Chapter 7: The Fires of Nuclear Fission

Parts of the Nuclear Power Station

(Nuclear Portion) steam generators, primary cooling system and nuclear reactor: hot heart of the power station, housed in steel vessile. (Non-Nuclear Portion): the turbines that run the electric generator, also the secondary cooling system

3 "Factors" of Fission

1) its size 2) number os of protons and neutrons it contains 3) the energy of the neutrons that bombard the nucleus to initiate the fission. **heavy nuclei is the key to splitting

Nuclear Power Plants

103 plants in the US. 20% of the world's energy is nuclear

Mass Number

A= number of PROTONS + NEUTRONS

Isotope Notation

A^ Z E (element symbol) A=mass number (on top) Z= atomic number (on bottom)

Radiocarbon Dating

C-14 is formed in the upper atomosphere, is oxidized to CO2, when a plant dies, the C-14 is NOT replenished, but continues to decay with a half life of 5730 years, the activity sample can be used to date the sample.

Worst Nuclear Power Plant Accident

Chernobyl, "nuclear" explosion did not occur, the fire and epxlosions of hydrogen blew vast quantites of radioactive material out of the reactor core and into the atmosphere. Iodine-131 was released (causes thyroid cancer),

Conversion of Mass to Energy

E (energy) =m (mass) c^2 (speed of light)

Einstein's Energy Equation

E (energy)= m (mass) c (speed of light= 9/0 x10^16 m^2 s^2) ^2

Radioactivity of elements

Elements with Z greater than 92 are naturally radioactive.

Leading user of nuclear power

France- 59 nuclear plants, generating 75% of their electricity.

Hormesis

Low doses of a harmful substance (such as radiation) may actually be beneficial

Nuclear Power Safety

Physical barriers such as steel and concrete are 3-4 feet thick, emergency shut down for the reactor as well

Radioactivity

Spontaneous decomposition of nuclei with emission of small, fast moving, high energy particles, and high energy electromagnetic radiation.

Nuclear fuel

U is formed into small ceramic pellets, they are inserted into long, verticle tubes within the reactor core. U atoms are struck by neutrons, they split or undergo fission, which releases heat--known as nuclear energy. Uses little mass to create LARGE amounts of energy.

Uranium for Dating

U-238 has a half life of 4.5 x 10^9 years decaying to Pb-206. Ages of rocks contaning uranium can be deturmined by measuring the ratio of Pb-206 to U-238--- puts the age of the earth at 4-4.5 billion years

Atomic Number

Z= number of PROTONS (same as ELECTRONS)

Beta Particle (b) (breaking a neutron appart)

a high speed electron (emitted from the nucleus); (0)^ -1 n; produced by radioactive nuclei, small light particles not in themselves harmful, called ionizing radiation (can ionize atoms or molecules), more penetrable than alpha particles, up to 3cm of tissue (not as much as gamma rays) MASS NUMBER (A) IS UNCHANGED, ATOMIC NUMBER (Z) GOES UP BY 1.

Linear, Nonthreshold Model

a linear relationship between the adverse effects and the radiation dose, with radiation being harmful at all doses, even low ones.

Breeder Reactor

a nuclear reactor that can produce more fissionable fuel (usually Pu-239) than it consumes (usually U-235)

Alpha Particle (a)

a positively charged helium isotope (emitted from the nucleus). (4)^ 2 He; produced by radioactive nuclei,small light particles not in themselves harmful, called ionizing radiation (can ionize atoms or molecules), least penetrable. MASS NUMBER (A) GOES DOWN BY 4, ATOMIC NUMBER (Z) GOES DOWN BY 2. 20x Beta= Alpha

Nuclear Fuel Cycle

a way of conceptualizing all the different processes that can happen when uranium ore is mined, processed, used to fuel a reactor, and then dealt with as waste. (depleted uranium, enriched uranium, and plutonium.

Radioactive Tobacco Leaves

accumulate on sticky surfaces of tobacco leaves, minerals remain on the leaves through the manufacturing process. Also Apatite fertilizer contributes to radiation in tobacco plants. The radium emits alpha and gamma radiation and lead-210 and polonium-210 lodge in the smokers' lungs for years. These particles contribute to cancer

Electromagnetic Radiation

all the different types of light (visible, infared, ultraviolet, microwave and gamma) - same as visible light

Nuclear Reactions

atomic numbers must balance AND mass numbers must balance (on each side of the equation) **use a particle or isotope to fill in the missing protons and neutrons

Nuclear Reaction vs. Chemical Reaction

chemical= involves electrsons; nuclear= involves nucleons, protons and neutrons re-arranged, small amount of mass LOST, mass converted to energy, involved binding energy (which holds the nucleus together).

Depleted Uranium (DU)

composed almost entirely of U-238 (~99.8%) because much of the U-235 that it once naturally contained has been removed.

