Part 21 Report - 1998-154

ACCESSION #: 9804270179 South Carolina Electric & Gas Company Gary J. Taylor P.O. BOX 88 Vice President Jenkinsville, SC 29065 Nuclear Operations (803) 345-4344 SCE&G A SCANA Company April 17, 1998 RC-98-0076 Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555 Gentlemen: Subject: VIRGIL C. SUMMER NUCLEAR STATION DOCKET NO. 50/395 OPERATING LICENSE NO. NPF-12 FINAL REPORT PURSUANT TO 10 CFR PART 21 (SSH 98-002) Ref: (a) Gary J. Taylor to Document Control Desk, RC-98-0045 dated March 02, 1998. (b) Darryl Hartley, Engine Systems, Inc. to George Robertson, SCE&G, 702115 dated March 18, 1998. This final report for the potential 10 CFR Part 21 reportable issue regarding the "A" Diesel Generator EG-B for the Virgil C. Summer Nuclear Station (VCSNS) is submitted as a followup to reference (a), pursuant to the requirements of 10 CFR 21.21(a)(2). The results of the additional troubleshooting and cause determination are attached. The vendor provided their response to VCSNS on 3/18/98 (Ref (b)). This evaluation concludes that the failure of the EG-B unit is not reportable under 10 CFR Part 21. Should you have any questions, please call Mr. Michael J. Zaccone at (803) 345-4328. Very truly yours, Gary J. Taylor GJT/mjz Enclosure c: Distribution NUCLEAR EXCELLENCE - A SUMMER TRADITION! Document Control Desk RC-98-0076 SSH 980002 Page 2 of 2 Distribution J. L. Skolds D. L. Abstance W. F. Conway R. J. Waselus R. R. Mahan R. L. Osborne R. J. White G. A. Robertson L. A. Reyes J. B. Knotts Jr. L. M. Padovan NRC Resident Inspector R. B. Clary INPO Records Center M. F. Miltner J & H Marsh & McLennan A. R. Koon NSRC G. E. Williams RTS (SSH 980002) T. L. Matlosz Files (818.18) B. C. Williams DMS (RC-98-0076) P. Ledbetter Attachment to Document Control Desk RC-98-0076 SSH 980002 Page 1 of 2 The Woodward governor hydraulic actuator (EG-B) unit was sent to Power Control Services of Engine Systems Inc. for an as-found evaluation and refurbishment following the speed oscillations which occurred during surveillance testing on 12/30/97. An interim report for 10 CFR Part 21 reportability was necessary due to additional troubleshooting and cause determination efforts for this hydraulic actuator. Speed oscillations occurred on the "A" diesel generator after opening the DG output breaker during surveillance testing (STTS#9721373) on 12/30/97. After extensive troubleshooting, it was determined that these speed oscillations were due to a problem with the Woodward governor hydraulic actuator (EG-B) unit. The EG-B unit was replaced and the oscillations disappeared. The EG-B unit (Serial No. 1380933) was sent to Power Control Services (Woodward representative) for a determination of the cause of the instability and for refurbishment. It was initially thought that several nicks found on the lower land area of the main relay plunger could have caused the instability. From the vendor evaluation, the nicks on the land area of the main relay plunger were a contributor to this problem; however, replacement of this plunger did not totally resolve the instability in the unit. Additional research was conducted to: 1) perform hot bore dimensional checks on the sub- governor power case, 2) replace parts in the unit to eliminate the instability, and 3) locate and review the previous repair records for the unit. 1) The hot bore checks have been completed on the power case with no problems identified. Also, the EG-B was reassembled using a new power case with the old relay plunger and instability was still observed. Additionally, the EG-B was disassembled and reassembled several times with a new power case and relay plunger, but the unit continued to exhibit instability. 2) Several other parts including bushings and seals were replaced, but the instability was still present. A replacement subgovernor was then built from a core unit and was identical to the original design with the exception of installing a new, upgraded ballhead and heavy duty buffer springs. With these changes the unit exhibited steadier operation. The original subgovernor with the upgraded ballhead was tested, showing a better response, but the unit still exhibited hunting. The original subgovernor containing both the heavy duty buffer springs and the upgraded ballhead was tested satisfactorily. The vendor stated in reference (b) that there was excessive gain on the mechanical part of the governor. Compensation for the instability could only be made by replacement of the original ballhead with an updated version and by replacement of the original buffer springs with heavy duty ones. Attachment to Document Control Desk RC-98-0076 SSH 980002 Page 2 of 2 3) Previous repair records for the EG-B unit were not located at the vendor's facility. This was attributed to the 1985 repair being performed at the Fort Collins, Colorado facility (nuclear units are now repaired at the Rocky Mount, North Carolina facility) and to computer changes which occurred at Woodward in the early 1990s. Plant records indicate that this EG-B had a history of hunting problems. The EG-B (Serial # 1380933) which failed during this event had been replaced in 1981, before initial plant criticality. Diesel setup and startup testing were occurring at this time, so this EG-B did not have any significant operating history. This EG-B was apparently having problems due to hunting, but no additional details were documented. It was stored in the warehouse until December, 1985, sent to Woodward for repair, and returned to VCSNS in April 1986. It was again stored in the warehouse until being placed in service from 11/11/97 until the 12/30/97 event. Essentially every subcomponent was inspected and compared against design specifications, therefore, instability of this EG-B unit was not due to a defect in design or hardware. Additionally, this unit was operated and maintained in the same manner as the other units onsite (which have an extensive failure-free service history), therefore, this problem was not due to improper operation or maintenance instructions. Per discussions with the vendor, instabilities experienced with EGBs in the past have been attributable to an identified failure mechanism. The instability observed with this specific EG-B is not typical and appears to be an isolated incident. In conclusion, this problem appears to be unique to EG-B, Serial # 1380933, and has not been previously observed by the vendor or otherwise reported by industry events. Based on the above, the cause of the speed oscillations has been determined to be a one-time, non-repeatable failure of the EG-B, and therefore, not reportable under 10 CFR Part 21. *** END OF DOCUMENT ***

Page Last Reviewed/Updated Friday, January 31, 2020