Neutrons Flashcards
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.
are expelled at a lower average kinetic energy than most other fission neutrons.
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
are produced from the radioactive decay of certain fission fragments
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.
Accounts for more than 99 percent of fission neutrons.
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
delayed
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
delayed
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
Delayed
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.
require a greater number of collisions to become a thermal neutron.
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.
cause fast fission of a U-238 nucleus.
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
delayed
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
fewer; less
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.
leak out of the core while slowing down.
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.
become a thermal neutron.
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
1.5 x 10^5
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 prompt fission neutron beginning to slow down.
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
1.5 x 10^7
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
prompt
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
6.5 x 10^7
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.
be absorbed in a B-10 nucleus.
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 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.
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
2.8 x 10^8
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 thermal neutron is absorbed by a fuel nucleus. Almost immediately, the nucleus fissions and
emits one or more prompt neutrons.
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 helium-4 nucleus in the fuel rod fill gas.
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
are responsible for less than one percent of all fissions.
