32.6 Fission

Which of the following statements about nuclear fission is true?

1. No new elements can be produced in a fission reaction.
2. Energy released in fission reactions is generally less than that from fusion reactions.
3. In a fission reaction, two light nuclei are combined into a heavier one.
4. Fission reactions can be explained on the basis of the conservation of mass-energy.

In a neutron-induced fission reaction of ²³⁹Pu, which of the following is produced along with ⁹⁶Sr and four neutrons?

1. $_{\textrm{ } \textrm{ } \textrm{ } 56}^{139} \text{Ba}$
2. $_{\textrm{ } \textrm{ } \textrm{ } 56}^{140} \text{Ba}$
3. $_{\textrm{ } \textrm{ } \textrm{ } 54}^{139} \text{Xe}$
4. $_{\textrm{ } \textrm{ } \textrm{ } 54}^{140} \text{Xe}$

(a) Calculate the energy released in the neutron-induced fission (similar to the spontaneous fission in the example)

given $m \left(^{\text{96}} \text{Sr}\right) = \text{95}.\text{921750}\textrm{ }\text{u}$ and $m \left(^{\text{140}} \text{Xe}\right) = \text{139}.\text{92164}$. (b) This result is about 6 MeV greater than the result for spontaneous fission. Why? (c) Confirm that the total number of nucleons and total charge are conserved in this reaction.

(a) Calculate the energy released in the neutron-induced fission reaction

given $m \left(\right. ^{\text{96}} \text{Sr} \left.\right) = \text{95} . \text{921750 u}$ and $m \left(\right. ^{\text{140}} \text{Ba} \left.\right) = \text{139} . \text{910581 u}$.

(b) Confirm that the total number of nucleons and total charge are conserved in this reaction.

Breeding plutonium produces energy even before any plutonium is fissioned. (The primary purpose of the four nuclear reactors at Chernobyl was breeding plutonium for weapons. Electrical power was a by-product used by the civilian population.) Calculate the energy produced in each of the reactions listed for plutonium breeding just following the example. The pertinent masses are $m \left(^{\text{239}} \text{U}\right) = \text{239}.\text{054289 u}$, $m \left(^{\text{239}} \text{Np}\right) = \text{239}.\text{052932 u}$, and $m \left(^{\text{239}} \text{Pu}\right) = \text{239}.\text{052157 u}$.

The electrical power output of a large nuclear reactor facility is 900 MW. It has a 35.0% efficiency in converting nuclear power to electrical.

(a) What is the thermal nuclear power output in megawatts?

(b) How many $^{\text{235}} \text{U}$ nuclei fission each second, assuming the average fission produces 200 MeV?

(c) What mass of $^{\text{235}} \text{U}$ is fissioned in one year of full-power operation?