ML18058B744
| ML18058B744 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/29/1993 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML18058B743 | List: |
| References | |
| NUDOCS 9304070210 | |
| Download: ML18058B744 (13) | |
Text
ATTACHMENT I Consumers Power Company Palisades Plant Docket 50-255 CRDM TESTING FREQUENCY TECHNICAL SPECIFICATIONS CHANGE REQUEST
--- 9304070210- 930329 PDR ADDCK 05000255 p
PDR Proposed Page
Table 4.2.2 Minimum Frequencies for Equipment Tests FSAR Section Test Frequency Reference
- 1. Control Rods Drop Times of ALL Full-Each Refueling 7.6.1.3 Length Rods Shutdown
- 2. Control Rods Partial Movement of ALL Every 92 Days 7.6.1.3 Rods (Minimum of 6 In)
- 3. Pressurizer Safety Set Point One Each Refueling 4.3.7 Valves Shutdown
- 4. Main Steam Safety Set Point Five Each Refueling 4.3.4 Valves Shutdown
- 5. Refueling System Functioning Prior to Refueling 9.11.4 Interlocks Operations
- 6. Service Water Functioning Each Refueling 9.1.2 System Valve Operation Actuation (SIS-CHP)
- 7. Primary System Evaluate Daily
- 4. 7.1 Leakage
- 8. Diesel Fuel Supply Fuel Inventory Daily 8.4.1 4-15 Amendment No 12, 81, 1 aa, 152, 155,
ATTACHMENT 2 Consumers Power Company Pali sades Pl ant Docket 50-255 CROM TESTING FREQUENCY TECHNICAL SPECIFICATIONS CHANGE REQUEST Existing Page Marked to Show Change
- 1. Control Rods
- 2. Control Rods
- 3. Pressurizer Safety Valves
- 5. Refueling System Interlocks
- 6. Service Water System Valve Actuation (SIS-CHP)
- 7. Primary System Leakage
- 8. Diesel Fuel Supply Table 4.2.2 Minimum Frequencies for Equipment Tests Test Drop Times of All Full-Length Rods Partial Movement of All Rods (Minirnun of 6 In)
Set Point Set Point Functioning Functioning Evaluate Fuel Inventory Frequency Each Refueling Shutdown One Each Refueling Shutdown Five Each Refueling Shutdown Prior to Refueling Operations Each Refueling Operation Daily Daily FSAR Section Reference 4.3.4 9.1.2 41f:td J'.meRa 1li 1 Q1,1es ~.l.7 8.4.1 Q1,1FiRg the FemaiRaeF ef sysle 1g, GRQ 2g aRa GRQ 11 uill ee tested eRse iR MaFsh 1991 iR Lie1,1 ef testiRg eRse e¥eFy tue ueeks.
4-15 Amendment No 12, 81, 133, 1 B2, 1 BB, Au~ust 21, 1 992
ATTACHMENT 3 Consumers Power Company Palisades Plant Docket 50-255 CRDM TESTING FREQUENCY TECHNICAL SPECIFICATIONS CHANGE REQUEST Figures
ATTACHMENT 4 Consumers Power Company Palisades Plant Docket 50-255 CROM TESTING FREQUENCY TECHNICAL SPECIFICATIONS CHANGE REQUEST History of CE Rack and Pinion Control Rod Drive Failures
ATTACHMENT 4 History of CE Rack and Pinion Control Rod Drive Mechanism Failures Introduction This section describes the experience with control rod drive mechanism (CROM) failures at C-E plants with rack-and-pinion CRDMs for the Palisades plant (PAL) and Fort Calhoun Station (FCS).
These failures are separated into two categories, trip failures and drive failures.
The trip failures are those which could have affected the ability of the control rod to fully insert, within the required time, upon a reactor trip. The drive failures are those where a control rod could not be moved by its CRDM motor.
Drive failures do not suggest a trip failure.
Control rods are demonstrated to be operable during startup tests following each refueling outage. These tests include:
- 1) fully withdrawing all rods (demonstrating the absence of mechanical binding), and 2) Rod drop tests (demonstrating the rods will fully insert within a specified time).
These startup tests have detected most of the Rack and Pinion CRDM trip failures. This experience is consistent with that for C-E plants with other types of CRDMs, i.e., magnetic jack control rod drives.
