Emergency Operating Procedure

EOP 8 Loss of One Loop Revision 1 11/22/63

A. Causes for an Limitations Imposed by an Idle Loop

• 1. A primary loop may be secured for any of the following reasons:
  • a. Loss of both primary pumps in one loop (electrical or mechanical failure.)
  • b. Excessive leakage of primary water into the steam generator.
  • c. Loss of all feed water to the steam generator. (Refer to EOP #11)
  • d. Closing of the quick-acting steam stop valve.

    The primary pumps in the affected loop must be stopped immediately to prevent the average primary coolant temperature in the non-steaming loop from rising too high, resulting in the lifting of the relieve valves on the secured steam generator. This also prevents the average primary coolant temperature in the steaming loop from decreasing too far, with the possible result of an increase in reactivity due to the sudden decrease in moderator temperature when the pumps in the affected loop are secured.

• 2. The limitations imposed by an idle loop are:
  • a. Maximum reactor power
    • (1.) Two pumps at full speed - 50% full power.
    • (2.) Two pumps at half speed - 20% full power.
  • b. The ships speed will be limited by the maximum reactor power.
  • c. At least one pump must be operating at full speed to permit the reactor to be operated with the start-run switch in the RUN position.
  • d. The rod bottom interlock prevents the starting of a primary pump in an idle loop unless all the control rods are fully inserted.

B. Action Required by Operator

• 1. Reduce reactor power to limitation of:
  • 50% - 2 pumps full speed
  • 20% - 2 pumps half speed
• 2. Close P.S. gate valves in loop to be idled.
• 3. Close steam stop valve SS-1V or SS-4V.
• 4. 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 panel "A".
• 5. Secure idle boiler by closing feedwater, blowdown and chemical addition valves. Maintain water level at 9 inches.
• 6. IF the port loop is the one that has been secured, transfer make up to the primary system from SL-121V to SL-6V and operate manually to maintain Pressurizer level. Secure SL-121V.