1. Nuclear Cycle Power Plants

2. The Atom The atom consists of two parts:
1. The nucleus which contains:
protons
neutrons
Orbiting electrons
(J. J. Thomson)

3. All matter is made up of elements (e.g. carbon, hydrogen, etc.).
The smallest part of an element is called an
atom.
Atom of different elements contain different numbers of protons.
The mass of an atom is almost entirely due to the number of protons and neutrons.

4. X A Z Mass number = number of protons + number of neutrons
Element symbol Z
Atomic number
= number of protons

5. X A Z A = number of protons + number of neutrons Z = number of protons
A – Z = number of neutrons
Number of neutrons = Mass Number – Atomic Number

6. Most of the isotopes which occur naturally are stable.
A few naturally occurring isotopes and all of the man-made isotopes are unstable.
Unstable isotopes can become stable by releasing different types of particles.
This process is called radioactive decay and the elements which undergo this process are called radioisotopes/radionuclides.

7. Composition of Matter
All of matter is composed of at least three fundamental particles (approximations):
Particle
Fig.
Sym
Mass
Charge
Size
Electron e x kg -1.6 x C 
Proton p x kg x C 3 fm
Neutron n x kg fm
The mass of the proton and neutron are close, but they are about 1840 times the mass of an electron.

8. Modern Atomic Theory
The Bohr atom, which is sometimes shown with electrons as planetary particles, is no longer a valid representation of an atom, but it is used here to simplify our discussion of energy levels.
The uncertain position of an electron is now described as a probability distribution—loosely referred to as an electron cloud.

9. Definitions
A nucleon is a general term to denote a nuclear particle - that is, either a proton or a neutron.
The atomic number Z of an element is equal to the number of protons in the nucleus of that element.
The mass number A of an element is equal to the total number of nucleons (protons + neutrons).
The mass number A of any element is equal to the sum of the atomic number Z and the number of neutrons N :
A = N + Z

10. Isotopes of Elements Helium - 4 Helium - 3 Isotopes of helium
Isotopes are atoms that have the same number of protons (Z1= Z2), but a different number of neutrons (N). (A1  A2)
Helium - 4
Helium - 3
Isotopes of helium

11. Nuclides The following are best described as nuclides:
Because of the existence of so many isotopes, the term element is sometimes confusing. The term nuclide is better.
A nuclide is an atom that has a definite mass number A and Z-number. A list of nuclides will include isotopes.
The following are best described as nuclides:

12. Atomic Mass Unit, u Proton: 1.007276 u Neutron: 1.008665 u
One atomic mass unit (1 u) is equal to one-twelfth of the mass of the most abundant form of the carbon atom--carbon-12.
Atomic mass unit: 1 u = x kg
Common atomic masses:
Proton: u
Neutron: u
Electron: u
Hydrogen: u

13. The Mass Defect
The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons.
The whole is less than the sum of the parts! Consider the carbon-12 atom ( u):
Nuclear mass = Mass of atom – Electron masses = u – 6( u) = u
The nucleus of the carbon-12 atom has this mass.

14. The Binding Energy
The binding energy EB of a nucleus is the energy required to separate a nucleus into its constituent parts.
EB = mDc2 where c2 = MeV/u
The binding energy for the carbon-12 example is:
EB = ( u)(931.5 MeV/u)
EB = 92.2 MeV
Binding EB for C-12:

15. Binding Energy per Nucleon
An important way of comparing the nuclei of atoms is finding their binding energy per nucleon:
Binding energy per nucleon
For our C-12 example A = 12 and:

16. Radioactivity a b- b+ g Examples are: Alpha particles a
As the heavier atoms become more unstable, particles and photons are emitted from the nucleus and it is said to be radioactive. All elements with A > 82 are radioactive. a b- b+ g
Examples are:
Alpha particles a
b- particles (electrons)
Gamma rays g
b+ particles (positrons)

17. Radioactivity
Radioactivity means that atoms decays. The reason for this decays is that they are instable. A atomic nucleus is instable when he is to heavy or when a balance is missing between the protons and the neutrons. Every atom which has got a higher number of nucleons (protons and neutrons togehter) than 210 is instable.