The Palisades FSAR accident analysis assumes that the most reactive rod sticks in the full out position for all events except those initiated by control rod motion.
In operating experience with these CRDMs, there have been 12 reported instances involving a total of 29 control rods which could not be fully inserted by gravity within the required time.
Of these 12, 10 were discovered during startup testing and 2 on reactor trips, and in neither trip case did the rod stick fully out of the core.
The observed problems were limited to the CRDM, none involved a difficulty with a control rod or CEA.
A search of reported events, including the Licensee Event Report (LER) data collected from NUREG-0020, "Licensed Operating Reactors Status Summary Report," was conducted for rack and pinion CRDM plants. The search revealed no occurrences of the subject surveillance detecting a potential control rod trip failure. Several cases of this surveillance detecting CROM drive failures have occurred.
The results of this search are contained in 2 tables, Table 1 is a list of potential control rods trip failures and Table 2 is a list of the CRDM drive failures.
Trip failures sorted by detection activity:
- 1.
83%; Rod Drop Tests or Trip Testing; 7 events involving 24 rods.
- 2.
10%; Rod Withdrawal; 3 events involving 3 rods.
- 3.
7%; Reactor Trip; 2 events involving 2 rods.
- 4.
0%; Bi-weekly Testing; 0 events.
Trip failures sorted by failure mechanism
- 1.
52%; Binding in the piston guide tube; 5 events involving 15 rods.
2 Fourteen of these failures had similar causes of a mechanical nature associated with undersized CROM uncoupling tools which had prevented full retraction of the connector nut locking pawl. Subsequent rotation of the connector nut resulted in bent castellations on the buffer piston causing interference between the piston and its guide tube in the lower tight clearance region. This problem was addressed by removing unsuitable uncoupling tools from service and performing torque tests on all control rods to verify that the rods were not sticking.
One additional trip failure had mechanical problems similar to the above 14 failures but it cannot definitely be attributed to the same cause.
- 2.
38%; Clutch problems; 4 events involving 11 rods.
A design review revealed that the friction force retarding clutch jaw separation could prevent separation of the clutch jaws unless a special lubrication program was employed.
A modification, replacing the splines with a bellows and chrome plating the lower jaw, was completed on 3-3-73.
No clutch failures have occurred since.
- 3.
10%; Events not in any particular category; 3 events involving 3 rods.
Summary The Palisades bi-weekly surveillance test is not effective in detection of CROM trip failures. All trip failures have been detected by other activities. The majority of the trip failures at Palisades (26 of 29) have been caused by 2 types of problems.
Mechanical binding, addressed by redesigning of the coupling tools, and clutch problems, which were resolved by modification of the clutches.
The remaining 3 trip failures are attributed to miscellaneous causes, addressed by repair or replacement of the affected parts.
KEY FOR TABLES 1 and 2 Tables I and 2 provide the following trip and drive failure information:
I.
Date of occurrence
- 2.
- 3.
Unit:
PAL FCS Discovery activity:
Trip Maneuvering Testing Exercising Unknown Rx SD Pali sades Pl ant
= Fort Calhoun Station
= trip power maneuvering, or reactor startup testing other than exerc1s1ng bi-weekly rod exercising,
= unknown reactor shutdown
- 4.
Number of rods involved in event
- 5.
Cause of Failure
- 6.
Problem description 3
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09/15/71 PAL 11/05/71 PAL 03/XX/72 PAL 06/02/72 PAL 08/29/72 PAL 10/26/72 PAL 03/29/75 PAL 04/XX/76 PAL 05/09/93 PAL 09/XX/82 PAL 11/15/84 PAL 08/10/85 PAL Testing Testing Trip Trip Test in Testing Testing Testing Rx SD (withdrawal)
Testing Rx SD (Withdrawal)
Rx SD (withdrawal) 2 1
4 4
11 1
Clutch Misc.
Misc.
Clutch Clutch Clutch Piston Binding Piston Binding Piston Binding Piston Binding Misc.
Piston Binding
. TABLE 1 - TRIP FAILlllES Control rod 4 failed to drop during test.
The rod did drop after a slight force was applied to clutch faces.
