Physik: Radioaktivität und Strahlungsarten

• These are study notes about physics and radioactivity.

Aufbau von Atomen (Atomic Structure)

• An oxygen atom (O-Atom) has 8 protons, 8 neutrons, and 7 electrons.
• Mass number is 17 and charge is +1 with 8 Protons and atomic number

Die 3 Zerfallsarten (The 3 Types of Decay)

• Alpha Decay (α-Zerfall): Occurs in elements with too much mass to be stable.

  • An example is the decay of Radium (Ra) into Radon (Rn): ²²⁶Ra₈₈ → ²²²Rn₈₆ + α

• Beta Minus Decay (β⁻-Zerfall): Occurs when elements have too many neutrons to be stable.

  • An example is the decay of Cesium (Cs) into Barium (Ba): ¹³⁷Cs₅₅ → ¹³⁷Ba₅₆ + β⁻

• Beta Plus Decay (β⁺-Zerfall): Occurs when elements have too many protons.

  • An example is the decay of Astatine (At) into Polonium (Po): ²¹⁰At₈₅ → ²¹⁰Po₈₄ + β⁺

Die 3 Strahlungsarten (The 3 Types of Radiation)

• Alpha Radiation (Alpha-Strahlung):

  • A Helium nucleus (α-particle) is ejected from the atomic nucleus.
  • Carries a +2e charge.
  • Can be shielded with paper.
  • Has weak penetration ability.
  • Can be detected with a Geiger-Müller counter.

• Beta Radiation (Beta-Strahlung):

  • An unstable atomic nucleus emits an electron or positron.
  • Carries a -e charge.
  • Can be shielded with a few millimeters of aluminum.
  • Penetration range in air is a few centimeters to meters.
  • Penetration range in soft tissue is a few millimeters to centimeters.
  • Can be detected with a Geiger-Müller counter.

• Gamma Radiation (Gamma-Strahlung):

  • An atomic nucleus transitions from a higher energy state to a lower, more stable state.
  • Has no charge.
  • Can be shielded with lead.
  • Has high penetration ability.
  • Can be detected with a Geiger-Müller counter.

Die Halbwertszeit (Half-Life)

• Halbwertszeit (Half-Life):

  • The time after which half of the nuclei of a given radioactive substance have decayed.
  • T₁/₂ represents the half-life.

• Das Zerfallsgesetz (The Decay Law):

  • N(t) = N₀ * (½)^(t/T₁/₂)
    • N(t): number of nuclei remaining after time t
    • N₀: initial number of nuclei
  • A(t) = A₀ * (½)^(t/T₁/₂)
    • Activity of the preparation (decays per second)

Die 5 As des Strahlenschutzes (The 5 As of Radiation Protection)

• Abstand halten (Maintain Distance)
• Abschirmen (Shielding)
• Aufenthaltsdauer kleinhalten (Minimize Exposure Time)
• Aktivität verringern (Reduce Activity)
• Aufnahme in den Körper vermeiden (Avoid Ingestion)

Die Kernspaltung (Nuclear Fission)

• If an atomic nucleus is unstable, it is radioactive.
• Nuclear fission refers to the splitting of heavy, unstable atomic nuclei into lighter, more stable nuclei, releasing energy in the process.
• When fission occurs between Uranium and a neutron: ₀¹n + ²³⁵U₉₂ → ²³⁶U₉₂ → ¹n₀ + ⁹⁰Kr₃₆ + ¹³⁹Ba₅₆ + E

Freiwerdende Energie (Released Energy)

• When talking about nuclear energy or using nuclear energy, it refers to the energy difference that corresponds to the mass defect between the original nucleus and the end product.
• This difference is known as the released energy.
• E = mc²

Calculations regarding nuclear fission

• First, the masses of the individual reactants and products are noted and the total masses are compared with each other.

• Mass of initial products

  • mU-235 = 235.04392996 u
  • mn = 1.008665 u

• Mass of end products

  • mKr-89 = 88.9176354 u
  • mBa = 143.922955 u
  • m3n = 3.025995 u

• mU-235 = 236.052595 u, mges = 235.8667854 u

  • Δm = 0.1858096 u

• The mass difference must now be converted into kg

  • (1 u ≈ 1.660538782 * 10⁻²⁷ kg)
  • 0.1858096 u * 1.660538782 * 10⁻²⁷ kg
  • = 3.085 * 10⁻²⁸ kg

• Insert into Einstein´s formula, c = 299792458 m/s

  • E = 3.085 * 10⁻²⁸ kg * (299792458 m/s)²
  • E ≈ 2.773 * 10⁻¹¹ J

• The energy of J into eV converted

  • MeV = 1.602176634 * 10 ⁻¹³ J
  • eV = 1.73080516 * 10⁻¹³ eV = 173.08 MeV
  • The energy of 173.08 MeV is released during uranium fission.

Nachweis von Radioaktiver Strahlung - Geiger-Müller-Zählrohr (Detection of Radioactive Radiation - Geiger-Müller Counter)

• Ionizing radiation penetrates through the window, striking an electron from a gas molecule.
• The electron is accelerated towards the wire with so much force that it soon has enough energy to ionize another gas molecule.
• This creates an electron avalanche that can be measured.

Der Begriff "ionisieren" ("To Ionize")

• Ionizing radiation has enough energy to change atoms by removing electrons and creating ions.