Lecture 3 Flashcards
What are the 4 decay series
- Thorium 4n
- Neptunium 4n+1
- Uranium 4n+2
- Actinium 4n+3
Why are certain elements the names of the decay series
- Occur naturally
- Parent members of their respective series
- have longest half life periods
How does the nuclear decay series work
- Decay by a series of alpha and beta emissions
- produce radioactive which are successively more stable until finally a stable isotope is reached
What does the Thorium series end in
- 208,82Pb
What does the Neptunium series end in
- 209,93Bi
What does the Uranium series end in
- 206,82Pb
What does the Actinium series end in
- 207,82Pb
What must all members of a decay series differ by
- A multiple of 4
What happens in radioactive equilibrium
- THe ratio of nucleo occuring is equal to the ratio of their half lives
What does the thorium series start with
- 232,90Th
What does the Neptunium series start with
- 241,94 Pu
What does the Uranium series start with
- 238,92U
What does the Actinium series start with
- 239,92U
What is half life period
- The time taken for half the radioactive nuclei in a sample to decay
What type of reaction is radioactive decay in terms of kinetics
- First order
- Doesn’t depend on size of sample
What is the differential equation for rate of decay
- A=dN(t)/dt=gammaN(t)
- A = activity- number of disintegrations per unit time of the radioactive sample
- N= number of nuclei
- Gamma= decay constant- units of time^-1
What is the integral equation for rate decay
- N(t) = N0e^-gamma.t
- A(t)= A0e^-gamma.t
- Anything proportional to N can be substituted in
- N0 is number of nuclei at time 0
- N is number remaining at time t
What does half life allow
- Each radioactive nuclide has a characteristic, constant half life (t1/2), the time required for half of the atoms in a sample to decay
- An isotopes half life allows us to determine how long a sample of a useful isotope will be available
- And how long a sample of an undesirable or dangerous isotope must be stored before it decays to a low enough radiation level that is no longer a problem
What is equation for half life
- t1/2= ln(2)/ gamma
- p29 has all equations to remember
What are the units for measuring radioactivity
- Becquerel- Bq- SI unit of activity corresponding to one disintegration per second
- Curie- activity of 1g of pure 226Ra, equivalent to 3.7*10^10Bq
