Nuclear Chemistry

Flashcards on Nuclear Stability and Radioactivity

Radioactive decay

Process by which an unstable nucleus emits a particle and/or energy from its nucleus in order to become more stable.

Transmutation

The nuclear change from one element into another.

Geiger Counter

Device that produces an electric current when radiation is present.

Alpha radiation

Consists of positively charged particles with a charge of +2 and a mass of 4 ( _2^4He ).

Beta radiation

Consists of negatively charged particles identical in their properties to electrons (_{-1}^0e).

Gamma radiation

Consists of high-energy photons of very short wavelength ( ^0_0\gamma ).

Positron decay

Consists of the antiparticle of the electron being emitted from a nucleus ( _{+1}^{0}e ).

Electron capture

Occurs when an inner electron is absorbed by the nucleus; also known as Inverse Beta Decay. Ex: ⁸²₃₇Rb + ⁰_-1e →⁸²₃₆Kr

Spontaneous fission

The splitting of a heavy nuclide into two lighter nuclides with similar mass numbers.

Half-life

The time required for the number of radioactive nuclides to reach half of their original value.

Induced Radioactivity

A stable nucleus made radioactive by bombarding it with neutrons, alpha particles, or small nuclides of elements.

Nuclear Fission

Splitting of a heavy nucleus with a neutron.

Nuclear Fusion

Light nuclei combine to form a heavy nucleus and energy.

Somatic Damage

Damage to the organism itself, resulting in sickness or death.

Genetic Damage

Damage to the genetic machinery, which produces malfunctions in the offspring of the organism.

Carbon-14 Dating

Comparing the amount of C-14 present in organic material to C-14 in the atmosphere to determine a relatively accurate age.

Chain reaction

A self-sustaining fission process caused by neutrons produced by the fission of U-235.

Reactor core

Contains fuel rods, control rods, and moderator in a nuclear reactor.

Fuel rods

Contain enriched U-235 pellets in a nuclear reactor.

Control rods

Placed between fuel rods to absorb neutrons and control the rate of fission in a nuclear reactor.

Moderator

Liquid water circulated through reactor core to remove and circulate heat and slow down neutrons.

What are the 7 practical uses of radioactivity?

Carbon-14 Dating, Food irradiation (preservation), Medical diagnosis (radioactive isotopes used to monitor), Cancer treatment (destroys unwanted cells with gamma radiation from radioactive isotopes), Smoke detectors (most contain americium-241), generation of electrical power (produces 10% of global power), weapons of mass destruction (9 countries posses over 12,000 nuclear weapons).

How to detect radioactivity?

Nuclear radiation forms ions by removing electrons from matter it passes through. The stripped-away electrons can then be detected.

How do Geiger Counters work?

• Device that produces an electric current when radiation is present

• Hollw tube in counter is filled with gas at low pressure

• Nuclear radiation enters tube and strips electrons from gaseous atoms

• Large number of electrons are attracted to the positive end of the Geiger tube, producing a short, intense electrical current

• Current is amplified by speakers.

What are the health effects of radiation?

Health Effects of Radiation

• Radiation damage is classified into two categories: 

  • Somatic Damage

    • Damage to the organism itself, resulting in sickness or death.

  • Genetic Damage

    • Damage to the genetic machinery, which produces malfunctions in the offspring of the organism.

Compare and contrast the penetrating power of alpha, beta, and gamma radiation

gamma > beta > alpha

Compare and contrast the ionizing power of alpha, beta, and gamma radiation

alpha > beta > gamma

What 4 factors does biological effect of radiation depend on?

• The energy of the radiation

• Penetrating ability of radiation

• Ionizing ability of radiation

• Chemical properties of radiation source

What are the two debated models for radiation damage?

Threshold (you can be exposed to some radiation before it starts to increase risk of cancer) and Linear - no threshold (your risk of getting cancer starts rising as soon as you come into contact with radiation)

How does Carbon-14 dating work?

• C-14 is produced in the atmosphere from interaction of N-14 atoms (in N₂) with cosmic radiation: ¹⁴₇N + ¹₀n -> ¹⁴₆C + ¹₁H

• C-14 is incorporated into the CO₂ in the air.

• C-14 is radioactive and decomposes via beta decay: ¹⁴₆C -> ¹⁴₇N + ⁰_-1e (Half-life of C-14 = 5730 years)

• The process of C-14 forming and decaying in the atmosphere is relatively constant

• Plants absorb C-14 from the intake CO₂. Additionally, C-14 continues to decay within the organism. Thus, a C-14 to C-12 ratio in a living organism is established.

• When a living organism dies, intake of C-14 stops.

• Remaining C-14 continues to decay at a steady rate.

• By comparing the amount of C-14 present in organic material to C-14 in the atmosphere, a relatively accurate age can be determined.

• C-14 dating is only a useful tool for organic material between 100 - 60,000 years.

What are the 3 stages of fission chain reaction in a nuclear reactor

• Subcritical: on average, less than one neutron from each fission event causes an additional fission event

• Critical: exactly one neutron from each fission event causes another fission event

• Supercritical: more than one neutron from each fission event causes an additional fission event

How do reactors work?

• Extracted energy is used to generate steam, which is sent through turbines to produce electricity

• Cool water from a natural source (river or sea) is used to condense steam used to turn the turbines

• Heated river/sea water is cooled in towers (using fans) before being released back into natural source.

How much waste will large reactors produce on average?

 typical large reactor will produce 27 tons of spent fuel rods each year.