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TEST > Heat transfer > Flashcards

Heat transfer Flashcards

1
Q

The transfer of heat from the reactor fuel pellets to the fuel cladding during normal plant operation is
primarily accomplished via __________ heat transfer.

A. conduction

B. convection

C. radiant

D. two-phase

A

conduction

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2
Q

Refer to the drawing of a fuel rod and coolant flow channel at the beginning of a fuel cycle (see figure
below).
Which one of the following is the primary method of heat transfer through the gap between the fuel
pellets and the fuel cladding?

A. Conduction

B. Connections

C. Radiation

D. Natural circulation

A

Conduction

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3
Q

During a loss-of-coolant accident, which one of the following heat transfer methods provides the most
core cooling when fuel rods are not in contact with the coolant?

A. Radiation

B. Emission

C. Convection

D. Conduction

A

Radiation

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4
Q

Reactor fuel rods are normally charged with __________ gas; which improves heat transfer by
__________.

A. helium; convection

B. helium; conduction

C. nitrogen; convection

D. nitrogen; conduction

A

helium; conduction

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5
Q

A nuclear power plant is operating at 60 percent power. Which one of the following is the primary
method of heat transfer from the outer surface of the steam generator tubes to the bulk feedwater?

A. Radiolysis

B. Radiation

C. Convection

D. Conduction

A

Convection

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6
Q

Which one of the following describes a heat transfer process in which convection is the most
significant mode of heat transfer?

A. From the fuel rods to the core barrel during core uncovery.

B. Through the tube walls in a steam generator during normal operation at 100 percent power.

C. From the fuel rods to the steam generators 24 hours after a trip of all reactor coolant pumps.

D. From the fuel pellet centerline to the fuel cladding during normal operation at 100 percent power.

A

From the fuel rods to the steam generators 24 hours after a trip of all reactor coolant pumps.

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7
Q

Which one of the following describes a heat transfer flow path in which conduction is the dominant
mode of heat transfer?

A. From the fuel rods to the core barrel during core uncovery.

B. From the main turbine exhaust steam to the atmosphere via main condenser cooling water and a
cooling tower during normal operation.

C. From the fuel rods to the steam outlet of the steam generators during a station blackout.

D. From a fuel pellet to the fuel cladding via the fuel rod fill gas during normal operation.

A

From a fuel pellet to the fuel cladding via the fuel rod fill gas during normal operation.

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8
Q

If excessive amounts of air are entrained/dissolved in the cooling water passing through a heat
exchanger, the overall heat transfer coefficient of the heat exchanger will decrease because the…

A. laminar layer thickness will decrease.

B. laminar layer thickness will increase.

C. thermal conductivity of the cooling fluid will decrease.

D. thermal conductivity of the cooling fluid will increase.

A

thermal conductivity of the cooling fluid will decrease.

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9
Q

Why is bulk boiling in the tubes of a single-phase heat exchanger undesirable?

A. The bubble formation will break up the laminar layer in the heat exchanger tubes.

B. The thermal conductivity of the heat exchanger tubes will decrease.

C. The differential temperature across the tubes will decrease through the heat exchanger.

D. The turbulence will restrict fluid flow through the heat exchanger tubes.

A

The turbulence will restrict fluid flow through the heat exchanger tubes.

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10
Q

Which one of the following pairs of fluids undergoing heat transfer in identical heat exchangers will
yield the greatest heat exchanger overall heat transfer coefficient?

A. Oil to water.

B. Air to water.

C. Steam to water.

D. Water to water.

A

Steam to water.

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11
Q

Which one of the following pairs of fluids undergoing heat transfer in identical heat exchangers will
yield the smallest heat exchanger overall heat transfer coefficient?

A. Oil to water.

B. Air to water.

C. Steam to water.

D. Water to water

A

Air to water.

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12
Q

A nuclear power plant is operating near 100 percent power. Main turbine extraction steam is being
supplied to a feedwater heater. Extraction steam parameters are as follows:
Steam pressure = 414 psia
Steam flow rate = 7.5 x 105 lbm/hr
Steam enthalpy = 1,150 Btu/lbm
The extraction steam condenses to saturated water at 414 psia, and then leaves the feedwater heater via
a drain line.
What is the heat transfer rate from the extraction steam to the feedwater in the feedwater heater?

A. 3.8 x 107 Btu/hr

B. 8.6 x 107 Btu/hr

C. 5.4 x 108 Btu/hr

D. 7.2 x 108 Btu/hr

A

5.4 x 108 Btu/hr

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13
Q

A nuclear power plant is initially operating at a steady-state power level with the following main
condenser parameters:
Main condenser pressure
= 1.2 psia
Cooling water inlet temperature = 60°F
Cooling water outlet temperature = 84°F
Due to increased condenser air inleakage, the overall heat transfer coefficient of the main condenser
decreases by 25 percent. Main condenser heat transfer rate and cooling water temperatures are
unchanged. Which one of the following is the steady-state main condenser pressure resulting from
the reduced heat transfer coefficient?

