ML13330B487
| ML13330B487 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/14/1989 |
| From: | Nandy F SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8903200024 | |
| Download: ML13330B487 (7) | |
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0 Southern California Edison Company P. 0.
BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 F. R. NANDY TELEPHONE MANAGER OF NUCLEAR LICENSING (818) 302-1896 March 14, 1989 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, Maryland 20852 Gentlemen:
Subject:
Docket No. 50-206 Standby Diesel Generators San Onofre Nuclear Generating Station Unit 1 The enclosed information is in response to recent NRC staff requests for additional information pertaining to the San Onofre Unit 1 standby diesel generators.
As requested by the NRC, Enclosure I describes the complete maintenance and surveillance program for the diesel generators.
Enclosure II contains SCE's responses to a number of specific items of interest to the NRC staff.
Enclosure III provides an assessment of the acceptability of diesel generator No. I engine base for continued operation.
If there are any questions, please call me.
Very truly yours, cc: 3. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3 8903200024 PDR AMICK4 o
P00O 2 O PIl
0 ENCLOSURE I DESCRIPTION OF STANDBY DIESEL GENERATOR MAINTENANCE AND SURVEILLANCE PROGRAM PROGRAM OVERVIEW The San Onofre Unit 1 diesel generator maintenance and surveillance (M/S) program is primarily based on the TDI diesel generator owners group recommendations contained in Reference A, the TDI Instruction Manual and TDI (Cooper Industries) correspondence on specific M/S issues, as applicable to San Onofre Unit 1. Supplementing these primary source documents are two additional documents: PNL-5600 (Reference B) and NUREG-1216 (Reference C).
The information included in Reference D, as modified and supplemented by References E and F and this submittal is used to interpret and implement NUREG-1216, PNL-5600 and the primary source documents.
The status of the M/S program with respect to Phase I and Phase II components is presented below.
TECHNICAL RESOLUTION OF PHASE I 1-Engine major overhaul frequency complies with the recommended frequency in owners group recommendations.
2-For air start valve capscrews, owners group recommendations as modified by PNL-5600 are implemented.
3-For auxiliary module wiring and terminations, there are no owners group or PNL-5600 recommendations.
4-For connecting rod bearing shells, owners group recommendations are implemented. Oil contamination analyses are performed monthly to satisfy PNL-5600 concern regarding deterioration of shells or other developing problems.
5-For connecting rods, owners group recommendations are implemented.
In addition, the pre-service inspections from Section 4.4.4.4.1 of PNL-5600 have been implemented.
Periodic inspections of connecting rods comply with owners group recommendations, as modified by PNL-5600 and NUREG-1216. (A summary of these modifications is provided in Reference D.)
6-For crankshafts, owners group recommendations as modified by PNL-5600, NUREG-1216 and References 0, E and F are implemented. A proposed license condition pertaining to periodic crankshaft inspection and prompt NRC notification is included in Reference F.
The contingency inspection plan is described in Reference E.
Enclosure I Page 2 7-For engine blocks, owners group recommendations are implemented. In addition, PNL-5600 and NUREG-1216, as summarized and commented on in Reference 0 are implemented. A proposed license condition pertaining to various engine block inspections and reporting requirements is included in Reference F.
8-For cylinder heads, owners group recommendations as modified by PNL-5600 and NUREG-1216 are implemented.
9-For straight shank cylinder head studs, there are no M/S recommendations made by the owners group, nor are there any in PNL-5600. The installation procedure for these studs complies with the TDI Instruction Manual.
10-For engine bases, owners group recommendations as modified by PNL-5600 and NUREG-1216 are implemented.
11-For fuel oil injection tubing, owners group recommendations as modified by PNL-5600 and NUREG-1216 are implemented.
12-For jacket water pumps, owners group recommendations are implemented. The site-specific Stone & Webster recommendations listed in Section 4.15.3.3.3 of PNL-5600 were all completed during Cycle 10 refueling.
