.AR EW-Ess. Cooling Water (Welch's Highlighted Notes)

Question 1

• Function/Purpose?
• Parameters?
• Pumps/Power Supplies?
• Auto Starts?
• Auto Trips?
• Room Cooling?

Answer 1

• Cools all essential components (Except the DGs) required for normal and emergency shutdown of the plant.
• Rejects heat to the Spray Pond system.
• Maintains ESF system cooling water < 135°F during DBLOCA
• Barrier between RCS and Spray Pond System.
  
  • EW pressure maintained lower than SP system at the EW HX (prevent a radioactive release)
• Backup source of cooling for SFP HXs, RCP’s, CEDM normal ACU’s, normal chillers, and nuclear sample coolers (NC X-tie).

Normal operating parameters:

• ~ 93 psig discharge pressure
• 13,800 to 16,800 gpm

Essential Cooling Water Pumps (EWA-P01 / EWB-P01)

• Normally both in standby
• PBA-S03 / PBB-S04
• Auto Starts [20 second TD] (can be reset from MCR HS)
  
  • SIAS
  • LOP
  • AFAS-1 or AFAS-2
  • CREFAS
  • CRVIAS
  • CSAS
• Auto Trips
  
  • Load Shed (LOP/LS)
  • Electrical Protection (can be reset from MCR HS)
• Room cooling:
  
  • Aux Bldg HVAC (HA) cools the pump room.

Essential Chilled Water (EC) cools the EW Pump Room Essential ACU. (Starts when EW Pump breaker closes)

Question 2

Radiation Monitors (SQ)?

A Train EW Cross-tie to NCW MOVs (UV-145 / 65)

• Auto Closure:
  
  • Train A ?…
  • low level in what?…
• Aligned also to …?

Answer 2

Radiation Monitors (SQ)

• RU-2 (train A) and RU-3 (train B)

A Train EW Cross-tie to NCW MOVs (UV-145 / 65)

• Auto Closure:
  
  • Train A SIAS (can be overridden) – ensures EW available for SDC HX
  • EW “A” Surge Tank low level
• SIAS bypasses the thermal overload protection of each valve.
• B train cross-tied with manual valves only.
• NCW can also be aligned to supply the SDC HX (used if EW not available for SDC HX)

Question 3

LCO 3.7.7 Essential Cooling Water (EW) System?

Answer 3

LCO 3.7.7 Essential Cooling Water (EW) System

• Both trains required to be operable in Modes 1-4.
• One train inoperable: restore in 72 hours or RICT
  
  • Requires associated SDC train to be declared inoperable (in Mode 4) (LCO 3.0.6 exception)
• Both trains inoperable: restore one within 1 hour or RICT (cannot voluntarily enter)
• Supports Containment Spray (SDC HX)
• Cools containment sump fluid (via SDC HX) as it is supplied to the RCS by the ECCS during an accident.
• Cool the unit from SDC entry conditions (T_cold < 350°F) to MODE 5 (210°F) during normal and post-accident operations.
• Isolation of EW to SDC HX would render both EW System and SDC system inoperable.
  
  • Outside of acceptable system limits.
  • EW isolated to EC chiller would only make EC inoperable.
• EW supplying NCW priority loads: EW train and Essential Chilled Water train are inoperable
• EW cross-tied only to Fuel Pool cooling, operability is maintained if flow balancing is performed.

Question 4

Refrigerant Head PCVs (RHPCV) / bypass valves

• PCVs downstream of the Essential Chiller condensers.
  
  • Refrigerant pressure in the condenser is used to position PCV.
  • Lowers the EW flow rate through the condenser at low chiller loads.
  • Manual override – Essential chiller is inoperable
• Bypass valves around the RHPCVs. (normally locked closed)
  
  • Ensures adequate condenser cooling during the most limiting EW system condition (17% degraded EW pump while being aligned to PC HXs).
  • 720 gpm minimum EW flow to condensers. (Adequate flow during DBA and EW at 132°F)
  • Bypass opened: degraded EW pump and aligned to PC HXs.
• Prevents “stacking”.
  
  • At low cooler load, flow rate through compressor to the condenser is excessively low.
  • Excessive EW heat removal in the condenser due to low EW temps causes hot gas to condense at too high of a rate causing condenser pressure to drop.
  • DP between the condenser and the cooler lowers, reducing the refrigerant flow rate to the cooler.
  • Liquid refrigerant “stacks” up in the condenser causing refrigerant level in the cooler to decrease.
  • Reduces cooling.
  • Chiller trips on low refrigerant temperature.
• Chiller will NOT trip on condenser low flow (defeated). Will trip on high condenser refrigerant pressure.

