ML20108E503
| ML20108E503 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 02/20/1985 |
| From: | Tucker H DUKE POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-85, REF-PT21-85-143-000 PT21-85-143, PT21-85-143-000, SD-414-85-01, SD-414-85-1, NUDOCS 8503120209 | |
| Download: ML20108E503 (3) | |
Text
I DUKE POWER GOMPANY P.O. HOX 33180 CIIAHLOTTE, N.C. 28242 HALB. TUCKER TELEPHONE vmmrarsinsar (704) 373-4531 05 f E8 22 rEbklee90,1985
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Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region Il 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 RE: Catawba Nuclear Station, Unit 2 Docket No. 50-414 Significant Deficiency No. 414/85-01
Dear Mr. O'Reilly:
Pursuant to 10CFR 50.55(e), please find attached Significant Deficiency Report No. 414/85-01 concerning Control Rod Drive Mechanism guide screws.
Very truly yours, k 8 f.JAc L /////
/
Hal B. Tucker LTP/mjf Attachment cc: Director Mr. Robert Guild, Esq.
Office of Inspection and Enforcement Attorney-at-Law U. S. Nuclear Regulatory Commission P. O. Box 12097 Washington, D. C. 20555 Charleston, S. C. 29412 NRC Resident Inspector Mr. Jesse L. Riley Catawba Nuclear Station Carolina Environmental Study Group Palmetto Alliance 854 Henley Place 2135 Devine Street Charlotte, North Carolina 28207 Columbia, South Carolina 29205 1NPO Records Center Suite 1500 1100 circle 75 Parkway Atlanta, Georgia 30339 DiGCIAI? COPY 8503120209 850220 PDR ADOCK 05000414 bM
e CATAWBA' NUCLEAR STATION-REPORT NUMBER: 4D 414/85-01 REPORT DATE:
February 20, 1985 l
FACILITY: Catawba' Nuclear Station Unit 2 IDENTIFICATION OF DEFICIENCY:
- Westinghouse, by' letter dated December 11, 1984.-notified Duke Power of an event at the Korean Unit 5 site concerning the Control Rod Drive Mechanism (CRDM) design similareto the ones at Catawba Unit 2.
It'was determined that.
the potential existed for a breech guide screw in the CRDM heavy drive rod
-to work loose and drop out of it's normal position. An inspection / test was performed applying 30 in. Ibs. reverse torque to the breech guide screws of the-Unit 2. drive rods and 15 of 57'were found to be unacceptable. This was reported as Nonconforming Item (NCI) CN-206.
INITIAL REPORT:
On January 21, 1985, C. Burger, NRC Region II, Atlanta, Ga. was notified of.
this deficiency by L. M. Coggins, D. M. Collings and T. L. Utterback of Duke Power Company, P. O. Box 33189, Charlotte, N. C. 28242.
COMPONENT AND/OR SUPPLIER:
CRDM Heavy Drive Rod Westinghouse EMD Cheswick Avenue Cheswick, PA 15024 s
DESCRIPTION OF DEFICIENCY The-following describes cause of the deficiency for the;following drive rod assemblies in which the breech guide screw unthreaded.(counter clockwise) during the initial inspection at the noted torque valves:' serial number 4185 (10 inch pounds), S/N 4294 (no torque), S/N 4300 (25 ~in. lbs.) S. N 4903 (no torque) and, S/N 5014 (20 in. Ibs.).
The following~20 drive rods had.
breech guide screws that moved or rotated a little, but did not become unthreaded with'40 in. 1bs. torque: serial numbers 4103, 4104, 4115, 4122, 4126, 4147, 4166, 4167,'4202, 4235, 4261, 4262, 4280, 4290, 4295, 4296, 4298,
~
4301, 4309, 4901.
The breech guide screw's function.is to provide alignment and guidance of the breech components during coupling and uncoupling of the drive rod from the rod cluster control assembly. The absence of-the guide screw does not effect coupling'and uncoupling..since the travel limits are incorporated into the.
coupling / uncoupling tool..However, if the 0.433 inch diameter by 0.52 inch long guide screw completely unthreads from the drive rod assembly,.it would fall down the annulus between the drive rod assembly.and the rod travel housing during control rod stepping.
It~can then lodge.on the latch assembly causing binding, misstepping or a stuck drive rod. The guide' screw Is locked into position by a pin that is intended to intersect the mating threads and which h0 */,
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is. welded to the guide screw,sto. hold it-in place. -The deficiency, occurs
'when the. pin fails.:to intersect the mating' threads,'allowingithe breech guide screw to unthread..
' ANALYSIS 0F. SAFETY' IMPLICATIONS:
If.:n,t corrected, one or more breech guide screws may have unthreaded, fallen out a0d lodged in'the latch. assembly such that potential ~ rod misstepping, binding.
Lor a'scuck driveline may have resulted.
CORRECTIVE' ACTION AND STATUS:
'An inspection / test. applying a reverse torque of 30.in. lbs. to the breech guide screw of all-the Unit 2 CRDM heavy drive rods has been completed. The results were that five screws unthreaded completely; twenty'other screws were. loose but did not unthread, even when checked to 40 inch pounds.
Westinghouse issued a Field Change Notice (FCN) DDPM10577 which contained inspection procedures and two types of repair procedures, one for rods with icose screws (but still in place) and one for rods without guide screws (removed during inspection). Westinghouse personnel performed the: inspection / test and repair of_the CRDM heavy drive rods beginning on January 23, 1985. Small screw movements of less than 15 degrees rotation were accepted. Movements greater than 15 degrees indicated a possible problem with the lock pin and therefore were unacceptable along with rods in which the guide screws unth'eaded during r
the inspection / test. The inspection / test resulted in eleven rods requiring repair, six in which the breech guide screw unthreaded completely.and five which had unacceptable rotational movement.
The following drive rods were repaired by installing a new breech. guide screw and lock pin: S/N's 4185,' 4280, 4294, 4300, 4903, and 5014. For drive' rods S/N's 4166, 4202,'4290, 4298 and 4901 which had unacceptable screw movement, an additional-lock. pin was installed a minimum-of 90' degrees from the original lock pin. All the repaired ~ rods were.
reinspected / tested and are now acceptable.
An inspection of the Unit 1 CRDM heavy drive' rods has also been conducted and reported in LER 413/84-29. Also, by letter dated December 12, 1984, from H. B. Tucker to J. P. Reilly, NRC Region II was notified of this potential deficiency on McGuire. Unit 2.
Westinghouse has reported this deficiency under 10CFR21.
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