13-For Type AE piston skirts, owners group recommendations as modified by PNL-5600 and NUREG-1216 are implemented (See Reference D for a summary of these modifications). The inspections will be performed with liquid penetrant, and, as appropriate, with eddy current.
14-For push rods, owners group recommendations are implemented. As clarified in References C and D, the additional PNL-5600 recommendations regarding push rod inspection are considered optional.
In accordance with PNL-5600, ball-end design push rods will not be used.
15-For rocker arm capscrews, owners group recommendations are implemented. PNL-5600 and NUREG-1216 do not contain any additional M/S items.
16-For turbochargers, owners group recommendations as modified by PNL-5600 and NUREG-1216 are implemented. A summary of these modifications is presented in Reference D. Since no Elliott redesign for nozzle rings is available, nozzle ring inspections will be continued in the future.
TECHNICAL RESOLUTION OF PHASE II The M/S program for the Phase II components is based on the primary source documents only, i.e., owners group.recommendations as supplemented by TDI Instruction Manual and applicable TDI (Cooper Industries) correspondence.
PNL-5600 and NUREG-1216 do not provide specific guidance for the Phase II components.
Enclosure I Page 3
,In accordance with Section 2.2 of PNL-5600, the additional improvement items found in Section 4.0 of PNL-5336 and Section 4.0 of PNL-5444 are treated as discretionary.
FUTURE CHANGES Future changes to the M/S program will be subject to the provisions of 10CFR 50.59.
REFERENCES (A) Letter from M. 0. Medford (SCE) to G. E. Lear (NRC), dated June 20, 1986, Revised TDI Diesel Generator M/S Program.
(B) Review of Resolution of Known Problems in Engine Components for Transamerica Delaval, Inc., Emergency Diesel Generators (PNL-5600), dated December 1985.
(C) Safety Evaluation Report Related to the Operability and Reliability of Emergency Diesel Generators Manufactured by Transamerica Delaval, Inc. (NUREG-1216), dated August 1986.
(D) Letter from M. 0. Medford (SCE) to the NRC, dated February 14, 1989, Standby Diesel Generators.
(E) Letter from K. P. Baskin (SCE) to the NRC dated February 22, 1989, Supplement to Amendment Application No. 156.
(F) Letter from K. P. Baskin (SCE) to the NRC, dated March 11, 1989, Supplement No. 2 to Amendment Application No. 156.
03750
ENCLOSURE II
- 1. Request:
Provide justification for using 150 start-stops instead of 50 start-stops in proposed license condition L().
Response
SCE will implement the 50 start-stop requirement on an interim basis, as clarified in Supplement No. 2 to Amendment Application No. 156, dated March 11, 1989.
- 2. Request:
With reference to proposed license condition L(5), provide justification why visual inspection with intense light is acceptable for cylinder block inspection in lieu of boroscopic inspections.
Response
Visual inspection under intense light is consistent with the owners group recommendations on periodic maintenance and surveillance, which were enclosed with SCE to NRC letter dated June 20, 1986. Visual inspection is also acceptable per Section 4.9.5.2 of PNL-5600. Considering that the engines have been in service since 1977, there is no advantage in using eddy current examination for monthly surveillance in lieu of visual inspection. Owing to only about 1/8" clearance between cylinder heads, use of boroscope is not practical.
- 3. Request:
Describe which of the connecting rod "pre-service inspections" described in Section 4.4.4.4.1 of PNL-5600 have been completed as part of design review and quality revalidation (DR/QR) and which have not.
Response
The pre-service inspections described in Section 4.4.4.4.1 of PNL-5600 have all been completed as part of DR/QR inspections.
- 4. Request:
Confirm that the following PNL recommendation for connecting rods, as incorporated in Appendix B of NUREG-1216, is in the diesel generator M/S program:
"The lengths of the two pairs of bolts above the crankpin should be measured ultrasonically before detensioning and disassembly of the bolts. If bolt tension is less than 93%
of the value at installation, the cause should be determined, appropriate corrective action should be taken, and the interval between checks of bolt tension should be reevaluated."
