EXAM 3 Flashcards
(120 cards)
1
Q
Charged particles
A
directly ionizing
2
Q
Neutral particles
A
indirectly ionizing
3
Q
true for transmutation
A
can occur through nuclear reactions (in which an outside particle reacts with a nucleus)
can occur through radioactive decay (where no outside particle is needed).
atoms of one element can be changed into atoms of another element
the conversion of one chemical element or isotope into another
4
Q
Beta particles being light, charged particles lose energy by
A
electron excitation
emitting photons as they are deflected around nuclei.
ionization.
5
Q
Gamma rays may interact with matter through
A
pair production
photoelectric absorption
Compton scattering
6
Q
Pair production requires that the gamma ray have at least 0.511 MeV energy.
A
False
7
Q
A gamma ray gains energy when it undergoes Compton scattering.
A
False
8
Q
Photoelectrons have the same kinetic energy as that of the gamma ray that produced them.
A
False
9
Q
The higher the value of the linear attenuation coefficient, the smaller the average depth of penetration of gamma rays.
A
True
10
Q
How do ionization chambers detect radiation?
A
Radiation ionizes atoms of a gas. The ions and electrons are collected at electrodes held at a high potential, and the resulting current is measured
11
Q
Name neutron classification by energy. (Several answers possible, check all that a re related to the question)
A
intermediate
fast
slow (thermal)
12
Q
check all that’s applied for prompt neutrons
A
constitute over 99% of fission neutrons
emitted at the time of fission
13
Q
What is the spent fuel?
A
Fuel assemblies that are discharged from reactors during refueling
14
Q
What is fuel burnup? What are the units of fuel burnup?
A
The energy produced per unit mass of the fuel.
MWdt/Tonne U
15
Q
Reactivity can be positive, zero or negative
A
True
16
Q
What is the other use of the water in LWR except for coolant and moderator?
A
Reflector
17
Q
Name all components of the 6-factor formula. Write the meaning of each of them.
A
PFNL is the fast non-leakage probability
PTNL is the thermal non-leakage probability
E is the fast-fission factor
p is the resonance escape probability (the probability for a neutron to escape resonance capture)
f is the thermal utilization factor
n is the number of fission neutrons produced per neutron absorbed in the fuel
18
Q
k- effective =1
A
the reactor is Critical
19
Q
k- effective>1
A
the reactor is Supercritical
20
Q
k- effective <1
A
reactor is Subcritical
21
Q
Check all that apply to delayed neutrons
A
constitute only less than 1% of all fission neutrons
22
Q
takes into account geometry of the reactor core
A
k- effective
23
Q
characterizes the multiplication properties of material in the reactor
A
k- infinite
24
Q
Why the Doppler feedback is strongly negative in the thermal reactor systems?
A
because their effective fissile content (U-235) is low
25
Compare k-infinite and k-effective
k-infinite > k-effective
26
a positive temperature - power reactivity feedback cycle would reduce the reactivity and tend to stabilize the system
False
27
Increased reactivity leads to a greater rate of power increase.
Increased power raises core temperatures.
Higher temperatures increase reactivity.
Is this example of a positive temperature - power reactivity feedback or negative?
a positive temperature - power reactivity feedback
28
Why Soluble poison can be added and dissolved in the coolant in the form of boric acid Only into the coolant of PWR, but not in BWR? Check all that is true
Plating can affect heat transfer as well as reactivity
Boiling can result in boron plating out on the fuel rods.
29
Doppler effect is positive for
fissile fuel
30
Doppler effect is negative for
fertile fuel
31
Why do we have burnable and soluble poisons? Check all that are true
To lower the initial reactivity
They gradually burn out as the U burns out
32
Name the PWR auxiliary system that is used for adding soluble boron the reactor coolant system in the form of boric acid.
