Cold Leg Accumulators(CLA)

Question 1

What is the purpose of the Cold Leg Accumulators?

Answer 1

1. Inject borated water into the cold leg of each reactor coolant loop during a LOCA that depressurizes the reactor coolant system below CLA pressure
2. The Cold Leg Accumulators are a passive, independent subsystem of ECCS that require no automatic or manual action

Question 2

How many Cold Leg Accumulators are there, what is their normal operating pressure, and where are they located?

Answer 2

1. 4 CLAs, one for each cold leg
2. There normal operating pressure is 585psig - 678psig (600psig for our purposes)
3. They are located in the containment outside of the secondary shield

Question 3

What are the Cold Leg Accumulators filled with?

Answer 3

1. Nitrogen overpressure

2. Water

Question 4

What type of LOCA are the Cold Leg Accumulators designed for?

Answer 4

A large or intermediate break loss of coolant accident

Question 5

How many Cold Leg Accumulators are sufficient to counteract the effects of a large break LOCA?

Answer 5

3 CLAs with a minimum volume in each
The fourth CLA is assumed to dump out of the break and bypass the core, but the volume will end up in the sump for injection/recirculation

Question 6

What are the basis for the Boron concentration limits?

Answer 6

1. Minimum - ensures the reactor remains subcritical after a large break LOCA
2. Maximum prevents Borazon precipitation(can block flow channels)

Question 7

What is the status of the Cold Leg Accumulator Discharge Isolation Valves?

Answer 7

They are normally open with power removed when the plant is operating

Question 8

What will cause the Cold Leg Accumulator Discharge Isolation Valves to automatically open?

Answer 8

1. Safety Injection

2. P-11(1955 psig)

Question 9

What will cause the Cold Leg Accumulator Discharge Isolation Valves to automatically close?

Answer 9

Auxiliary Shutdown Panel to LOCAL

Question 10

When are the Cold Leg Accumulator Discharge Isolation Valves opened?

Answer 10

During the startup when pressure is between 800-1000psig because the CLAs are incapable of injecting at that pressure

Question 11

Where is nitrogen for the Cold Leg Accumulators supplied from?

Answer 11

The 650 pound nitrogen header

Question 12

What will automatically close the Nitrogen Supply Isolation Valve?

Answer 12

Phase ‘A’ Isolation signal

Question 13

What will automatically close the Nitrogen Supply Valve to the CLA?

Answer 13

If temperature drops to less than or equal to 65F the valve closes to prevent freezing of the inlet nozzle to the CLA. If temperature rises to 66F the valve will open

Question 14

How many valves are located in the discharge piping of the Cold Leg Accumulator and why?

Answer 14

1. There is one motor operated isolation valve which is normally open
2. There are two check valves to protect the CLA from NC system leakage

Question 15

Where are the Nitrogen Vent Isolation Valves controlled from?

Answer 15

The Control Room

Question 16

What is the precaution when venting the Cold Leg Accumulators?

Answer 16

Nitrogen will displace oxygen so it’s important to verify personnel are not effected during venting evolutions

Question 17

Which Cold Leg Accumulators provide a nitrogen blanket to Pressurizer PORVs?

Answer 17

CLA ‘A’

CLA ‘B’

Question 18

How are the Cold Leg Accumulators filled?

Answer 18

The CLAs are filled with water from the FWST using the NI pumps(NI Pump A is the preferred pump)

Question 19

What will cause the Cold Leg Accumulator Water Supply Isolation Valve to automatically close?

Answer 19

Safety Injection signal

Question 20

Where can the Cold Leg Accumulators be drained to?

Answer 20

1. FWST using the normal fill valves

2. Accumulator sample valves(preferred method)

Question 21

What will cause the Cold Leg Accumulator Sample Valves to automatically close?

Answer 21

Phase ‘A’ Isolation signal

Question 22

What will cause the Nitrogen Supply Isolation Valve to the Cold Leg Accumulators to automatically close?

Answer 22

Phase ‘A’ Isolation