2- Energy From The Nucleus Flashcards
What are the two fissionable isotopes used commonly in nuclear reactors?
Uranium-235 (most often)
Plutonium-239
What do most (uranium) nuclear reactors use and why?
Enriched uranium (235) because naturally occurring uranium is non-fissionable
How does fission occur?
The fissionable isotopes nucleus must absorb a neutron. Then the nucleus splits into two smaller nuclei. Whist this happens, a few neutrons are emitted and a great amount of energy is released
What does a control rod do in a nuclear reaction?
Absorb fission neutrons to ensure only one neutron per fission goes on to produce further fission on average
What is nuclear fusion?
The process of forcing two nuclei close enough together to form a single, larger, nucleus - two light nuclei collide at high speed
What is an example of nuclear fusion?
Process in which energy is released by stars
What problems are faced when producing energy from nuclear fusion in reactors?
Nuclei will naturally repel each other so they must be heated to very high temperatures, because of this the reaction must be contained by a magnetic field
What are the issues of everything nuclear?
Different sorts of background radiation
What are some examples of nuclear background radiation?
Radon gas (from rocks deep underground) alpha particles emitted Cosmic rays (outer space) Food and drink, air travel, nuclear weapon testing Medical sources (X-rays) have ionising effects
What is useful about uranium and plutonium?
If stored properly, they can be chemically removed and used again
What should workers do to reduce radiation exposure?
Keep as far away as possible
Spend as little time close as possible
Shield themselves with concrete and lead
How do most scientists believe the universe was created?
Through ‘the big bang’.
From a hot glowing ball of radiation, nuclei of the lightest element formed. Over millions of years as the earth temperatures fell uncharged atoms were formed
How were stars originally formed?
From a cloud of helium and hydrogen, dust and gas were pulled together by gravitational attraction to form stars. The intense heat formed visible light
What is a galaxy and a bit about it?
A very large group of stars held together by their own gravity, our galaxy is called the Milky Way (one of billions of galaxy’s)
Each galaxy has masses of empty space between them
How does a protostar form? How does it get hotter and brighter?
Gravitation forces pill clouds of dust and gas together to form a protostar
As it becomes denser, the nuclei of light elements (such as hydrogen) fuse together releasing energy which makes the core hotter and brighter
What is a main sequence star and how does it form from a protostar?
As a protostar runs becomes denser, the star is stable because the inward force of gravity and outward force of radiation from the core are balanced. This process goes on for billions of years
What happens when a main sequence star runs out of hydrogen nuclei?
It swells, cools down and turns red
After a star runs out of hydrogen, what happens will depend on the stars size, if the main sequence star has a low mass, what will be formed and how?
A red giant, our sun is an example - Helium and other elements fuse to form heavier elements
From a red giant, what will be formed and how?
A white dwarf, Fusion stops and the star will contract to form a white dwarf
From a white dwarf, what will be formed and how?
A black dwarf, Eventually no more light is emitted and the star becomes a black dwarf
After a star runs out of hydrogen, what happens will depend on the stars size, If the main sequence star has a high mass, what is formed and how?
A red supergiant, Stars much larger than the sun will swell to become a red supergiant, which continues to collapse
What happens when the star explodes?
It explodes in a supernova, the outer layer is thrown into space while the core is left as a neutron star - if it is large enough, it can form a black hole
How are chemical elements formed?
By the fusion processes in stars - the nuclei of lighter elements fuse to form the nuclei of heavier elements releasing large amounts of energy
How is the solar system formed?
The sun forms at the centre of gas and rock. It’s kinetic energy then allows the gas to escape, leaving rocks to orbit it. The sun evaporates ice.
Rocky planets form near the sun and planets with gas form further away