Chemical Volume Control System (CVCS). Or Chemical Shim
33
Positive reactivity feedback
enhances the condition that produced it
34
Negative reactivity feedback
decreases the condition that produced it
35
DEFINE a Burnable poison
Burnable poison is used to lower the initial reactivity
36
What is the Non-burnable poison
Material that maintains a constant negative reactivity worth over the life of the core
37
DEFINE the Chemical shim
Adding the Burnable soluble poison in the coolant by an auxiliary system
38
Fixed burnable poisons have advantages over chemical shim because
-Fixed burnable poisons do not make the moderator temperature reactivity coefficient less negative as chemical shim does.
True
39
Do we use fixed non-burnable poisons in the reactor core?
Yes, to prevent excessive flux and power peaking near moderator regions of the reactor
40
What is fission product poisoning?
Accumulation of fission products with significant absorption cross-section
41
DESCRIBE how equilibrium samarium-149 concentration varies with a reactor power level
Equilibrium concentration of Sm-149 is independent of neutron flux and power level
42
The equilibrium concentration and the poisoning effect build to an equilibrium value during reactor operation for Sm is reached in approximately at what time?
20 days
43
DESCRIBE how samarium-149 concentration changes following a reactor startup
Samarium-149 does not peak as Xenon-135 does, but increases slowly to a maximum value
44
Helium- 3 does not have a significant effect on the reactivity of a reactor
False
45
How samarium-149 is produced during reactor operation?
Sm-149 is in the decay chain of the fission product neodymium 149
46
DESCRIBE how xenon-135 concentration changes following a reactor shutdown from steady-state conditions.
The Xe concentration peaks at about 10-11.6 h and then decreases for the next 30-40h
47
DESCRIBE how equilibrium xenon-135 concentration varies with reactor power level.
The equilibrium value for Xe135 increases as power increases
48
The higher the power of the R before the shutdown, the higher concentration of Xe
True
49
50
STATE the approximate time following a reactor shutdown at which the reactor can be considered "xenon free."
40 h
51
LIST two methods of production for xenon-135 during reactor operation
-It is produced directly by some fission
-It is produced by tellurium-135 decay chain
52
Chose what is true for production of Xe
Tellurium-135 decay chain can be ignored in production of Xe
53
DESCRIBE how xenon-135 concentration changes following a reactor shutdown from steady-state conditions.
The Xe concentration peaks at about 10-11.6 h and then decreases for the next 30-40h
54
What information does the fission product yield curve provide?
-The probability of production of a fission product with a given mass number.
-That the most likely fission products are those with mass numbers between89 and 101 and between 133 and 144 for thermal fission of 235U
-That symmetric fission is less likely than asymmetric fission
(ALL OF THE ABOVE)
55
The amount of energy released during fission is equivalent to the
difference between the binding energy of the compound nucleus and the sum of the binding energies of the fission product nuclei.
56
Why is 235U a good reactor fuel?
It can fission with thermal neutrons
57
Fission products are a major concern in nuclear power technology because
ALL OF THE ABOVE
58
Fission products undergo β− decays usually followed by the release of gamma rays
Delayed Stage
59
Fission fragments are formed
Prompt Stage
60
Most of the energy of fission is released
Prompt Stage
61
Lasts a fraction of a second
Prompt Stage
62
May last thousands of years
Delayed Stage
63
Neutrons are always released in every fission event.
Prompt Stage
64
Gamma rays can be released.
Both prompt and delayed stages
65
If a 236U compound nucleus fissions emitting two neutrons, which of the following examples are the most probable masses of the two fragments?
94 and 130
66
Which of the following statements about fission is true?
More neutrons are released during the delayed stage than the prompt stage
67
Which of the following contribute(s) to cause fission?
ALL
-Coulombic repulsion
-Overcoming the nuclear force
-Kinetic energy of incident neutron
-Binding energy of incident neutron
68
If a = 14 % of the fissions in a reactor occur in 239Pu and the rest in 235U, what is the overall value of the delayed neutron fraction, β?
β235 = 0.0065
β239 = 0.0021
0.00588
69
If a = 7 % of the fissions in a reactor occur in 239Pu and the rest in 235U, what is the overall value of the delayed neutron fraction, β?
β235 = 0.0065
β239 = 0.0021
0.0062
70
The average prompt neutron yield for thermal fission of 235U is very nearly equal to
2.42
71
Delayed neutrons are delayed because
they are emitted by the excited daughter products of certain fission products following b- (-) decay
72
Which of the following isotopes does NOT fission with thermal neutrons?
