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Catawba Nuclear Station > Residual Heat Removal System(ND) > Flashcards

Residual Heat Removal System(ND) Flashcards

1
Q

What are the primary purposes of the Residual Heat Removal System?

A
  1. Transfer heat from the Reactor Coolant System to the Component Cooling System - reduces the temperature of the Reactor Coolant System to cold shutdown temperatures.
  2. Serves as part of the ECCS system(low head) during a Design Basis Event.
  3. Provides auxiliary Containment Spray if required.
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2
Q

What are the secondary functions of the Residual Heat Removal System?

A
  1. Transfer refueling water between the Refueling Water Storage Tank(FWST) and the Refueling Cavity.
  2. Overpressure protection for the Reactor Coolant System.
  3. Reactor Coolant letdown for shutdown pressure control and purification.
  4. Provides auxiliary Pressurizer Spray.
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3
Q

What is the Residual Heat Removal System Mission Time?

A
  1. The ND pumps supply long term core cooling either via RHR to maintain cold shutdown for non-LOCA accidents or sump recirculation for LOCA accidents.
  2. The ND system mission time is based on the ECCS mission time, which is 30 days. ECCS mission time is based on Containment Sump screen evaluation.
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4
Q

What is the system designator for the Residual Heat Removal System?

A

ND

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5
Q

What is the basic ND Injection Phase flow path?

A

Normally aligned to inject from the FWST, through the ND Heat Exchangers, to the NC Cold Legs when a Safety Injection signal is received. If NC pressure is higher than ND pumps’ discharge pressure they will run on minimum flow.

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6
Q

What is the basic ND Recirculation Phase flow path?

A

When the Refueling Water Storage Tank(FWST) volume reaches the low-level setpoint, the ND suction is automatically aligned for the recirculation phase of operation. The ND pumps will take a suction off of the Containment Sump, cool that water through the ND Heat Exchangers, and provide pressure and flow to the Safety Injection(NI) pumps and the Chemical and Volume Control(NV) pumps. The NI and NV pumps then inject into the core through the NC Cold Legs.

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7
Q

What level in the FWST will cause an automatic ND suction shift to the Containment Sump?

A

Approximately 20 percent

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8
Q

What is the basic ND Normal Cooldown flow path?

A

The ND pumps take a suction from the B and C Hot Legs. Reactor Coolant flows through the ND Heat Exchangers to remove decay heat. Flow is then returned to the NC system via the Cold Legs.

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9
Q

Where are the ND Suction From NC Hot Leg Valves operated from?

A
  1. MC-11
  2. Auxiliary Shutdown Panel
  3. Standby Shutdown Facility(ND-2A and ND-37A)
  4. Alternate Source of power from opposite train MCCs(ND-1B and ND-37A)
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10
Q

What are the design characteristics of the ND pumps?

A
  1. Single Stage
  2. Vertical
  3. Centrifugal Pump
  4. Design flow 3300gpm at 163psig
  5. Shutoff head is approximately 200psig
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11
Q

What cools the ND Pump Seal Water Heat Exchangers?

A

Component Cooling(KC)

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12
Q

Where can the ND Pumps be operated from?

A
  1. Control Room

2. Auxiliary Shutdown Panel

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13
Q

What is the power supply to the ND Pumps?

A
  1. ETA

2. ETB

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14
Q

What are the design characteristics of the ND Heat Exchangers?

A
  1. Each Heat Exchanger is 100% capacity
  2. Vertical shell and U-tube type
  3. Cooling is provided by the Component Cooling System(KC)
  4. Rate of heat removal for the NCS is controlled by the position of the Heat Exchanger Outlet Valves(ND-26 and ND-60).
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15
Q

What is the purpose of the Hot Leg Loop Suction Relief Valves(ND-3 and ND-38)?

A

They protect the system from inadvertent over pressurization during plant cooldown or startup when the Hot Leg Suction Valves are open.

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16
Q

What is the setpoint for the Hot Leg Loop Suction Relief Valves?

A

450psig, and capable of relieving 900gpm

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17
Q

What is the purpose of the FWST to ND Pump Suction Valves(FW-27A and FW-55B)?

