Emergency Operating Procedure

EOP 2 Loss of All AC Power to the Main Bus

Revision 1, 2/6/64

A. Symptoms

• 1. All power lost - only ship's emergency lighting an vital bus remains.
• 2. Reactor scrammed automatically due to loss of power.
• 3. The propulsion turbine ahead throttle valve will start closing due to Scram signal as soon as the emergency generator starts.
• 4. The emergency diesel generator will start. Availability of emergency power will be indicated on the mimic bus (RCP of main console).

  [RCP is Right Center Panel.]

• 5. The emergency cooling system will be put into operation automatically. The lights indicating condition of DK system will go out. The indicating lights for the Emergency Cooling System Actuator will shift from WHITE to GREEN indicating that the emergency cooling system master relay has operated.
• 6. EOP #6 Loss of Instrument Air symptoms will occur within a few minutes.

B. Immediate Actions

• 1. Verify that the maneuvering valve is closed or close it.
• 2. Push SCRAM BUTTON to insure that all rods have scrammed.
• 3. Check that the emergency diesel generator has started: If not, push the emergency cooling system actuator start button on the console to put the emergency cooling system into operation.
• 4. Valves PR-2V, PR-3V, PE-1V and PE-3V will stay in their previous position. Close them if necessary.
• 5. Send an operator to the emergency cooling panel on the navigation bridge deck.
• 6. Check emergency cooling system flow on the emergency cooling panel.
• 7. Shut off blowdown from steam drums by closing SS-21V and SS-22V.
• 8. Control DK heat removal from primary system, and pressurizer water level with DK cooler control valve DK-20V using emergency make-up pump DK-P3 as necessary to maintain pressurizer level.

C. Follow-Up Action

• 1. Change console switches of charge pumps and booster pumps to OFF position.
• 2. If ADGs to not start automatically, inspect auxiliary diesel generators and turn selector switches to MANUAL. Open Manual Valve on air line to starting motor and attempt to start the diesel.

  If ADGs do not start and synchronize automatically, manually balance the loads.

  If ADG operation cannot be attained shortly, feed the main board from the EDG. See SOP 6111 par. C)

• 3. Repair one or both auxiliary diesel generators if repairs are required.

  If only one auxiliary diesel generator can be placed in service, proceed with a normal shutdown. If both auxiliary diesel generators can be placed in service, enough power is available to allow a startup at reduced power.

• 4. Start corrective measures to allow placing the turbine generators in service if possible.

D. Discussion

A loss of power from either turbine-generator will normally result in an immediate automatic startup of the two 750 KW auxiliary diesel generators and automatic tripping of the ship's non-vital loads. The casualty considered here is a loss of all power to Bus 1 and Bus 2 of the main switchboard which will occur only if both turbine-generators trip from the line and both diesel generators fail to start up and synchronize. Among the possible causes of such a failure are the following:

• a. Mechanical or electrical failure of both turbine-generators and both diesel generators.
• b. Failure of both turbine-generators followed by failure of the synchronizer.
• c. Bus fault in the bus tie breaker section of the main switch-board.
• d. Flooding of the machinery space.

On loss of all power to the main busses, the 300 KW emergency diesel generator will start automatically, and the emergency cooling system will go into operation. Emergency sea water pump DK-P1 and emergency canned pump DP-P2 will start, and valves DK-4V, DK-19V, DK-20V, DK-21V, and DK-32V will be opened to the full open position by their motor operators. The ship's emergency lighting will operate from the 120V A-C/D-C temporary bus. All other equipment necessary for safe operation of the ship will operate from the 450 V A-C bus or the 120 V A-C bus of the emergency switchboard. Operation of the emergency diesel generator will be indicated by its WHITE light on the mimic panel. Closing of the emergency diesel generator circuit breaker will be indicated by its BLUE light. The 120V, single phase, A-C bus will be available for critical instrumentation provided the D-C/A-C MG sets are not lost as a result of the same accident which caused loss of power to the main buses. Operation of these motor generators will be indicated by their WHITE lights on the mimic board. Closed circuit breakers on the 120V bus will be indicated by the Blue circuit breaker closed lights.

The immediate results of loss of power on the main buses will be loss of power to all four primary pumps with primary flow decaying quickly to a very low value. The operator's first concern is to check that the measures necessary to protect the reactor from damage have proceeded automatically. He might ensure that all rods have scrammed and that the emergency cooling system has started along with the emergency diesel generator. Since the emergency cooling system is controlled from the emergency cooling panel on the navigation bridge deck, an operator must go to the emergency cooling system as soon as it starts, to isolate the emergency cooling system from the console if necessary and to control the rate of cooling.

Subsequent action, in general, should be that required to place the 750 KW auxiliary diesel generators in operation allowing a normal shutdown if one generate can be started or resumption of operation if both can be started. Action should then be initiated to restore the turbine-generators to operation leading up to restoration of normal plant operation.