U238
73
Which of the following isotopes is (are) fissile?
-U 233
-Pu 241
74
What is the minimum threshold energy required for an isotope to fission?
Critical energy
75
Why are delayed neutrons important in reactor operation?
They make it possible to control power increases in a reactor
76
Conversion of 238U to 241Pu is an example of
a breeding reaction.
77
Fission products most often decay by
Beta (-) decay followed by gamma ray emission
78
Weight fraction changes in the fuel are so small (only a few percent) that they have no consequence on the operation or safety of the reactor
False
79
Decay heat is generated by the radioactive decay of fission products
True
80
Decay heat is generated only after a reactor is shut down and not while it is operating
False
81
More prompt neutrons result from thermal fission of 239Pu than from thermal fission of 235U
True
82
Nuclear reactor shielding problems are concerned mainly with
Gamma-rays, neutrons
83
studies have shown that alpha and neutron radiation cause greater biological damage for a given energy deposition per kg of tissues than gamma radiation does
True
84
Alpha particles have
HIGH-LET
85
protons have
HIGH-LET
86
neutrons have
HIGH-LET
87
gamma rays have
LOW-LET
88
give 3 parameters that buildup factors depend on
- radiation type
- particle energy
- medium
- distanced traveled
- response type
89
Radiation counters
the rate of generation of radiation-induced pulses can be used to measure the rate at which radiation particles traverse to
90
energy spectrometers
by measuring both the number of pulses and the distribution of pulse
91
dosimeters
the average current can be used as a measure of the amount of ionization or energy deposition
92
photons of what energies are important in radiation shielding design and analysis?
10eV- 20MeV
93
List at least 5 gamma rays sources
radioactive decay, neutron capture reactions, inelastic neutron scattering reactions, fission, fusion, spallation, annihilation
94
Prompt fission neutrons
Neutrons which are omitted within milliseconds of the fission event
95
Photoneutrons
neutrons which results from the absorption of a gamma ray reaction
96
delayed fission neutrons
neutrons which are released during the decay of certain fission product
97
From what shell the electron- ejection during fluorescent radiation will produce enough energy to produce X-ray that we concern with
K-shell
98
Prompt fission gammas
emitted during the fission process
99
fission product gammas
emitted by the decay of fission product
100
capture gammas
emitted immediately after the capture of a neutron reaction
101
activation gammas
emitted during the radioactive decay of an isotope form from a neutron capture
102
Inelastic gammas
emitted by nuclei which has been excited by inelastic collision with fast neutrons
103
For want incident particles and what material bremsstrahlung is important?
High Z material, small mass incident particles
104
what is the inelastic scattering threshold?
The minimum energy that an incident particle must have to induce an inelastic scattering reaction
105
roentgen
the amount of x or gamma radiation which produces carrying one electrostatic unit (esu) of 1 change in cubic centimeter
106
REM
A biological dose unit take in account the relative biological effect of the various type of radiation
107
The RBE
The biological damage from one rad of Y compared with the biological damage from one rad of gamma
108
By what bonding the biological tissue is characterized?
Covalent bond
109
a dose of radiation
The total quantity of radiation received
110
the dose rate
The quantity of radiation being received per unit time
111
equivalent dose
a dose quantity calculated for individual organs
112
The radiation weighting factor
A dimensionless factor used to determine the equivalent dose from the absorbed dose average over a tissue or an organ
113
KERMA
Kinetic Engergy of Radiation produced per unite MAss in matter
114
Radiation doses received at high dose rate are less significance than the same doses received at a low high dose rate (T/F)
False
115
Atomic Radiation
The emission of particle or X-ray from an atomic source
115
medical radiation protection
The protection of patients
115
occupational radiation protection
The protection of worker
115
In radiation protection, there are three ways how to protect people from identified external radiation sources. Name them.
Limiting time, Distance, Shielding
116
public radiation protection
The protection of individual
116
Contamination
Bits of radioactive material in the air or water or in any surface
