32.1 Diagnostics and Medical Imaging

A neutron generator uses an $\alpha$ source, such as radium, to bombard beryllium, inducing the reaction $^{4} \text{He} + ^{9} \text{Be} \rightarrow ^{\text{12}} \text{C} + n$. Such neutron sources are called RaBe sources, or PuBe sources if they use plutonium to get the $\alpha$ s. Calculate the energy output of the reaction in MeV.

The purpose of producing $^{\text{99}} \text{Mo}$ (usually by neutron activation of natural molybdenum, as in the preceding problem) is to produce $^{\text{99m}} \text{Tc}.$ Using the rules, verify that the $\beta^{- }$ decay of $^{\text{99}} \text{Mo}$ produces $^{\text{99m}} \text{Tc}$. (Most $^{\text{99m}} \text{Tc}$ nuclei produced in this decay are left in a metastable excited state denoted $^{\text{99m}} \text{Tc}$.)

the table indicates that 7.50 mCi of $^{\text{99m}} \text{Tc}$ is used in a brain scan. What is the mass of technetium?

(a) Neutron activation of sodium, which is 100%$^{\text{23}} \text{Na}$, produces $^{\text{24}} \text{Na}$, which is used in some heart scans, as seen in the table. The equation for the reaction is $^{\text{23}} \text{Na} + n \rightarrow ^{\text{24}} \text{Na} + \gamma$. Find its energy output, given the mass of $^{\text{24}} \text{Na}$ is 23.990962 u.

(b) What mass of $^{\text{24}} \text{Na}$ produces the needed 5.0-mCi activity, given its half-life is 15.0 h?