Plant Operating Standard

CC-CI-49 Containment Cooling and Containment Isolation

Normal Operations

• 1. One fan is operating with the second fan serving as a standby. The capacity of the operating fan is sufficient to maintain the upper containment temperature below 140F and the lower containment temperature below 115F.
• 2. Both main cooling coils are operating. These coils maintain the average upper containment temperature below 140F, the lower containment below 115F, and the dome below 150F.
• 3. The containment isolation system is in AUTO position for normal operation (including the steam stop valves).
• 4. The oxygen concentration in the containment vessel atmosphere is being maintained at about 8% by inerting with nitrogen.

[The original plan was for the containment vessel to remain inerted, and for personnel to wear self contained breathing apparatus, "gas diving", when entering it. There was an accident, described in "One Upon A Nuclear Ship", and someone nearly died. After that the procedure was changed to purge the containment vessel before entering, and then re-inert it after words. This involved having a truck of nitrogen in one of the cargo holds, and running an additional pipe to it.]

Minimum Condition for Reactor Operation

• 1. Containment cooling system shall maintain the highest temperature in the containment vessel below 150F.
• 2. The containment isolation system is in AUTO position, and all isolation valves are operable to perform their isolation function.
• 3. The oxygen concentration in the containment vessel atmosphere shall be below 10% when the primary system temperature is above 400F and the control rod drive hydraulic system pressure is above 500 psig.
• 4. All containment vessel hatches shall be in place, secured and leak tested prior to criticality, with shielding in place, and there will be no access to the containment with the reactor critical.
• 5. The containment vessel leakage rate must be determined quarterly with an internal pressure of approximately 60 psig.

  [The 60 psig. leak testing operation once damaged the primary system pumps, due to inflicting negative pressure against the cans enclosing the rotors in the pump motors, which then rubbed through.]

Containment Entry, Reactor Shutdown

• 1. The containment vessel must be purged at least one (1) hour prior to entry. The containment purge valves must be closed at all times except when in use for their designed purpose, and when so in use, will be attended in order that immediate closure can be made if the need arises.
• 2. The air lock shall be used for normal access to the containment. Other hatches may not be opened until sufficient time has elapsed since the shutdown to permit replacing the hatch prior to fuel melting in the event of a loss of reactor coolant.
• 3. Entry to the containment through the airlock must be controlled as follows:
  • a. With primary system temperature above 300F, one door of the airlock must be closed at all times.
  • b. With primary system temperature below 300F, but with the primary system pressure above 250 psig or up to and including 2200 psig, both airlock doors may be open, but they shall be continually manned to effect closure if necessary.
  • c. When the primary system temperature is less than 200F, the various containment hatches may be open under the conditions stipulated in paragraph 2.
• 4. Initial entry is to be made under the auspices of the Health Physics group; full protective clothing and face masks are to be worn until atmospheric conditions are established and Health Physics surveys made. They will establish the ambient and surface radiation levels which exist, and the concentration of carbon dioxide and oxygen in the containment atmosphere, as well as the presence of any airborne radioactivity.
• 5. All subsequent entries will be made in accordance with the requirements of Radiation Control Work Permits, which are to be required for this entry.
• 6. Personnel shall never entry or remain in the containment alone (except for the brief period required for an individual to pass through the airlock).