pzr

Question 1

LIST the functions of the pressurizer and pressurizer relief tank

Answer 1

• Establishes normal operating pressure during startup
• Maintains coolant pressure during steady state operation, preventing bulk boiling and enabling coolant to remove core heat.
• Limits the pressure changes caused by thermal expansion and contraction during plant transients to acceptable values.
• Prevents reactor coolant system from exceeding the 2735 psig safety limit value.

Question 2

STATE which reactor coolant loops the surge line and spray line are connected to

Answer 2

Spray: loops 1 and 3 cold legs
Surge: Loop 3 hot leg

Question 3

LIST the pressurizer heater groups

Answer 3

Control, A-D

Question 4

STATE the two functions of the pressurizer spray bypass flow

Answer 4

• 1 gpm through each spray line
• Maintains the spray lines warm to prevent thermal stresses to spray line and nozzle.
• Equalizes boron concentration (to prevent reactivity addition during outsurge).

Question 5

DESCRIBE two design methods used to limit the temperature of the PRT

Answer 5

• Relief discharges enter PRT via sparger pipe located below PRT water level (sparger creates mixing action with water to help cool relief flow)
• PRT provided with pump & heat exchanger (cooled by PCCW train ‘B’) to cool tank contents & recirculate back through a spray header.
• RMW enters PRT via Recirulation line for tank makeup

Question 6

DESCRIBE why a nitrogen blanket is maintained on the PRT

Answer 6

• Prevents introduction of air to minimize corrosion

* Prevents build up of explosive mixture of hydrogen

Question 7

DESCRIBE how the PRT is protected from overpressurization

Answer 7

• Two Rupture Discs protect PRT from overpressure

* Blow out to containment if pressure exceeds 91 psig

Question 8

DESCRIBE how the pressurizer acts to maintain system pressure on insurges

Answer 8

• Less heat transfer, so cold leg temp increases
• Tave increases Density decreases
• RCS inventory (volume) increases
• Rx coolant expands into pressurizer compressing the steam bubble
• PZR pressure increases above saturation and bubble condenses which pressure decreases
• Large insurge may cause spray actuation

Question 9

DESCRIBE how the pressurizer acts to maintain system pressure on outsurges

Answer 9

Steam demand is increasing (turbine load increases)
• more heat transfer, so cold leg temp decreases
• Tave decreases Density increases
• Coolant contracts and water flows from Pzr.
• Pzr. Level drops and bubble expands
• PZR pressure decreases below saturation which causes liquid to flash to steam, so pressure increases
• Large outsurege may cause heater actuation

Question 10

DRAW the Pressurizer and PRT and their associated piping. Include interconnections with the Reactor Coolant and Charging systems, as well as potential inlets to the PRT from other major systems

Answer 10

PZR
PRT
2 PORTVs
3 Safeties
3 sprays
1 surge
Head vent
Letdown reliefs
RHR reliefs
N2
RMW
PRT pump
RCDT pumps