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TEST > Neutrons > Flashcards

Neutrons Flashcards

1
Q

Delayed neutrons are fission neutrons that…
A. are released at the instant of fission.
B. are responsible for the majority of U-235 fissions.
C. have reached thermal equilibrium with the surrounding medium.
D. are expelled at a lower average kinetic energy than most other fission neutrons.

A

are expelled at a lower average kinetic energy than most other fission neutrons.

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2
Q

Delayed neutrons are neutrons that…
A. are responsible for the majority of U-235 fissions.
B. are expelled within 1.0 x 10-14 seconds of the fission event.
C. have reached thermal equilibrium with the surrounding medium.
D. are produced from the radioactive decay of certain fission fragments

A

are produced from the radioactive decay of certain fission fragments

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3
Q

Which one of the following is a characteristic of a prompt neutron?
A. Expelled with an average kinetic energy of 0.5 MeV.
B. Usually emitted by the excited nucleus of a fission product.
C. Accounts for more than 99 percent of fission neutrons.
D. Released an average of 13 seconds after the fission event.

A

Accounts for more than 99 percent of fission neutrons.

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4
Q

A neutron that is expelled 1.0 x 10-2 seconds after the associated fission event is a __________
neutron.
A. thermal
B. delayed
C. prompt
D. capture

A

delayed

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5
Q

A neutron that is expelled 1.0 x 10-6 seconds after the associated fission event is a __________
neutron.
A. thermal
B. prompt
C. delayed
D. capture

A

delayed

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6
Q

Which one of the following types of neutrons has an average neutron generation lifetime of 12.5
seconds?
A. Prompt
B. Delayed
C. Fast
D. Thermal

A

Delayed

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7
Q

In a comparison between a delayed neutron and a prompt neutron produced from the same fission
event, the prompt neutron is more likely to… (Assume that both neutrons remain in the core.)

A. require a greater number of collisions to become a thermal neutron.
B. be captured by U-238 at a resonance energy peak between 1 eV and 1000 eV.
C. be expelled with a lower kinetic energy.
D. cause thermal fission of a U-235 nucleus.

A

require a greater number of collisions to become a thermal neutron.

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8
Q

In a comparison between a delayed neutron and a prompt neutron produced from the same fission
event, the prompt neutron is more likely to… (Assume that both neutrons remain in the core.)

A. cause fast fission of a U-238 nucleus.
B. be captured by a U-238 nucleus at a resonance energy between 1 eV and 1000 eV.
C. be captured by a Xe-135 nucleus.
D. cause thermal fission of a U-235 nucleus.

A

cause fast fission of a U-238 nucleus.

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9
Q

A neutron that is released 1.0 x 10-10 seconds after the associated fission event is classified as a
__________ fission neutron.

A. delayed
B. prompt
C. thermal
D. spontaneous

A

delayed

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10
Q

In a comparison between a prompt neutron and a delayed neutron produced from the same fission
event, the delayed neutron requires __________ collisions in the moderator to become thermal; and is
__________ likely to cause fission of a U-238 nucleus. (Assume that both neutrons remain in the
core.)

A. more; more
B. more; less
C. fewer; more
D. fewer; less

A

fewer; less

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11
Q

In a comparison between a delayed neutron and a prompt neutron produced from the same fission
event, the prompt neutron is more likely to…

A. be captured by a Xe-135 nucleus.
B. cause thermal fission of a U-235 nucleus.
C. leak out of the core while slowing down.
D. be captured by a U-238 nucleus at a resonance energy.

A

leak out of the core while slowing down.

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12
Q

In a comparison between a delayed neutron and a prompt neutron produced from the same fission
event, the delayed neutron is more likely to…

A. leak out of the core.
B. cause fission of a U-238 nucleus.
C. become a thermal neutron.
D. cause fission of a Pu-240 nucleus.

A

become a thermal neutron.

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13
Q

During a brief time interval in a typical reactor operating steady-state near the beginning of a fuel
cycle, 1.0 x 103 delayed neutrons were emitted.
Approximately how many prompt neutrons were emitted during this same time interval?

A. 1.5 x 10^5
B. 6.5 x 10^6
C. 1.5 x 10^7
D. 6.5 x 10^8

A

1.5 x 10^5

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14
Q

Which one of the following types of neutrons in a reactor is more likely to cause fission of a U-238
nucleus in the reactor fuel? (Assume that each type of neutron remains in the reactor until it interacts
with a U-238 nucleus.)