A. 1.7 psia

B. 2.3 psia

C. 3.0 psia

D. 4.6 psia

A

1.7 psia

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14
Q

Which one of the following pairs of fluids undergoing heat transfer in identical heat exchangers will
yield the greatest heat exchanger overall heat transfer coefficient?

A. Oil to water.

B. Steam to water.

C. Air to water.

D. Water to water.

A

Steam to water.

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15
Q

A nuclear power plant is operating near 100 percent power. Main turbine extraction steam is being
supplied to a feedwater heater. Extraction steam parameters are as follows:
Steam pressure = 500 psia
Steam flow rate = 7.0 x 105 lbm/hr
Steam enthalpy = 1,135 Btu/lbm
The extraction steam condenses to saturated water at 500 psia, and then leaves the feedwater heater via
a drain line.
What is the heat transfer rate from the extraction steam to the feedwater in the feedwater heater?

A. 3.2 x 108 Btu/hr

B. 4.8 x 108 Btu/hr

C. 5.3 x 108 Btu/hr

D. 7.9 x 108 Btu/hr

A

4.8 x 108 Btu/hr

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16
Q

During steady-state power operation, core thermal power can be most accurately determined by
multiplying the total mass flow rate of the…

A. reactor coolant by the change in temperature across the core.

B. reactor coolant by the change in enthalpy in the steam generators.

C. feedwater by the change in enthalpy in the steam generators.

D. feedwater by the change in temperature across the core.

A

feedwater by the change in enthalpy in the steam generators.

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17
Q

A reactor is currently producing 200 MW of core thermal power. Reactor coolant pumps are adding
an additional 10 MW of thermal power to the reactor coolant system. The core is rated at 1,330 MW.
Which one of the following is the current core thermal power output in percent?

A. 14.0 percent

B. 14.3 percent

C. 15.0 percent

D. 15.8 percent

A

15.0 percent

18
Q

The power range nuclear instruments have been adjusted to 100 percent based on a heat balance
calculation. Which one of the following would cause indicated reactor power to be greater than
actual reactor power?

A. The reactor coolant pump heat input term was omitted from the heat balance calculation.

B. The feedwater flow rate used in the heat balance calculation was lower than actual feedwater flow
rate.

C. The steam pressure used in the heat balance calculation was 50 psi higher than actual steam
pressure.

D. The enthalpy of the feedwater was miscalculated to be 10 Btu/lbm higher than actual feedwater
enthalpy.

A

The reactor coolant pump heat input term was omitted from the heat balance calculation.

19
Q

Which one of the terms in the equation, Q̇ = UA(T1-T2), is affected the most, and therefore most
responsible for the initial increase in heat transfer rate from the reactor fuel during a minor (3 percent)
steamline break? (Assume no initial change in reactor power.)

A. U

B. A

C. T1

D. T2

A

T2

20
Q

The power range nuclear instruments were just adjusted to 100 percent power, as determined by a heat
balance calculation. Which one of the following would result in indicated reactor power being
greater than actual reactor power?

A. The feedwater temperature used in the heat balance calculation was higher than actual feedwater
temperature.

B. The reactor coolant pump heat input term was omitted from the heat balance calculation.

C. The feedwater flow rate used in the heat balance calculation was lower than actual feedwater flow
rate.

D. The steam pressure used in the heat balance calculation was higher than actual steam pressure.

A

The reactor coolant pump heat input term was omitted from the heat balance calculation.

21
Q

A secondary heat balance calculation is being performed at 90 percent reactor power to calibrate
reactor power instrumentation. Which one of the following will result in a calculated reactor power
that is less than actual reactor power?

A. Steam generator pressure indication is 20 psi greater than actual steam generator pressure.

B. Steam generator water level indication is 3 percent less than actual steam generator water level.

C. Feedwater flow rate indication is 3 percent greater than actual feedwater flow rate.

D. Feedwater temperature indication is 20°F less than actual feedwater temperature.

A

Steam generator pressure indication is 20 psi greater than actual steam generator pressure.

22
Q

The power range nuclear instruments have been adjusted to 100 percent based on a heat balance
calculation. Which one of the following will result in indicated reactor power being lower than actual
reactor power?

A. The feedwater temperature used in the heat balance calculation was 20°F higher than actual
feedwater temperature.

B. The reactor coolant pump heat input term was omitted from the heat balance calculation.

C. The feedwater flow rate used in the heat balance calculation was 10 percent higher than actual
feedwater flow rate.

D. The steam pressure used in the heat balance calculation was 50 psi lower than actual steam
pressure

A

The feedwater temperature used in the heat balance calculation was 20°F higher than actual
feedwater temperature.

