NS

Question 1

What are the 3 purposes of NS?

Answer 1

o Removes thermal energy from containment in the event of a LOCA in conjunction with the ECCS which subcools the RX by direct injection
o Keeps containment below 15 psig after all ice has melted (~1 hr) while steam generation in the core is continuing.
o Removes iodine from the post-accident containment atmosphere

Question 2

List 7 CR indications/alarms?

Answer 2

o RN to NS HX flow
o NS HX outlet temp
o Containment pressure
o Pump amps
o NS pump flow
o NS/ND sump level
o Stat lights for Train A/B CPCS inhibit for VX and NS
Light lit will prevent pump (or fan) from starting

Question 3

o Prevent exceeding the design negative pressure in containment and prevent inadvertent operation of NS
o 4 pressure switches per train that prevent/terminate spray or CARF below 0.35psig
 1 for each set of NS discharge valves and a pump
o Failures
 If a pressure switch has failed and NS will not run, operator may put the CPCS panel into Test and spin the test potentiometer to get the component to reposition.

Answer 3

CPCS

Question 4

What is the interlock dealing with the suction valves from RX Sump?

Answer 4

Interlocked to prevent opening (NS-1/18) unless NI-184/185 are open and the FWST suction valves (NS-3/20) are closed

Question 5

What is it cooled by and when does it start, NS Pump Room AHU?

Answer 5

o RN cooled
o Auto starts
When the respective pump starts
 Ss signal (Starts both rooms even if pumps are off)
o Maintains room below 145 degrees (TS limit)

Question 6

What is the NS HX cooled by?

What EMF monitors it?

Answer 6

o RN cooled

Outlet monitored by EMF-45, no auto actions

Question 7

Interlocks associated with Containment Isolation Valves of NS?

Answer 7

Normally closed MOV’s
Two per train (each pump discharge is one train)
Interlocks
At least one discharge vale must be open and energized to start its respective pump
Both valves closed or with power removed will trip their respective pump
Pump will trip if valves open and they loose power
CPCS must be met

Question 8

What must be meet to Initiate Containment Spray?

Answer 8

Manual from CR only
CPCS must be greater than 0.35 or the discharge valves will not open and the pump will not start
If pressure drops below 0.35 after NS pumps are running
CPCS will stop the pumps and close the valves
Pressure increasing over 0.35 will give the valves and the pump a manual start permissive
Swap to sump
S/I and Seq are reset
FWST at 20 inches
Containment pressure above 3 psig
Sump above 3’