Download 193008 - Thermal Hydraulics

Thermodynamics
Thermal Hydraulics
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193008 – Thermal Hydraulics
OGF - Polling
1. Convection heat transfer improves when nucleate
boiling begins on the surface of a fuel rod because:
© Copyright 2016
193008 – Thermal Hydraulics
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B.
steam bubble formation decreases
coolant flow rate along the fuel rod.
steam bubble formation increases
coolant flow rate along the fuel rod.
a steam blanket begins to form along the
surface of the fuel rod.
the motion of the steam bubbles causes
rapid mixing of the coolant.
as
A.
OGF - Polling
2. How does the convective heat transfer coefficient
vary from the bottom to the top of a fuel assembly if
reactor coolant enters the fuel assembly as
subcooled water and exits as superheated steam?
Increases continuously.
Increases, then decreases.
Decreases continuously.
Decreases, then increases.
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3. Departure from nucleate boiling should not be
allowed to occur in the core because...
193008 – Thermal Hydraulics
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B.
as steam bubbles begin to blanket the fuel
rod, the radiative heat transfer decreases.
as steam bubbles in the coolant form and
then collapse, water hammer occurs.
as steam bubbles begin to blanket the fuel
rod, its temperature rises sharply.
as steam bubbles form in the coolant, voidsinduced reactivity changes cause
undesirable power changes.
as
A.
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4. Which one of the following parameter changes will
reduce the departure from nucleate boiling ratio?
Decreasing reactor power.
Increasing pressurizer pressure.
Increasing reactor coolant flow rate.
Increasing reactor coolant temperature
193008 – Thermal Hydraulics
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5. How does the critical heat flux vary from the bottom
to the top of a typical fuel assembly during normal
100 percent power operation?
Increases continuously.
Increases, then decreases.
Decreases continuously.
Decreases, then increases.
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6. Which one of the following is most likely to result in
fuel cladding damage?
193008 – Thermal Hydraulics
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Operating at 110 percent of reactor vessel
design pressure.
An inadvertent reactor trip from 100 percent
power.
Operating at a power level that exceeds the
critical heat flux.
Operating with saturated nucleate boiling
occurring in a fuel assembly.
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OGF - Polling
7. Which one of the following describes a function of
core bypass flow?
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Provides a means of measuring core flow
rate.
Prevents boron precipitation in the core
baffle area.
Prevents excessive reactor vessel wall
differential temperature.
Provides cooling to various reactor vessel
internal components.
Pr
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A.
OGF - Polling
8. Which one of the following must exist for natural
circulation flow to occur?
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193008 – Thermal Hydraulics
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The heat source must be larger than the
heat sink.
The heat source must be located higher
than the heat sink.
The heat sink must be larger than the heat
source.
The heat sink must be located higher than
the heat source.
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OGF - Polling
9. During the reflux boiling method of core cooling,
steam from the reactor core is condensed in the
__________ side of a steam generator and flows
back into the core via the __________. (Assume the
steam generators contain U-tubes.)
hot leg; hot leg
cold leg; hot leg
hot leg; cold leg
cold leg; cold leg
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OGF - Polling
10. A reactor coolant system natural circulation
cooldown is in progress with steam release from
the steam generator (SG) atmospheric steam relief
valves (operated in manual control). If high point
voiding interrupts natural circulation, which one of
the following will occur? (Assume feedwater flow
rate, SG relief valve position, and core decay heat
level are constant.)
© Copyright 2016
193008 – Thermal Hydraulics
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SG level will increase and SG pressure will
increase.
SG level will increase and SG pressure will
decrease.
SG level will decrease and SG pressure will
increase.
SG level will decrease and SG pressure will
decrease.
SG
A.
OGF - Polling