23
Q

The power range nuclear instruments have been adjusted to 100 percent based on a heat balance
calculation. Which one of the following will result in indicated reactor power being higher than
actual reactor power?

A. The feedwater temperature used in the heat balance calculation was 20°F higher than actual
feedwater temperature.

B. The reactor coolant pump heat input term was omitted from the heat balance calculation.

C. The feedwater flow rate used in the heat balance calculation was 10 percent lower than actual
feedwater flow rate.

D. The ambient heat loss term was omitted from the heat balance calculation.

A

The reactor coolant pump heat input term was omitted from the heat balance calculation.

24
Q

The power range nuclear instruments have been adjusted to 100 percent based on a calculated heat
balance. Which one of the following will result in indicated reactor power being lower than actual
reactor power?

A. The feedwater temperature used in the heat balance calculation was 20°F higher than actual
feedwater temperature.

B. The reactor coolant pump heat input value used in the heat balance was 10 percent lower than
actual reactor coolant pump heat input.

C. The feedwater flow rate used in the heat balance calculation was 10 percent higher than actual
feedwater flow rate.

D. The operator miscalculated the enthalpy of the steam exiting the steam generators to be 10 Btu/lbm
higher than actual.

A

The feedwater temperature used in the heat balance calculation was 20°F higher than actual
feedwater temperature.

25
Q

The power range nuclear instruments have been adjusted to 100 percent based on a calculated heat
balance. Which one of the following will result in indicated reactor power being lower than actual
reactor power?

A. The feedwater temperature used in the heat balance calculation was 20°F lower than actual feed
water temperature.

B. The reactor coolant pump heat input term was omitted from the heat balance calculation.

C. The ambient heat loss value used in the heat balance calculation was only one-half the actual
ambient heat loss.

D. The feedwater flow rate used in the heat balance calculation was 10 percent higher than actual
feedwater flow rate.

A

The ambient heat loss value used in the heat balance calculation was only one-half the actual
ambient heat loss.

26
Q

The power range nuclear instruments were adjusted to 100 percent based on a calculated heat balance.
Which one of the following would cause indicated reactor power to be lower than actual reactor
power?

A. The feedwater temperature used in the heat balance calculation was 10°F lower than actual
feedwater temperature.

B. The reactor coolant pump heat input term was omitted from the heat balance calculation.

C. The feedwater flow rate used in the heat balance calculation was 10 percent lower than actual
feedwater flow rate.

D. The steam pressure used in the heat balance calculation was 50 psi lower than actual steam
pressure.

A

The feedwater flow rate used in the heat balance calculation was 10 percent lower than actual
feedwater flow rate.

27
Q

Two of the parameters listed below are used for calculating core thermal power using the standard heat
balance method. Which one of the following identifies the two parameters?

Reactor Coolant
Mass Flow Rate

Feedwater
Temperature

Steam Generator

Pressure
Steam

Generator
Water Level

A.
Yes
No
Yes
No

B.
No
Yes
Yes
No

C.
Yes
No
No
Yes

D.
No
Yes
No
Yes

A

Reactor Coolant
Mass Flow Rate- NO

Feedwater
Temperature-
YES

Steam Generator
Pressure
-YES

Steam Generator
Water Level
- NO

28
Q

The power range nuclear instruments were adjusted to indicate 100 percent based on a heat balance
calculation. Which one of the following would cause indicated reactor power to be higher than actual
reactor power?

A. The steam pressure used in the heat balance calculation was 50 psi higher than actual steam
pressure.

B. The ambient heat loss value used in the heat balance calculation was twice the actual ambient heat
loss.

C. The feedwater flow rate used in the heat balance calculation was 10 percent lower than actual
feedwater flow rate.

D. The
feedwater temperature used in the heat balance calculation was 20°F higher than actual
feedwater temperature.

A

The ambient heat loss value used in the heat balance calculation was twice the actual ambient heat
loss.

29
Q

When performing a heat balance calculation to determine core thermal power, the measured thermal
power is __________ by a value associated with the reactor coolant pumps (RCPs); the adjustment is
needed because __________ of the flow energy added to the reactor coolant by the RCPs is converted
to thermal energy of the reactor coolant.

A. decreased; nearly all

B. decreased; a small fraction

C. increased; nearly all

D. increased; a small fraction

A

decreased; nearly all

30
Q
A
31
Q
A
32
Q

Two of the parameters listed below are used for calculating core thermal power using the standard heat
balance method. Which one of the following identifies the two parameters?

A

D.

