1. Absorption of Nuclear Radiation & Radiation Effects on Matter: Atomic and Nuclear Physics
Dr. David Roelant

2. Atomic and Molecular Weight

3. Problem 1
Using the data in the table below, compute the atomic weigh of naturally occurring oxygen.
Isotope
Abundance (%)
Atomic Weight
16O
99.759
17O
0.037
18O
0.204

4. Solution to Problem 1
Using the data in the table below, compute the atomic weigh of naturally occurring oxygen.
Isotope
Abundance (%)
Atomic Weight
16O
99.759
17O
0.037
18O
0.204

5. Atomic and Nuclear Radii

6. Increase in Mass Relative to Observer of a Moving Mass

7. Particle Wavelengths

8. Energy levels of hydrogen atom
E =13.58 eV
E = eV
E =10.19 eV
Energy, eV
E =0 eV

9. Introduction to Nuclear Engineering by J.R. Lamarsh
Decay Scheme of 60Co
Introduction to Nuclear Engineering by J.R. Lamarsh

10. Radioactivity Calculations

11. Decay Chain Radioactivity

12. Fundamental Laws Governing Nuclear Reactions
Conservation of nucleons
Conservation of charge
Conservation of momentum
Conservation of energy

13. Balancing Nuclear Equations

14. Balancing Nuclear Equations

15. Problem 2
One of the reactions that occurs when 3H (tritium) is bombarded by deuterons (2H nuclei) is
3H (d,n)4He
where, d refers to the bombarding deuteron.
Compute the Q-value of this reaction.

16. Solution to Problem 2
The Q-value is obtained from the following neutral atomic masses (in amu):
The Q-value in amu is Q = – = amu. Since 1 amu = MeV, Q = x = MeV.
The Q-value is positive and so this reaction is exothermic. This means, for instance, that when stationary 3H atoms are bombarded by 1 – MeV deuterons, the sum of the kinetic energies of the emergent α–particle (4He) and neutron is = MeV

17. Binding Energy per Nucleon as a Function of Atomic Mass Number
Introduction to Nuclear Engineering by J.R. Lamarsh

18. Atomic Density

19. Nuclear radiation absorption p. 165
Counting efficiency (self, abs s-d, det, geom.)
Ionization, excitation, bremsstrahlung, positron annihilation, Cerenkov (.6MeV) (fig. 7.9)

20. Problem 3
The density of sodium is 0.97 g/cm3. Calculate its atomic density.

21. Solution to Problem 3
The density of sodium is 0.97 g/cm3. Calculate its atomic density.
The atomic weight of Na is
It is usual to express atomic densities as a factor x 1024

22. Interaction of Radiation with Matter
(in entire target area)

23. Problem 4
A beam of 1-MeV neutrons of intensity 5 x 108 neutrons/cm•s strikes a thin 12C target. The area of the target is 0.5 cm2 and it is cm thick. The beam has a cross-sectional area of 0.1 cm2. At 1 MeV, the total cross section of 12C is 2.6 b.
At what rate do interactions take place with the target?
What is the probability that a neutron in the beam will have a collision in the target?

24. Solution to Problem 4
It should be noted that the in the cross section cancels the in atom density. This is the reason for writing atom densities in the form of a number x 1024
In 1 sec, a total of IA = 5 x 108 • 0.1 = 5 x 107 neutrons strike the target. Of these, 5.2 x 105 interact. The probability that a neutron interacts in the target is therefore: 5.2 x 105 / 5 x 107 = x Thus, only about 1 neutron in 100 has a collision while traversing the target.

25. Collision Density

26. Neutron Attenuation

27. Compound Nucleus Formation
56Fe + n (elastic scattering)
56Fe + n’ (inelastic scattering)
57Fe + γ (radiative capture)
55Fe + 2n (n, 2n reaction)

28. Elastic Scattering

29. Energy Loss in Scattering Collisions
Fig Elastic Scattering of a Neutron by a Nucleus
Introduction to Nuclear Engineering by J.R. Lamarsh

30. The Energy Released in Fission
Introduction to Nuclear Engineering by J.R. Lamarsh

31. ɣ-Ray Interactions with Matter
In nuclear engineering problems only three processes must be taken into account to understand how Ɣ-rays interact with matter.
The Photoelectric Effect
Pair Production
Compton Effect

32. Photoelectric Effect
Incident ɣ-ray interacts with an entire atom, the ɣ-ray disappears, and one of the atomic electrons is ejected from the atom.
The hole in the electronic structure is latter filled by a transition of one of the outer electrons into the vacant position.
The electronic transition is accompanied by the emission of x-rays characteristic of the atom or by the ejection of an Auger electron.

33. Dependence of Z on Photoelectric Cross Section
where, n is a function of E shown in Fig Because of the strong dependence of σpe on Z, the photoelectric effect is of greatest importance for the heavier atoms such as lead, especially at lower energies.
Introduction to Nuclear Engineering by J.R. Lamarsh

34. Pair Production
Photon disappears and an electron pair – a positron and a negatron – is created.
This effect doesn’t occur unless the photon has at least MeV of energy.
Cross section for pair production (σpp) increases steadily with increasing energy.
Pair production can take place only if vicinity of a Coulomb field.

35. Compton Effect
Elastic scattering of a photon by an electron, in which both energy and momentum are conserved.
A Compton cross section per electron (eσC) decreases monotonically with increasing energy from a maximum value b (essentially 2/3 of a barn) at E = 0, which is known as the Thompson cross section, σT.

36. Attenuation Coefficients
Macroscopic ɣ-ray cross sections are called attenuation coefficients.
Mass attenuation coefficient (μ/ρ)
Introduction to Nuclear Engineering by J.R. Lamarsh

37. Introduction to Nuclear Engineering by J.R. Lamarsh

38. Introduction to Nuclear Engineering by J.R. Lamarsh

39. Introduction to Nuclear Engineering by J.R. Lamarsh

40. Problem 5
It is proposed to store liquid radioactive waste in a steel container. If the intensity of ɣ-rays incident on the interior surface of the tank is estimated to be 3 x 1011 ɣ-rays/cm2•sec and the average ɣ-ray energy is 0.8 MeV, at what rate is energy deposited at the surface of the container?

41. Solution to Problem 5
It is proposed to store liquid radioactive waste in a steel container. If the intensity of ɣ-rays incident on the interior surface of the tank is estimated to be 3 x 1011 ɣ-rays/cm2•sec and the average ɣ-ray energy is 0.8 MeV, at what rate is energy deposited at the surface of the container?
Steel is a mixture of mostly iron and elements such as nickel and chromium that have about the same atomic number as iron. So as far as ɣ-ray absorption is concerned, there, steel is essentially all iron. From table 3.8, μo/ρ for iron at 0.8 MeV is cm2/g. The rate of energy deposition is then: