Emergency Operating Procedure
EOP 3 Rupture in Secondary System Revision 1 2/6/64
- 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
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
- 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.
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
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
My text copyright 2020 Tommy Johnson, all rights reserved. I believe the Savannah documentation is property of
MARAD or the US government.