Shield Cooling

Question 1

Is the shield cooling system safety related and what is its purpose?

Answer 1

Not safety related.

Closed loop cooling system

Removes heat from the biological shield surrounding the reactor vessel thereby limiting stresses in the structural concrete.

Question 2

What is the design function of the shield cooling system?

Answer 2

Maintains structural concrete temperature less than 165°F

Maximum normal heat load on the system at full power is 120,000 BTU/hr.

• Each coil set is capable of removing 180,000 BTU/hr
• Heat Exchanger is capable of removing 200,000 BTU/hr
• Each pump is capable of handling 100% of the required cooling water flow for removing 180,000 BTU/hr.

Question 3

P-77A/B, Shield Cooling Pumps

Answer 3

P-77A/B, Shield Cooling Pumps

Capacity - 180 gpm each (100%)

Discharge Pressure –approximately 61 psig

P-77A from MCC 2

P-77B from MCC 1

Question 4

P-77A/B auto starts how?

Answer 4

Pump control switch in “Pull to Standby”

PS-0935 at 35 psig starts pump

• Brings in EK-1302

Question 5

E-64, Shield Cooling Heat Exchanger

Answer 5

E-64, Shield Cooling Heat Exchanger

Heat Removal - 200,000 BTU/hr

Shell - CCW

• Normal Flow 126 GPM
• CHP - 0 GPM

Tube - Shield Cooling Water

HX outlet butterfly valve (MV-CC106) is manually throttled to control system temperature.

Question 6

Shield Wall Cooling Coils

Answer 6

Shield Wall Cooling Coils

Two sets of coils with 3 coil sections in each set

Design Pressure – 75 psig

Design Temperature – 200°F

Normal flow rate is 38 to 43 gpm per coil section and 134 to 154 gpm per coil set (wall section + slab section = coil set).

Question 7

CV-0932 & CV-0934, Coil Inlet Supply Valves

Answer 7

CV-0932 & CV-0934, Coil Inlet Supply Valves

Air operated, fail open diaphragm valves

C-08/03

• Two position OPEN-CLOSE key operated switch
• Red and Green position indicating lights

Interlocked with associated flow alarm so that when valve is closed, low flow alarm is bypassed

Question 8

What does the shild wall coil relieve at?

Answer 8

Each wall coil has a relief valve for overpressure protection due to thermal expansion (100 psig)

Question 9

What are the flow indications for wall coils?

Answer 9

FI-0928, FI-0929, FI-0931 for A Coil

FI-0934, FI-0935, FI-0936 for B Coil

Question 10

What temperature indications are there in the control room?

Answer 10

TE-0931 (TE-0933) – provides control room indication

High temperature alarm at 120°F via TIA-0931 (TIA-0933)

Question 11

What alarms on low flow?

Answer 11

FS-0932 (FS-2104) – provides control room alarm when in-service coil flow decreases to ≤ 80 gpm

Alarm bypassed when inlet supply valve CV-0932 (CV-0934) is closed.

Question 12

What is the design of the Floor Slab Coils?

Answer 12

Two sets of coils with each having 1 section

Design Pressure – 75 psig

Design Temperature – 200°F

Normal flow rate through floor coil is 20 to 25 gpm

Local flow and temperature indication

• FI-2110 (FI-2111)
• TI-2110 (TI-2111)

Question 13

T-62, Shield Cooling Surge Tank

Answer 13

T-62, Shield Cooling Surge Tank

• Capacity - 1,700 gallons
• Design Pressure - 50 psig
• Design Temperature - 200°F

Maintains positive suction head on Shield Cooling Pumps.

Provides surge volume for Shield Cooling Water expansion and contraction.

Provides a point for the addition, recirculation and sampling of chemicals for the system.

Question 14

CV-0927 Shield Cooling Surge Tank Makeup Valve

Answer 14

CV-0927 Shield Cooling Surge Tank Makeup Valve

Air operated diaphragm valve – fails closed

Level Switch (LS-0927) controls tank level

• Opens valve at 23% (34”) and closes valve at 86% (74”)

Makeup supplied from T-81, Primary System Makeup Water Tank

Question 15

CV-0939 Containment Isolation

Answer 15

CV-0939 Containment Isolation

C-13 by two-position OPEN-CLOSE control switch

Automatically closes on Containment High Pressure (CHP) or Containment High Rad actuation (CHR)

Question 16

EK-1303, “REACTOR SHIELD CLG LO FLOW”

Answer 16

EK-1303, “REACTOR SHIELD CLG LO FLOW”

• Actuated by FS-0932 (FS-2104) at 80 gpm
• Check one pump running
• Shift in-service coils
• If necessary, start standby pump

Question 17

EK-1302, “REACTOR SHIELD CLG PUMPS DISCH LOW PRESS

Answer 17

EK-1302, “REACTOR SHIELD CLG PUMPS DISCH LOW PRESS

• Actuate by PS-0935 at 35 psig
• Standby pump starts on low pressure
• Verify standby pump starts - align switches
• Check surge tank level normal
• If low pressure is due to leakage then shift in-service coils

Question 18

EK-1301, “SHIELD CLG PUMPS TRIP

Answer 18

EK-1301, “SHIELD CLG PUMPS TRIP

• Actuated by “b” contact in breaker
• Standby pump starts at 35 psig lowering
• Verify standby pump starts – align switches
• If both pumps tripped or cannot be started, then initiate plant shutdown

Question 19

EK-1304, “REACTOR SHIELD CLG HI TEMP”

Answer 19

EK-1304, “REACTOR SHIELD CLG HI TEMP”

• Actuated by TIA-0931 (TIA-0933) at 120°F
• Check coil outlet temperature
• Check CCW to CNTMT normal
• Start standby pump
• Place standby coil in service
• If flow cannot be restored and Shield Cooling Return temperature rises to greater than 165°F, then initiate plant S/D

Question 20

EK-1305, “SHIELD CLG SURGE TANK T-62 HI LO LEVEL”

Answer 20

EK-1305, “SHIELD CLG SURGE TANK T-62 HI LO LEVEL”

• Actuated by LIA-0927, High – 95%, Low – 4.5%
• CV-0927, Surge Tank Makeup Control Valve opens at 23%, closes at 86%
• If high level, then close CV-0939, Shield Cooling Surge Tank Inlet Isolation until level returns to normal
• If low level, then check open CV-0939, Shield Cooling Surge Tank Inlet Isolation and one P 79, Primary System M/U Transfer Pump running
• If necessary, then bypass CV-0927, Surge Tank Makeup Control Valve using MV CD148, Shield Cooling Makeup CV Bypass
• If level remains high, then direct Chemistry Department to check for CCW in-leakage
• If level remains low, then check for leakage by shifting in-service coils

Question 21

SOP-29 Requirements

Answer 21

SOP-29 Requirements

Shield Cooling System shall be in operation prior to PCS temperature exceeding 165°F

Minimum flow

• Shield wall coil 30 gpm
• Floor slab coil 20 gpm

Maximum system flow

• 154 gpm; limited by heat exchanger.

Flow Balancing

• Minimum ratio – 5 (wall coil) to 1 (floor coil)