Topic 9: Radionuclide production Flashcards
Specific activity
Ratio of radionuclide activity to the total mass of the element present (MBq/g)| (Non-radioactive element is known as the ‘carrier’ – High specific activity is sometimes called ‘carrier-free’ or ‘without carrier’)
Nuclear medicine requires a (low/high) specific activity?
high
Label the parts
Top: Control rods
Outer: concrete shield
Nuclear Fuel
Graphite core
Reactor vessel
What does the graphite core do in the nuclear reactor
Graphite core (moderator) slows down fission neutrons because slower neutrons are more efficient at creating further fission events
What do the control rods do?
Create a controlled chain reaction: controlling the fission rate. They absorb many neutrons withouth themselves fissioning.
- ideally each fission event creates one further event
- not enough creates a runaway reaction / meltdown
- more rods would slow down or shut off the reactor.
What does the coolant do in the nuclear reactor?
Regulates the vast thermal energy that is emitted as a by product of the fission reactions.
Nuclear Fission?
A nucleus of an atom splits into smaller, lighter nuclei producing free neutrons and gamma photons and a large amount of energy.
How do you produce radionuclides using bombardment
Nuclear bombardment reactions are nuclear reaction in which a nucleus is bombarded or struck by another nucleus or nuclear particle. Here fission or fusion may occur.
What are two common modes of radionuclide product by bombardment
?
if we want the same element - Electron capture - neutron with a gamma ray coming out
Different element we can bombard with neutrons and protons coming
What are the produced radionuclides from bombardment like?
low specific activity because mixture of radioactive and stable material
Neutron rich
Often decay by beta
Generally have long half-lives
Cyclotron?
proton attracted by the dees which flip polarity constantly, gaining energy and making a circular direction of travel, and it will get a larger and larger radius, and you will use an extraction foil and fire it at a target.
two types of cyclotrons
positive ion
Inefficient
upto 30% of beam lost
Negative ion.
foil strips of electrons creating positive ion
magnetic beam on +ve ion directs beam to target
almost 100% efficient. non-activating (cold)
Cyclotron production evaluation?
produces neutron deficient isotropes
- decay by beta+ or e.c
most have different z number.
high specific activity
produces biologically important isotopes such as c-11, n-13, o-15.
Describe the process of the Mo99/Tc99m generator
We like technetium why?
Because it emits gamma rays only because it is at this metastable state after previous beta or alpha emission.
Mo99 -> Tc99m - > Tc99
Explain the emissions of all these types of producing methods of radionuclides
1) Naturally occuring
2) Fission
3) Neutron bombardment
4) Cyclotron
5) Generator
1) Naturally occuring
2) Fission
3) Neutron bombardment
4) Cyclotron
5) Generator
How much is the decay of the daughter? and what are the assumptions?
the daughter has a much shorter half life
all daughter and no parent is eluted from the generator
describe the graph
the amount of technetium is eluted and builds up again but you cant have more activity of the daughter than the parents
if we elute too early we will not recover the full activity available to us
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