ML20087A862
| ML20087A862 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 05/28/1970 |
| From: | Robert Carlson, Pomeroy D US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20086U000 | List:
|
| References | |
| FOIA-95-36 50-219-70-04, 50-219-70-4, NUDOCS 9508070199 | |
| Download: ML20087A862 (10) | |
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U. S. ATOMIC ENERGY COMMISSION l.
REGION I I
DIVISION OF C(EPLIANCE Report of Inspection COReportNo.219/70-h l
l Licensee:
JERSEY CENTRAL POWER & LIGHT CO. (Oyster Creek 3 i
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License No. DPR-16 Category C r
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Dates of Inspection:
April 21, 22 and 23, 1970 l
I Dates of Previous Inspection:
March 18 - 20, 1970 s
Inspected by:
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D. L. Pomeroy, ITiia tor Enginebr, CO:HQ Date' 2&h*
. os c Reviewed by :
R. T. Carlson, Senior Reactor Inspector, CO:I 3atd Proprietary Information:
None SCOPE A special, announced in2pection was conducted to review recent reported operating difficulties with the control rod drive (CRD) system
- and to 'ssess the licensee's j
a program for evaluation and correction. The assigned inspector, D. L. Caphton, CO:I, was present during the first day of the inspection.
SUMMARY
3 The reactor was shut down on April 19, 1970, by the licensee because of deteriorating operation of the control rod drive system. After an examination of the first two drives removed from the reactor, the licensee decided to rebuild all the drives.
On March 23, 1970, stall flow tests on each CDR indicated leakage in excess of '
3 gpm for 108 drives.
(See Section II.A.)
On April 14, 1970, 52 drives required increased drive water pressure to unlatch.
(See Section II.B.)
One or more drives failed to fully insert during the last three scrams.
(See Section II.C.)
Examination of the first four CRD's indicated broken stop and drive piston seals, swollen index tubes and plugged cooling water orifices.
(See Section III.)
DETAILS 1.
Persons Contacted Jersey Central T. McCluskey, Station Superintendent J. Carroll, Operations Supervisor D. Ross, Technical Supervisor W. Riggle, Maintenance Supervisor
- Inquiry Memoranda 219/70-D and 70-E, April 9 and 17, 1970.
9500070199 950227 PDR FOIA DEKOK95-36 PDR
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N. Goodenough, QA Section g
N. Biglieri, Design Engineer, CRD's (San Jose)
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II.
Result of Record Review A.
Withdrawal Stall Flow Tests Periodic measurements of the flow to each CRD with the drive fully with-drawn ure undertaken in December, 1969. One criterion in the GE CRD Manual for accepting a new or rebuilt drive is that the withdrawal stall flow shall be less than 1.1 gpm (drive pressure 250 psi above reactor pressure). Normal seal wear is expected to increase this flow to about 2 gpm.
Previous discussions with GE representatives indicate that 3 gpm is considered to be abnormally high seal leakage. The upper range of the flow instrument is 5 gpm.
The following are the results of four withdrawal stall flow tests, with each test including 136 drives.
(One drive has been out of service since the CRD screen changing program in October,1969.)
Date of Test Number of Drives Greater than 3 gpm Greater than 5 gpm 12/ 5 /69 35 7
1/30/70 79 37 3/ 4 /70 94 54 3/23/70 108 65 According to the GE CRD Manual these tests indicate that increased leakage is being experienced at one or more of the following points:
1.
The collet piston seals 2.
The drive piston internal seals 3.
The stop piston seals B.
,High Pressure to Unlatch During the recovery from scram No. 42 on April 7,1970, the normal CRD I
drive water header pressure of 250 pounds per square inch differential (psid) was insufficient to cause unlatching for 38 of the drives. During the recovery from scram No. 43 on April 14, 1970, the normal pressure was insufficient for unlatching 52 drives. The drives were unlatched in each case (with one exception) by
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! e increasing the drive water pressure. Three drives on April 7 and five on April 14 required pressure above 400 psid.
