rcs

Question 1

STATE the function of the Reactor Coolant System

Answer 1

• The RCS transports the thermal energy produced in the reactor core to the steam generator.
• It forms a boundary to contain the fission products that may be released from the fuel.

Question 2

STATE the function of the Reactor Coolant System component: Reactor Coolant Pumps

Answer 2

The Reactor Coolant Pumps move coolant through the loops to transport thermal energy from the reactor core to the steam generators.

Question 3

STATE the function of the Reactor Coolant System component: Steam Generators

Answer 3

The Steam Generators remove heat from the RCS and generate steam to drive the turbine generator

Question 4

STATE the function of the Reactor Coolant System component: Reactor Vessel

Answer 4

The Reactor Vessel contains all of the core internals, i.e., core support structures, core (fuel assemblies), control rods, and other components

Question 5

STATE the function of the Reactor Coolant System component: Pressurizer

Answer 5

• The Pressurizer establishes and maintains pressure in the RCS and acts as a surge volume.

Question 6

STATE the function of the Reactor Coolant System component: Reactor Vessel Head Vent

Answer 6

• The Reactor Vessel Head Vent allows for the removal of air from the vessel head region during an RCS fill and vent, and also for the venting of gases such as hydrogen during an accident.
• The Reactor Vessel Head Seals provide a method to seal the reactor head to the vessel when the closure bolts are fully torqued

Question 7

STATE the function of the Reactor Coolant System component: Loose Parts Monitoring

Answer 7

The Loose Parts Monitoring System detects the impact of loose objects inside the RCS and warns the operator of their presence

Question 8

DESCRIBE how Flow and temperature are measured in a reactor coolant loop

Answer 8

• Three flow measurements are taken in each loop crossover leg using differential pressure transmitters
• One high pressure penetration and three low pressure penetrations for three flow transmitters per loop
• Each Loop has the following temperature indications:
• Cold leg: 1 NR and 1WR RTD’s

• Hot Leg: 3 NR and 1 WR RTD’s

Question 9

DESCRIBE how RCS level is measured

Answer 9

• Different methods to measure RCS based on condition of the plant :
• Pressurizer Level: Startup / Shutdown / Normal Ops
• RVLIS: Post Accident Monitoring
• RCS Sightglass : Outage
• Ultrasonic Detector: Outage

Question 10

DESCRIBE the flow path of primary and secondary fluids through the steam generator.

Answer 10

• Primary side flowpath:
• From the reactor vessel into the hot leg side of the SG
• Through the U-tubes
• Out the cold leg side to the RCP suction.
• Secondary side flowpath:
• From the feed piping through the J-tubes
• Into the downcomer annulus and up into the tube bundle region
• Steam/water mixture enters the swirl vane (1st stage) moisture separators, exits and enters the chevron (2nd stage) moisture separators
• Then through the flow restrictor into the main steam line

Question 11

DESCRIBE the purpose of the “J tubes” on the steam generator feed ring

Answer 11

• The “J” tubes direct incoming feedwater into the recirculating water plenum just above the downcomer annulus.
• The “J” tubes are designed to prevent water hammer in the feedring and feedwater line by minimizing drain down of the feed ring during momentary losses of feedwater.

Question 12

DESCRIBE the principles of operation of the moisture separation equipment in the steam generator.

Answer 12

• In the 1st stage (swirl vane) seperator the steam/water mixture rises through the separator tubes.
• Moisture droplets are thrown to the interior surface of the tube by the swirl vane blades and is carried up the inner surface by vapor flow.
• Moisture travels over the slotted lip and down the outer barrel.
• This water becomes part of the recirculation flow.
• The 2nd stage (chevron) moisture separator is a two-tiered device consisting of chevron type separator plates.
• They force the steam flow to make several directional changes as it passes through the bank.
• The separated moisture clings to the chevron plates and also becomes recirculation flow.

Question 13

DESCRIBE the function of the following RCP component: impeller

Answer 13

Imparts velocity to the coolant entering the pump suction

Question 14

DESCRIBE the function of the following RCP component thermal barrier heat exchanger

Answer 14

Limits heat transfer from the hot reactor coolant to the area of the pump radial bearing (i. e. inside the thermal barrier).

Question 15

DESCRIBE the function of the following RCP component radial bearing.

Answer 15

Minimizes lateral motion of the shaft.

Question 16

DESCRIBE the function of the following RCP component flywheel

Answer 16

Stores rotational inertia when the pump is running and prolongs the coastdown time of the pump in the event of a loss of power.

Question 17

DESCRIBE the function of the following RCP component anti-reverse rotation device

Answer 17

Prevents the pump shaft of an idle RCP from rotating in the reverse direction when other RCPs are running.

