Deck 45: Applications of Nuclear Physics

Question 1

A beam of 1-MeV gamma rays incident on a piece of 0.50-cm thick lead is reduced by 50% of its initial value.How thick must the lead be to reduce the beam to one percent of its initial value?

A)1.1 cm
B)2.2 cm
C)3.3 cm
D)4.4 cm
E)8.4 cm

Answer 1

3.3 cm

Question 2

One rad is

A)the amount of radiation that deposits 10−² J of energy into 1 kg of absorbing material.
B)the amount of ionizing radiation that will produce 1/3 × 10−⁹ C of electric charge in 1 cm³ of air under standard conditions.
C)the amount of radiation needed for ionization of an atom.
D)the amount of radiation needed for dissociation of a molecule.
E)the amount of radiation that deposits one erg of energy in 1g of material.

Answer 2

the amount of radiation that deposits 10−² J of energy into 1 kg of absorbing material.

Question 3

Find the number of nuclei per unit volume (n = nuclei/cm³)for lead.
Atomic weight = 202.7
Density = 11.5 g/cm³
Avogadro's number = 6.02 × 10²³

A)2.51 × 10²²
B)3.42 × 10²²
C)2.93 × 10²²
D)2.94 × 10²³
E)2.05 × 10²¹

Answer 3

3.42 × 10²²

Question 4

A neutron is known to undergo beta decay (n → p + e− +
))A reasonable mean lifetime for free neutrons is

A)10 years
B)10 hours
C)10 days
D)10 minutes
E)10−²³ s

Question 5

What energy is needed (in MeV)so two deuterium atoms moving together will reach the necessary 10−¹⁴ m for fusion?

A)0.511
B)0.14
C)2.5
D)4.3
E)1.0

Question 6

One roentgen is defined as

A)the amount of ionizing radiation that will produce 1/3 × 10−⁹ C of electric charge in 1 cm³ of air under standard conditions.
B)the amount of radiation that deposits 10−² J of energy into 1 kg of absorbing material.
C)the amount of radiation needed for ionization of an atom.
D)the amount of radiation needed for dissociation of a molecule.
E)the amount of radiation that deposits 1 erg of energy in 1 g of air.

Question 7

A neutron is characterized by the term "thermal neutron" when

A)its energy is of the order kT,where T is on the order of 0°C.
B)its energy is of the order kT,where T is on the order of 0 K.
C)its energy is of the order kT,where T is on the order of 273°C.
D)its energy is of the order kT,where T is on the order of 100°C.
E)its energy is of the order kT,where T is on the order of 0°R.

Question 8

A self-sustained chain reaction occurs when the reproduction constant,K,is equal to

A)3.0
B)2.0
C)2.5
D)1.0
E)0.5

Question 9

How fast must two deuterium atoms be moving so they can overcome the Coulomb force of repulsion,and attain the necessary 10−¹⁴ m for fusion? (m(
)= 2.014 1 u)

A)3.9 × 10⁶ m/s
B)1.3 × 10⁶ m/s
C)2.6 × 10⁶ m/s
D)5.2 × 10⁶ m/s
E)3.7 × 10⁶ m/s

Question 10

Find the unknown atomic number and mass number respectively,for the following reaction

A)141,53
B)140,54
C)53,41
D)54,140
E)54,141

Question 11

The nuclear probability of interacting with neutrons depends most strongly on the neutron's

A)mass
B)area
C)volume
D)speed
E)charge

Question 12

A principal mechanism for energy loss during nuclear fusion is bremsstrahlung.This loss is associated with

A)x-rays emitted due to electron-ion collisions.
B)radiation losses due to T⁴ losses.
C)conduction losses associated with ΔT.
D)convection losses associated with ΔT.
E)neutron collisions with atoms of moderator.

Question 13

Approximately how fast is an ion of helium moving if it is in a plasma with a temperature of 10⁸ K? m(He)= 4.002 603 u and u = 1.66 × 10−²⁷ kg.

