Week 1: Pressurizer

Question 1

What is the function of the Pressurizer?

Answer 1

Serves as a surge volume for the RCS

Maintains RCS pressure high enough to preclude DNB and low enough to prevent damage to RCS

Provide means to relive pressure during an overpressure condition.

Provide for overpressure protection when system pressure is below normal operating temperature.

Question 2

What is the design basis of the Pressurizer?

Answer 2

System designed to accommodate the following transients w/o Rx trip:

Loading or unloading at 5%/min w/ auto rod control
Instantaneous (step) load changes of +/- 10% w/ auto rod control
Step load reduction of 50% w/ auto rod control and Steam Dump Valves (System) operating.

Question 3

What components make up the Pressurizer?

Answer 3

Heaters, variable and backup
2 spray valves
2 PORVs
3 Safety Valves
PZR Relief Tank
4 Pressure Transmitters
4 Level Transmitters
3 Temperature Elements

Question 4

What is the function and setpoints of the Pressurizer Heaters?

Answer 4

The Variable heaters cycle on and off to maintain PZR pressure between 2220-2250 psig.
The Backup heaters turn on at 2210 psig in the event that the variable heaters cannot maintain pressure on their own.

Question 5

What is the function and setpoints of the Pressurizer Spray Valves?

Answer 5

The Spray valves begin to open at 2260 psig and are full open at 2310 psig. This is done to reduce pressure back into the normal operating band.

Question 6

What is the function and setpoints of the Pressurizer PORVs?

Answer 6

The PORVs open at 2335 psig and shut at 2315 psig. They seek to limit PZR pressure increases before the Rx trip/PSSVs actuate.

Question 7

What is the function and setpoint of the Pressurizer Safety Valves?

Answer 7

The PSSVs actuate at 2485 psig to protect the RCS from overpressurization.

Question 8

What is the function of the Pressurizer Relief Tank?

Answer 8

To serve as a surge volume for any water relieved from the Pressurizer through the PORVs or PSSVs.

Question 9

Describe the Pressurizer Level Control program.

Answer 9

557 deg. F is 25%
588.5 deg. F is 61.5%
Linear ramp between them

Question 10

Describe the protection setpoints associated with Pressurizer Level.

Answer 10

92% - Level Rx trip if P-7 present
17% - Heaters off & Letdown Isolation

Question 11

Describe the Pressurizer Pressure control setpoints.

Answer 11

2485 Safeties Relief
2385 Rx Trip Hi P
2335 PORVs open
2315 PORVs shut (on decreasing)
2310 Sprays on (full open)
2260 Sprays ramp open
2250 High band heaters off
2235 Normal Setpoint
2220 Low band heaters on
2210 backup heaters on (decreasing), off at 2218 (increasing)
2185 Low P PORV iso block valves auto (auto resets on increasing)
1970 P-11 for SI manual bypass (auto resets on increasing)
1885 Rx Trip Lo P
1849 SI injection