Emergency Operating Procedure

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

A. Symptoms

B. Immediate Action

C. Follow-Up Action

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.

My text copyright 2020 Tommy Johnson, all rights reserved. I believe the Savannah documentation is property of MARAD or the US government.