Later the same day a second control rod failed to drop immediately.
Examination of the clutch surfaces disclosed a slight deposit of epoxy and some foreign material hampering the movement of the clutch jaw. The epoxy application during the installation of new springs had been excessive.
The remainder of the clutch jaws were reworked.
Control rod 27 failed to dro *on a tri signal due to a broken clutch ada ter shaft.
During a trip a control rod took 10 seconds to drop to 90% inserted.
The motor drove the rod inward about 6 inches before it fell. Disassembly revealed worn chrome plating on a small area of the piston had allowed stainless steel to stainless steel contact between the piston and guide tube resulting in excessive friction, a sli ht bow in the rack which caused the rubbing.
Control rod 5 did not drop from the lower electrical limit (3 inches withdrawn) on a trip signal.
The clutch lower jaw was tapped and the jaws disengaged. The clutch assembly was replaced.
The failure was attributed to an unusual ratcheting operation in when the drive mechanism was inadvertently driven against the upper mechanical hard sto immediately before the failure.
Four control rods failed to tri durin testin, due to de radation of lubrication on the s line surfaces.
CROM 19 seal leakage required the plant to be shutdown.
After inspection it was determined that one of the three collar setscrews had backed out and lodged between the rotating seal half skirt and the seal housing.
This had caused the seal leakage. All control rods were trip tested from the lower limit (3").
The clutch halves failed to separate on four CRDMs.
Inspection revealed the presence of boron salt and moisture inside the motor packages of these four CRDMs.
During CROM torque and control rod drop testing control rod 30 failed to drop properly when the clutch switch was opened.
Successive testing showed rough operation coupled with slow or incomplete rod drops.
The gear box, su art tube, and seal housin were re laced.
During performance of rod drop timing 11 CRDMs failed to withdraw the rod or exhibited slower than usual drop times.
The problem was bent castellations on the buffer piston (causing galling of the piston and guide tube}
caused by connector nut awls not being fully released when the cou ling tools were inserted.
During.preparations for a reactor startup control rod 8 could not be withdrawn due the to the castellations on the buffer piston being bent outward such that upward motion of the rod caused the castellations to dig into the inner surface of the iston uide tube.
During drop time testing, following autoclave gasket replacement, control rod 37 stopped at 30 inches and was.
subsequently driven to the bottom.
The CROM drive package was replaced and drop timing was repeated.
The rod stopped at heights of 19" and 131".
The connector nut locking pawl was deformed and grooved at the bottom; a castellation of the top of the buffer piston was chipped and bent outward, axial grooves were found in the piston guide tube; the pin holding the locking pawl to the connector nut was bent; and shavings were noted on the upper bearin of the bevel ear housin.
With the reactor shutdown and a cooldown to cold shutdown in progress. Control rod 1 would not withdraw and the seal was leaking.
It appeared there was some kind of binding in the rod.
The seal housing and drive package were replaced. Subsequent examination showed a failure of the seal housing.
The stationary and rotating faces of the seal were found in a severe] de raded condition.
While in hot shutdown it was noticed that control rod 28 would not withdraw.
The plant went to cold shutdown.
The buffer piston castellation was in contact with the support tube.
XX/XX/71 PAL Unknown 1
12/23/71 PAL Manuvering 1
01/28/72 PAL Manuverin 04/XX/72 PAL Manuvering 2
11/26/72 PAL Exercising 01/XX/73 PAL Exercising 10/26/74 PAL Unknown 06/29/75 PAL Unknown 1
07 /13/75 PAL Exercising 1
07/27/75 PAL Exercising 1
07/27/75 PAL Manuvering 1
07/28/75 PAL Exercisin 08/26/76 PAL Manuvering 08/27/76 PAL Manuvering 04/20/78 PAL Manuvering 1
Brake Brake Brake Brake Short Brake Cont actor Short Brake Brake Brake Motor Brake then Motor Brake Brake TABLE 2 - DRIVE FAILIEES During a test, a rod would drive erratically. It finally failed to drive in either direction.
The CROM drive package was removed and it was found that one of the two allen head setscrews that attach the brake disc to the shaft had backed out so as to interfere with the motor rotating element.
Thus even with the brake energized, the motor could not turn freely.
