SCI 270: On Nuclear Technology Practice Problems  

5. Radioactive Decay Energy

  1. The rest masses of 64Ni28, and 64Zn30 are 63.9280 and 63.9291 amu respectively. It is well known that 64Cu29 under goes electron emission, positron emission, and electron capture of the beta decay process. The overall half life of 64Cu29 is 12.9 h. From the energies of decay Edecay given below, evaluate the mass of 64Cu29, and complete the blanks below. (See the Lecture Notes on Radioactive Decays - transmutations of nuclides)

    Note the relationship between the overall decay constant and the partial decay constant:

    Overall l = S lpartial       or       lpartial = fraction * loverall

    Decay
    reaction
    Decay
    energy
    MeV
    Percentage Partial
    half-life
    Mass of 64Cu29
    Cu ® b- + ____0.58 40 _____ h ______
    Cu ® b+ + ____0.66 19 _____ h ______
    Cu + e- ® ____ no data 41 _____ h not a blank
    Comment on the two masses of Cu so evaluated:

    __________________________________________________________

    __________________________________________________________



    _____-thermic___

  2. Is the process of converting a pair of proton and antiproton into neutron and antineutron exothermic or endothermic?

    How much energy is required or released in this conversion?

    Mass of protonMass of neutronAmount of energy

    ________________

    ________________

    ________________

    How can the energy be supplied or removed in this process?

    Brief comment please:

    ______________________________________________________________

  3. A freshly purified uranium sample containing 0.071 g of 235U and 0.929 g of 238U. Their half-lives are 7.1e8 y and 4.51e9 y respectively for 235U and 238U. respectively

    What is the total decay rate in Bq immediately after they were purified? Ignore the radioactive decay products of the two nuclides.
    The decay rate is:

    _____________________________________________________ Bq __

Answers to Assignment 5 is available, but do your part first. Your skills make you happy.

e-mail address: cchieh@uwaterloo.ca