Question 18

DESCRIBE the principles of operation of the three seals in the RCP seal package. Include the destination of seal leak-off from each seal and the normal leak-off rate expected.

Answer 18

• Seal injection flow from the charging pump enters the RCP at approximately 8 gpm is provided to each pump. 5 gpm flows downward through thermal barrier and then into the RCS. Approximately 3 gpm flows upward to the entrance of #1 seal.
• All but 3 gph of #1 seal leakage flow is returned to the CVCS via the #1 seal leakoff piping. The 3 gph flows through #2 seal and is directed to the Reactor Coolant Drain Tank via the #2 seal leakoff piping
• Approx. 800 cc/hr injection flow is provided to the #3 seal by the #3 seal standpipe. Half of this water leaks past the inner dam and joins #2 seal leak-off flow to the RCDT. The remaining water leaks past the outer dam and is directed to the containment sump

Question 19

DESCRIBE why a minimum back pressure (VCT pressure) must be maintained on the number one seal

Answer 19

Minimum VCT pressure (15 psig) ensures #2 seal gets adequate flow.

Question 20

DESCRIBE the function and operation of the RCP lift oil system

Answer 20

• The oil lift system provides an initial film of lube oil between the thrust bearing shoes (both sets) and the thrust runner, and also between the upper shaft journal and the radial bearing pads

Question 21

DESCRIBE the operation of the RCP motor lube oil cooling system and air cooling system.

Answer 21

• The lower bearing sump is cooled by PCCW flowing through the tubes that encircles the inside of the sump.
• The upper bearing oil cooler is an externally mounted shell and U-tube type heat exchanger. Oil is pumped through the shell side by the shaft driven oil pump immersed in the upper oil reservoir. PCCW cools the heat exchanger.
• The motor has a totally enclosed air cooling system. Air is circulated from the motor frame through cooling slots to the two fin type (radiator) heat exchangers and then back into the motor frame. Air is circulated by integral vanes on the rotor. The HXs are cooled by PCCW.

Question 22

DESCRIBE how seal injection flow to the RCPs is adjusted.

Answer 22

• Manual seal injection throttle valves are located upstream of CS-HCV-182 and outside containment in the mechanical penetration area. These valves are adjusted to balance flow to the RCPs.
• CS-HCV-182 is used to adjust all four seal injection flow rates from the MCB

Question 23

SUMMARIZE the conditions that will cause an automatic trip of a reactor coolant pump.

Answer 23

• Phase overcurrent
• Phase differential current
• Ground fault
• Locked rotor
• Sustained low voltage on the 13.8 kV bus (trips both pumps on that bus)
• Low frequency downstream of the RCP breaker (trips all four pumps if one pump on each bus sees underfrequency)

Question 24

SUMMARIZE the purpose of and entry conditions for abnormal operating procedure OS1201.04, RCS Valve Stem Leakage. DESCRIBE the NSO’s actions directed by this procedure

Answer 24

• Abnormal RCDT level or run times on RCDT pumps.

* Computer alarms associated with a high stem leakoff condition.

Question 25

DESCRIBE the normal line-up of the reactor vessel flange leak-off system. Include what indication(s) the operator would have of a leak past a flange seal

Answer 25

• Reactor Leak-off system is normally aligned to detect leakage from the inner seal

Question 26

DESCRIBE the process by which the RCP radial bearing will be cooled and seal water supplied if seal injection flow is lost.

Answer 26

• When normal seal injection flow (pressure) is lost, pressure within the RCS drives flow from the RCP suction through the TBHX and into the thermal barrier.
• The cooled RC water flows upward, cooling the radial bearing and #1 and #2 seals. The #1 seal leakoff path is unchanged.

Question 27

DRAW a basic diagram of the RCS that includes major piping penetrations, similar to Figure 3.5 in the Reactor Coolant System Detailed System Text, Revision 8

Answer 27

4 loops
4 RCPs
4 S/Gs
Normal charging to loop 1 Cold Leg
Alternate charging to loop 4 Cold leg
Accum, SI, RHR to loop cold legs
HHI to all 4 loops cold loops
PZR spray from loop 1 and 3 Cold legs
PZR surge line from loop 3 Hot leg
Flow detectors in the intermediate legs
RCDT pumps from the intermediate legs
Sample system from loop1 and 3 hot legs
Normal letdown and RCDT pumps from loop 3 intermediate legs
Excess letdown from loop 3 Cold leg
SI discharge to loop 2 and 3 hot legs
RHR suction from loops 1 and 4 hot legs