(The pressure instrumentation in the control room reads up to 400 psi above reactor pressure.)
One drive (42-19) on April 14 could not be unlatched and withdrawn even using pressures above 400 psid. This drive was declared unoperable and valved i
out of service. Following the shutdown on April 19 this drive was successfully_un-
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1atched after repeated attempts.
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4 C.
Scrams to the 02 Position On three occasions following a scram, one or more drives were found to be latched at the first notch (02 position, 6 inches withdrawn) rather than fully inserted (00 position). Attachment 1 gives the details graphically. The drives were subsequently driven to 00, indicating that no mechanical interference existed.
It is theorized by GE that the scram motion is stopped between 02 and 00 and that the drive then settles back to 02.
The cause of the stoppage is theorized to be high leakage of reactor water through the top pair of stop piston seals. This leakage causes a high back pressure in the buffer zone above the moving drive piston, balancing the force of the scram water. GE believes that the large buffer flow area between position 04 and 02 will prevent the back pressure from building up below the 02 position and thus prevent the drive from stopping further withdrawn than 02.
D.
Scram Dump Fill Time The station event recorder was used to determine the time from the initiation of a reactor scram to the filling of the scram dump volume to 37 gallons.
(At 37 gallons, a high dump volume scram occurs.)
In February, the time was measured to be about 26 seconds. The April 7 scram measured 10.6 seconds and the April 17 scram 8 seconds.
E.
Scram Times A review of scram times to 10, 50 and 90% insertion for the last three scrams indicated normal drive performance. A review of the scram buffer times (last 10% of travel) indicated a wide variation (from 0.2 to 0.7 seconds for the drives that went to 00).
F.
Control Rod Exercising Following the April 14 scram with two CRD's out of service, daily rod exercising was required.* Records of this were available for April 16, 17, and 18, but not April 15.
These records indicated that several drives could not be moved with the normal notching sequence and required the use of the notch over-ride system. Many drives required over 250 psid drive water pressure, some more than the maximum gauge reading of 400 psid.
- Technical Specification 4.2D.
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. G. -October 1969 CRD Rebuilding I
During the October 1969 internal filter removal program, 22 CRD's were I
rebuilt. The records for this work indicated that the following was found during the drive examination:
f Stop Piston Seals Drive Piston, Internal Drive Piston, External I;
Broken 61%
Buffer seals broken 68%
Seals broken 14%
Worn 10%
Buffer springs broken 68%
Seals worn and Stuck 5%
Up seals broken 52%
scored 18%
Up springs broken 64%
Collet piston Down seals broken 43%
rings stuck 14%
Down springs broken 43%
No records were available to indicate if any index tubes were measured or replaced during this rebuilding.
III. Results of CRD Inspection The inspectors observed the removal from the reactor and disassembly of the first four CRD's.
The following summarizes the principal findings of the inspec-tions:
A.
Seals 1.
Stop piston seals - all four seals on all four drives were broken.
2.
Two of the four drives had broken drive piston internal seals and springs.
3.
Collet seals on all drives appeared normal.
B.
Index Tubes Two of the four drives examined had swollen index tubes. The swelling was in the area of the threaded connection to the drive piston and ranged from a 20-40 mils diametrical increase.
C.
Cooling Water Orifices Three of the four drives were found to have plugged or partially plugged cooling water orifices. The material found was not the normal reactor crud but white or transparent material.
It has not been identified nor has its source been located.
D.
Dirt and Radiation Levels The drives were found to be relatively free from foreign material. One of the three drives had a 10 mil inner filter.
Examination of this drive did not reveal a detectably cleaner condition. A small amount of dirt was found in the external filters.
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A Radiation levels in the drive area were lower than expected by GE and JC personnel. The spud-filter end of the drive readev 60 mrem gamma on contact.
These parts are removed from the drive first and stored in a pail of water until i
reassembly begins.. A selective review of peicil dosimeter records indicated 7
personnel exposures generally less than 10 mrem per day. No instances of i
personnel contamination were observed.
