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| {{Adams
| | #REDIRECT [[05000237/LER-1976-068-03, /03L-0:on 761212,CRD F-5 Found to Uncouple & Overtravel When Withdrawn to Position 48 Following 50% Core Scram Testing.Caused by Loosened Inner Filter.Crd F-5 to Be Disassembled & Insp]] |
| | number = ML20027A358
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| | issue date = 10/27/1978
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| | title = /03X-1 on 761212:during 50% Core Scram Testing CRD F-5 Uncoupled & Overtraveled When Withdrawn to Position 48.Unlatched Inner Filter & Abnormally Long Uncoupling Rod Resulted in Uncoupling CRD F-5 During Testing
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| | author name = Wujciga J
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| | author affiliation = COMMONWEALTH EDISON CO.
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| | addressee name =
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| | addressee affiliation =
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| | docket = 05000237
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| | license number =
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| | contact person =
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| | document report number = LER-76-068-03X, LER-76-68-3X, NUDOCS 7811210304
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| | package number = ML17173A373
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| | document type = LICENSEE EVENT REPORT (SEE ALSO AO RO), TEXT-SAFETY REPORT
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| | page count = 2
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| }}
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| {{LER
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| | Title = /03X-1 on 761212:during 50% Core Scram Testing CRD F-5 Uncoupled & Overtraveled When Withdrawn to Position 48.Unlatched Inner Filter & Abnormally Long Uncoupling Rod Resulted in Uncoupling CRD F-5 During Testing
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| | Plant =
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| | Reporting criterion =
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| | Power level =
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| | Mode =
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| | Docket = 05000237
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| | LER year = 1976
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| | LER number = 68
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| | LER revision = 3
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| | Event date =
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| | Report date =
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| | ENS =
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| | abstract =
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| }}
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| =text=
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| {{#Wiki_filter:.
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| '4 RC F C.t M %d U. S. NUCLEAR HEGULATORY COMtilSSla!I LICENSEE EVENT REPORT UPDATE REPORT:
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| PREVIOUS REPORT DATE 1/10/77 CONTROL SLOCC l l
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| l l
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| l l lh (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) i e
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| 4 9 LICENSEE CODE 14 l$
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| LICEP.SE NYCJER 25
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| ;ts LICENSE TYPE JJ Si CAT Sd COTJ'T lolil
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| F 6
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| 60 61 DOCKET rsu'.tSER M
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| 69 E'.'ENT O ATE 74 75 RE*CRT CATE 80 EVENT DESCRIPTION AND PRO 9ABLE CONSEQUENCES h lo l2l l During 50% cora scram testing, CRD F-5 uncoupled and overtraveled when withdrawn to l
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| t o 13 I 16os. 48. Insertion to pos. 44 and subsecuent withdrawal to pos. 48 showed drive Io I4 i irecoupled. Second scram and withdrawal to pos. 48 uncoupled drive.
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| CRD F-5 then l
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| ~
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| l o f s !
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| inserted to "0" and disarmed.
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| Three symmetrical drives also inserted. Safety sig-l l o is 1 I nificance minimal since uncoupling occurred only at pos. 48.
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| CRD uncoupling has l
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| loccurred several times in past.
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| I cialI l
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| 3 9 80 SYSTENt
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| ==CAUSE==
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| CAUSE COVP.
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| ;0 SEQUENTf AL OCCURRENCE REPORT REVISION
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| 40 el 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTICNS 27 l i ; a l l Unlatched inner filter and abnormally long uncoupling rod resulted in uncoupling CRD l g.
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| l[ F-5 during testing.
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| Drive had been overhauled in Jan. 1975.
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| A pull test on inner i
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| ,,,,,j filter has now been incorporated in the overhaul and reassembly procedure.
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| Revised l procedure and improved QA coverage believed adequate to prevent future similar events.;
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| g,;3; it i il I S 9 83 ST 86 POWER oTHER STATUS 15 RY DISCOVERY OESCRIPTION
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| ATTACIDIE'IT TO LICENSEE EVENT REPORT 76-068/03X-1 COMMONWEAL'IH EDISON COMPANY (CWE)
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| DRESDEN UNIT-2 (ILDRS-2L DOCKET #050-237 Follow 1ng 50% core scram testing, CRD F-5 was found to uncouple and overtravel when withdrawn to position 48 An insertion'to position 44 and subsequent withdrawal to position 48 showed the drive to be recoupled.
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| A second scram and withdrawal to position 48 again uncoupled the drive.
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| CRD F-5 was then inserted to position 00 and disarmed.
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| The three symmetrical
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| (
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| drives in the remaining quadrants were also fully inserted.
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| On 12/30/76, an on-site review determined that a loosened inner filter caused the blade and drive to uncouple at position 48.
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| It was also de-termined that the loosened filter could not exert sufficient pressure to uncouple the blade except when the drive was fully withdrawn to position 48; upon insertion, the blade and drive automatically recoupled.
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| Since the possibility of uncoupling the blade existed only when the drive was withdrawn to position 48, CRD F-5 was then declared operable.
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| As a pre-cautionary measure, an Operating Order was issued to ensure that a coupling check was performed whenever drive F-5 was withdrawn to position 48.
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| Also,-
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| ~_
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| if a subsequent uncoupling occurred, immediate action was to be taken to ensure that the drive's status complied with Tech Spec section 3.3.B.1.
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| As mentioned above, symptom and performance evaluations indicated that a loosened inner filter had caused the blade and drive to uncouple at the fully withdrawn position.
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| Loosening of the filter could have resulted f, rom
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| (
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| improper installation and latching spring fatique.
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| On October 6, 1977 CRD F-5 was disassembled and inspected per control Rod Drive Inspection and Maintenance Procedure DMP 209.
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| To assure a comprehensive inspection a special operating procedure (SOP 216) was prepared and followed.
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| Upon inspection it was found that the inner filter was unlatched.
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| In addition the distance between the CRD flange and the end of the fully seated uncoupling rod was abnormally long (173.406 + 0.375 in.) The abnormal length, coupled with an unlatched inner filter, resulted in the uncoupling of the CRD.
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| ~
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| CRD F-5 had been last overhauled in January, 1975.
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| Since May, 1975 a 20 to 30 pound pull test on the inner filter has been incorporated in the overhaul and reassembly procedure. Control Rod Drives overhauled and re-assembled under this revised procedure have not experienced uncoupling.
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| The revised procedure, coupled with improved Quality Control Coverage of CRD overhaul and reassembly, are believed to be adequate to prevent future CRD uncoupling.
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