Chernobyl - Ukraine – April 26, 1986 – Experiments being conducted on reactor.  Multiple serious safety violations. – Reactor Explodes.  31 deaths.  116,000 people evacuated.  24,000 evacuees received high doses of radiation.  Increased thyroid cancer in children.

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