Recording-2025-03-05T09_34_19.512Z

Isotopes and Decay

• Definition of Isotopes

  • Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons.

  • The total of protons and neutrons is called the atomic mass; thus, isotopes differ in atomic mass.

• Stability of Isotopes

  • Elements can be classified as stable or unstable based on their isotopes.

  • Stable Isotopes: Do not undergo radioactive decay.

  • Unstable Isotopes: Can decay into other elements or isotopes, often through various pathways.

• Decay Pathways

  • Large isotopes generally emit alpha particles (2 protons and 2 neutrons) as a means of decay due to instability caused by excess particles.

  • Smaller isotopes may need to adjust their proton-neutron ratio, indicating their proximity to the "zone of stability."

  • Above the zone: These isotopes typically need to reduce neutrons, which can occur through neutron emission or conversion of neutrons into protons.

  • Below the zone: They may have too few neutrons, resulting in decay processes such as electron capture or proton-to-neutron conversion.

Radioactive Decay and Half-Life

• Half-Life

  • The time required for half of a given quantity to decay into another isotope is termed its half-life.

  • The half-life is indicative of the decay rate but is unpredictable until measured.

  • Understanding kinetics in chemical reactions is crucial; while rates can be measured, predictions can be challenging.

Public Perception of Nuclear Science

• Negative Perception

  • Public concerns often center around nuclear weapons, high-profile nuclear accidents, and their devastating consequences.

  • Major incidents include Chernobyl, Fukushima, and Three Mile Island.

  • Chernobyl is often viewed as a catastrophic failure due to poor safety practices during experiments which led to a severe meltdown.

  • Conversely, the Fukushima event, while tragic, resulted in more casualties from the subsequent tsunami than from the radiation itself.

• Concerns Regarding Radiation

  • Common worries include radiation sickness and the storage of nuclear waste.

  • Despite public fear, the benefits of radiation in treatments are substantial. It plays a critical role in medical interventions and diagnostics.

Medical Applications and Effects of Radiation

• Therapeutic Uses

  • A significant portion of the population has undergone diagnostic or therapeutic procedures using isotopes.

  • Technetium-99m is a widely utilized isotope in medical imaging.

  • Radiation can be beneficial, especially in oncology for targeting rapidly dividing cancer cells.

• Ionization Effects

  • Radiation can ionize atoms, primarily water, within biological tissues, creating free radicals.

  • Free Radicals: Positively charged particles that can damage DNA and cellular structures, leading to mutations or cancers.

  • Ionizing radiation can disrupt critical biological functions and cellular processes, intensifying the need for caution in exposure.

Types of Radiation and Their Penetration Depths

• Alpha Particles

  • Relatively large and positively charged, alpha particles have minimal penetration, only traveling about 0.5 mm in skin.

  • External exposure poses low risk, but internal exposure can be harmful due to direct contact with biological tissues.

• Beta Particles

  • Smaller and negatively charged, beta particles can penetrate tissues up to 4 mm.

  • Their ability to penetrate means internal exposure could be problematic.

• Gamma Rays

  • No mass and high energy; gamma radiation can penetrate deeply, up to 50 cm in tissue and 400 m in air.

  • Generally, external gamma exposure is less concerning as they pass through the body without interaction.

Radiation Safety and Risk Assessment

• Acute Radiation Exposure

  • High doses of radiation received over a short period can cause immediate health effects, including acute cell damage or death.

  • Cancer treatments aim to deliver targeted doses to cancer cells while minimizing damage to healthy tissues.

• Chronic Radiation Exposure

  • Long-term exposure results in a cumulative effect leading to an increased risk of developing cancers over time.

  • Radiation dosage is measured in Sieverts, which accounts for biological effects and exposure type.

• Typical Background Radiation

  • An average person is exposed to approximately 3 millisieverts per year from natural sources, including cosmic rays and food (notably bananas).

Medical Isotopes and Imaging Techniques

• Sources of Medical Isotopes

  • Australia’s isotopes largely stem from the Australian Light Water Reactor and local medical cyclotrons.

  • The production aligns with the need for short-lived isotopes for effective medical imaging and treatment.

• Imaging Technologies

  • Computer Assisted Tomography (CAT) and other imaging methods employ gamma rays from isotopes such as Technetium-99m.

  • Positron Emission Tomography (PET) utilizes positron emitters to create diagnostic images by detecting gamma particle emissions.

• Example Case

  • Radiolabeled compounds, such as fluoro-deoxy-glucose (FDG), target areas of increased metabolic activity, such as cancers, enabling precise diagnosis and treatment planning.