ECCS

Question 1

STATE the two functions of the Emergency Core Cooling System (ECCS).

Answer 1

• Remove the stored and fission product decay heat from the reactor core so that fuel rod damage, to the extent that it would impair effective cooling of the core, is prevented.
• Provide additional shutdown reactivity following initiation of any of the following design base accidents (DBA):
• Loss of Coolant Accident (LOCA)
• Rod Ejection Accident
• Loss of Secondary Coolant Accident (Steam or feedwater system break)
• Steam Generator Tube Rupture (SGTR)

Question 2

LIST the five ECC subsystems

Answer 2

1. Refueling Water Storage Tank (RWST)
   • Source of primary grade, borated, injection water
2. High Head Injection System (HHI)
   • Charging pumps inject borated water at elevated RCS pressure
3. Intermediate Head Injection System (IHI)
   • Safety Injection pumps inject borated water at intermediate RCS pressure
4. Safety Injection Accumulators
   • Refill reactor vessel downcomer for major LOCAs
5. Low Head Injection System (LHI)
   • RHR pumps inject borated water at low RCS pressure

Question 3

RECALL the RWST parameters that have Technical Specification limits

Answer 3

• 477,000 gallons required by Tech Specs
• Boron Concentration - 2400 to 2600 ppm (COLR)
• Tech Spec temperature 50 to 98°F

Question 4

DESCRIBE how to fill the RWST

Answer 4

Filled from the Control Room using the Boric Acid Blender

Question 5

DESCRIBE the function of the primary component cooling water supplied to the safety injection pumps (SIPs).

Answer 5

PCCW used for oil coolers ~ 45 gpm

And heat exchangers

Question 6

For each of the ECC subsystem related pumps, DESCRIBE the specific means to prevent pump overheating when pumping against shutoff head.

Answer 6

There is recirc flow back through a cooler back to the pump suction (CCP, RHR) or to the RWST (SIP)

Question 7

RECALL the sequence of injection as the ECCS responds to decreasing pressure in the RCS.

Answer 7

HHI at < 2600#
IHI at < 1530#
Accumulators at < 650#
LHI at < 200#

Question 8

EXPLAIN the function of the flow throttling valves located in the branch discharge lines of the high head and intermediate head injection flow paths

Answer 8

Orifices and throttle valves provide for flow balancing and prevention of runout

Question 9

EXPLAIN why and how a quarterly flow test of the ECCS pumps is performed

Answer 9

Pump runs are conducted quarterly to ensure the pump can achieve it’s rated head and flow while on recirculation.
Conducted to prove that the safety related pumps are operable.
A component lineup verification is performed monthly on the ECCS to ensure the alignments are correct.