IV..QA and Requalification Program At the time of the inspection the QA program had not been fully developed and the requalification program had not been planned..
i A QA representative from GPU was assigned to each of the two work shifts.
They were provided with a disassembly report form (Attachment 2) but were not j
provided with any reassembly check sheets. This was discussed with Mr. Riggle
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who stated that he would review the GE CRD manuals and work up a form for their
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i At the close of the inspection a pressure seal test report form had been printed.for use during the final leak test. The form (Attachment 3) was set up so that either the 160 psig or the 200 psig demineralized water header could be used for the test. The inspector observed that the pressure correction to the allowable leakage had been made in the wrong direction.
Mr. Riggle stated that this would change before the form was used.
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02 10 18 26 3h h2 50 WEST t
Rods at 02 i
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i CORE ARRANGEMENT JERSEY CENTRAL POWER & LIGHT '
CONTROL CELLS C0 Report No. 219/70-$ ;
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DISASSDfBLY REPORT CONTROL ROD DRIVE 23?E179 )
Flang2 Ns.
Plant Identification Serial No.
Date Removed from Location RADIATibN LEVELS AS REMOVED: At Coupling Spud Max. Along Drive At Flange At Outer Screen
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RADIATIDH LEVELS AFTER CLEANING: At Coupling Spud' Max. Along Drive At Flange At Outer Screen Using the DISASSD(BLY INSTRUCTION & the INSPECTION INSTRUCTION in GEI-29808 as guides.
l check the following items. Comument on any observations that could contribute to drive 1
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failure that are not listed on this form.
UNCOUPLING ROD'ASSY. -- Are tack welds securef l
Is right drive number on rod?
t1LTERS & COUPLING SPUD - What is condition of threads?
l Are the Fingers Bent?
Condition of Wear Surface L
Condition of Outer Filter Amount of Dirt i
Condition of Inner Filter Amount of Dirt I
CfLINDER TUBE & FIANGE - Bore Condition is Honing Required?
Is 0-Ring Sealing Area OK7 Condition of Strainer Did you replace the ball retainer 0-Ring?
Has the Collet Housing area been dented? (use sleeve as gage)
DRIVE PISTON ASSY. -- Are Seal Grooves OK7 Did Magnet Housing Seal Cups come out freely?
Are Seal Cups OK?
Condition of Seals & Bushings per the sketch & number below.
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- INDEX TUBE -- Indicate Corrosion & Nicks by following key.
L 48 46 44 42' 06 04 02 00 TT 3
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Check Bow 1
COLLET AND PISTON ASSDiBLY - Are Rings free in grooves?
'l Are Grooves OK7 Are Fingers OK7
'tingers free on Retainer?
Is Collet Spring corroded?
le Guide Cap Chipped?
-In there Wear on ID of Guide Cap?
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PISTON TUBE ASSEMBLY ~ Chart any Corrosion r
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Condition of 0-Rings Are Spring Washers OK7 i
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'. ATTACHMENT 2 Page 2 of h es.
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.STOP PISTON ~~ Condition of Grooves Was Stop Piston tir,ht on Piston Tube?
Was Stop Piston ReI rilled?
D Condition of Seals 4 Bushings per the Sketch and Numbers Below y
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2 3
4 5
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I COMMENTS 1
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PRESSIRE SEAL TEST REPORT FORM 6
FRE-DISASSEMBLY i
'AllowedMi,/ Min.
Actual ML/ Min.
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160 psig.
200 psig.
I Coupling Spud 211' 189 W
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Collst Port 1267 1135 Over Pressure Water Port Ph5 757 Total 2323 2081 s
POST ASSEMBLY P-0VER Allowed ML/ Min.,
Actual MLJ4 tin.
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~l 160 psig.
200 psig.
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Coupling Spud 1267 1135 Collect Port 2 958 26h9
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Under. Pressure Water Port 885 757 3
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Note errors discussed in section IV.
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ATTACHMENT 3 I