A)10⁶ m/s
B)10⁴ m/s
C)10² m/s
D)10 m/s
E)1 m/s

Question 14

Approximately how much uranium (in kg)must undergo fission per day to provide 1 000 MW of power? (Assume an efficiency of 30%).The nuclear reaction is
)
m(n.= 1.008 665 u
m(U.= 235.043 915 u
M(Ba)= 140.913 9 u
M(Kr)= 91.897 3 u
U = 1.66 × 10−²⁷ kg

A)1.0
B)3.5
C)2.3
D)4.6
E)0.1

Question 15

Calculate the half-value thickness (in mm)of lead if it reduces the intensity of a beam of x-rays whose wavelength is 10 pm by a factor of two.(Assume the linear absorption coefficient of lead is 43 cm−¹ for x-rays of wavelength 10 × 10−¹² m. )

A)0.24
B)0.20
C)0.12
D)0.16
E)0.18

Question 16

What is the average kinetic energy (in keV)of an ion that has a temperature of
10⁸ K?

A)8.2
B)13
C)4.3
D)16
E)21

Question 17

A rem (roentgen equivalent in man)is defined as (the product of)

A)the dose in RBE.
B)the dose in roentgen and the RBE factor.
C)the dose in rad times the dose in roentgen.
D)the dose in rad and the RBE factor.
E)the dose in rad and energy of radiation.

Question 18

How much energy (in MeV)is released when a
Fissions to
And
In the reaction
m(n.= 1.008665 u
m(U.= 235.043915 u
M(Ba)= 140.9139 u
M(Kr)= 91.8973 u
U = 1.66 × 10−²⁷ kg

A)100
B)50
C)200
D)150
E)250

Question 19

A thermal neutron has an energy (in eV)on the order of

A)40
B)0.4
C)4
D)0.04
E)400

Question 20

Which of the following is not a radiation detector?

A)cloud chamber
B)Geiger counter
C)scintillation counter
D)neutron activation
E)spark chamber

Question 21

A beam of high-energy α-particles is incident upon a person and deposits 0.35 J of energy in 0.80 kg of tissue.What dose in rads and what equivalent dose in rems does the individual receive? [RBE α = 20]

Question 22

When a beam of nuclear radiation of initial intensity I₀ passes through a thickness x of material,the intensity of the beam exiting the material is I =

A)I₀e−μx.
B)I₀eμx.
C)I₀(e−μx − 1).
D)I₀(eμx − 1).
E)I₀(1 − e−μx).

Question 23

Radiant energy reaching the Earth from the sun is not sufficient to keep the Earth's surface temperature comfortable for life.Of the following,the most likely source of the additional thermal energy is from

A)fusion of hydrogen nuclei in the Earth's core.
B)fusion of high Z nuclei in the Earth's core.
C)fission of radioactive nuclei inside the Earth.
D)fission of radioactive nuclei in cosmic rays.
E)deflection of radioactive nuclei in cosmic rays.

Question 24

When a nucleus at rest spontaneously splits into fragments of mass m₁ and m₂,the ratio of the velocity of m₁ to the velocity of m₂ is

A) .
B) .
C)−1.
D) .
E) .

Question 25

The reaction
Is known as a ____ reaction.

A)beta capture
B)beta emission
C)neutron capture
D)neutron emission
E)photon emission

Question 26

The nuclear reaction(s)that is(are)most likely to be employed in fusion reactors on Earth is(are)

A) .
B) .
C) .
D)all of the above.
E)only (a)and (b)above.

Question 27

When a nucleus at rest spontaneously splits into fragments of mass m₁ and m₂,the ratio of the momentum of m₁ to the momentum of m₂ is

A) .
B) .
C)−1.
D) .
E) .

