Dr Pusey

www.puseyscience.com

Syllabus pointsNeutron‐induced nuclear fission is a reaction in which a

heavy nuclide captures a neutron and then splits into smaller radioactive nuclides with the release of energy

A fission chain reaction is a self‐sustaining process that may be controlled to produce thermal energy, or uncontrolled to release energy explosively if its critical mass is exceeded

Nuclear fusion is a reaction in which light nuclides combine to form a heavier nuclide, with the release of energy

More energy is released per nucleon in nuclear fusion than in nuclear fission because a greater percentage of the mass is transformed into energy

Learning goals Define:

Fission Neutron-induced fission Chain reaction Critical mass

Recall that fission is only possible for two isotopes, Uranium-235 and Plutonium-239

Describe the fission process Describe how the velocity of incoming neutrons can affect the fission

process Compare and contrast controlled and uncontrolled fission reactions Define:

Fusion

Describe the fusion process Explain why the fusion process releases more energy (per nucleon) than

the fission process Compare and contrast energy emission from a fission reaction, fusion

reaction and decay processes

What is Fission? NUCLEAR FISSION occurs when an atomic nucleus

splits into two or more pieces. This is often triggered by the absorption of a neutron. – HP p. 180

Example 1Identify the unknown quantities (A, Z, X, Y) in the fission reactions below.

a) 01𝑛 + 92

235𝑈 → 𝑍𝐴𝑋 + 38

93𝑆𝑟 + 201𝑛

b) 01𝑛 + 92

235𝑈 → 𝑍88𝑋 + 54

𝐴𝑌 + 1201𝑛

c) 01𝑛 + 92

235𝑈 → 3587𝐵𝑟 + 𝑍

143𝐿𝑎 + 𝑥01𝑛

d) 01𝑛 + 92

235𝑈 → 𝑍𝐴𝑋 + 36

92𝐾𝑟 + 301𝑛

Example 1Identify the unknown quantities (A, Z, X, Y) in the fission reactions below.

a) 01𝑛 + 92

235𝑈 → 54141𝑋𝑒 + 38

93𝑆𝑟 + 201𝑛

b) 01𝑛 + 92

235𝑈 → 3888𝑆𝑟 + 54

136𝑋𝑒 + 1201𝑛

c) 01𝑛 + 92

235𝑈 → 3587𝐵𝑟 + 57

143𝐿𝑎 + 601𝑛

d) 01𝑛 + 92

235𝑈 → 56141𝐵𝑎 + 36

92𝐾𝑟 + 301𝑛

Example 2

A typical fission reaction can be seen below:

01𝑛 + 92

235𝑈 → 56141𝐵𝑎 + 36

92𝐾𝑟 + 301𝑛

If there is a loss of mass of 0.215 u calculate how much energy is released from this fission reaction.

Example 2

A typical fission reaction can be seen below:

01𝑛 + 92

235𝑈 → 56141𝐵𝑎 + 36

92𝐾𝑟 + 301𝑛

If there is a loss of mass of 0.215 u calculate how much energy is released from this fission reaction.

Example 3

Calculate the amount of energy released by the fission reaction shown below:

01𝑛 + 92

235𝑈 → 54141𝑋𝑒 + 38

93𝑆𝑟 + 201𝑛

Isotope Mass (u)

Uranium-235 235.043930

Xenon-141 140.92665

Strontium-93 92.914026

Example 3

Calculate the amount of energy released by the fission reaction shown below:

01𝑛 + 92

235𝑈 → 54141𝑋𝑒 + 38

93𝑆𝑟 + 201𝑛

Isotope Mass (u)

Uranium-235 235.043930

Xenon-141 140.92665

Strontium-93 92.914026

Example 4

mass of neutron = 1.674 95 × 10–27 kg,mass of Uranium-235 = 3.903 05 × 10–25 kg,mass of Barium-144 = 2.389 92 × 10–25 kgmass of Krypton-89 =1.476 53 × 10–25 kg

a What is the decrease in the mass of the nuclear particles involved in this fission reaction?b How many joules of energy are released during the fission of this uranium-235 nucleus?c Express the decrease in mass as a percentage of the mass of the initial nuclear particles. d If a 5 kg lump of pure uranium-235 completely underwent fission, how much energy (in joules) would be released?

Example 5

If you build a Nuclear reactor using Uranium 235 (previous slide), how many fission reactions per second are required to power Dr Pusey’s PlayStation 4 (110 Watts)?

ResourcesAV

Tyler DeWitt – Nuclear Fission (8:59)

Crash Course – Nuclear Chemistry (part 2): Fission and fusion (11:18) – Following this slide!

Bang Goes the Theory – Inside a nuclear reactor core (3:52)

ANSTO – OPAL research reactor animation (3:55)

Harvard Lecture Demonstrations – Mousetrap Fission (2:27)

Simulation

Nuclear Fission – pHet simulation

From: http://nuclear.duke-energy.com/2013/01/30/fission-vs-fusion-whats-the-difference/

Example 1Identify the unknown quantities (A, Z, X, Y) in the fusion reactions below.

a) 𝑍2𝐻 + 𝑍

3𝐻 → 𝑍𝐴𝑋 + 0

1𝑛

b) 12𝐻 + 1

𝐴𝐻 → 𝑍3𝑋 + 0

1𝑛

c) 12𝑋 + 2

3𝑌 → 𝑍4𝐻𝑒 + 𝑍

𝐴𝐻

Example 1Identify the unknown quantities (A, Z, X, Y) in the fusion reactions below.

a) 12𝐻 + 1

3𝐻 → 24𝐻𝑒 + 0

1𝑛

b) 12𝐻 + 1

2𝐻 → 23𝐻𝑒 + 0

1𝑛

c) 12𝐻 + 2

3𝐻𝑒 → 24𝐻𝑒 + 2

1𝐻

Example 2

Calculate the amount of energy released by the fusion reaction shown below:

12𝐻 + 1

3𝐻 → 24𝐻𝑒 + 0

1𝑛

Isotope Mass (u)

Deuterium (Hydrogen-2) 2.014101

Tritium (Hydrogen-3) 3.016049

Helium-4 4.002602

Example 2

Calculate the amount of energy released by the fusion reaction shown below:

12𝐻 + 1

3𝐻 → 24𝐻𝑒 + 0

1𝑛

Isotope Mass (u)

Deuterium (Hydrogen-2) 2.014101

Tritium (Hydrogen-3) 3.016049

Helium-4 4.002602

ResourcesAV

PhD Comics – What is fusion, video and simulation (7:56)

Further Reading

Scientific American - Fusion Experiment Breakthrough

How did you go? Define:

Fission

Neutron-induced fission

Chain reaction

Critical mass

Recall that fission is only possible for two isotopes, Uranium-235 and Plutonium-239

Describe the fission process

Describe how the velocity of incoming neutrons can affect the fission process

Compare and contrast controlled and uncontrolled fission reactions

Define:

Fusion

Describe the fusion process

Explain why the fusion process releases more energy (per nucleon) than the fission process

Compare and contrast energy emission from a fission reaction, fusion reaction and decay processes