Shield Cooling

Question 1

What is the purpose of the Shield Cooling System

Answer 1

Designed to maintained structural concrete temperature less than 165 F, preventing weakening of the concrete due to moisture loss

Question 2

When is the Shield Cooling System required to be in service?

Answer 2

When PCS temperature > 165 F

Question 3

What is required if concrete temperature can’t be maintained below 165 F?

Answer 3

Commence a controlled plant shutdown

Question 4

What are the power supplies for P-77A/B, Shield Cooling Pumps

Answer 4

P-77A - MCC-2

P-77B - MCC-1

Question 5

What are the control room controls for the shield cooling pumps?

Answer 5

• 3 position handswitch CLOSE/TRIP/PULL TO STANDBY
• CLOSE - starts pump
• TRIP - stops pump
• PULL TO STANDBY - places pump in standby. pump will auto start on low pressure of 35 psig

Question 6

What is the low discharge pressure alarm setpoint for the shield cooling pumps?

Answer 6

35 psig

Question 7

How many shield cooling coil sets are there?

Answer 7

2 (A and B)

Question 8

How many coils are in each shield cooling coil set?

Answer 8

1 floor slab coil and 3 wall coils

Question 9

What are the shield cooling temperature and flow alarms?

Answer 9

120 F

80 gpm

Question 10

CV-0932/0934, Coil Inlet Supply Valves, design features

Answer 10

• Fail open
• OPEN/CLOSE keyswitch in Control Room
• Interlocked so when the valve is closed, its coil set low flow alarm is bypassed

Question 11

Shield Cooling Surge Tank design features

Answer 11

• Sized such that the tank will not overflow from a temperature rise from 60 F to 212 F
• Makeup water is from T-81

Question 12

CV-0939, Shield Cooling Containment Isolation Valve

Answer 12

• Closes on CHP/CHR

- Normally closed to isolate makeup water from the tank, because CV-0927, Surge Tank Makeup Valve, leaks by

Question 13

How are chemicals added to the Shield Cooling System?

Answer 13

Chem add tank on east mezzanine is no longer used. Sodium Nitrite is added directly to the tank