T9 Neutrons Assignment
- Country :
Australia
Q.1 Consider thermal neutron capture by 109Cd
- Write the reaction equation.
- Calculate the Q-value for this reaction.
- Is the activation product stable or radioactive? (consult an appropriate reference)
- If radioactive, what is its decay mode? And what does it decay to?
If stable, is its binding energy per nucleon (B/A) greater or less than that of the initial isotope?
Q.2 Consider the following n-gamma reaction:
1H(n,y)2H
where an incident neutron is captured by the target proton, forming a 2H nucleus (i.e. a deuteron).
Q. When the incident neutron is captured by the struck proton, why is a gamma ray emitted?
Hint: compare the mass defects of the initial and final nuclei
(this is fundamentally the calculation of the Q value!)
Q.3 Calculate the Q-value for the spontaneous decay of a free proton into a neutron and a positron. Comment.
Q.4 Consider the process of neutron activation of a metallic sample that was previously not radioactive.
- What is the role of the moderator in a neutron activation experiment?
- Define the term cross section as it relates to nuclear reactions. What 4 parameters does cross section depend upon?
- The reaction rate R is relevant to the production of new isotopes by neutron capture. For this problem we will irradiate a thin circular foil (5.00 cm diameter and 1.25 mm thick) made from 1007Au. The density of Gold is 19.32 g/cm3 and the molar mass of Gold is 196.96655 g/mol. The cross section for the reaction 197Au(n,?) 198Au by thermal neutrons is 98.70 barns.
Determine the reaction rate if the neutron flux from an AmBe neutron source = 3.5 x 109 neutrons cm-2 s-1, and the neutrons are being thermalised by a moderator surrounding the source and foil. [3+4+3 = 10 marks]