SCI 270: On Nuclear Technology Practice Problems
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## 5. Radioactive Decay Energy and Particles

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- + 64Zn0.58 40 _32.3_ h_63.9297_amu
Cu ® b+ + 64Ni0.66 19 _67.9_ h _63.9398_amu
Cu + e- ® 64Ni no data 41 _31.5_ h not a blank
Comment on the two masses of Cu so evaluated:
These masses are within experimental error. There are many sources of errors in these measurements. The decay energis may have errors.

___endo-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
_1.00727661_amu_
or 938.259 MeV
_1.00866520_amu_
or 939.5527 MeV

__2.587 MeV___

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

 Brief comment please: The energy can be supplied in the form of kinetic energy. Protons and antiprotons with total kinetic energy equal or greater than 2.587 MeV (or 1.294 MeV each) will be sufficient theoretically.

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: __decay rate of U-235 = 5629__ Bq __ __decay rate of U-238 = 11450__ Bq __ __Total decay rate = 17079__Bq __