Exercises+with+Fission+and+Nuclear+Reactors

 

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.
 * 1: **


 * Nuclide 1 || Mass Excess (keV) || Nuclide 2 || Mass Excess (keV) ||
 * 235 U || 40915 || 236 U || 42411 ||
 * 238 U || 47306 || 239 U || 50741 ||
 * 239 Pu || 48585 || 240 Pu || 50122 ||


 * 2: **

Find the answers to the following questions:


 * 1) A specific thermal fission of 239 Pu gives 99 Y + 2 neutrons + X. Which nuclei is X?
 * 2) Calculate the Q-value for the above fission from a mass table.
 * 3) Use a mass table to calculate the residual heat, that is the energy developed from disintegration after fission has taken place.
 * 4) A part of this energy is of no importance for the safety of the reactor, explain why.


 * 3: **

 1.0 g 239 Pu is irradiated with a neutron flux of 1.0•10 14  n cm -2 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> s -1 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">. Assume that all the fissions have the same Q-value as the one calculated under 2.b.


 * 1) <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Calculate the developed effect from fission in plutonium during the irradiation.
 * 2) <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">How much 240 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Pu is formed after 100 days of irradiation?


 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">4: **<span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> In a thorium breeder reactor, fissile 233 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">U is formed from fertile 232 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Th.


 * 1) <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Write down the nuclear reaction and how the disintegration occurs.
 * 2) <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">A specific thermal fission of 233 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">U gives 99 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Y + 2 neutrons + X. Which nuclei is X?
 * 3) <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"><span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Assume one ton thorium is irradiated with a neutron flux of 1.0 •10 14 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">n cm -2 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> s -1 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">. How long does it take to generate 100 grams of 233 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">U?
 * 4) <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">What is the disintegration rate of this uranium?

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