Equipment Failure Procedure
CRD-86 Control Rod Drive System 10/22/62
A. Control Rod Drive Mechanism Failure
(Control rod drive line inoperable mechanically, electrically, or control rod stuck)
- 1. Condition is characterized by repeated disengagement on a withdrawal signal and/or no
inward movement on an insert signal.
- 2. Stall current on drive motor will result in "High Motor Temperature" alarm and, if
insert signal continues, ultimate burnup of the motor. Branch breaker to disabled motor should
be opened immediately.
- 3. Initial trouble-shooting action to be taken is:
- a. A check of drive motor relay fuses in the event of no rod movement in either direction.
- b. A check for high balance pressure in the event of repeated disengagement.
- c. A check of "High Motor Temp." alarm lights in the event of inability to insert rod.
- 4. If symptoms of problem indicate control rod is obstructed on inward travel, render
rod incapable of scram by isolating individual hydraulic channel.
- 5. Take the disabled control rod drive line out of service by disconnecting its jack from
the Bailey patch panel and tagging out its control switches at the console.
- 6. Log disabled rod as "rod unavailable for scram" and refer to "Minimum Conditions for
Reactor Operation", Plant Operating Standards CRD-86
- 7. Plant cooldown and containment entry for repairs should be undertaken only after an
investigation at the Electrical Equipment Room definitely shows the problem to be located inside
B. Occurrence of a Control Rod Drive "High Motor Temperature" Alarm
- 1. Refer to Section A for action where a "High Motor Temp." alarm is involved in a stuck
- 2. IF alarm occurs during extensive rod movement but clears after rod movement has been
stopped for a period of time, check for proper balance pressure and determine that hydraulic
channel is not isolated.
- 3. If rod involved in this alarm can be moved at normal speed in both directions, it need
not be termed a "stuck rod". Limit further movement of control rod where possible.
- 4. Tag control switch at console.
- 5. At first outage check blower motor of rod in question.
C. Failure Of Control Rod Position Indicator At Console
- 1. Failure of position transmitting selsyn on the drive mechanism will have following
- a. Lost position indication on the left wing panel of the console.
- b. Lost position indication on the 21 position selector switch for the individual drive
- c. Lost group indication at the center desk of the console if the affected drive is
patched into the left-hand vertical row of the Bailey patch panel plugs; i.e.;
A-1, B-1, C-1, D-1, or E-1.
- 2. Failure of position receiving selsyns at any of the three locations mentioned above
will affect only that individual selsyn, allowing operation to continue using one of the other
two position indicators.
- 3. In the event of a lost group position indication due to a failed position transmitting
selsyn, restore group indication by patching another rod of the same group into the left-hand
plug of the Baily patch panel.
- 4. Position indicator failure on one rod in a banked group can be tolerated.
- 5. Failure of a second position indicator in a banked group will require either plant
shutdown for repair or alternate group patching at the Bailey patch panel to allow leaving
the rods with failed position indicators either full in or full out.
- 6. Place tags on failed position indicators, noting limitation of affected drive mechanism.
D. Operating Hydraulic Pump Trips Due To Overload Or "Power Failure Hydraulic Supply"
- 1. Standby unit should start automatically and restore pressure.
- 2. Switch standby unit to operation and reserve unit to standby service. Supply electrical
power to each unit from separate sections of the main switchboard.
- 3. Correct difficulty on failed unit.
- 4. Should second unit fail, standby unit will automatically start and reactor operation can
- 5. Failure of third unit will automatically scram reactor.
E. Failure Of One OR More Rod Drives To Scram Properly
- 1. Refer to "Minimum Conditions for Reactor Operations", Plant
Operating Standards CRD-86 for continued operation with rods unable to scram properly.
- 2. If during a reactor plant scram any control rods fail to scram, check hydraulic oil
cleanliness. Oil flushing with fresh filters and test scrams will be required if oil cleanliness
is found to be grossly out of specifications.
F. Hydraulic System Failure - Oil Leak Inside Containment Vessel
- 1. Oil leak will be indicated by rapid reduction in reservoir oil level or possible
indication of low pressure either in an individual hydraulic channel or on the high pressure
- 2. In the event of diminishing oil level and accumulator oil and gas low pressure alarms on
a particular channel, isolate that hydraulic channel and observe results. That control rod
must then be logged as "unavailable for scram".
- 3. A large leak will result in automatic tripping of the hydraulic power units on low level
and subsequent scram. Leak must be repaired prior to startup.
- 4. Gradual dropping of oil level (use 2 inches per day as a guide) may be attributed to
heavy weeping. Makeup oil may be used until earliest outage.
G. Transducer Valve Failure
- 1. Balance pressure failure will transfer control automatically to the other valve.
- 2. Mechanical transducer failure alarm will require manual switching to the other valve.
- 3. Failure of the second valve should be met with an attempt to limit rod travel as much
as possible. Slight reduction in rod speed can be anticipated.
- 4. Repair of failed valves should be attended to at next outage.
H. Hydraulic Oil Failed To Meet Cleanliness Specifications
(Refer to POS CRD-86 for specifications)
- 1. If an oil sample and the check sample both show oil cleanliness to be out of
specifications, immediately place another unit on operational.
- 2. Replace the oil filters on the secured unit.
- 3. Continue to operate the system, sampling the oil daily until oil cleanliness is
- 4. Frequent occurrence of this condition will require inspection and possible cleaning
of the hydraulic reservoirs.
I. Failure Of A Hydraulic Oil Cooler
- 1. Condition is serious if water is found in hydraulic system and/or oil is found in the
- 2. Immediately isolate cooler in use and valve in the standby cooler.
- 3. Close oil return valves to operation and standby unit. Leave equalizing header valves
open. Reserve power unit reservoir can then be used as a settling point for water.
- 4. First evidence of pump failure or hydraulic valve malfunction due to water in the
oil will be cause for reactor shutdown.
My text copyright 2020 Tommy Johnson, all rights reserved. I believe the Savannah documentation is property of
MARAD or the US government.