ML20247D039
| ML20247D039 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 09/06/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CP-89-018, CP-89-18, TXX-89667, NUDOCS 8909140170 | |
| Download: ML20247D039 (3) | |
Text
__.
JU W
w7
!r.
a.
' 1.
Log Jf TXX-89667
=
o"
'::L File.# 10110' V
i.
=
=
908.3 lilELECTRIC.
o September 6, 1989 Esecutive We iYesident
- 10. S.' Nuclear Regulatory. Commission J
Attn: Document Control Desk Washington, D. C.
20555-
SUBJECT:
COMANCHE PEAK STFAH ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 SOLDERING DEFICIENCIES IN ELGAR INVERTERS SDAR:
CP-89-018 (FINAL REPORT)
Gentlemen:
On June 26, 1989. TU Electric verbally notified the NRC.of a potentially reportable deficiency under the provisions of 10CFR50.55(e) concerning printed circuit (PC) boards in Elgar inverters. Our last report was' logged TXX-89493 and dated July 26, 1989.. After further evaluation, it has been concluded that
.this deficiency.is reportable pursuant to 10CFR50.55(e). The required
.information follows.
Description During start-up activities, cracks and broken solder joints have been identified on' printed circuit boards in Elgar inverters which are part of the Uninterruptable Power Supply (UPS) System.
Specifically, three types of deficiencies were identified:
'I.
Cracked solder joints connecting terminal blocks to inverter gate drive L
boards and static switch drive boards in CPI-ECIVEC-01 and Lt.
[-
- 2. Defects in solder joint of transformer T101 on inverter gate drive i
board TBZ in CP1-ECIVEC-01.
- 3. Broken solder joints in back of connector pins on inverter gate drive boards in CPI-ECIVEC-01, 02, 03, and 04.
-Based on inspections performed at the Elgar facility, a review of the Elgar Quality As" ce program, discussion with other users of Elgar equipment and examination of the deficiencies by Elgar and TU Electric, it has been concluded that the probable cause of the observed deficiencies was a result of the trouble shooting and repair to which these boards were subjected at CPSES, 8909140170 890906 ff)1
{DR ADOCK0500gg4b.
I t
400 North OHve Street LB 81 Dallas. Texas 75201
};
@At
(.
e l
.~
1.
TXX-89667 September 6, 1989 Page 2 of 3 primarily as a result of problems related to the concerns of IE Notice (IEN) 08-57.
This Notice discussed.the sensitivity of Elgar inverter performance to proper torquing of the silicon controlled rectifiers (SCR's).
Prior'to the IE Notice, the importance of SCR torquing for proper.Elgar inverter operation was not recognized, and was not specified in applicable vendor supplied maintenance instructions used at CPSES.- Discussions with Elgar Corporation concluded tnat improper torquing of SCR's may result in drive board and logic board failures as well-as SCR failure. Therefore,' torque related c?erability problems occurring prior to IEN 88-57 resulted in frequent trouble shooting and handling of the boards resulting in the pulling of connectors and terminal blocks loose from their soldered connections.
The defective solder joint on transformer T101 in CPI-ECIVEC-01 was not observed in other inverters and is therefore considered isolated.
TU Electric had been asked by its project reviewer.to provide a preliminary look at this issue when the IEN was being developed. At the' time TU Electric reported that it appeared not to impact CPSES since Elgar had indicated that, the CPSES inverters were not involved in any design concerns and some torquing information had been ?btained by CPSES from a subvendor. TU Electric also steted, however, that the final and formal response would be part of the 10CFR50.55(e) review process. That preliminary information was incomplete and is superseded by the final report provided herein.
These deficiencies are considered applicable to all of the Unit I and Unit 2 Elgar inverters and, as discussed in IEN 88-57, are potentially applicable to other electrical components utilizing SCR's.
Reviews performed in response to the IEN did not identify other equipment utilizing SCR's that had inadequate guidance on proper torque.
Safety Significance The UPS inverters are essential for the generation of 118 volt vital A.C.
during normal and accident conditions.
In the event these deficiencies had remained uncorrected, the operability of the inverters could not be relied upon.
These deficiencies represent significant damage to these inverters and required extensive evaluation to establish the adequacy of the inverters to perform their intended safety function. As a result, this issue meets the criteria for deportability pursuant to 10CFR50.55(e).
)
TXX-89667 Septett%r 6, 1989 Page 3 of 3 Corrective Action Broken solder joints identified to date have been corrected.
SCR's in Unit 1 Class IE inverters have been torqued in accordance with Elgar recommendations.
A general inspection and evaluation of the Unit 1 Class 1E inverters by Elgar personnel has been scheduled for early September.
Any additional problems identified will be corrected.
Proper torque values and techniques for torquing of SCR's in Elgar inverters were incorporated into applicable vendor technical manuals as a result of IEN 88-57.
In addition, Elgar will provide guidance for CPSES to use in developing a training program to preclude recurrence. An inspection of Elgar inverters in Unit 2 will be performed by Elgar or trained TU Electric persornel.
Any deficiencies identified will be corrected.
The actions described above will be completed for Unit 1 by Unit I fuel load l
and for Unit 2 by Unit 2 fuel load.
Sincerely,
- X
/,
William J. Cahill, Jr.
WJH/ddm c - Mr. R. D. Hartin, Region IV Resident Inspectors, CPSES (3)
_ _ _ _ _ _ _ _