Question 28

A radioactive sample with decay rate R and decay energy Q has power output

A) .
B)RQ.
C)Q²R.
D)equal to any of the above.
E)equal to (a)or (c)above.

Question 29

The theory of nuclear astrophysics is that all the heavy elements like uranium are formed in the interior of massive stars.These stars eventually explode,releasing these elements into space.If we assume that at the time of the explosion there were equal amount of U-235 and U-238,how long ago did the star(s)explode that released the elements that formed our Earth? The present U-235/U-238 ratio is 0.0070.[The half-lives of U-235 and U-238 are 0.7 × 10⁹ yr and 4.47 × 10⁹ yr.]

Question 30

When a fast neutron collides with a hydrogen or deuterium nucleus,the most likely result is that

A)the neutron has an appreciable gain in kinetic energy,the gain being greatest for head-on collisions.
B)the neutron has an appreciable gain in kinetic energy,the gain being greatest for oblique collisions.
C)the neutron has an appreciable loss in kinetic energy,the loss being greatest for head-on collisions.
D)the neutron has an appreciable loss in kinetic energy,the loss being greatest for oblique collisions.
E)the neutron is absorbed by the hydrogen or deuterium nucleus.

Question 31

How much kinetic energy must a deuterium ion (charge 1.6 × 10−¹⁹ C)have to approach to within 10−¹⁴ m of another deuterium ion? (1 MeV = 1.6 × 10−¹³ J)

Question 32

Radioactive technetium,a gamma emitter,is taken up by the heart muscle in a medical test.The detector for the radiation emitted from the heart could be a

A)Tokamak.
B)quarter-wavelength antenna.
C)Geiger counter.
D)photoelectric tube.
E)diffraction grating.

Question 33

In order to control a nuclear reactor,control rods can be pulled out of or pushed into the reactor core by remote control.These rods control the reactor by

A)slowing down the fast neutrons so the neutrons can be absorbed by ²³⁸U.
B)speeding up slow neutrons so the neutrons can be absorbed by ²³⁸U.
C)slowing down fast neutrons so they cannot initiate further fusion reactions in ²³⁵U.
D)speeding up fast neutrons so they cannot initiate further fusion reactions in ²³⁵U.
E)capturing thermal neutrons so they cannot initiate further fission reactions in ²³⁵U.

Question 34

In neutron capture by an atomic nucleus,the mass number of the nucleus changes by

A)−2.
B)−1.
C)0.
D)+1.
E)+2.

Question 35

In neutron capture by an atomic nucleus,the atomic number changes by

A)−2.
B)−1.
C)0.
D)+1.
E)+2.

Question 36

Background radiation from cosmic rays and radioactive nuclei in our surroundings is about 0.13 rem/year.Suppose we assume this all comes from cosmic rays which have an RBE factor of 1.0.The RBE factor for the most dangerous types of radiation is 20.How many rads of the most dangerous radiation could a 100-year-old person have been exposed to in her lifetime without having gone over the recommended limit of 0.5 rem/year?

A)0.37
B)0.50
C)1.85
D)13
E)37

Question 37

In the Lawson number what do the n and
Stand for?

A)ion density,critical ignition temperature.
B)ion density,confinement time.
C)neutrino density,confinement time
D)ion density,critical ignition temperature
E)neutrino density,reaction mean life.

Question 38

A nuclear reactor is said to be critical when the average number of neutrons from each fission event that cause(s)another fission event is

A)<1.
B)1.
C)>1.
D)any of the above.
E)only (b)or (c)above.

Question 39

How many grams of deuterium (atomic mass = 2.0141 u)must be fused to helium (atomic mass 4.0026 u)in one second to produce 3000 MJ of energy? [1 u = 1.66 × 10−²⁷ kg]

Question 40

How many grams of U-235 must be fissioned every day to produce 1000 MW of electricity in a nuclear power plant that is 1/3 efficient? [Assume 208 MeV/fission and 1 MeV = 1.6 × 10−¹³ J]