The setscrew was replaced and both setscrews were secured with Locktite.
Subsequently all 45 drive motors were removed and the associated brakes were inspected. A total of 13 brake units re uired the setscrews to be tightened and conse uently all screws were again coated with Locktite.
While withdrawing regulating group 4, control rod 39 stopped driving approximately four inches below remainder of other rods.
Ins ection revealed that the brake had been dra in.
Control rod 35 could not be withdrawn be and 107.2 inches due to im ro er o eration of the motor brake.
Control rod 35 failed to move with the remainder of its group.
On the same day control rod 39 continued to coast, due to brake slippage, to a position 8.9 inches lower than the highest rod in its group.
An inspection of CROM motor packages revealed that about 60% of the brakes contained dowel pins in varying degrees of looseness (the dowel pins position the stationary brake disk).
In addition some of the CRDMs had oil or grease film on the disks. Three of the four dowel pins for the brake of CROM 35 had backed out of their dowel holes in the yoke and were rubbing firmly against the brake rotating disk. Grease on the disk of CROM 39 may have been enough to allow the sli a e.
Control rod 26 was inserted six inches but could not be withdrawn to its original full out position due to a short in motor brake wire.
During exercising, the operator had difficulty driving control rod 6 to its original position.
The control relay was cycled after which the CROM operated normally.
During a subsequent outage the CROM motor was disassembled and inspected.
The end play was found to be excessive, which allowed the brake to jam at the upper limit of travel.
The excessive lay was corrected and the CROM o erated normall.
Control rod 19 withdrew erraticall unless its contactor was manuall ushed in.
The contacts were cleaned.
Control rod 19 would not withdraw due to shorted motor leads.
Contr.ol rod exercising revealed that control rod 27 would not insert.
The rotating element of the brake assem~
was loose.
One of the set screws had backed out of the rotating element.
Control rod exercising revealed that control rod 14 would not respond to either an insert or withdrawal signal.
Particles from brake linin s were found between brake coil and stationar shaft.
While decreasing power, control rod 33 could withdraw but would not insert due to particles from brake linings between brake coil and stationary shaft.
Control rod 27 drive failed to o erate due to a bad motor.
Control rod 39 failed to withdraw during power escalation.
The apparent cause of CROM 39 failure was an intermittent brake failure which caused the motor winding to open due to excessive current.
The motor/brake assembly was re laced.
During a power reduction, difficulty was experienced in operating control rod 37.
Disassembly of the brake revealed an excessive amount of residue from the brake disk causin a dra in effect. LER 76-30)
Control rod 38 misaligned by more than eight inches from the remaining rods in its group because the brake was not always releasing.
The motor-brake-gearbox assembly was re laced.
TABLE 2 - DRIVE FAIL~ES
~
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06/05/78 PAL Unknown 09/17/78 PAL Unknown 1
11/19/81 PAL Testing 1
11/19/81 PAL Testing 1
11/20/84 PAL Testing 1
05/23/85 PAL Exercising 1
05/23/85 PAL Exercising 1
08/18/85 PAL Rx SD 08/27/85 PAL Testing 09/12/85 PAL Unknown 01/16/86 PAL Rx SD 03/26/86 PAL Rx SD 1
05/31/88 PAL Unknown 1
11/16/88 PAL Rx SD 1
03/01/89 PAL Rx SD 1
12/20/89 PAL Unknown Brake Motor Short Broken Wire During testing of CRDMs, control rod 3 could not be moved.
The failure was caused by the backing out of a set screw in the brake assembly.
Control rod 39 could not be withdrawn.
The cause was shorting of motor windings from water which apparently had entered the drive package as a result of seal leakage.
While performing refueling surveillance test, control rod 1 would not respond to drive signals.
The cause was a short circuit in the CRDM cable.
While performing refueling surveillance test control rod 7 would not respond to drive signals.
The cause was a broken wire in a panel board multi-pin connector.
Clutch While performing a surveillance test prior to going critical control rod 41 failed to move correctly. The clutch bellows assembly was found torn from the moveable clutch jaws.
The clutch would not engage.
Synchro While exercising control rods, control rod 43 was found to indicate continual insertion and withdrawal when turned on.
The synchro was damaged by moisture from leaking seals.
