AECM-87-0157, Forwards Responses to NRC Comments Re Limited Deferral of Insps on Div II Emergency Diesel Generator.Specifics Re Engineering Survey & Mods to Turbochargers Addressed

Forwards Responses to NRC Comments Re Limited Deferral of Insps on Div II Emergency Diesel Generator.Specifics Re Engineering Survey & Mods to Turbochargers Addressed

ML20237J057
Person / Time
Site:	Grand Gulf
Issue date:	08/21/1987
From:	Kingsley O SYSTEM ENERGY RESOURCES, INC.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
AECM-87-0157, AECM-87-157, TAC-65683, NUDOCS 8708250285
Download: ML20237J057 (11)

Text

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k ..

EYETEM ENERGY

. REEMJRCEE. INC.

Otun D KtG1EY.JR IE7$cm August 21, 1987 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Document Control Desk Gentlemen:

SUBJECT:

Grand Gulf Nuclear Station Unit 1

1. Docket No. 50-416 License No. NPF-29 Limited Deferral of Inspecti "s on the Division II EDG, Suppleinental Information AECM-87/0157 System Energy Resources, Incorporated (SERI) provided the basis for incorporating certain remaining inspections on the Division II Emergency Diesel Generator into a later scheduled 5-year confirmatory inspection. The above basis was provided by letter dated June 30, 1987 (AECM-87/0065).

During the NRC staff review of the above report, NRC comments were generated.

The comments and SERI responses were discussed with members of NRC Staff by telephone conference on August 10, 1987. This letter documents SERI's response

.to the NRC staff coments. The NRC comments and SERI responses are provided as an attachment to this letter.

If additional information is needed to support the NRC staff's review please contact this office.

Yours truly, C

ent M N cc: (See Next Page)

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AECM-87/0157 Page 2 cc: Mr. T. H. Cloninger (w/a)

Mr. R. B. McGehee (w/a)

Mr. N. S. Reynold.; (w/a)

Mr. H. L. Thomas (w/o)

Mr. R. C. Butcher (w/a)

Dr. J. Nelson Grace, Regional Administrator (w/a)

U. S. Nuclear Regulatory Commission Region II 101 Marietta St., N. W., Suite 2900 Atlanta, Georgia 30323 Mr. L. L. Kintner, Project Manager (w/a)

Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 J16AECM87081101 - 2

l* Attachment to AECM-87/0157-Rev. 1 NRC COMMENTS ON THE DIVISION II EDG-INSPECTION WITH SERI RESPONSE l 1. NRC COMMENT l

l Provide specifics regarding Duke Engineering /SERI survey, such as the )

l number of utilities, a breakdown of components, a description of the inspection results which lead to the conclusion of "no major operational-

. problems". ,

SERI RESPONSE-o The eleven nuclear utilities which utilize TDI EDGs were surveyed.

Seven of those utilities have the DSRV-16-4 EDGs.

o The. components surveyed were the components for which inspections are:

proposed for deferral to the 5 year confirmatory inspection (letter dated June 30,1987,AECM-87/0065).

o. No.new problems were identified by Duke Engineering as a result of.

the survey.

o Minor deficiencies reported during the survey were further evaluated by SERI. The affected components were the piston pin assembly, the cylinder heads and their intake and exhaust valves,-and the main bearing shells. None of the deficiencies reported by the utilities surveyed or by SERI were judged to have a detrimental affect on EDG operation.

o .SERI participates as a member of the' Duke TDI EDG " clearinghouse" which provides periodic updates of owners TDI/EDG performance and reliability. No_ significant concerns with similar components have been reported to date through this process.

2. NRC COMMENT Modifications were performed on the turbocharger to preclude thrust bearing failures; however, the RF01 turbocharger inspection revealed distressed thrust bearings. This information contradicts the previous staffSERregardingturbochargers(SSERNo,6).

SET.1 RESPONSE o SSER 6 states that the drip lubrication or auxiliary lube oil pump activation prior to a planned start provides the turbocharger with sufficient lube oil.

o Rotor float measurements are performed every 18 months in order to determine wear on the thrust bearing.

