Essential Chilled Water (EC)

Question 1

Per LCO 3.7.10, when are BOTH trains of Essential Chilled Water required?

Answer 1

LCO 3.7.10 Two EC trains shall be OPERABLE
APPLICABILITY: MODES 1, 2, 3, and 4.

Question 2

What is the makeup to the Essential Chilled Water surge tank

Answer 2

• Demineralized Water (DW) is normal makeup water to the Expansion Tank
• CST (CT) (backup)
• Fire Protection

Question 3

What happens to the EC chiller on a loss of EW?

Answer 3

• Condenser high refrigerant pressure (actuates on loss of EW to the condenser)
  o Does NOT trip on low EW flow

Question 4

What is the purpose of the Hot Gas Bypass line?

Answer 4

Hot Gas Bypass
* Prevent surging during low load conditions. (Compressor can’t pump the gas well).
* Hot gas bypass re-directs some of the flow back to the cooler.

Question 5

What is the purpose of the Refrigerant Head Pressure Control Valve (located on the EW outlet from the condenser)?

Answer 5

This valve is necessary to prevent “stacking” which occurs during cold or low load conditions.