CINCH NucWik

1. The mass number of a given nucleus increases by one unit when a neutron is captured. Table 6.1 gives information about mass excess for three important isotope pairs. Calculate the difference in average binding energy between the pairs of nuclide and discuss why the ²³⁸U/²³⁹U pair differs so greatly from the other two pairs in regards to utilization of nuclear energy.
2. Find the answers to the following questions:
   • specific thermal fission of ²³⁹Pu gives ⁹⁹Y + 2 neutrons + X. Which nuclei is X?
   • Calculate the Q-value for the above fission from a mass table.
   • Use a mass table to calculate the residual heat, that is the energy developed from disintegration after fission has taken place.
   • A part of this energy is of no importance for the safety of the reactor. Explain why.
3. ²³⁹Pu is irradiated with a neutron flux of 1.0 * 10¹⁴ n cm^-2s^-1. Assume that all the fissions have the same Q-value as the one calculated under 2.b.
   • Calculate the developed effect from fission in plutonium during the irradiation.
   • How much ²⁴⁰Pu is formed after 100 days of irradiation?
4. In a thorium breeder reactor, fissile ²³³U is formed from fertile ²³²Th.
   • Write down the nuclear reaction and how the disintegration occurs.
   • A specific thermal fission of ²³³U gives ⁹⁹Y + 2 neutrons + X. Which nucleus is X?
   • Assume one ton of thorium is irradiated with a neutron flux of 1.0 * 10¹⁴ n cm^-2 s^-1.
     How long does it take to generate 100 grams of ²³³U?
   • What is the disintegration rate of this uranium?

Table 6.1