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A few small countries have built or are capable of building nuclear bombs, as are some terrorist groups. Two things are needed—a minimum level of technical expertise and sufficient fissionable material. The first is easy. Fissionable material is controlled but is also available. There are international agreements and organizations that attempt to control nuclear proliferation, but it is increasingly difficult given the availability of fissionable material and the small amount needed for a crude bomb. The production of fissionable fuel itself is technologically difficult. However, the presence of large amounts of such material worldwide, though in the hands of a few, makes control and accountability crucial.

Section summary

  • There are two types of nuclear weapons—fission bombs use fission alone, whereas thermonuclear bombs use fission to ignite fusion.
  • Both types of weapons produce huge numbers of nuclear reactions in a very short time.
  • Energy yields are measured in kilotons or megatons of equivalent conventional explosives and range from 0.1 kT to more than 20 MT.
  • Nuclear bombs are characterized by far more thermal output and nuclear radiation output than conventional explosives.

Conceptual questions

What are some of the reasons that plutonium rather than uranium is used in all fission bombs and as the trigger in all fusion bombs?

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Use the laws of conservation of momentum and energy to explain how a shape charge can direct most of the energy released in an explosion in a specific direction. (Note that this is similar to the situation in guns and cannons—most of the energy goes into the bullet.)

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How does the lithium deuteride in the thermonuclear bomb shown in [link] supply tritium ( 3 H ) as well as deuterium ( 2 H ) size 12{ {} rSup { size 8{2} } H} {} ?

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Fallout from nuclear weapons tests in the atmosphere is mainly 90 Sr and 137 Cs , which have 28.6- and 32.2-y half-lives, respectively. Atmospheric tests were terminated in most countries in 1963, although China only did so in 1980. It has been found that environmental activities of these two isotopes are decreasing faster than their half-lives. Why might this be?

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Problems&Exercises

Find the mass converted into energy by a 12.0-kT bomb.

0.56 g

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What mass is converted into energy by a 1.00-MT bomb?

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Fusion bombs use neutrons from their fission trigger to create tritium fuel in the reaction n + 6 Li 3 H + 4 He size 12{n+ rSup { size 8{6} } "Li" rightarrow rSup { size 8{3} } H+ rSup { size 8{4} } "He"} {} . What is the energy released by this reaction in MeV?

4.781 MeV

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It is estimated that the total explosive yield of all the nuclear bombs in existence currently is about 4,000 MT.

(a) Convert this amount of energy to kilowatt-hours, noting that 1 kW h = 3 . 60 × 10 6 J size 12{1`"kW" cdot h=3 "." "60" times "10" rSup { size 8{6} } `J} {} .

(b) What would the monetary value of this energy be if it could be converted to electricity costing 10 cents per kW·h?

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A radiation-enhanced nuclear weapon (or neutron bomb) can have a smaller total yield and still produce more prompt radiation than a conventional nuclear bomb. This allows the use of neutron bombs to kill nearby advancing enemy forces with radiation without blowing up your own forces with the blast. For a 0.500-kT radiation-enhanced weapon and a 1.00-kT conventional nuclear bomb: (a) Compare the blast yields. (b) Compare the prompt radiation yields.

(a) Blast yields 2.1 × 10 12 J size 12{2 "." "10" times "10" rSup { size 8{"12"} } `J} {} to 8.4 × 10 11 J size 12{8 "." 4 times "10" rSup { size 8{"11"} } `J} {} , or 2.5 to 1, conventional to radiation enhanced.

(b) Prompt radiation yields 6 . 3 × 10 11 J size 12{6 "." 3 times "10" rSup { size 8{"11"} } `J} {} to 2.1 × 10 11 J size 12{2 "." "10" times "10" rSup { size 8{"11"} } `J} {} , or 3 to 1, radiation enhanced to conventional.

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(a) How many 239 Pu size 12{ {} rSup { size 8{"239"} } "Pu"} {} nuclei must fission to produce a 20.0-kT yield, assuming 200 MeV per fission? (b) What is the mass of this much 239 Pu size 12{ {} rSup { size 8{"239"} } "Pu"} {} ?

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Assume one-fourth of the yield of a typical 320-kT strategic bomb comes from fission reactions averaging 200 MeV and the remainder from fusion reactions averaging 20 MeV.

(a) Calculate the number of fissions and the approximate mass of uranium and plutonium fissioned, taking the average atomic mass to be 238.

(b) Find the number of fusions and calculate the approximate mass of fusion fuel, assuming an average total atomic mass of the two nuclei in each reaction to be 5.

(c) Considering the masses found, does it seem reasonable that some missiles could carry 10 warheads? Discuss, noting that the nuclear fuel is only a part of the mass of a warhead.

(a) 1 . 1 × 10 25 fissions , 4.4 kg

(b) 3.2 × 10 26 fusions size 12{3 "." 2 times "10" rSup { size 8{"26"} } `"fusions"} {} , 2.7 kg

(c) The nuclearfuel totalsonly 6kg, soit isquite reasonablethat somemissiles carry10 overheads.The massof thefuel wouldonly be60 kgand thereforethe massof the10 warheads,weighing about10 timesthe nuclearfuel, wouldbe only1500 lbs.If thefuel forthe missilesweighs 5times thetotal weightof thewarheads, themissile wouldweigh about9000 lbsor 4.5tons. Thisis notan unreasonableweight fora missile.