J16AECM87081101 - 4

Attachment to AECM-87/0157 Rev. 1 o At RF01, rotor float measurements were found to be slightly out of the manufacturer's specification. This finding prompted the thrust bearing inspection. The inspection revealed some pitting and scoring of the thrust bearing. Both turbocharger were replaced as part of the corrective action.

o Both turbocharger were operating satisfactorily prior to the inspection.

o Subsequent evaluation determined that the time period between prelube with the auxiliary lube oil pump and engine start had become excessive due to requirements to air roll, manual barring over of engine, and Inservice Inspection of the starting air check valves. I The operating procedures have been revised to require an engine start immediately following the auxiliary lube oil pump prelube. The turbocharger rotor float will be checked at RF02 to verify the effectiveness of this change.

o The turbocharger bearing prelube oil " drip" system flow rate was measured during RF01'. As a result, the drip system was adjusted to bring the flow rate within DR/QR requirements.

3. NRC COMMENT It would appear for components such as connecting rods and cylinder heads that the machine was torn down to inspect these components and the opportunity existed to complete all the inspections at RF01. However, SERI elected not to complete the above inspections at RF01. Provide SERI's basis for not completing these inspections at the time of disassembly.

SERI RESPONSE o The original intent of the RF01 deferral was to perform a 50%

inspection at RF01 due to the schedule constraints of the outage.

Cylinders 5-8 left and right bank were to be fully disassembled /

inspected and cylinders 1-4 left and right bank would remain assembled.

o Components determined to have abnormalities or excessive wear were subjected to an engineering evaluation. Based on the results of the engineering evaluation, additional like components were inspected.

o SERI committed to inspect the connecting rod female threads on cylinders 1-4 with the rods in place in the engine. However, due to i

circumstances encountered early in the inspection, the quality of l- the inspection was determined to be marginal with the rods installed.

At this point, SERI made a conservative decision to remove the remaining connecting rods to improve the quality of the female thread l inspections and to provide access to the connecting rods, pistons, i

i J16AECM87081101 - 5

Attachment to AECM-87/0157 Rev. I connecting rod bearings, cylinder heads, etc. in the event conditions were discovered which would warrant their removal. This decision was implemented at the optimum point in the schedule and resulted in minimal schedule impact.

o Connecting rods 1-4 were removed and placed in a rack with the associated pistons attached.

o Complete disassembly of the pistons (1-4 left and right bank) piston pin assemblies, and the associated preparation for inspection would have added considerable time to the outage critical path. In addition, no abnormalities were noted in the pistons from cylinders 5-8 (left and right bank) which would have required inspections of the remaining pistons from cylinders 1-4 (left and right bank).

o All cylinder heads were removed in order to facilitate the piston connecting rod removal. The original scope of the inspection included cylinders 5-8 (left and right bank) only. Due to the inspection results (See Comment #4), the scope was expanded to include cylinders 1-4 (left and right bank). The expanded scope only included the inspections necessary to identify the type flaw that rejected four (4) heads from cylinders 5-8. Performing additional inspections would provide delay in cylinder head reassembly, a crucial step in maintaining the Division II D/G outage schedule.

o Certain inspections were performed on components outside the original 50% scope which were accessible and did not lengthen the original schedule. For example liquid penetrant examination of the cylinder block liner landing areas on cylinders 1-4 (left and right bank) was performed when the cylinder liners were removed for non-DR/QR maintenance.

4. NRC COMMENT Regarding inspection of the cylinder heads, particularly the sequence of inspection the differences between the June 30, 1987 submittal and revised information on cylinder heads can not be reconciled.

SERI RESPONSE The information provided in the letter dated June 30,1987(AECM-87/0065) regarding Magnetic Particle (MT) inspection results of cylinder heads requires clarification. The information provided in that letter described the inspection results for a Group III cylinder head from the GGNS warehouse that was to be used as a replacement (see Table 1).

Table 1 provides the inspections /results of all cylinder heads presently on the Division II EDG, Table 2 describes the inspection performed on the cylinder head intake and exhaust valves.

