Emergency Operating Procedure

EOP 3 Rupture in Secondary System Revision 1 2/6/64

A. Symptoms

• 1. Important annunciators which may be actuated.
  • a. LOW TEMPERATURE STBD. LOOP.
  • b. LOW TEMPERATURE PORT LOOP.
  • c. HIGH OR LOW LEVEL STBD. BOILER DRUM.
  • d. HIGH OR LOW LEVEL PORT BOILER DRUM.
  • e. HIGH FLOW TOTAL STEAM (If leak is between flow nozzle and maneuvering valve).
  • f. HIGH STEAM FLOW STBD. BOILER (If leak is between flow nozzle and maneuvering valve).
  • g. HIGH STEAM FLOW PORT BOILER (If leak is between flow nozzle and maneuvering valve).
  • h. LOW FLOW TOTAL STEAM (If leak is upstream of flow nozzle).
  • i. LOW LEVEL DEAERATOR HEATER WATER.
  • j. HIGH TEMPERATURE CONTAINMENT DOME (If leak is between boiler and containment vessel).
  • k. HIGH PRESSURE CONTAINMENT LOW RANGE (If leak is between boiler and containment vessel).
• 2. Steam pressure is low.
• 3. Shaft RPM has dropped accompanied by and increase in reactor power.
• 4. Reactor may scram due to over flux trip or low primary system pressure.
• 5. Difference in steam flow and feed water flow does not balance with blowdown rate. Steam flow may not indicate normal.
• 6. Low coolant temperature at reactor inlet.
• 7. Level in deaerating feedwater heater continues to drop.
• 8. Noise of escaping steam may be apparent.

B. Immediate Action

• 1. If reactor has not scrammed, and it is readily apparent that the leak is upstream of the main steam stops, scram reactor and isolate the offending loop by:
  • a. Closing the main steam stop SS-1V STBD or SS-4V PORT.
  • b. Closing the main feedwater valves SS-13V STBD or SS-16V PORT.
  • c. Closing the primary system isolation gate valves PS-6V STBD and PS-5V or PS-4V PORT and PS-3V.
  NOTE: If the port loop is isolated (PS-4V & PS-3V) make up to the P.S. must be through SL-6V. This can be operated manually from the main console.
• 2. IF reactor has scrammed, push scram button to insure that all rods have scrammed.
• 3. Close PISTON-OPERATED STEAM STOP valves to preserve steam if possible. (SS-1V and SS-4V)
• 4. Isolate a steam leak by closing main feed water stop valves SS-13V and SS-16V. If leak continues after first valve is shut, close the other one.
• 5. Acknowledge annunciators as convenient.
• 6. Start the emergency cooling system and the emergency diesel generator by pressing start button labeled Emergency Cooling System Actuator (RWD) on the control console.

  [RWD is Right Wing Desk.]

• 7. Close the primary gate valves to isolate the loops (this will cause the primary pumps to stop running).
• 8. Check that 750 KW diesels have started and automatically paralleled on to the main bus by noting meters (RCP) on the console.

  [RCP is Right Center Panel.]

• 9. Close boiler blowdown valves to conserve secondary water.

C. Follow-Up Action

• 1. Determine location of leak and attempt to isolate. Conditions recorded before steam valves were closed may be interpreted as follows:
  • a. Abnormal steam flow in one loop will indicate a rupture in the steam system. (The failure will have to be outside C.V. downstream of Quick Closing Valves to pass through flowmeter.)
  • b. Abnormal feed water flow with little immediate change in steam flow accompanied by a drop in drum water level, indicates a leak in the feed water system or in steam lines inside C.V. or upstream of flowmeter.
• 2. Check pressure, temperature and humidity in containment vessel. Abnormally high readings will indicate a leak inside the vessel. Location of a leak in the engine room may be determined visually. If a steam leak at either place cannot be found and the drum water level continues to drop, the leak is in the feed water line inside the containment or in the reactor compartment.
• 3. Close all feed water regulator valves SS-8V, 11V, 14V and 17V. At this point, flow to and from the boilers is shut off. If the pressure in either steam drum continues to drop, the leak is in that drum or immediate connecting piping. In this case the drum must be allowed to vend dry. Since it is isolated, startup may be accomplished with the other boiler.
• 4. Check pressure in deaerator feedwater heater. IF it is dropping, attempt to isolate by closing valves.
• 5. The location of the leak should be known from the above steps.
• 6. Start up the auxiliary boiler (cyclotherm) to supply hotel steam until the steam system can be restarted.
• 7. If leakage has been confined to one of the boilers or its individual high pressure piping, all valves in that system should be kept closed.

  PORT				STARBOARD
  SS-4V	Steam Stops		SS-1V
  SS-16V	Feed Stops		SS-13V
  SS-22V	Blowdown Valves		SS-21V
  SS-11V	Feedwater Regulators	SS-8V
  SS-17V		"	"	SS-14V
  SS-10V	Manual Stops		SS-7V
  SS-20V		"	"	SS-19V
  BF-28V	Chem Add Valves		BF-29V
  

  After securing the loop which contains the affected boiler, start up the plant on the other loop if it can be determined that the leak has not caused damage to equipment or instrumentation. The startup procedure will be the normal startup procedure except that the primary gate valves are left closed, and the primary pumps are not operated in the affected loop. Also, the power level should be reduced in proportion to the number of pumps operating.

• 8. If the leak is part of either the steam system or feedwater system which is common to both boilers (And cannot be isolated), the leak must be repaired before startup.
• 9. Secure the emergency cooling system after normal flow is established in the primary system.

D. Discussion

A large leak or major rupture in the secondary system will result in a loss of secondary water, a drop in drum water level, and a reduction of pressure in this system. Rapid flashing of steam in either boiler will result in an equally rapid cooling of the secondary cooling water. This, in turn, will cause a reduction in the temperature of the primary cooling water passing through the boiler during this flashing period. The outlet temperature on the primary side of the boiler could drop as much as 15F in fifteen seconds if the rupture were very large.

The reactor acts to maintain a constant average system temperature. A reduction in primary boiler outlet temperature will, therefore, cause a reactivity addition when the colder coolant leaving the boiler arrives at the core inlet some 7.5 second after the rupture. The reactivity addition may result in an overpower excursion which will be shut down automatically when the power reaches 120 per cent of full power.

If the leak cannot be controlled or if it is not readily apparent which drum is affected, the operator should scram the reactor, close the piston operated steam stop valves, and start the emergency cooling system. As soon as the emergency cooling system is operating, the primary flow should be stopped by closing the primary system gate valves. This will turn off the primary pumps. In order to conserve boiler water, the boiler blowdown valves should be closed. An attempt should then be made to determine the area of the leak. If the leak has occurred in the engine room, it may be that operating personnel can report the area of the failure. IF the area of the leak as not been determined in the manner, a systematic isolation of various parts of the system will provide some information regarding its location. This is accomplished by first shutting off all the lines leading to and from the boilers. If the leak continues, the boilers will vent dry. However, a feedwater leak which continues requires that the main feed pump be shut off.

Subsequent operations will permit a complete plant shutdown or a startup using the undamaged equipment.