SCI 270: On Nuclear Technology Practice Problems  

9. Nuclear Fission Energy and Reactions

  1. Give the nuclear reactions for the syntheses of neptunium and plutonium used in the fast breeder reactor for their productions.

    Nuclear reaction:
    Half lives:
    239Np ______________ 239Pu ______________


  2. Consult a handbook or a nuclear data source and give the range of known (or synthesized) plutonium isotopes. Which one has the longest half life and what is its decay mode?

    Range of mass numbers
    of Pu isotopes: From ________ to _________
    Isotope with the
    longest half life ____________
    (modes): _____________________________



  3. Assume the thermal-neutron induced fission of 235U (mass = 235.0439) gives two fragments of mass 140 and 93, and the some neutrons. After having consulted the properties of nuclides of mass numbers 140 and 93, we know that 140Ce (mass = 139.90539) and 93Nb (mass = 92.90638) are stable nuclides. Write the nuclear reaction equation for this fission process. Estimate the total energy (including energies of beta-decay of the fission products) in this fission process.

    released: _ Q = ___________ MeV/fission
    released: _ Q = ___________ J/mole


  4. How much natural uranium must be processed in order to produce 1.0 kg of 235U, if only 50% of this isotope is extracted from natural uranium? What methods are used to separate 235U from natural uranium?

    of 235U ___________ %;   238U ________________ %
    Amount of natural
    uranium required: _________________ kg
    Methods used for extracting 235U:

    1. Gas diffusion of UF6 based on mass difference. _

    2. ________________________________________________

    3. ________________________________________________

    4. ________________________________________________

The following question are provided to help your study

  1. What is a moderator? What are the desirable properties of a compound to make it a good moderator? Why are heavy water and graphite used as moderator for nuclear reactors using natural uranium as fuel, but normal distilled water not a suitable moderator?



  2. Assume the abundance of 235U to be 5.0% when the earth was created. Calculate the age of the earth from the distribution of 235U and 238U (now 0.72 % and 99.28 %). Note that the assumption may not be valid.

    This problem may be a challenge to some of you, but hint will be given on the page linked below.

Answers to Practice Problems 9 are available, but do your part first. Your skills are tested and they are yours forever.