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Flashcards in Shutdown Cooling Deck (13)

What is purpose of SDC?

Removes PCS decay heat during Rx shutdown.  Transfers heat from PCS to CCW

Cool PCS from 300°F to refueling temp assuming CCW inlet temperature of 90°F


What are SDC design limits?


270 psia.

SDC Hxs will cool the PCS to 130°F and maintain it at 130°F 27 ½  hours after reactor shutdown with 90°F CCW temperature and a fully irradiated core


Draw and label a one-line diagram of the Shutdown Cooling System showing system interfaces and the following major components:

  • P-67A/B, LPSI Pumps
  • E-60A/B, Shutdown Cooling Heat Exchangers
  • Shutdown Cooling control room operated valves
  • RV-0401, SDC Water Return Line Relief
  • RV-3164, SDC Suction Relief



Describe power supplies, controls and interlocks for MO-3015/3016.


  • Switches at C-33 and Control Room are in parallel, either switch will open/close the valve.

Power Supplies

  • MO-3015 - MCC-1
  • MO-3016 - MCC-2


  • PS‑0104A - MO-3015
  • PS‑0104B - MO-3016
    • PCS <275 psia (260 psig) allows openning
    • Procedural pressure limit is <265 psia to enable MO‑3015 and 3016 to be opened.


What is the basis for the procedural limitations / interlocks on opening MO-3015/3016?

Set to not violate the equipment limitations. 

  • 265 psia maintains the plant pressure less than the LTOP pretrip alarm setpoint.  
    • Pretrip alarm setpoint was established to prevent exceeding 270 psia.
    • 270 psia setpoint is based on the limitation of the shutdown cooling piping. 
  • Instrumentation inaccuracies and corrections for pressure due to instrumentation location reduce the 300 psia value to 270 psia.


What is required on SDC to protect agains over pressure?

  • LTOP System is operable with channels in SDC position.
  • PCS is vented via a vent path capable of relieving 167 gpm at a PCS pressure of 315 psia.


With the PCS pressurized, what limitations are on MO-3015/3016 operating ability if already open?

When the PCS is pressurized AND MO-3015 and MO‑3016 are OPEN, THEN power shall be maintained to at least one of the two valves.  This prevents an unisolable PCS leak if RV-3164 fails open.


What is purpose, setpoint and relief path of RV-0401?


  • Protects piping between MO-3015 & 3016

Setpoint: 2485 psig

Relieves to the PSDT, T-74


What is purpose, setpoint and relief path of RV-0402/0403?

RV‑0402 and RV‑0403

  • Setpoint: 500 psi
  • Protect the SDC Hxs (tube side) and piping from pressure developed due to an increase in ambient temperature in safeguards room.
  • Relieve to the Engineered Safeguards Sump.


What is purpose, setpoint and relief path of RV-03164, SDC Suction Relief?

RV-3164 SDC Suction Relief

  • Setpoint: 300 psig
  • Overpressure protection for SDC suction piping.  Postulated event is intermediate letdown pressure controller failure/misoperation while in solid plant pressure control with SDC in operation.
  • Relieves to the Quench Tank, T-73


What are the LPSI Pumps Inlets from SIRWT Valves?

  • MO-3189 (P-67B suction) from SIRWT
  • MO-3198 (P-67A suction) from SIRWT


What are the LPSI Pumps Inlets from SDC Valves?

MO-3190 (P-67B suction from PCS)

MO-3199 (P-67A suction from PCS)


What are the LPSI pump specs?

Single Stage, Horizontal, Centrifugal

3,000 gpm

o   Maximum Flow - 4,500 gpm

o   Minimum Flow - 163 gpm

·         Design Head - 350 ft

o   Shutoff Head - 410 ft

·         Horsepower - 400

·         Seals - Mechanical

·         NPSH Required at 3,000 gpm - 11 ft

Maximum Normal Suction Pressure - 270 psia