18. Radioactive Decay Radioactive decay results in the emission of either:
an alpha particle (a),
a beta particle (b),
or a gamma ray(g).

19. Alpha Decay
An alpha particle is identical to that of a helium nucleus.
It contains two protons and two neutrons.
The center of the atom contains a tight ball of neutrons and protons, which is held together by the strong nuclear force, unless it is too large. Unstable nuclei may undergo alpha decay, in which they emit an energetic helium nucleus.

20. X Y + He Alpha Decay A Z A - 4 Z - 2 4 2 unstable atom alpha particle
more stable atom

21. Alpha Decay Rn
222 86 He 4 2 Ra
226 88

22. Beta Decay
A beta particle is a fast moving electron which is emitted from the nucleus of an atom undergoing radioactive decay.
Beta decay occurs when a neutron changes into a proton and an electron.

23. Beta Decay
As a result of beta decay, the nucleus has one less neutron, but one extra proton.
The atomic number, Z, increases by 1 and the mass number, A, stays the same.

24. Beta Decay b -1 At
218 85 Po
218 84

25. Beta Decay X A Z Y
Z + 1 + b -1 Po
218 84 Rn 85 + b -1

26. Gamma Decay
Gamma rays are not charged particles like a and b particles.
Gamma rays are electromagnetic radiation with high frequency.
When atoms decay by emitting a or b particles to form a new atom, the nuclei of the new atom formed may still have too much energy to be completely stable.
This excess energy is emitted as gamma rays (gamma ray photons have energies of ~ 1 x J).

27. Gamma Rays
The change of potential energy experienced by an electron moving from a place where the potential has a value of V to a place where it has a value of (V+1 volt). This is a convenient energy unit when dealing with the motions of electrons and ions in electric fields; the unit is also the one used to describe the energy of X-rays and gamma rays. A keV (or kiloelectron volt) is equal to 1000 electron volts. An MeV is equal to one million electron volts. A GeV is equal to one billion (109) electron volts. A TeV is equal to a million million (1012) electron volts.’

28. Gamma
Explorer XI launched first satellite in 1961 was the first gamma ray receiver.
It picked up fewer than 100 cosmic gamma-ray photons total.
CGRO satellite.
The moon gives off more Gamma Rays than the sun.
Mirrors don’t work

29. Gamma

31. Gamma-Ray Burst over 40 Seconds

32. The Half-Life
The half-life T1/2 of an isotope is the time in which one-half of its unstable nuclei will decay. No
Number of Half-lives
Number Undecayed Nuclei 1 4 3 2

33. Half-Life (Cont.)
The same reasoning will apply to activity R or to amount of material. In general, the following three equations can be applied to radioactivity:
Mass Remaining
Number of Half-lives:

34. Nuclear Fission
When atoms are bombarded with neutrons, their nuclei splits into 2 parts which are roughly equal in size.
Nuclear fission in the process whereby a nucleus, with a high mass number, splits into 2 nuclei which have roughly equal smaller mass numbers.
During nuclear fission, neutrons are released.

35. Nuclear Fission There are 2 types of fission that exist:
1. Spontaneous Fission
2. Induced Fission

36. Spontaneous Fission
Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei.
Such spontaneous decays are accompanied by the release of neutrons.

37. Induced Fission
Nuclear fission can be induced by bombarding atoms with neutrons.
The nuclei of the atoms then split into 2 equal parts.
Induced fission decays are also accompanied by the release of neutrons.

