What is the decay mode of cobalt-60?
beta decay
The cobalt-60 isotope undergoes beta decay with a half-life of 5.272 years. Cobalt-60 decays to Nickel-60 plus an electron and an electron antineutrino. The decay is initially to a nuclear excited state of Nickel-60 from which it emits either one or two gamma ray photons to reach the ground state of the Nickel isotope.
At what rate does the cobalt-60 source decay?
Cobalt-60 decays continuously. The time taken to lose 50% of its initial activity, i.e., its half-life, is 5.26 years. Usually 10% of the cobalt-60 is replenished annually.
What average energy comes from the cobalt-60 machine?
This isotope, usually designat- ed as cobalt 60, disintegrates with a half-life of 5.3 years, emitting radiation which consists of low energy, 0.31 MeV, beta rays, and much higher energy, 1.17 and 1.33 MeV, gamma rays; these latter for many purposes may be consi- dered essentially monoenergetic with an average energy …
How does cobalt-60 machine work?
Cobalt-60 systems, like the Gamma Knife, deliver radiation beams through 192 circular pinholes in a fixed helmet worn by the patient. The pinhole radiation meets at the tumor site, delivering a high dose, while the surrounding healthy tissue and critical brain structures receive minimal radiation.
How do you find the half-life of cobalt-60?
The half life is the time taken for the mass of the substance to decrease by a half. In this case, the amount of substance remaining is 20% of the initial amount (0.1 g out of initial 0.5 g). So it would take 2.32 half lives to decay this much, which is 2.32 x 5.2 which is 12.064 years.
What percent of Co-60 source will remain after 1 year?
1 For cobalt-60, which has a half-life of 5.27 years, 50% remains after 5.27 years (one half-life), 25% remains after 10.54 years (two half-lives), 12.5% remains after 15.81 years (three half-lives), and so on.
What radiation does cobalt-60 emits?
gamma rays
Cobalt-60 emits two high energy gamma rays, making cobalt-60 both an internal and external hazard. The primary exposure pathways of concern are ingestion (drinking water and fish consumption), and exposure by inhalation and external exposure.
What are the properties of cobalt-60?
Cobalt (chemical symbol Co) is a hard, gray-blue metal that is solid under normal conditions. Cobalt is similar to iron and nickel in its properties and can be magnetized like iron.
What is alpha and beta decay?
Alpha decay – A common mode of radioactive decay in which a nucleus emits an alpha particle (a helium-4 nucleus). Beta decay – A common mode of radioactive decay in which a nucleus emits beta particles. The daughter nucleus will have a higher atomic number than the original nucleus.
What is the decay constant for the radioactive disintegration of cobalt-60?
In a given cobalt-60 source, since half of the 6027Co 27 60 Co nuclei decay every 5.27 years, both the amount of material and the intensity of the radiation emitted is cut in half every 5.27 years.
Is cobalt-60 stable or unstable?
Cobalt-60 is the longest-lived radioactive isotope of cobalt, with a half-life of 5.27 years. It is produced by irradiating the stable isotope cobalt-59 with neutrons in a nuclear reactor.
What are Cobalts chemical properties?
Properties Of Cobalt
- It is a hard ferromagnetic, silver-white, lustrous, brittle element.
- It is stable in air and does not react with water.
- Like other metals, it can also be magnetized.
- With dilute acids, it reacts slowly.
- The metal melts at 1495 °C and boils at 2927 °C.
What is the half life of a Cobalt 60 decay?
Cobalt-60 decays, with a half-life of 5.3 years, to the element nickel-60 by the emission of a 0.32 MeV beta particle. The nickel-60 daughter nuclide is formed at an excited energy state, and loses this energy immediately with the emission of two gamma rays of energies 1.17 and 1.33 MeV, settling at a stable nuclear state.
What happens to Cobalt 60 in brachytherapy?
The particle emitted is absorbed by the cobalt metal and the sources encapsulation such that it doesn’t contribute meaningfully to the dose distribution. Cobalt 60 has been largely replaced by other Iridium-192 in high dose rate brachytherapy and by linear accelerators in external beam radiation therapy.
What is the composition of a Cobalt 60 alloy?
Cobalt-60 is produced by neutron bombardment of stable cobalt in a nuclear reactor. Small nickel-plated slugs of the radioactive metal are loaded into a sealed alloy cylinder typically 10 × 450 mm and doubly encapsulated in a corrosion-resistant steel pencil. An array of such pencils is built into a rack typically 1–2 m 2.