Thermodynamic Processes Flashcards
Condensate depression is the process of…
A. removing condensate from the turbine exhaust steam.
B. spraying condensate into the turbine exhaust steam.
C. heating turbine exhaust steam above its saturation temperature.
D. cooling turbine exhaust steam below its saturation temperature.
cooling turbine exhaust steam below its saturation temperature.
Excessive heat removal from the low pressure turbine exhaust steam in the main condenser will result
in…
A. thermal shock.
B. loss of condenser vacuum.
C. condensate depression.
D. fluid compression.
condensate depression.
Main condenser pressure is 1.0 psia. During the cooling process in the condenser, the temperature of
the low pressure turbine exhaust decreases to 100°F, at which time it is a…
A. saturated liquid.
B. saturated vapor.
C. subcooled liquid.
D. superheated vapor.
subcooled liquid.
Which one of the following explains why condensate subcooling is necessary in a nuclear power plant
steam cycle?
A. To provide a better condenser vacuum.
B. To maximize overall steam cycle thermal efficiency.
C. To provide net positive suction head for the condensate pumps.
D. To minimize turbine blade and condenser tube erosion by entrained moisture
To provide net positive suction head for the condensate pumps.
Which one of the following is the approximate condensate subcooling in a steam condenser operating
at 26 inches Hg vacuum with a condensate temperature of 100°F?
A. 2°F
B. 19°F
C. 25°F
D. 53°F
25°F
Which one of the following is a positive effect of having condensate depression in the main
condenser?
A. Increased secondary cycle efficiency.
B. Increased feedwater temperature entering the steam generators.
C. Increased net positive suction head available to the condensate pumps.
D. Increased inventory in the main condenser hotwell.
Increased net positive suction head available to the condensate pumps.
A nuclear power plant is operating at 80 percent power with 5°F of condensate depression in the main
condenser. If the condensate depression increases to 10°F, the steam cycle thermal efficiency will
__________; and the condensate pumps will operate __________ cavitation.
A. increase; closer to
B. increase; farther from
C. decrease; closer to
D. decrease; farther from
decrease; farther from
What is the approximate value of condensate depression in a steam condenser operating at 2.0 psia
with a condensate temperature of 115°F?
A. 9°F
B. 11°F
C. 13°F
D. 15°F
11°F
What is the approximate condensate depression in a condenser operating at 28 inches Hg vacuum with
a condensate temperature of 100°F?
A. Less than 2°F
B. 3F to 5°F
C. 6F to 8°F
D. 9F to 11°F
Less than 2°F
Condensate is collecting in a main condenser hotwell at 90°F with a condenser pressure of 28 inches
Hg vacuum. Which one of the following will improve steam cycle efficiency?
A. Main condenser cooling water flow rate decreases by 5 percent with no change in condenser
vacuum.
B. Main condenser cooling water inlet temperature decreases by 10°F with no change in condenser
vacuum.
C. Main condenser vacuum decreases to 27 inches Hg vacuum due to buildup of noncondensible
gases.
D. Steam flow through the turbine decreases by 10 percent with no change in condenser vacuum.
Main condenser cooling water flow rate decreases by 5 percent with no change in condenser
vacuum.
The steam cycle thermal efficiency of a nuclear power plant can be increased by…
A. decreasing power from 100 percent to 25 percent.
B. removing a high-pressure feedwater heater from service.
C. lowering condenser vacuum from 29 inches to 25 inches.
D. decreasing the amount of condensate depression (subcooling)
decreasing the amount of condensate depression (subcooling)
A nuclear power plant is operating at 90 percent of rated power. Main condenser pressure is 1.69 psia
and hotwell condensate temperature is 120°F.
Which one of the following describes the effect of a 5 percent decrease in cooling water flow rate
through the main condenser on steam cycle thermal efficiency?
A. Efficiency will increase because condensate depression will decrease.
B. Efficiency will increase because the work output of the main turbine will increase.
C. Efficiency will decrease because condensate depression will increase.
D. Efficiency will decrease because the work output of the main turbine will decrease.
Efficiency will decrease because the work output of the main turbine will decrease.
A nuclear power plant is operating at 80 percent power with 5°F of condensate depression in the main
condenser. If the condensate depression decreases to 2°F, the steam cycle thermal efficiency will
__________; and the condensate pumps will operate __________ cavitation.
A. increase; closer to
B. increase; farther from
C. decrease; closer to
D. decrease; farther from
increase; closer to
What is the approximate value of condensate depression in a condenser operating at 27 inches Hg
vacuum with a condensate temperature of 100°F?