38. The Fission Process
A neutron travels at high speed towards a uranium-235 nucleus. U
235 92 n 1

39. The Fission Process
A neutron travels at high speed towards a uranium-235 nucleus. U
235 92 n 1

40. The Fission Process
A neutron travels at high speed towards a uranium-235 nucleus. U
235 92 n 1

41. The Fission Process
The neutron strikes the nucleus which then captures the neutron. U
235 92 n 1

42. The Fission Process
The nucleus changes from being uranium-235 to uranium-236 as it has captured a neutron. U
236 92

43. The Fission Process The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.

44. The Fission Process The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.

45. The Fission Process The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.

46. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba n 1 92 36 Kr n 1

47. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba n 1 92 36 Kr n 1

48. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba n 1 92 36 Kr n 1

49. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba n 1 92 36 Kr n 1

50. Fission Process
An induced nuclear fission event. A slow-moving neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons.

51. U + Ba n 3 Kr U + Cs n 2 Rb Nuclear Fission Examples 235 92 141 56 13 Kr 36 U
235 92 + Cs
138 55 n 1 2 Rb 96 37

52. Energy from Fission
Both the fission fragments and neutrons travel at high speed.
The kinetic energy of the products of fission are far greater than that of the bombarding neutron and target atom.
EK before fission << EK after fission
Energy is being released as a result of the fission reaction.

53. Energy from Fission
total mass before fission > total mass after fission
mass difference, m = total mass before fission – total mass after fission
This reduction in mass results in the release of energy.

54. The energy released can be calculated using the equation:m c2
E = mc2
Where:
E = energy released (J)
m = mass difference (kg)
c = speed of light in a vacuum (3 x 108 ms-1)

55. Energy from Fission
The energy released from this fission reaction does not seem a lot.
This is because it is produced from the fission of a single nucleus.
Large amounts of energy are released when a large number of nuclei undergo fission reactions.

56. H + He n Energy Nuclear Fusion 2 1 4 3
In nuclear fusion, two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number. H 2 1 + He 4 n 3
Energy

57. The Fusion Process H 2 1 H 3 1

58. The Fusion Process H 2 1 H 3 1

59. The Fusion Process H 2 1 H 3 1

60. The Fusion Process H 2 1 H 3 1

61. The Fusion Process

62. The Fusion Process

63. The Fusion Process

64. The Fusion Process

65. The Fusion Process n 1 He 4 2
ENERGY

66. The Fusion Process n 1 He 4 2
ENERGY

67. The Fusion Process n 1 He 4 2
ENERGY

68. The Fusion Process n 1 He 4 2
ENERGY

69. Nuclear Fusion
The electrostatic force caused by positively charged nuclei is very strong over long distances, but at short distances the nuclear force is stronger. As such, the main technical difficulty for fusion is getting the nuclei close enough to fuse. Distances not to scale.

70. Energy from Fusion E = mc2 Calculate: The mass difference.
m = total mass before fission – total mass after fission
The energy released per fusion.
E = mc2

71. REACTORS AND TYPES

72. Types of reactors Boiling water reactor Pressurized water reactors
CANDU reactor
Liquid-metal fast-breeder reactor

73. FAST BREEDING REACTORS
GFBR: Gas- Cooled fast breeding reactor system
LMFBR: Liquid Metal Cooled Fast Breeding Reactor
SFBR: Sodium Fast Breeding Reactor
LFR: Lead Fast Reactor cooled with lead
MSR: Molten Salt Reactor fuelled with molten salts
SCWR: Super-Critical Water-cooled Reactor.
VHTR: Very High Temperature Reactor cooled with helium at 1000deg C.

74. Pressurized Water Reactors
Operate with thermal neutrons
Steam is generated outside the reactor in a secondary heat transfer loop

75. Boiling Water Reactor
water is converted to steam, and then recycled back into water by a part called the condenser, to be used again in the heat process.
steam generated inside the reactor goes directly to the turbine

77. COMPONENTS OF CANDU REACTOR
1.Fuel bundle. 2.Reactor core. 3.Adjuster rod. 4.Heavy water pressure reservoir. 5.Steam generator. 6.Light water pump. 7.Heavy water pump. 8.Fuelling machines. 9.Heavy water moderator. 10.Pressure tube. 11.Steam going to steam turbine. 12.Cold water returning from turbine. 13.Containment building made of reinforced concrete.