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This problem gives some idea of the magnitude of the energy yield of a small tactical bomb. Assume that half the energy of a 1.00-kT nuclear depth charge set off under an aircraft carrier goes into lifting it out of the water—that is, into gravitational potential energy. How high is the carrier lifted if its mass is 90,000 tons?

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It is estimated that weapons tests in the atmosphere have deposited approximately 9 MCi of 90 Sr size 12{ {} rSup { size 8{"90"} } "Sr"} {} on the surface of the earth. Find the mass of this amount of 90 Sr size 12{ {} rSup { size 8{"90"} } "Sr"} {} .

7 × 10 4 g size 12{7 times "10" rSup { size 8{4} } `g} {}

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A 1.00-MT bomb exploded a few kilometers above the ground deposits 25.0% of its energy into radiant heat.

(a) Find the calories per cm 2 size 12{"cm" rSup { size 8{2} } } {} at a distance of 10.0 km by assuming a uniform distribution over a spherical surface of that radius.

(b) If this heat falls on a person’s body, what temperature increase does it cause in the affected tissue, assuming it is absorbed in a layer 1.00-cm deep?

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Integrated Concepts

One scheme to put nuclear weapons to nonmilitary use is to explode them underground in a geologically stable region and extract the geothermal energy for electricity production. There was a total yield of about 4,000 MT in the combined arsenals in 2006. If 1.00 MT per day could be converted to electricity with an efficiency of 10.0%:

(a) What would the average electrical power output be?

(b) How many years would the arsenal last at this rate?

(a) 4 . 86 × 10 9 W size 12{4 "." "86" times "10" rSup { size 8{9} } `W} {}

(b) 11.0 y

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Questions & Answers

What is conductivity
Saud Reply
It is the ease with which electrical charges or heat can be transmitted through a material or a solution.
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how to find magnitude and direction
Arjune Reply
how to caclculate for speed
Arjune
derivation of ohms law
Kazeem Reply
derivation of resistance
Kazeem
R=v/I where R=resistor, v=voltage, I=current
Kazeem
magnitude
Arjune
A puck is moving on an air hockey table. Relative to an x, y coordinate system at time t 0 s, the x components of the puck’s ini￾tial velocity and acceleration are v0x 1.0 m/s and ax 2.0 m/s2 . The y components of the puck’s initial velocity and acceleration are v0y 2.0 m/s and ay 2.0
Arjune
Electric current is the flow of electrons
Kelly Reply
is there really flow of electrons exist?
babar
Yes It exists
Cffrrcvccgg
explain plz how electrons flow
babar
if electron flows from where first come and end the first one
babar
an electron will flow accross a conductor because or when it posseses kinectic energy
Cffrrcvccgg
electron can not flow jist trasmit electrical energy
ghulam
free electrons of conductor
ankita
electric means the flow heat current.
Serah Reply
electric means the flow of heat current in a circuit.
Serah
What is electric
Manasseh Reply
electric means?
ghulam
electric means the flow of heat current in a circuit.
Serah
a boy cycles continuously through a distance of 1.0km in 5minutes. calculate his average speed in ms-1(meter per second). how do I solve this
Jenny Reply
speed = distance/time be sure to convert the km to m and minutes to seconds check my utube video "mathwithmrv speed"
PhysicswithMrV
d=1.0km÷1000=0.001 t=5×60=300s s=d\t s=0.001/300=0.0000033m\s
Serah
A puck is moving on an air hockey table. Relative to an x, y coordinate system at time t 0 s, the x components of the puck’s ini￾tial velocity and acceleration are v0x 1.0 m/s and ax 2.0 m/s2 . The y components of the puck’s initial velocity and acceleration are v0y 2.0 m/s and ay 2.0
Arjune
why we cannot use DC instead of AC in a transformer
kusshaf Reply
becuse the d .c cannot travel for long distance trnsmission
ghulam
what is physics
Chiwetalu Reply
branch of science which deals with matter energy and their relationship between them
ghulam
Life science
the
what is heat and temperature
Kazeem Reply
how does sound affect temperature
Clement Reply
sound is directly proportional to the temperature.
juny
how to solve wave question
Wisdom Reply
I would like to know how I am not at all smart when it comes to math. please explain so I can understand. sincerly
Emma
Just know d relationship btw 1)wave length 2)frequency and velocity
Talhatu
First of all, you are smart and you will get it👍🏽... v = f × wavelength see my youtube channel: "mathwithmrv" if you want to know how to rearrange equations using the balance method
PhysicswithMrV
nice self promotion though xD
Beatrax
thanks dear
Chuks
hi pls help me with this question A ball is projected vertically upwards from the top of a tower 60m high with a velocity of 30ms1.what is the maximum height above the ground level?how long does it take to reach the ground level?
mahmoud
what is scalar quantities
babatunde
scaler quantity are quanties that have only direction and no magnitude
Natsu
ice Point
babatunde
please guys help, what is the difference between concave lens and convex lens
Vincent Reply
convex lens brings rays of light to a focus while concave diverges rays of light
Christian
for mmHg to kPa yes
Matthew
it depends on the size
Matthew Reply
please what is concave lens
Vincent
a lens which diverge the ray of light
rinzuala
concave diverges light
Matthew
thank you guys
Vincent
A diverging lens
Yusuf
What is isotope
Yusuf
each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element. "some elements have only one stable isotope
Karthi
what is wire wound resistors?
Naveedkhan Reply

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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