Radioactivity Presentation

Radioacti vity Radioactive decay transforms a nucleus by emitting different particles. •ALPHA DECAY •BETA DECAY •GAMMA DECAY

Alpha In ALPHA decay, the nucleus Decay releases a HELIUM nucleus-an alpha particle.

Beta In BETA decay, the nucleus Decay either emits an electron and

antineutrino (or a positron and neutrino) or Captures an atomic electron and emits a neutrino.

(Note: Both alpha and beta decays change the original nucleus into the nucleus of different chemical element.)

Gamma In GAMMA decay, the nucleus lowers Decay its internal energy by emitting a photon- a gamma ray. This decay does not modify the chemical properties of the atom.

Comparison of ALPHA BETA & GAMMA

Nuclear Chain Reaction

The principle of chain reaction is very easy therefore: a U235 nucleus is hit by a neutron, upon which fission occurs at a high probability. The neutrons produced in this process can cause more fission; moreover, the already mentioned 200 MeV energy is released each

The neutronic state can be characterized by the so called multiplication factor (k). This is the ratio of the number of neutrons in a neutron "generation" and the number of neutrons in the preceding generation.

Nuclear Fuel Cycle

APPLICATIO NS Radioactive Dating Space Exploration Nuclear Reactors Smoke Detectors Nuclear Medicines Magnetic Resonance Imaging

Radioactive Naturally occurring radioactive isotopes Dating such as C are used to date objects that 14

6

were living once, such as wood. For example, from the study of artifacts found at the site, scientist determined that Stonehenge was built nearly 4000 years

Space Sojourner used Alpha particles to Exploration identify chemical elements present in Martian rocks. On earth nuclear reactions are used in many areas from criminal investigations to art authentication.

Nuclear NuclearReactors reactors use the fission of U or Pu nuclei to produce 235

239

electrical power. Reactors and most other nuclear applications generate radioactive waste; disposal of this waste is a subject current research.

Smoke Many Detectors smoke detectors use a small mount of the alpha emitter Am 241

to ionize the air. Smoke entering the detector reduces the current and sets off the alarm.

Nuclear Radioactive isotopes such as Co Medicine and I are commonly use in the

60

131

diagnosis and treatment of diseases. Positron emitters such as F18 are used in positron emission terminology (PET) to generate images of brain activity.

Magnetic Resonance Imaging MRI makes use of atomic transitions involving the magnetic field of a nucleus to study the local chemical environment. This technique accurately maps the density of hydrogen to produce three dimensional images of the human body.