Control Rods

composed of a neutron absorber (like cadmium or boron) can absorb fewer or more neutrons. bathed in primary coolant

Gamma Rays (y)

electromagnetic radiation with very high energy, most are HARMFUL, pure energy; no charge impact (0)^ 0 y; the most penetrable of the 3 rays, several dozens of tissue.

Products

final products (right side of the equation)

Food Irradiation

food can be irradiated with gamma rays from 60^Co or 137^Cs. ex; irradiated milk has a 3 month shelf life without refrigeration. USDA aproved meats and eggs, irradiated fruits ripen slower

Background Radiation

from rocks, the earth's core, living in a home, soil

Nuclear Waste Policy Act (1982)

high-level radioactive waste will be disposed of UNDERGROUND, in a deep geologic repository in Yucca Mountain, Nevada.

Vitrification

in which the spent fuel elements or other mixed waste are encased in ceramic or glass. (waste trapped in solid glass)

Low-Level Waste (LLW)

includes radioactively contaminated protective clothing, tools, filters, rags, medical tubes, and many other items.

High-Level Waste (HLW)

is "irradiated" or used nuclear reactor fuel

Uranium Hexaflouride (UF6)

known as "hex", solid at room temp, but vaporizes when heated to 135 F- Uranium ore is converted to UF4, which reacts with Fluoride

Primary Coolant

liquid that comes in direct contact to carry heat away.

Mass Defect

mass ----> energy

Curie (Ci)

meauser of the radioactivity of a sample, approximately equivalent to the activity of one gram of radium. 1 Ci= 3.7 x10 ^10

Neutron

no net electric charge; (1)^0 n

Nuclear Fuel Disposal

nuclear fuel cannot "explode" and doesn't burn, it is too weak to explode, the uranium must be 20-90% "enriched" to be weapons grade, the French used molten glass mixture to enclose waste in along with a steel container, and burried in a pit

Nuclear Fuel Energy Content

nuclear fuel pellet (the size of the tip of a pinky finger) is equivalent to energy provided by 1,780 pounds of coal. The heat released by fission boils water into steam which drives the turbine generator- producing electricity

Explosive Fission

occurs only if a critical mass of U-235 is quickly assembled all in one place.

Uranium-235

only nuclide existing in nature that is FISSILE with thermal neutrons.

RAD

radiation absorbed dose, the measure of energy deposited in tissue and is defined as the absorption of .01 Joule of radiant energy per kilo of tissue.

Nuclear Radiation

radiation emitted by the nucleus (such as alpha, betta or gamma)

Controlling Nuclear Fission

reaction controlled by RODS among the tubes holding the fuel, which ABSORB neutrons and prevent them from hitting atoms that can fission, it can speed up or slow down the reaction by varying the NUMBER of control rods. Water also serves as a moderator which slows down the neutrons and increases fission. Fission cannot occur if the neutrons are moving TOO quickly, so water SLOWS the reaction. The hotter the watter, the slower the reaction occurs.

REM

roentgen equivalent man, a measuer of the dose of radiation recieved that takes into accoun the damage caused to human tissue, calculated by multiplying Q by the number of RADs.

Moderator

slows the neutrons, making the fission production more effective.

Reactants

starting materials (left side of the equation)

Fission

the SPLITTING of atoms that are very large, so that they are not as stable. STEPS: 1) Initiation (reaction of a single atom starts the chain; U-235 plus a neutron) 2) Propagation (U-236 fission releases neutrons that initiate other fissions) 3) Termination

Critical Mass

the amount of fissionable fuel required to sustain a chain reaction.

Radioactive Decay Series

the characteristic pathway of radioactive decay that begins with a radioisotope and progresses through a series of steps to eventually produce a stable isotope. ex; radon is part of uranium's decay series therefore it is always present when uranium is there.

Enriched Uranium

the percent composition of Uranium-235 has been INCREASED through isotope separation. Naturally 99.284% of uranium is 238, only .711% is 235.

Spent Nuclear Fuel (SNF)

the radioactive material remaining in fuel rods after they have been used to generate power in a nuclear reactor.

Uranium Mill Tailings

the reisdues remaining after the processing of natural ore to extract uranium and thorium

Nuclear Fission

the splitting of a large nucleus into smaller ones with the release of energy, becaue the total mass of the products is slightly less than the total mass of the reactants. One fission event produces two or three neutrons which in turn cause another fission event (a chain reaction).

Half Life

the time it takes for 1/2 of a sample to decompose, each time it decreases by a half of what is left.

Sievert (Sv)

unit used internationally equal to 100 REM. 1 REM= .0100 Sv.

Geiger Counter

used to detect radioactive substances

Secondary Coolant

water in the steam generators that don't come in contact with the reactor.