J16AECM87081101 - 6

7-Attachment to AECM-87/0157 Rev. 1 Table 1-Inspection Results Cylinder. heads 5-8; 4:cy11nder heads were. rejected L Left and Right bank using the Magnetic Particle Test.

Ultrasonic, Magnetic Particle, These (4) heads were replaced.

~

Liquid Penetrant (8 cylinder .with Group III heads which had successfully passed inspection.

1 heads)

Cylinder heads 1-4-' 4 cylinder heads were rejected.

Left and Right bank using the Magnetic Particle Test.

Magnetic Particle These (4) heads were replaced (8 cylinder heads) with Group'III heads which had.

successfully passed inspection.

9 Group III Cylinder heads I cylinder head rejected using

-from GGNS warehouse ,

the Liquid; Penetrant Test.

Ultrasonic, Magnetic Particle, Liquid Penetrant In summary, all (16) heads installed on the Division II EDG have been inspected utilizing magnetic particle (MT) examination. Twelve of the sixteen have been fully inspected utilizing Ultrasonic, Magnetic Particle-and Liquid Penetrant examinations. Eight of'the sixteen heads currently installed on the Division II EDG are category Group III.

Table 2 Component Inspection 02-360B Cylinder head Visual of valve seating (Cylinders intake and exhaust valves 1-8LeftandRightbank, entire' engine)

Dimensional check of valve guide clearances (12 heads)

Visual of valve stems and seats (cylinders 1-8LeftandRightbank, entireengine)

Liquid Penetrant of stem heads (Cylinders 5-8 left and right bank)'

Evaluation of Heads Removed From Service The MT examination performed on the cylinder head fire decks consisted of' a wet fluorescent method. The original scope of examination. consisted of.

cylinder heads 5 through 8 left and right bank (8 heads). During.the J16AECM87081101 _ _ _ . - - - _ - _ _ _ _ - _ _ _ -

I Attachment to AECM-87/0157 Rev. I examination, four (4) heads were identified as possessing linear indications on the fire deck or in the intake / exhaust ports. In compliance with original commitments, the discontinuities were evaluated and the examination scope was expanded to include the remaining cylinder heads.

Examination of the remaining heads identified four (4) others containing similar indications.

For the purpose of expediting the outage, the eight questionable heads were replaced with Group III heads meeting all DR/QR requirements allowing the replaced heads to be evaluated at a later date.

IMO Delaval Engineering was requested to evaluate the anomalies identified i on the eight (8) rejected heads. IMO Delaval recommended light surface grinding (.060") of the indications as a method in determining their severity and origin. Through this process one (1) head was determined as acceptable and the others as requiring repair by IM0 Delaval. The flaws were minor in nature and located in areas unexpected for service induced flaws. The areas containing the flaws were in the low stress areas of the head thus indicating the flaws may have originated during the manufacturing process. The flaws appeared to have no impact on head performance and no evidence of leakage could be identified. Since these heads were Group I heads, conservatism was used in the evaluation that resulted in the decision for repair.

5. NRC COMMENT Provide a more detailed description of the metal transfer finding on the piston pin assembly.

Provide drawings of the piston pin assembly.

Provide pictures of the metal transfer to the piston pin.

SERI RESPONSE The piston pin assembly (see attached drawings) connects the piston skirt to the master or link rods of the connecting rod assembly. The connection is designed for full rotation between the pin and the bushing that is installed in the rod eyes. The clearance maintained at this location is 0.010" to 0.015". The interface between the piston skirt and the pin assembly is known as the full floating piston pin. This connection is made without the use of bushings or bearings with a designed clearance of .0u2" to .004". The pin assembly is held in its horizontal position within the piston by retaining rings located at each end of the piston pin, Rotation is not required at this point, but in IM0 Delaval's experience rotation is sometimes noticed. The metal transfer that occurs is a result of the tight clearances that are maintained between the piston pin and the piston skirt (.002" to .004"). Due to the increased I hardness of the piston pin in comparison to the piston skirt, the metal transfer occurs from the skirt to the pin. IM0 Delaval indicates that thi3 transfer is acceptable since rotation between the two components at this location is not required.

Pictures of the metal transfer to the piston pin were previously provided

} to the NRC Project Manager in July, 1987.

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