A. A thermal neutron.
B. A prompt fission neutron beginning to slow down.
C. A delayed fission neutron beginning to slow down.
D. A fission neutron at a U-238 resonance energy.

A

A prompt fission neutron beginning to slow down.

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15
Q

During a brief time interval in a typical reactor operating steady-state at the beginning of a fuel cycle,
1.0 x 105 delayed neutrons were emitted.
Approximately how many prompt neutrons were emitted in the reactor during this same time interval?

A. 1.5 x 10^5
B. 6.5 x 10^6
C. 1.5 x 10^7
D. 6.5 x 10^8

A

1.5 x 10^7

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16
Q

A neutron that appears 1.0 x 10-16 seconds after the associated fission event is classified as a
__________ fission neutron.

A. delayed
B. prompt
C. thermal
D. spontaneous

A

prompt

17
Q

During a brief time interval in a typical reactor operating steady-state near the beginning of a fuel
cycle, 4.25 x 105 delayed neutrons were produced.
Approximately how many prompt neutrons were produced in the reactor during this same time
interval?

A. 1.5 x 10^6
B. 6.5 x 10^6
C. 1.5 x 10^7
D. 6.5 x 10^7

A

6.5 x 10^7

18
Q

In a comparison between a delayed neutron and a prompt neutron produced from the same fission
event, the delayed neutron is more likely to… (Assume that each neutron remains in the core unless
otherwise stated.)

A. cause fission of a U-238 nucleus.
B. travel to an adjacent fuel assembly.
C. be absorbed in a B-10 nucleus.
D. leak out of the core.

A

be absorbed in a B-10 nucleus.

19
Q

Which one of the following is the process that produces the majority of delayed neutrons in an
operating nuclear power plant reactor?

A. A thermal neutron is absorbed by a fuel nucleus. After a period of time, the nucleus fissions and
releases a delayed neutron.
B. A thermal neutron is absorbed by a fuel nucleus. The fuel nucleus fissions. During the decay
process of the fission products, a delayed neutron is emitted.
C. A fast neutron is absorbed by a fuel nucleus. After a period of time, the nucleus fissions and
releases a delayed neutron.
D. A fast neutron is absorbed by a fuel nucleus. The fuel nucleus fissions. During the decay
process of the fission products, a delayed neutron is emitted.

A

A thermal neutron is absorbed by a fuel nucleus. The fuel nucleus fissions. During the decay
process of the fission products, a delayed neutron is emitted.

20
Q

During a brief time interval in a typical reactor operating steady-state near the beginning of a fuel
cycle, 4.25 x 1010 prompt neutrons were produced.
Approximately how many delayed neutrons were produced in the reactor during this same time
interval?

A. 2.8 x 10^8
B. 6.5 x 10^8
C. 2.8 x 10^9
D. 6.5 x 10^9

A

2.8 x 10^8

21
Q

Which one of the following is the process that produces the majority of prompt neutrons in an
operating nuclear power plant reactor?

A. A thermal neutron is absorbed by a fuel nucleus. Almost immediately, the nucleus fissions and
emits one or more prompt neutrons.
B. A thermal neutron is absorbed by a fuel nucleus. Almost immediately, the fuel nucleus fissions
and produces fission products. During the decay of the fission products, one or more prompt
neutrons are emitted.
C. A fast neutron is absorbed by a fuel nucleus. Almost immediately, the nucleus fissions and emits
one or more prompt neutrons.
D. A fast neutron is absorbed by a fuel nucleus. Almost immediately, the fuel nucleus fissions and
produces fission products. During the decay of the fission products, one or more prompt neutrons
are emitted.

A

A thermal neutron is absorbed by a fuel nucleus. Almost immediately, the nucleus fissions and
emits one or more prompt neutrons.

22
Q

Which one of the following nuclei will cause the greater loss of kinetic energy from a 2.1 MeV fission
neutron during a head-on collision? (Assume that each nucleus is stationary just prior to the collision
and the neutron is elastically scattered in all cases.)

A. A helium-4 nucleus in the fuel rod fill gas.
B. An oxygen-16 nucleus in the reactor coolant.
C. A zirconium-90 nucleus in the fuel cladding.
D. A uranium-235 nucleus in a fuel pellet.

A

A helium-4 nucleus in the fuel rod fill gas.

23
Q

Delayed neutrons are fission neutrons that…

A. have an average lifetime of about 80 seconds.
B. have an average kinetic energy of about 2 MeV.
C. are responsible for less than one percent of all fissions.
D. are in thermal equilibrium with the surrounding medium

A

are responsible for less than one percent of all fissions.

TEST (22 decks)

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