ML20084R577
| ML20084R577 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/12/1975 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 155-75, AO-50-249-75-13, RO-50-249-75-13, NUDOCS 8306150203 | |
| Download: ML20084R577 (4) | |
Text
';-- ?g Comm:;nw: nIth Edison i3/ One First *Mnat Plan. CH::no. Ilkno.s q '
Address
'y to: Post O'hce Box 767 V *.
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Chicago,....nois 60690 is BBS Ltr. #155-75 Dresden Nuclear Power Station R. R. 91 Morris, Illinois 604 Q March 12, 1975 o?
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/g' 1.h'(,j Mr. James G. Koppler, Regional Director j
e Directorate of Regulatory Operation-Region III U. S. Nuclear Regulatory Co=ission M
ir '#8 799 Roosevelt Road E's ' /
Glen Ellyn, Illinois 60137
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SUBJECT:
REPORT OF H2:CRI'tJ, OCCUERE:CE PER SECTICN 6.6.A 0F Tl bCIR!IC/Ji SPECIFICATIO]
U-3 D:CESSIVE CCNT30L ROD SCR!lI TIIGS
References:
- 1) Regulatory Ouide 1.16 Rev 1 Appendix A
- 2) Notification of Region III of U. S. Nuclear Regulatory Conriission Telephone:
P. Johnson,1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br /> on Ihrch 4,1975 Telegram:, J. Keppler,1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br /> on I' arch 4,1975 Report Number: '50-249/1975-13 Report Date: March 12, 1975 Occurrence Dato: March 2, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois 60450 IDETIFICATION OF OCCURRE:CE U-3 control rod drive scram times failed to :ncet a limiting condition for operation as defined in section 3 3.C.1 of the Technical Specifications.
CONDITIC'?S PRIOR TO OCCURR ECE Unit 3 was in the run r:odo opere. ting at a power level of 910 IcJt and 270 Dle.
DESCRIPTION OF OCCURRE:CE On l' arch 2,1975, the 1 week 25 control rod drive (CRD) cera:a testing curveillance was in progress. Upon coupletion of testing the 25 drives, it 8306150203 750312 l
PDR ADOCK 05000249 l
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Mr. Janca G. Keppler March 12,197p
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U was determined that drive J-9 had exceeded the 25 drive average for the 90T insertion time by* greater than 0.75 cecc. The eight drives around J-9 were then scram tected. Of these eight drivco, J-8 had a 905 incertion time exceeding the 25 drive average by greater than 0.75 cecc. It una then necessary to scram two more drives to ecmplete the cicht around J-8.
An 1:tmediate evaluation was mado of the 90% times and average to check against technical specification limits. As 905 times have been the most lir.iting in the past, these were the only ones carefbily analyzed at that time.
Drive J-9 was ceram.ed a cceend timo on March 2 after the long time was noted.
The drive tested satisfactorily on the cecond test and met all limits.
Further evaluation led to the discovery at about 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on March 4 that specification 3 3.C.1 of the technical crecificationc could not be met. The section that could not be met was the 55 and 20$ limits for the averago of the scrara insertion times for the three fastect control rods of all groups of four control reds in a two by two array. The maximum time allowabic for 5% insertion is 0 398 cccc cnd for 20% incertion in 0.954 secs. The actual times obtained are listed below:
5% Insertion 20% Insertion 10
.47
.35 53 10 1.19
.86 1.19 9
.33 57
.33 9
.83 1.38 80 8
51
.40 56 8
1.18 1.04 1.25 H
J K
H J
K RESULTS OF THE EVALUATION OF THE 2X2 ARRAYS Th w e u o, u 19,
- y. $9 Sg..,.g, g
,g Drives J-10, K-10, K-9 55 avc.403 secs 203 avs.950 ceca Drives K-9, K-8, J-8 55 avs.430 secs 205 ave 1.03 seca Drives H-9, H-8, J-8 55 avs.413 oces 203 avs 1.017 ceco DESIGNATICM OF APPAR NT CAUSE OF OCCURRF:CR (Equipment Failure)
The cause of the occurrence appears to be due to deterioration of the drive scalc. This condition has been noted in the past and is being monitored closely.