Brake Control rod 31 failed to drive out. It was declared inoperable, then retested and declared operable. On June 6, rod 31 again experienced trouble while exercising.
The problem was attributed to failure in motor brake.
Contactor While exercising rods in cold shutdown control rod 23 would raise but then drift back down.
The auxiliary contacts for the motor control contacts on the brake circuitry had failed.
Contactor While performing refueling surveillance, control rod 23 drove in when the controller was placed in manual.
The auxiliary contacts of the motor contactor, which operate the brake, were sticking.
The two left side auxiliary contacts were reclaced and CRDM 23 was retested satisfactorilv.
Limit During performance of a surve.illance test, control rod 28 did not withdraw correctly. The failure occurred due to Switch a loose setscrew on the synchro coupling which allowed the electric limit switches to move out of place.
Motor or During surveillance testing with the reactor shutdown control rod 23 would not insert.
The cause of the failure Brake is not recorded, but the CRDM drive package and cable were replaced and retested satisfactorily.
Brake Diode Bearing Brake Cail Bearing During surveillance testing in hot shutdown control rod 4 failed to move.
A set screw on the brake shaft had backed out and was binding on the housing.
Control rod 20 would not move.
A brake diode had shorted, blowing fuses, causing loss of power to the motor.
A routine check determined that control.rod 6 would not move up.
Excessive moisture in the drive package had caused the lower motor bearing to rust and seize.
During a reactor startup, control rod 43 would not insert but could be withdrawn.
The brake coil was grounded.
Control rod 41 was driving slower than other rods in the group causing a four inch deviation.
The top bearing of the upper clutch was binding.
TABLE 2 - DRIVE FAILURES
,/
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- < DATE:: { :::, tOin: :::: :::: A&HWtY:t::: ::: IIBos:::: twumUie\\<
11/05/84 FCS Unknown 1
12/01/84 FCS Unknown 12/11/84 FCS Unknown 12/11/85 FCS Testing 1
01/11/86 FCS Rx SD 01/12/86 FCS Rx SD 04/07/86 FCS Unknown 06/23/86 FCS Unknown 1
03/18/87 FCS Rx SD 06/09/87 FCS Rx SD 10/01/90 FCS Rx SD 01/17/92 FCS Unknown 1
NOTE:
Fort Calhoun Station descri tion entries were taken fran a contractor re rt without editin Unknown Control rod 41 would not withdraw during surveillance test - re laced drive mechanism.
Contactor Control rod 25 would not drive in.
The mechanical interlock on control relays was sticking. Interlock was re laced and tested for ro er o eration.
Motor or Brake Diode Control rod 41 was sticking.
Installed new clutch coil assembly due to damage of original during disassembly.
Installed new motor and brake.
CROM 28 would not run during a maintenance procedure.
The rectifier bridge failed. Rectifier bridge and one f re laced and tested.
Diode CROM 27 stuck at approximately 32" withdrawn and would not drive in or out. A defective rectifier and two fuses were re laced.
Motor CROM 26 would not drive in either direction, the unit was in a refuelin shutdown.
Re laced worn ear motor.
Contactor CROM 37 would not withdraw from 120 inches, unit at full power.
Mechanical interlock lubricated, tested, and returned to service.
Short
- Clutch, Switches Unknown CROM 26 began inserting into core - motor and break had loose leads causin short-installed new motor and brake.
CROM 31 would not drive rod, unit in refueling shutdown.
Attributed to normal wear of clutch package and limit switches out of ad"ustment.
Re laced clutch acka e and ad"usted limit switches.
Control rod 31 did not drive u, unit in refuel in shutdown.
CROM re laced with as are.
Brake During a reactor shutdown control rod 24 would not insert beyond 94".
Rod drop test switch was used to insert rod.
The CROM was replaced with a new unit and the rectifier and two fuses were replaced.
It is suspected that the CROM brake assembly seized due to normal wear which caused a rectifier to short, in turn blowing at least one fuse.
Contactor At 100% power while performing a periodic maintenance activity, control rod 36 had a noticeable time delay befo~
the rod would move.
During the next outage the cause was determined to be that the control rod up and down contactors were out of adjustment.
The contacts were realigned and proper CROM operation was verified.
~3