A
  1. They are normally open for the injection flow path.
  2. Closed when the ND System is aligned for decay heat removal, or when ECCS is aligned for recirculation mode.
  3. Manually operated from MC-11
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18
Q

What is the purpose of the Containment Recirculation Sump Suction to ND Pump Valves(NI-185A and NI-185B)?

A
  1. Normally closed
  2. Can be manually operated from MC-11
  3. Opened when ECCS is aligned for recirculation mode.
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19
Q

What is the purpose of the ND Pump Discharge Relief Valves(ND-31, 35, and 64)?

A
  1. Protect the ND System from over-pressurization due to valve back-leakage from the NC System.
  2. Relieve to the Recycle Holdup Tank(RHT)
20
Q

What is the setpoint for the ND Pump Discharge Relief Valves?

A

600psig

21
Q

What is the purpose of the ND Pump Minimum Flow Isolation Valves?

A
  1. Protects the pumps from cavitation at low flow conditions.
22
Q

When will the ND Pump Minimum Flow Isolation Valves automatically open and close?

A
  1. Automatically opens when the associated pump is running and flow from pump discharge is less than 500gpm
  2. Automatically closes when the ND Pump discharge flow is greater than 1400gpm, or when the associated ND pump is secured.
23
Q

What is the purpose of the Component Cooling to ND HX Valves(KC-57A and KC-82B)?

A
  1. Air operated valves that control KC flow to the ND Heat Exchanger to support shutdown operations
  2. Controls for 5000gpm KC flow
  3. Will fail open during a Safety Injection
  4. Will fail open during transfer to ASP
24
Q

What is the purpose of the ND Heat Exchanger Outlet Control Valves(ND-26 and ND-60)?

A
  1. Air operated butterfly control valves
  2. Normally open
  3. Used to establish the heat removal rate from ND
  4. Manually controlled from MC-11
  5. Can be controlled locally using “manual loaders”
25
Q

What is the purpose of the ND Heat Exchanger Bypass Control Valves(ND-27 and ND-61)?

A
  1. Air operated butterfly control valves on ND Heat Exchanger bypass line that automatically maintain the desired total system flow.
  2. Controlled from MC-11 normally(normally set to 3300gpm)
  3. Fails closed on a Safety Injection signal to prevent bypassing the ND Heat Exchanger.
  4. Can be controlled locally via local M/A station when associated ASP is placed in LOCAL
26
Q

What is the purpose of the ND Header to NC Cold Leg Valves(ND-173A and ND-178B)?

A
  1. Normally open with power removed to preclude inadvertent closure.
  2. If ND is required for ECCS Hot Leg Recirculation these valves will be closed.
27
Q

What is the purpose of the ND Pump Crossover Line Valves(ND-32A and ND-65B)?

A
  1. Normally open
  2. Allows either train of ND to inject into NCS during accident conditions
  3. Controlled from MC-11
28
Q

What is the purpose of the ND System Return to FWST Valve(ND-33)?

A
  1. Normally locked closed
  2. Used for:
    A. Transferring reactor coolant water between the NCS and the FWST
    B. Transferring reactor coolant water from Refueling Cavity to the FWST
    C. Gravity fill of the NCS during a loss of RHR
29
Q

What is the purpose of the ND Header A and B Hot Leg Injection Isolation Valve(ND-183B)?

A
  1. Normally closed with power removed

2. Used to align ND in Hot Leg recirculation if neither NI train can be aligned

30
Q

What is the purpose of the ND Train to Auxiliary Pressurizer Spray Valves(ND-90 and ND-91)?

A
  1. Normally closed with power removed
  2. Allows aligning ND to the NC Pressurizer for Auxiliary Spray
  3. Controlled from MC-11
31
Q

What is the purpose of the Pressurizer Aux Spray Control Valve?

A
  1. Normally closed
  2. Controls flow of ND water into the Auxiliary Pressurizer Spray Header.
  3. Controlled from MC-11
32
Q

What is the purpose of the ND Heat Exchanger Outlet to Letdown Heat Exchanger Valves(ND-24A and ND-58B)?

