Shutdown Cooling

Question 1

What is purpose of SDC?

Answer 1

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

Question 2

What are SDC design limits?

Answer 2

300°F

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

Question 3

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

Answer 3

Draw

Question 4

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

Answer 4

Controls

• 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

Interlocks

• 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.

Question 5

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

Answer 5

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.

Question 6

What is required on SDC to protect agains over pressure?

Answer 6

• 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.

Question 7

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

Answer 7

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.

Question 8

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

Answer 8

RV-0401

• Protects piping between MO-3015 & 3016

Setpoint: 2485 psig

Relieves to the PSDT, T-74

Question 9

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

Answer 9

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.

Question 10

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

Answer 10

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

Question 11

What are the LPSI Pumps Inlets from SIRWT Valves?

Answer 11

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

Question 12

What are the LPSI Pumps Inlets from SDC Valves?

Answer 12

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

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

Question 13

What are the LPSI pump specs?

Answer 13

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