1. Key areas
Nuclear equations to describe radioactive decay, fission and fusion reactions with reference to mass and energy equivalence including calculations.
Coolant and containment issues in nuclear fusion reactors.

2. What we will do today:
Go over examples of nuclear reactions in ‘symbol form’.
Carry out problems on the above.
Find out about Einstein’s famous equation E = mc2
Describe how we use the equation above in nuclear energy and discuss some of the safety issues in nuclear reactors.

3. Radioactive decay examples

4. Example 1
Identify the particle emitted at each stage in the decay series shown:
(a) (b) (c)
226 Ra → 222 Rn → 218 Po → 218 At
Atomic No down by 2 = Alpha
Atomic No up by 1 = Beta

5. Example 2 91 Pa 92 U 93 Np 94 Pu (Proactinium) (Uranium) (Neptunium)
We do not have to learn values from the periodic table. All information will be included in any relevant questions
Information from part of the periodic table is shown below: 91 Pa
(Proactinium) 92 U
(Uranium) 93 Np
(Neptunium) 94 Pu
(Plutonium)

6. Example 2
Identify the missing isotope at each stage in the decay series shown:
α β β α
242 Pu → (a) → (b) → (c) → (d) 94

7. Example 2
New mass number is 242 – 4 = 238; new atomic number is 94 – 2 = 92; from periodic table the element with atomic number 92 is U (Uranium);
isotope is: 238 U 92

8. Example 2 Mass number is unchanged = 238
new atomic number is = 93; from periodic table the element with atomic number 93 is Np (Neptunium);
isotope is: 238 Np 93

9. Example 2 In the same way it can be found that: 238 Pu 94 234 U 92
Note: In both alpha and beta decay there may be gamma radiation given off as well, although we cannot conclude this from a study of isotopes formed.

10. Nuclear Fission
In fission, a large nucleus splits into two nuclei of smaller mass with the release of several neutrons and energy.

11. Nuclear Fission
This Fission can occur at random (spontaneous) with a fixed half-life, or stimulated.
In stimulated fission, the nucleus is hit by an incident neutron causing it to undergo fission.
When measured it is found that:
“The mass of the nucleus before the fission is bigger than the mass of all components after the collision.”

12. E = mc2
This lost mass is converted into energy according to Einstein’s famous equation:
E = mc2
E - Energy (J)
m – mass (kg)
c – velocity of light (3x108ms-1)
NB: only c is squared – c2 = 9x1016

13. Example 236U 92 3.901 x 10-25 kg 134Te 52 2.221 x 10-25 kg 98Zr 401n
0.017 x kg
Calculate the energy released in the following reaction:

14. Example Find the energy given out by this reaction
235U n → 134Te + 98Zr + 4 1n
First find the mass both before and after
Mass LHS: x x = x kg
Mass RHS: x x x (0.017 x 10-25)
= x kg
Difference in mass, Δm = x – x 10-25
= x kg
E = mc2 = x x (3x108)2
E = 2.7 x J

15. Nuclear Fusion Fusion is process of joining things together.
Nuclear fusion is when two light nuclei combine to form a nucleus of larger mass number and a neutron.
Like in fission, there is a decrease in mass after the fusion, this loss in mass produces the Energy (E = mc2)
However, the energy released is produced as kinetic energy of the fusion products.
Fusion only occurs at massive temperatures, this explains why the energy released by the Sun and other stars is produced by nuclear fusion.

16. Nuclear Fusion diagram (no need to copy)
Note the two smaller nuclei forming a larger nucleus.

17. Recognising Fission and Fusion
In Fission reactions, the large nucleus is at the start of the reaction. In Fusion it is at the end.
In stimulated Fission reactions, the reactants (on LHS) will contain a neutron, eg:
235U n → 134Te + 98Zr + 4 1n

18. 2000 Qu: 18 E

19. Coolant and Containment issues in Nuclear Fusion Reactors
There are a number of safety issues and concerns surrounding nuclear fusion reactors that are up for debate. These are mainly:
Coolant – As nuclear fusion creates incredibly high (and potentially dangerous) temperatures, coolants are required to remove the excess energy.
Containment – After the nuclear fuel has been used in can still remain dangerously radioactive for a number of years. It has to be kept in thick concrete and hidden away from the general public.

20. Past Paper Questions
Old Higher

21. 2001 Qu: 20 E

22. 2003 Qu: 20 A

23. 2008 Qu: 20 D

24. 2010 Qu: 18 D

25. Past Paper Question 2000 Qu: 29 a 2004 Qu: 30 2006 Qu: 29 b

26. Past Paper Questions
Revised and CfE Higher

27. 2012 D

28. 2012 B

29. 2013 D

30. 2014 E

31. CfE Specimen Paper

32. CfE Specimen Paper