78. Liquid-Metal Fast-Breeder Reactors
breeder reactors are designed to produce more fissile material than they consume
the fission reaction produces heat to run the turbine while at the same time breeding plutonium fuel for the reactor.

79. Overview of Fast Breeder Reactors
Produce more fissile material than is consumed
Technology first developed in the 1950’s
Utilize uranium 60 times as efficienctly as PWRs
Cooled by liquid metal

80. Fast Breeder Reactors vs. Pressurized Water Reactors
FBR
Fuel is enriched to 15-20%
Moderator: none
Heat transfer by liquid metal or metal alloys
Typically sodium
Reactor under low pressure
~1.2 fissile atoms produced per fission
PWR
Fuel is enriched to 3-5%
Moderator: water
Heat transfer by water
Reactor under high pressure
Fissile material is only consumed

81. Breeding Fuel Theory Practice
Each fission produces on average 2.4 neutrons
Fissile material: U-235, Pu-239 or Pu-241
Critical reaction
One neutron per fission causes another fission
1.4 neutrons are left over to enrich depleted fuel
Practice
Typical FBR produces about 1.2 fissile atoms per consumed fissile atom
Can produce enough fissile material in 10 years to replace spent fuel and enough to power another reactor for 10 years

82. FBR Design Highly enriched uranium or plutonium
Control rods (same material as core)
Depleted uranium
Heat is transferred from primary to secondary sodium
Heat is transferred from secondary sodium to water
Figure: Baksiden, modified by Martin Metzner

83. Liquid Metal Coolant Typical metal used is sodium Advantages of sodium
Some reactors use lead, lead-bismuth alloy, or sodium fluoride salt
Advantages of sodium
Low melting temperature (98°C)
High boiling temperature (892°C)
High heat capacity
System can run at low pressure
Risks of sodium
Burns when it comes in contact with air or water
Poisonous fumes

84. Future of Fast Breeders
Next generation may use noble gases such as helium or argon instead of sodium
Increase in the breeding ratio
Believed that a ratio of 1.3 will be possible
Smaller reactors
Lower maintenance and repair costs
Higher reactor temperatures
Can be used for thermochemical hydrogen production

85. NUCLEAR SAFETY

86. Nuclear Power Stations
Dukovany and Temelín
Water-cooled Water-moderated Energy Reactor
pressure vessel of the reactor and the primary circuit piping include a very small contents of cobalt, this results in a lower activation of material and also a lower irradiation of personnel

87. qualified personnel, quality documentation, use of operating experience, technical control, protection against radiation, fire safety, etc.
each of the four reactor units is controlled from the independent unit control room
the reactor unit chief, primary part operator and the secondary part operator.  

88. Unit control room

89. Safety system
Basic precondition of the power station safety is a continuous removal of heat generated in the reactor core. Safety systems consist of a high-pressure and low-pressure emergency pumps, sprinkler system pumps, reservoirs with boric acid solution, heat exchangers, pressurized-water containers, pipelines, fittings, condensing troughs and towers and gas tanks.

90. Leakage of cooling water
security systems would pump cooling water under and over the reactor core and sprinkle the hermetic boxes.
disruption of the main circulation piping → pressure of steam generated in hermetic boxes increase → steam into condensing troughs → condense
facilities are doubled or tripled, and dimensioned in such an extent that the leakage of radioactive substances to environment would be reduced to a minimum.

91. Fast shut-down 37 control rod assemblies
power supply for all the control rod assemblies in the upper positions is discontinued
control rod assemblies starts moving downwards by their own mass into the reactor core, and the fission reaction is terminated within 12 seconds.

92. Spent fuel storage

93. Radioactive waste repository
Mines Richard institutional waste
Bratrství – ex-uranium mine
Hostim – not used

94. State Office for Nuclear Safety
Administration and supervision
The Radiation Monitoring Network
The Emergency Response Cente