Enclosure II W
Page 2
Response
The above quoted recommendation is in the diesel generator M/S program.
- 5. Request:
Confirm that at least 25% quality revalidation inspection of the new Group III cylinder heads has been performed (see NUREG-1216).
Response
The Group III cylinder heads presently installed on diesel generators Nos. 1 and 2 were purchased to the owners group acceptance criteria. To SCE's knowledge, each head received liquid penetrant inspection, magnetic particle inspection and ultrasonic measurement of the fire deck thickness.
- 6. Request:
Provide results of engine base metallographic examination and justification that DG#l engine base is adequate for continued service.
Response
See Enclosure III for this information.
- 7. Request:
Provide information on experience with reliability of turbochargers in recent years.
Response
Since completion of the DR/QR inspections on diesel generator Nos. 1 and 2, which.were reported by SCE letters to NRC dated May 19, June 20, and July 21, 1986, one turbo charger failure has occurred. This failure occurred during Cycle 10 inspections and resulted in water leakage from the casing. The defective turbocharger was replaced with a spare turbocharger. Root cause determination indicated cause of failure to be a casting defect in the intermediate casing of the turbocharger.
03570
ENCLOSURE III ENGINE BASE EXAMINATION FOR WIDMANSTAETTEN GRAPHITE A sample was removed from the base of each diesel engine and sent to Failure Analysis Associates (FaAA) for analysis for Widmanstaetten graphite.
Upon examination, the diesel generator (DG) No. 2 sample did not reveal any evidence of Widmanstaetten graphite. The microstructure was typical of a pearlitic grey cast iron. Chemistry and tensile.strength were within nominal ranges expected for ASTM A-48, class 40 grey cast iron.
The DG No. 1 sample exhibited microstructural features typically associated with the presence of Widmanstaetten graphite. The volume fraction of Widmanstaetten graphite observed by FaAA was less than that observed in the original DG 103 at Shoreham. The chemistry and tensile strength of the test specimen were typical of ASTM A-48, class 40 grey cast iron. FaAA's conclusion is that the mechanical strength of the DG No. 1 base is probably less degraded than that measured in the original Shoreham DG 103.
DG No. 1 engine base is considered safe for continued operation based on the following reasons:
- 1. The structural integrity of the DSRV engine base and main bearing caps was evaluated by Failure Analysis Associates (FaAA) for the Owners Group. The results of this evaluation are documented in Report No. FaAA-84-6-53, dated June 1984. FaAA found that the structural loads for the DSRV-20-4 engine are lower than those for the DSRV-16-4 engine, which has a similar engine base and which was analyzed in detail.
FaAA further concluded that adequate margins of safety for ultimate and fatigue loading exist in the critical areas of the DSRV-16-4 engine base. Based on these two conclusions and the additional reasons listed below, the presence of Widmanstaetten graphite in the DG No. 1 engine base can be accommodated without compromising the safety function of the diesel engine.
- 2. DG No. 1 engine base has demonstrated about thirteen years of successful operational history since its fabrication.
- 3. DR/QR engine base inspections for themiddle main bearing saddle area and the bearing cap mating surfaces were performed on DG No. 1 in 1985 with no adverse findings.
- 4. DR/QR pre-load torque requirements and pre-stressing requirements for the main bearing caps were also implemented as part of DR/QR.
- 5. FaAA identified inappropriate disassembly operation as the cause of cracking in the Shoreham DG 103 engine base.
- 6. In accordance with the owners group recommendations, a visual inspection of accessible areas of the base assembly is performed at each refueling. This inspection includes the area adjacent to the nut pockets of each bearing saddle and is conducted after a thorough wipe down of the surfaces, using good lighting.
If required by the NRC, the DR/QR inspections and torque verifications of 1985 will be repeated at the next major engine overhaul to gain additional assurance of continued engine base integrity.