Answer 4

Refrigerant Head PCVs (RHPCV) / bypass valves

• PCVs downstream of the Essential Chiller condensers:
  
  • Refrigerant pressure in the condenser is used to position PCV.
  • Lowers the EW flow rate through the condenser at low chiller loads.
  • Manual override – Essential chiller is inoperable
• Bypass valves around the RHPCVs. (normally locked closed):
  
  • Ensures adequate condenser cooling during the most limiting EW system condition (17% degraded EW pump while being aligned to PC HXs).
  • 720 gpm minimum EW flow to condensers. (Adequate flow during DBA and EW at 132°F)
  • Bypass opened: degraded EW pump and aligned to PC HXs.
• Prevents “stacking”:
  
  • At low cooler load, flow rate through compressor to the condenser is excessively low.
  • Excessive EW heat removal in the condenser due to low EW temps causes hot gas to condense at too high of a rate causing condenser pressure to drop.
  • DP between the condenser and the cooler lowers, reducing the refrigerant flow rate to the cooler.
  • Liquid refrigerant “stacks” up in the condenser causing refrigerant level in the cooler to decrease.
  • Reduces cooling.
  • Chiller trips on low refrigerant temperature.
• Chiller will NOT trip on condenser low flow (defeated). Will trip on high condenser refrigerant pressure.

Question 5

EW Surge Tanks (1 per train)

Level & Function?

Answer 5

EW Surge Tanks (1 per train)

Level Function

48” High level alarm

26” Makeup isolates (“high”)

22” Makeup starts (“low”)

18” Low level alarm

17” (A train only) Auto closes the NCW cross-tie MOVs

14” Makeup isolates (prevent depleting DW inventory)

Question 6

EW Surge Tanks (1 per train):

Normal level range?

normal/backup/emergency?/alt water make up to it?

N2 used? for what?

EW vs SP pressures?

Hi/Lo Alarms?

Answer 6

EW Surge Tanks (1 per train):

Normal level range:

• 22 – 26” during standby
• 22 – 47” during system operation.
• Makeup SOVs (EWA-LV-91 and 92) auto open / close
  
  • Fails closed.
• DI water (DW) is the normal source of water
• Backup available from CT or CM
• Fire protection (FP) can be aligned with a hose connection
• Relief valve (15 psig) and vacuum breaker
• N2 from service gases (GA) added to prevent oxygen intrusion / corrosion (1 psig)
  
  • Back pressure regulating valve vents to the Auxiliary Building HVAC system.
  • Not required for NPSH
• Levels / N2 pressure bands maintain EW HX pressure below spray pond system pressure.
• Hi / Lo Pressure Alarms: 5 psig / 0.3 psig

Question 7

MCR Alarms:

• ESS CLG WTR SYS TRBL
  
  • Surge Tanks Hi-Lo level
  • Pump Discharge Temp High
  • Pump Electrical Overload
  • Surge Tank Hi-Lo pressure
• ESS CLG WTR PUMP A DSCH PRESS HI-LO
  
  • Alarm response directs stopping the associated Essential Chiller if the EW pump is stopped and chiller is running
• ESF EQPT RMS LVL HI
  
  • EW Pump or HX Room Hi Levels

Answer 7

MCR Alarms:

• ESS CLG WTR SYS TRBL
  
  • Surge Tanks Hi-Lo level
  • Pump Discharge Temp High
  • Pump Electrical Overload
  • Surge Tank Hi-Lo pressure
• ESS CLG WTR PUMP A DSCH PRESS HI-LO
  
  • Alarm response directs stopping the associated Essential Chiller if the EW pump is stopped and chiller is running
• ESF EQPT RMS LVL HI
  
  • EW Pump or HX Room Hi Levels

Question 8

TLCO 3.8.102 - MOV Thermal Overload (TOLs) Protection and Bypass devices:

Answer 8

TLCO 3.8.102 - MOV Thermal Overload (TOLs) Protection and Bypass devices:

The Thermal Overload protection devices, integral with the motor starter, of each valve used in safety systems shall be FUNCTIONAL.

Applicability: Whenever the MOV is required to be OPERABLE/FUNCTIONAL.

Question 9

73ST-9EW01 - EW sytem ST

Answer 9

73ST-9EW01 - EW sytem ST

Ensure EW pumps meet DB criteria PDM group will gather vib data & to gather pumps pressure data.