Emergency Operating Procedure

EOP 11 Loss of Steam Generator Level

General

Loss of level in the steam generators due to a leak in the feedwater piping is covered in EOP #3. This procedure deals with a loss of level due to loss of feedwater caused by other casualties, e.g., feed pumps, feedwater valves, leak in feed pump suction, etc.

A. Symptoms

• 1. Important annunciators which may be actuated.
  • a. LOW LEVEL STBD BOILER DRUM.
  • b. LOW LEVEL PORT BOILER DRUM
  • c. LOW FLOW TOTAL STEAM
  • d. LOW STEAM PRESSURE
• 2. Steam pressure and flow drop off.
• 3. Shaft rpm has dropped.
• 4. Low level in one or both boilers.

B. Immediate Action

• 1. Push scram button to unsure that rods have scrammed and to start emergency cooling system if level is lost in both drums.
• 2. If level is lost in only one steam generator:
  • a. Stop PS pumps in that loop.
  • b. Start closing reactor inlet valve in that loop.
  • c. Close quick-closing stop valve on steam generator in which level is lost.
  • d. Close feedwater, blowdown and chemical feed valves on steam generator in which level is lost.
  • e. Reduce reactor power to less than 50%.
  • f. Adjust shaft rpm accordingly.
• 3. Notify bridge.
• 4. If reactor is scrammed, proceed to recover as in step 6 below and succeeding steps.
• 5. Proceed on one loop operation if securing of only one loop was required.
  • a. Turn the average temperature selector switch to the position associated with the loop to be operated.
  • b. Switch the high temperature scram selector switch from the coincidence position to the single position. This switch is located on the temperature coincidence alarm panel inside auxiliary cabinet "A".
• 6. Ascertain problem with feedwater supply and rectify.
• 7. Add feedwater to affected drum(s) slowly to avoid chill shocking the drum(s), until level indication is recovered.
• 8. Shut down the reactor if it is still operating on one loop and make a normal startup with both loops.

  [There is an interlock which does not permit a PS pump to be started unless the rods are all bottomed, if a loop is shutdown, a full restart is required.]

• 9. Make any needed corrections to the water chemistry in the drum(s).