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Conceptual questions

Explain why the fission of heavy nuclei releases energy. Similarly, why is it that energy input is required to fission light nuclei?

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Explain, in terms of conservation of momentum and energy, why collisions of neutrons with protons will thermalize neutrons better than collisions with oxygen.

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The ruins of the Chernobyl reactor are enclosed in a huge concrete structure built around it after the accident. Some rain penetrates the building in winter, and radioactivity from the building increases. What does this imply is happening inside?

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Since the uranium or plutonium nucleus fissions into several fission fragments whose mass distribution covers a wide range of pieces, would you expect more residual radioactivity from fission than fusion? Explain.

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The core of a nuclear reactor generates a large amount of thermal energy from the decay of fission products, even when the power-producing fission chain reaction is turned off. Would this residual heat be greatest after the reactor has run for a long time or short time? What if the reactor has been shut down for months?

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How can a nuclear reactor contain many critical masses and not go supercritical? What methods are used to control the fission in the reactor?

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Why can heavy nuclei with odd numbers of neutrons be induced to fission with thermal neutrons, whereas those with even numbers of neutrons require more energy input to induce fission?

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Why is a conventional fission nuclear reactor not able to explode as a bomb?

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Problem exercises

(a) Calculate the energy released in the neutron-induced fission (similar to the spontaneous fission in [link] )

n + 238 U 96 Sr + 140 Xe + 3 n,

given m ( 96 Sr ) = 95.921750 u and m ( 140 Xe ) = 139.92164 . (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) 177.1 MeV

(b) Because the gain of an external neutron yields about 6 MeV, which is the average BE/ A for heavy nuclei.

(c) A = 1 + 238 = 96 + 140 + 1 + 1 + 1, Z = 92 = 38 + 53 , efn = 0 = 0 size 12{A=1+"238"="96"+"140"+1+1+1,`Z="92"="38"+"53",`"efn"=0=0} {}

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

n + 235 U 92 Kr + 142 Ba + 2 n,

given m ( 92 Kr ) = 91 . 926269 u and m ( 142 Ba ) = 141 . 916361 u .

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

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

n + 239 Pu 96 Sr + 140 Ba + 4 n ,

given m ( 96 Sr ) = 95 . 921750 u and m ( 140 Ba ) = 139 . 910581 u size 12{m \( "" lSup { size 8{"140"} } "Ba" \) ="139" "." "910581"`u} {} .

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

(a) 180.6 MeV

(b) A = 1 + 239 = 96 + 140 + 1 + 1 + 1 + 1, Z = 94 = 38 + 56 , efn = 0 = 0 size 12{A=1+"239"="96"+"140"+1+1+1+1,`Z="94"="38"+"56",`"efn"=0=0} {}

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Confirm that each of the reactions listed for plutonium breeding just following [link] conserves the total number of nucleons, the total charge, and electron family number.

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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 [link] . The pertinent masses are m ( 239 U ) = 239.054289 u , m ( 239 Np ) = 239.052932 u , and m ( 239 Pu ) = 239.052157 u .

238 U + n 239 U + γ 4.81 MeV

239 U 239 Np + β + v e 0.753 MeV

239 Np 239 Pu + β + v e size 12{"" lSup { size 8{"239"} } "Np" rightarrow "" lSup { size 8{"239"} } "Pu"+β rSup { size 8{ - {}} } +v rSub { size 8{e} } } {} 0.211 MeV

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The naturally occurring radioactive isotope 232 Th size 12{"" lSup { size 8{"232"} } "Th"} {} does not make good fission fuel, because it has an even number of neutrons; however, it can be bred into a suitable fuel (much as 238 U size 12{"" lSup { size 8{"238"} } U} {} is bred into 239 P size 12{"" lSup { size 8{"239"} } P} {} ).

(a) What are Z size 12{Z} {} and N size 12{N} {} for 232 Th size 12{"" lSup { size 8{"232"} } "Th"} {} ?

(b) Write the reaction equation for neutron captured by 232 Th and identify the nuclide A X produced in n + 232 Th A X + γ .

(c) The product nucleus β size 12{β rSup { size 8{ - {}} } } {} decays, as does its daughter. Write the decay equations for each, and identify the final nucleus.

(d) Confirm that the final nucleus has an odd number of neutrons, making it a better fission fuel.

(e) Look up the half-life of the final nucleus to see if it lives long enough to be a useful fuel.

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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 235 U size 12{"" lSup { size 8{"235"} } U} {} nuclei fission each second, assuming the average fission produces 200 MeV?

(c) What mass of 235 U size 12{"" lSup { size 8{"235"} } U} {} is fissioned in one year of full-power operation?

(a) 2 . 57 × 10 3 MW size 12{2 "." "57" times "10" rSup { size 8{3} } `"MW"} {}

(b) 8.03 × 10 19 fission/s size 12{8 "." "04" times "10" rSup { size 8{"19"} } `"fission/s"} {}

(c) 991 kg

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A large power reactor that has been in operation for some months is turned off, but residual activity in the core still produces 150 MW of power. If the average energy per decay of the fission products is 1.00 MeV, what is the core activity in curies?

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Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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