IR 05000237/1986018
| ML17199F820 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/26/1986 |
| From: | Muffett J, Smeenge R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML17199F819 | List: |
| References | |
| 50-237-86-18, 50-249-86-22, NUDOCS 8607020009 | |
| Download: ML17199F820 (4) | |
Text
~---- ---- ------
U.S. NUCLEAR REGULATORY COMMISSION REGION II I Reports No. 50-237/86018(DRS); 50-249/86022(DRS)
Docket Nos. 50-237; 50-249 Licenses No. DRP-19; DRP-25 Licensee:
Commonwealth Edison Company P. 0. Box 767 Chicago, Illinois 60690 Facility Name:
Dresden Nuclear Power Station, Units 2 and 3 Inspection At:
Morris, Illinois Inspection Conducted:
June 18, 1986 Inspector:
_J~~-H.J)D.,,* r R. Smeenge
~ _x---~ 1'tr'--
Approved By: J. W. Mu~~f~
Plant Systems Section Inspection Summary tof z.<o /Bra Date Inspection on June 18, 1986 (Reports No. 50-237/86018(DRSJj_§Q~242/8§Q££JDR~Jl Areas Inspected:
Special reactive inspection by a regional inspector of Electro-Hydraulic CuriLrul (EHC) system hydro.ulic fluid mig1~u.tion to the ceiling of the cable tunnel area which had dripped into cable trays causing degradation of cable jacket Results:
No violations or deviations were identified; however, further NRC inspection of the licensee's corrective action and implementation of a surveillance program related to monitoring cable insulation degradation is planned.
DETAILS Persons Contacted
- R. Zentner, Assistant Superintendent, Maintenance L. Sebby, Master Electrician
- M. Strait, Station Nuclear Engineering
- Denotes those attending the June 18, 1986 exit intervie The inspector also contacted and interviewed other licensee and contractor personnel during this inspectio.
Background On June 9, 1986, the licensee notified the NRC that hydraulic fluid from an Electro-Hydraulic Control (EHC) system had migrated to the ceiling of the floor below and dripped into the cable trays located in the cable tunnel are The hydraulic fluid is a phosphate-ester fire resistant fluid which had a deleterious effect on the polyvinylchloride (PVC)
jackets of the electrical cables. A large number of the cables in the upper most trays had visible outer jacket damage (blisters, cracks and plasticization).
One of two upper trays had cover plates installed which localized damage to the areas directly below the seams in the cover plate The other upper tray, which did not have cover plates, collected the fluid which then flowed along the cables and bottom of the tray causing damage over approximately 30 linear feet in one area and several feet in another are The fluid collected in the upper trays dripped through seams to the trays below and caused localized damage to the cables in the lower tray The source of the fluid was identified as the EHC system pump and coolant unit. This unit is set in a shallow concrete pit in the floor which is intended to contain spilled or leaking fluid. At the time of this inspection there was about one inch of fluid collected in the bottom of the pit. The licensee stated that this very viscous fluid migrated through small cracks in the concrete over to the ceiling of the cable tunne One leak was approximately 20 feet and another was approximately 35 feet from the EHC uni In October 1975, the Quad Cities Nuclear Power Station had a very similar occurrence where EHC fluid leaked through the floor onto cable trays and caused damage to cable outer jackets. At that time the NRC issued IE Circular 77-06 which warned licensee's of the deleterious effects of hydraulic fluid on electrical cables. This IE Circular emphasized the importance to minimize the probability of leakage, overflow or inadvertant spill of fluid and to provide for prompt cleanup of spills or leakag * Information from various cable manufacturers and the manufacturer of the phosphate-ester EHC fluid identified that polyvinylchloride (PVC) and neoprene are affected severely by the EHC fluid. Other polymers such as polyethylene, teflon, silicone rubber, nylon and butyl rubber are identified as acceptable for use in the areas where EHC fluids are use The EHC fluid has a very low conductivity ratin Inspection Details The NRC inspector reviewed the short term corrective action in progres Cables are being lifted out of the trays and the trays are washed down with detergent to remove all traces of the flui Each cable is then visually inspected for damage and washed with detergen Damaged jackets are removed and the inner conductor insulation is visually examine The inner conductor insulation is then washed with detergent and drie The inner conductor insulation then is touched to locate any areas where the insula-tion may have been degraded by the fluid as indicated by it being tacky, softened, cracked, blistered or swelling. Cables with no damage indicated are returned to the clean tray. Cables which have had the damaged jackets removed and cleaned are visually examined by a management person who tags the cable with a band of yellow tape to identify that the cleanup has been completed and is acceptable. After this review, repairs can be complete The damaged jackets are removed beyond the point where the jacket no longer feels tacky. Three half lap layers of Scotch 33# tape is applied over the section of cable where the jacket has been remove The tape extends 1-2 inches over the good cable jacket. The repaired cable is then returned to the cleaned tra The NRC inspector observed that damage jacket repairs had been performed in areas from 1 inch up to approximately 20 feet. This cleanup and repair is being accomplished in accordance with written instructions attached to the work request The two upper trays with the most damage contain both Unit 2 nnd Unit 3 safety system power (CT13MI) and control cables (CT13TM).
The licensee stated that all the damage to the cables was localized to the outer jacket and that there was no evidence that the conductor insulation had been degrade The NRC inspector did not find any visual damage to conductor insulation. Visual inspection, by the NRC inspector, found the detergent appeared to have removed the fluid from the trays and cables. Tray CT13MI has 73 cables, all of which required some repair. Tray CT13TM has approximately 90 cables of which 60 have been identified as requiring repai.
Safety and Environmental Qualification Si]~jficants Jackets on cables are not intended to provide an electrical insulation functio The jacket provides mechanical protection of the cable conductors during normal useage and installation. Electrical insulation is provided by the conductor insulatio The cables inspected were not located in a
I ___ _
harsh environmen Cables are environmentaly qualified with and without a jacket. The Scotch 33# tape has been environmentally qualified to cover splice The licensee is applying the tape to provide mechanical protection for the conductor insulation. At this time there does not appear to be any safety or environmental qualification significanc.
Future Corrective Action The licensee has not completed their evaluation of what future corrective action will be take In discussion between the NRC inspector and the licensee the following actions are being considered: Providing sealed hip roof covers for the upper most cable trays (previously only l of 2 had a flat cover). Surveillance of the cable tunnel area at least one time per day (presently there are no schedule visual surviellance of the area).
c. Surveillance and cleanup of the fluid source, the pit where the EHC pump is locate Reinspection of the damaged area at a later date to determine if corrective action at this time was adequat The licensee's future corrective action is considered an open item and followup inspections are planned by the NRC to monitor the actions as well as conductor insulation integrity (237-86018/0l(DRS);
249-86022/0l(DRS)). Open I terns Open items are matters which have been discussed with the licensee, which will be reviewed further by the inspectors, and which involves some action on the part of the NRC or licensee or bot An open item disclosed during this inspection is discussed in Section.
Exit Interview The inspector met with licensee representatives (denoted in Paragraph 1)
at the conclusion of the inspectio The inspector summarized the scope and findings of the inspection noted in this repor The inspector also discussed the likely informational content of this inspection report with regard to documents or processes reviewed by the inspector during this inspectio The licensee did not identify any such documents/processes as proprietar