33
Q

A PWR nuclear power plant has 2 steam generators (SG). Feedwater enters each SG at 3.3 x 106
lbm/hr with an enthalpy of 419 Btu/lbm. Steam exits each steam generator at 800 psia with 100
percent steam quality.
Ignoring all other heat gains and losses, what is the reactor core thermal power?

A. 667 MW

B. 755 MW

C. 1,334 MW

D. 1,510 MW

A

1,510 MW

34
Q

Reactor coolant enters a reactor core at 545°F and leaves at 595°F. The reactor coolant flow rate is
6.6 x 107 lbm/hour and the specific heat capacity of the coolant is 1.3 Btu/lbm-°F.
What is the reactor core thermal power?

A. 101 MW

B. 126 MW

C. 1,006 MW

D. 1,258 MW

A

1,258 MW

35
Q

A reactor is operating with the following parameters:
Reactor power
= 100 percent
Core ΔT
= 42°F
Reactor coolant system flow rate
= 100 percent
Average reactor coolant temperature = 587°F
A station blackout occurs and natural circulation is established with the following stable parameters:
Decay heat rate
= 2 percent
Core ΔT
= 28°F
Average reactor coolant temperature = 572°F
What is the core mass flow rate in percent?

A. 2.0 percent

B. 2.5 percent

C. 3.0 percent

D. 4.0 percent

A

3.0 percent

36
Q

A nuclear power plant is initially operating at 80 percent power with a core ΔT of 48°F when a station
blackout occurs. Natural circulation is established and core ΔT stabilizes at 40°F. If reactor coolant
mass flow rate is 3 percent, which one of the following is the current core decay heat level?

A. 1 percent

B. 2 percent

C. 3 percent

D. 4 percent

A

2 percent

37
Q

During a nuclear power plant outage, 5 percent of all steam generator (SG) tubes were plugged due to
wall thinning. Full power reactor coolant system flow rate and average reactor coolant temperature
(Tave) have not changed. Given the following 100 percent power conditions before the outage:
Tave = 578°F
TS/G = 538°F
Which one of the following will be the approximate SG pressure after the outage when the plant is
returned to 100 percent power? (Assume the overall heat transfer coefficients for the S/Gs did not
change.)

A. 960 psia

B. 930 psia

C. 900 psia

D. 870 psia

A

930 psia

38
Q

A nuclear power plant is operating with the following parameters:
Reactor power
= 100 percent
Core ΔT
= 60°F
Reactor coolant system flow rate = 100 percent
Average coolant temperature
= 587°F
A station blackout occurs and natural circulation is established with the following stable parameters:
Decay heat
= 1 percent
Core ΔT
= 30°F
Average coolant temperature = 572°F
What is the core mass flow rate in percent?

A. 2.0 percent

B. 2.5 percent

C. 3.0 percent

D. 4.0 percent

A

2.0 percent

39
Q

During a nuclear power plant outage, 6 percent of all steam generator (SG) tubes were plugged.
Full-power reactor coolant system flow rate and average reactor coolant temperature (Tave) have not
changed. Given the following 100 percent power conditions before the outage:
Tave = 584°F
TS/G = 544°F
Which one of the following will be the approximate SG pressure after the outage when the plant is
returned to 100 percent power?

A. 974 psia

B. 954 psia

C. 934 psia

D. 914 psia

A

974 psia

40
Q

During a nuclear power plant outage, 5 percent of all steam generator (SG) tubes were plugged.
Full-power reactor coolant system flow rate and average reactor coolant temperature (Tave) have not
changed. Given the following 100 percent power conditions before the outage:
Tave = 588°F
TS/G = 542°F
Which one of the following will be the approximate SG pressure after the outage when the plant is
returned to 100 percent power?

A. 998 psia

B. 979 psia

C. 961 psia

D. 944 psia

A

961 psia

41
Q

A nuclear power plant is operating at power. Total feedwater flow rate to all steam generators is 7.0
x 106 lbm/hr at a temperature of 440°F. The steam exiting the steam generators is at 1,000 psia with
100 percent steam quality.
Ignoring all other heat gain and loss mechanisms, what is the reactor core thermal power?

A. 1,335 MW

B. 1,359 MW

C. 1,589 MW

D. 1,612 MW

A

1,589 MW

42
Q

A nuclear power plant is operating with the following stable steam generator (SG) and feedwater (FW)
parameters:
SG pressure
= 1,000 psia
Total SG steam flow rate = 1.0 x 107 lbm/hr (dry, saturated steam)
Feedwater inlet temperature = 470°F
Based on the above information, what is the thermal power output of the reactor?

A. 740 MW

B. 1,328 MW

C. 2,169 MW

D. 3,497 MW

A

2,169 MW

TEST (22 decks)

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