Radioactive Disintegration (Introduction to Radiochemistry)
Radioactive disintegration is a stochastic proces, which means a random process, that can be described statistically. In this task you will learn about the secular radioactive equilibrium, and how any measure of a radioactive source is stated with uncertainty.
In a sample with N radioactive atoms of a particular nuclide, the number of atoms that disintegrates with the time dt will be proportional with N, see the formula below.
where λ is the disintegration constant and A is the rate of disintegration.
The above equation can be solved into the following:
Nt = N0e - λt (eqn 2)
N0 is the number of atoms of the nuclide at hand present at t = 0. The time past when half of the nuclides has disintegrated is called the half-life.
N = N0/2 can be placed into equation 1 to give the following connection between the disintegration constant and the half-life:
The half-life is a characteristic value for each radioactive nuclide. A radioactive nuclide will often disintegrate into a product that is radioactive as well: Nucleus 1
Assume that at the time t = 0, N0 of the mother is N1(t =0), N2(t=0) and N3(t=0), the change in number of mother- and daughter nuclides can then respectively be described through the following equations:
dN1 = -λN1dt (eqn 4)
dN2 = λ1N1dt - λ2N2dt (eqn 5)
If the half-life of the mother is much less than that of the daughter, equation 6 can be simplified into:
whereis the saturation factor and .
The above equation can be further reduced by the assuption that t >> T1/2(2) (the observed time is much larger than the daughters half-life).
- (eqn 9)
When λ2N2 = λ1N1.equation 9 is called a secular radioactive equilibrium and can be written as