A. 2°F
B. 4°F
C. 8°F
D. 16°F
16°F
A main condenser is operating at 28 inches Hg vacuum with a condensate outlet temperature of 92°F.
Which one of the following is the approximate amount of condensate depression?
A. 5°F
B. 9°F
C. 13°F
D. 17°F
9°F
Main turbine exhaust enters a main condenser and condenses at 126°F. The condensate is cooled to
100°F before entering the main condenser hotwell. Assuming main condenser vacuum does not
change, which one of the following would improve the thermal efficiency of the steam cycle?
A. Increase condenser cooling water flow rate by 5 percent.
B. Decrease condenser cooling water flow rate by 5 percent.
C. Increase main condenser hotwell level by 5 percent.
D. Decrease main condenser hotwell level by 5 percent.
Decrease condenser cooling water flow rate by 5 percent.
A nuclear power plant is maintained at 2,000 psia with a pressurizer temperature of 636°F. A
pressurizer relief safety valve is leaking to a collection tank which is being held at 10 psig. With dry
saturated steam in the pressurizer vapor space, which one of the following is the approximate
temperature of the fluid just downstream of the relief valve?
A. 280°F
B. 240°F
C. 190°F
D. 170°F
240°F
A pressurizer relief valve is leaking by with the leakage being collected in a pressurizer relief tank.
The pressurizer pressure is 2,200 psia and the relief tank pressure is 5 psig.
With dry saturated steam in the pressurizer vapor space, which one of the following is the condition of
the fluid just downstream of the relief valve?
A. Superheated steam
B. Subcooled liquid
C. Dry saturated steam
D. Wet vapor
Wet vapor
A nuclear power plant is operating at 100 percent power. As main steam escapes to atmosphere via a
main steam flange leak, which one of the following steam parameters will increase?
A. Enthalpy
B. Pressure
C. Specific volume
D. Temperature
Specific volume
A reactor coolant system is being maintained at 1,000 psia. A leaky pressurizer safety/relief valve is
slowly discharging to a collection tank, which is maintained at 5 psig.
With dry saturated steam in the pressurizer vapor space, what is the approximate enthalpy of the fluid
entering the collection tank? (Assume no heat is lost from the discharge line.)
A. 1,210 Btu/lbm
B. 1,193 Btu/lbm
C. 1,178 Btu/lbm
D. 1,156 Btu/lbm
1,193 Btu/lbm
What is the approximate temperature and phase of the fluid just downstream of the pressurizer relief
valve if it sticks partially open with 2,200 psia in the pressurizer and a 50 psia backpressure?
(Assume the pressurizer vapor space contains dry saturated steam.)
A. 281°F, saturated
B. 281°F, superheated
C. 332°F, saturated
D. 332°F, superheated
281°F, saturated
A routine nuclear power plant shutdown is in progress with a steam bubble (dry saturated steam) in the
pressurizer. Pressurizer pressure is 415 psig and pressurizer pressure and level are slowly decreasing.
The operator suspects a pressurizer power-operated relief valve (PORV) is partially open but the
position indicating lights are not working.
Which one of the following will be the approximate PORV tailpipe temperature if the PORV is
partially open? (Assume downstream pressure is 15 psia and no heat is lost from the tailpipe.)
A. 212°F
B. 280°F
C. 330°F
D. 450°F
330°F
A heatup and pressurization of the reactor coolant system (RCS) is in progress following a
maintenance shutdown. RCS pressure is 800 psia with a steam bubble (97.5 percent quality saturated
steam) in the pressurizer. Pressurizer power-operated relief valve (PORV) tailpipe temperature has
been steadily rising. PORV downstream pressure is 30 psia.
Which one of the following will be the approximate PORV tailpipe temperature if a PORV is leaking
by? (Assume no heat is lost from the tailpipe.)
A. 262°F
B. 284°F
C. 302°F
D. 324°F
284°F
A nuclear power plant is operating at 100 percent power with steam generator pressure at 900 psia. A
steam generator safety valve is leaking dry saturated steam to atmosphere.
Which one of the following is the approximate temperature of the escaping steam once it reaches
standard atmospheric pressure?
A. 532°F
B. 370°F
C. 308°F
D. 212°F
308°F