A
  1. Normally Closed
  2. Allows aligning ND to the Chemical and Volume Control(NV) System for letdown
  3. Allows for system cleanup during shutdown conditions when NC system pressure is low
  4. Controlled from MC-11
33
Q

What is the purpose of the NV Flow to Letdown Heat Exchanger Valve(NV-135)?

A
  1. Normally closed
  2. Controls the flow of ND water into the Letdown Heat Exchanger
  3. Normally controlled from MC-10
  4. Has a local manual loader for control during fire
34
Q

What is the purpose of the ND Supply to NV and NI Pumps Valves(ND-28A and ND-136B)?

A
  1. Normally closed
  2. Controlled from MC-11
  3. Aligns ND discharge to suction of the NI and NV pumps during ECCS “Piggy-Back” recirculation mode.
35
Q

What is the purpose of the ND Pump to Auxiliary NS Spray Header Valves(ND-43A and ND-38B)?

A
  1. Normally closed
  2. Controlled from MC-11
  3. Allows ND to provide backup to the Containment Spray(NS) System
36
Q

What is the power supply to the ND Motor Operated Valves?

A

Essential 600 VAC MCCs

37
Q

What is the ND system interrelationship with Refueling Water(FW)?

A

FWST emergency suction source for ND Pumps & allows ND to fill & drain refueling cavity from/to FWST during outages

38
Q

What is the ND system interrelationship with the Auxiliary Shutdown Panel(ASP)?

A

Controls available when in LOCAL to put the ND system in service in RHR mode

39
Q

What is the ND system interrelationship with the Standby Shutdown Facility(SSF)?

A

Controls available for ND-2A and ND-37A, Hot Leg Suction Valves

40
Q

What is the ND system interrelationship with the Safety Injection System(NI)?

A

ND provides suction to NI Pumps in Cold Leg Recirculation(CLR) on FWST low-low level

41
Q

What is the ND system interrelationship with the Chemical and Volume Control System(NV)?

A
  1. ND provides suction to NV Pumps in Cold Leg Recirculation(CLR) on FWST low-low level
  2. ND also supplies a low pressure letdown to the inlet of the Letdown Heat Exchanger during normal shutdown and plant heat/cooldown operations.
42
Q

What is the ND system interrelationship with the Component Cooling System(KC)?

A

Cooling for the ND Pump motor stators, motor bearing oil reservoirs, ND pump seal water heat exchangers, and ND Heat Exchangers.

43
Q

What is the ND system interrelationship with the Containment Valve Injection Water System(NW)?

A

Injects water between the discs of double disk gate valves at a pressure higher than Containment design pressure preventing leakage past these valves & reducing potential off-site dose.

44
Q

What is the ND system interrelationship with the Reactor Coolant System(NC)?

A

ND system provides water and boron from the FWST during a LOCA, provides for normal heatup and cooldown, provides low temperature overpressure protection(LTOP) at low NC system temperatures.

45
Q

What is the precaution and limitation about operating the ND Pumps at low flow conditions?

A

The ND pumps shall NOT be operated at flows less than 500gpm for more than 3 continuous hours.

46
Q

What is the purpose for supplying alternate power to ND Hot Leg Suction Isolation Valves ND-1B and ND-37A?

A
  1. The valves are located inside Containment and may not be readily accessible for manual operation.
  2. The alternate source of power is only expected to be used on one train due to the loss of normal safety related power supply.
  3. Open/Close Pushbuttons are located on the alternate power supply MCC.
  4. When the valves are controlled using alternate power all interlocks are disabled.
47
Q

What is the basic procedure for supplying alternate power to ND Hot Leg Suction Isolation Valves ND-1B and ND-37A?

A
  1. Verify normal and alternate power supplies are OFF
  2. Normal and alternate power supplies are red tagged OFF and maintenance personnel remove fuses for the valve.
  3. The appropriate electrical penetration box is opened and the normal power supply cables are disconnected. The alternate power supply cables are then connected utilizing the proper PPE.
  4. The tags on the alternate power supply breaker are cleared and the breaker is closed.
  5. The respective valve can now be manipulated at the face of the alternate MCC breaker using E-30 Switch.

Catawba Nuclear Station (72 decks)

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