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Physics > Nuclear > Flashcards

Nuclear Flashcards

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1
Q

Describe Rutherford’s experiment

A

He fired a beam of alpha particles at thin gold foil, which was surrounded by a circular screen detector, which was used to detect alpha particles deflected at any angle

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2
Q

What did Rutherford find and what did he expect

A

They expected that the alpha particles would be deflected, instead 99.5% of the alpha particles went straight through the foil, while a small number were deflected by a large angle.Some were even deflected by more than 90 degrees

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3
Q

From Rutherford’s experiment what did he conclude

A
  • Atoms have a small positively charged nucleus at the centre
  • Most of the atom must be empty space because most of the alpha particles passed straight through
  • The nucleus must have a large positive charge
  • The nucleus must be small
  • Most of the mass must be in the nucleus
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4
Q

How does J.J Thomson’s theory differ to Dalton’s

A

Dalton believed that matter was made up of tiny spheres that couldn’t be broken up, and that each element was made up of a different type of atom
Whereas Thomson suggested that atoms were spheres of positive charge with tiny negative electrons (Plum Pudding Model), and that electrons could be removed

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5
Q

Factors that affected the accuracy of Rutherford’s experiment

A
  • The location of the alpha source meant that it was impossible to detect a head on collision resulting in a scattering angle of 180
  • He assumed the only force between the alpha particle and gold nucleus was electrostatic, but alpha particles contain Hadrons meaning they will also interact via the strong force
  • The finite size of the alpha particles introduces an uncertainty in the calculation of the closest approach
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6
Q

What is Alpha’s range in air

A

Up to 10cm

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7
Q

What is Beta’s range in air

A

About 1m

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8
Q

What is Gamma’s range in aie

A

10’s-100’s of metres

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9
Q

How are the types of radiation effected by magnetic fields

A 
Alpha= Deflected as charged
Beta= Deflected significantly as low mass
Gamma= No effect
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10
Q

Uses of alpha

A

Smoke Detector

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11
Q

Uses of Beta

A

PET scanners

Rolling out metals

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12
Q

Uses of Gamma

A

Radiotherapy
Medical Tracers
Sterilisation of Equipment

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13
Q

Define Intensity

A

Intensity of electromagnetic radiation is the radiation energy passing per second through an area of 1m^2 normal to the radiation

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14
Q

What is the inverse square law for Gamma radiation, and what does it assume

A

I=k/x^2
As it spreads out in a spherical direction
It assumes that while the gamma intensity is being measured the source activity is unchanged so only works for sources with a long enough half-life

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15
Q

Origins of background radiation

A
  • Radioactive Radon gas released from some rocks such as Granite
  • Cosmic Rays
  • Medical Applications
  • Radioactive isotopes in living things
  • Waste from nuclear industry and fallout from nuclear weapons testing
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16
Q

Define Background Radiation

A

A radiation does rate at a specified location, which is generated by natural and artificial ionising radiation sources existing in the environment

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17
Q

How do you calculate corrected count rate

A

Corrected Count rate= Measured count rate - Background Count Rate

18
Q

What is radioactive decay

A

It is the process by which an unstable nucleus loses energy by emitting radiation. The decay is a random event, however if a large enough number of atoms are studied it is possible to predict the most likely proportion of them that will decay in a given time

19
Q

What is the decay constant

A

The probability of an individual nucleus of a particular radioisotope decaying per second

20
Q

What is activity and what’s its symbol

A

The number of decays per second, Bq

21
Q

Define Half-Life

A

The average time taken for half of the radioactive nuclei in a sample to decay

22
Q

2 formulas to calculate number of moles

A

No. of Moles= Mass/Molar Mass

No. of Moles= No. of Particles/ Avogadro’s Number

23
Q

When is a nucleus unstable

A
  • It has too many neutrons
  • It has too few neutrons
  • Its too heavy
  • It has too much energy
24
Q

Typical value for nucleus radius

A

x10^-15

25
Q

How can we estimate nuclear radius

A
  • Closest approach of alpha particles

- Through electron diffraction

26
Q

What does the formula E=mc^2 show

A

That the mass of a body is a measure of its energy content, if the energy is transferred to or from a body, its mass changes

27
Q

Define the atomic mass unit

A

Being 1/12th of the mass of 12g of Carbon-12

28
Q

state what is meant by binding energy, and explain how it arises,

A

The binding energy of a nucleus is the energy needed to separate the nucleus into its constituent nucleons.(or the energy released when the nucleus is formed from individual nucleons) The potential energy of the nucleons decreases when they come together under the strong force.

29
Q

What is the critical mass of fuel

A

The minimum mass required to establish a self-sustaining chain reaction

30
Q

Why is energy released during fission

A

Because the new smaller nuclei will have a higher binding energy per nulceon

31
Q

What is fission

A

It is splitting nucleons into smaller parts

32
Q

`How can you induce fission

A

By making a neutron enter a Uranium-235 nucleus, causing it to become unstable- only thermal neutrons can be captured in this way

33
Q

What is the function of a moderator in a thermal reactor plant

A

-It absorbs excess energy, slowing down the fast fission neutrons

34
Q

What materials are used for moderators and why

A

Carbon Dioxide, Water and Lithium
The must have a low probability of absorbing neutrons. Choosing a moderator with a similar mass to the neutrons is more efficient at slowing neutrons down

35
Q

What is the function of control rods

A

Absorbs neutrons to control the rate at which fission occurs

36
Q

What material is used for control rods and why

A

Commonly Boron as it has a high probability of absorbing neutrons

37
Q

What is the function of the coolant

A

It is the material that passes through the reactor, and absorbs the heat energy generated by fission. The heat energy is transferred to convert water into high pressure steam

38
Q

What material is used for the coolant and why

A

Water or Carbon Dioxide gas

The material must have a high specific heat capacity or be able to be pumped very quickly around the system

39
Q

What’s the difference between a fast neutron and a thermal neutron

A

A thermal neutron is in thermal equilibrium with its surroundings,, is much slower and has less KE than a fast neutron

40
Q

How is High Level Waste Stored

A

Stored as liquid in water cooled tanks. Requires thick concrete to shield operators from high levels of radiation

41
Q

His is Intermediate Level Waste stored

A

Some stored in vaults, and some mixed in cement inside stainless steel drums. Requires thick concrete walls to shield operator

42
Q

How is Low Level Waste Stored

A

Compacted to a fraction of its original volume and stored in steel drums in concrete vaults

Physics (9 decks)

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