/EEYSIS OF OCCURREN'CE There was no danger to plant personnel or to the public from this occurrence.
If a scram had occurred, the 50% and 90% times were uithin cpecc and the reactor would have been safety chutdown. The clower 55 and 205 times may have resulted in a slightly higher preocura during the worst cace trip (Turbine trip uith bypann valve failurc), but thic would have been offset by the fact that the unit 10 only operating at 50% rower, and is considerably below tne limiting ceran reactivity curve.
CORRECTIVP ACTION The inmediate corrective action following discovery of the occurrence was to ochedule retecting of the 5 questionable drives. At about 11:00 rm on
fr. Jam:s G. K:pp
~3- -
March 12, 1975 March 4, 1975 tho 5 questionabic drives (H-8, H-10, J-9, K-8 and K-10) plus an additional 25 drives, different frcm the original 25 drives, colected at randem throuGhout the core, woro serem tested. The drives mot all technical specification limits. To analyze the 2X2 arrays, the times obtained from the test of March 2,1975 were used for the other four drives (H-9, J-8, J-10 and K-9).
Below are the times obtained:
55 20%
10
.45
.35
.37 10
.97 86 85 9
.33 59
.33 9
.83 1.46
.80 8
.37
.40
.43 8
.85 1.04
.95 H
J K
H J
K Results of the evaluation of the 2X2 arrays were:
Drives H-9, H-10, J-10 55 avg. 377 cecc 20% avs.887 coes Drives J-10, K-10, K-9 5% avs.350 cece 20% avs.837 secs Drives K-9, K-8, J-8 5% avg. 387 seco 20% avg.930 secs Drives H-9, H 8, J-8 5% avg. 367 coes 20% avg. 907 secs The two week test is not required until March 16, 1975, but a special test was conducted on March 9 for the purpoco of this investigation. It uas again necescary to scram test the eight drives around J-9 and J-8.
The 5% and 20%
insertion times for the arrays in question are listed belou:
5%
23 iv
.45
.2y
.51 lu 1.uy
.u 1.26 9
.32 56 32 9
.81 1.44
.78 8
31
.40 51 8
.79 1.04 1.17 H
J K
H J
K RESULTS OF THE EVALUATION OF THE 2X2 ARRAYS UERE:
Drives H-9, H-10, J-10 5% avg..353 cces 20% ave.877 cecc Drives J-10, K-10, K-9 55 avs.373 coes 20% avs.923 cees Drives K-9, K-8, J-8 5% avs.410 socc 20% avs.997 seco Drivcc H-9, H-8, J-8 5% avs.343 secs 20% avg.880 seca Drives K-8 and J-9 could not meet either of the 5% or 20% limits. Drives K-8 and J-9 wore then dcolared inoperable per section 3 3.A.2.d of the technical specifications. There was no prob 1cm meeting specification 3 3.A.1 with one of these drives left at 48, so K-8 was incerted and dicarmed. Mirror symnctric rod F-8 was also inserted to enhance core monitoring capabilitics.
Drivo 'J-9 was left at ivacition "48".
Analytical evaluations are underway to determine if section 3 3. A.1 cm be not with both J-9 and K-8 at "48".
If not, K-8 will be left at "00"/.
The 2 week scram test is due on March 16, 1975 Another drive will be chocen to replace J-9 in the comple of 25 operable centrol rods.
In addition, J-9, and K-8, if it is at position "48", will alco be tected to gather further data on rod drivoc with clow Jerrn times. No further laport will be iccued on their perfomance. Tlicy vi.:.1 be overhauled during the next refueling outage, along uith a number of other drives. The outage is presently scheduled to con: nonce about May 1, 1975 m
m_ _. _. _ _. _ _ _ _ _ _ _ _ _
~4-reh 12, 1975 e
' Fr. Jam:s G. Keppler u
FAILIGE DATA The control rod drivas, model 7 P.D3 144B', have experienced t*m problems in the pact.
- 1) Uncoupling at pocition 48, caused by improper installation of the inner filter, expericnced only on unit 2, and 2) coal ucar, causing excessive 90% scram times.
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B. B. St,cphenson Superintendent BBS: cap Pile /AEC s
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