ML20238F307

Forwards Response to NRC Bulletin 87-001, Thinning of Pipe Walls in Nuclear Power Plants. Insp Revealed Hatch Components within Guidelines

ML20238F307
Person / Time
Site:	Hatch, Vogtle, 05000000
Issue date:	09/08/1987
From:	Gucwa L GEORGIA POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
IEB-87-001, IEB-87-1, SL-3155, TAC-67443, TAC-67444, NUDOCS 8709160069
Download: ML20238F307 (10)

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. Georgia Power Company -

333 Piedmont Avenue

... Atlanta, Georgia 30308

!. Teloptone 404 52641526 Malling Address.

t Fbst Ofuce Box 4543 Atlanta, Georgia 30302 b

Georgia Power L T. Gucws . UC W'N" ""C W"*

Manager Nuclear Safety

. and Licensing SL-3155 0451U X7GJ17-C110 September 8, 1987 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Hashington, D. C. 20555 PLANT HATCH - UNITS 1, 2 NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57 NPF-5 PLANT V0GTLE - UNIT 1 NRC DOCKET 50-424 OPERATING LICENSE NPF-68 RESPONSE TO NRC BULLETIN NO. 87-01,

" THINNING 0F PIPE HALLS IN NUCLEAR POWER PLANTS Gentlemen:

By the subject generic letter dated July 9,.1987, NRC requested that Georgia Power . Company submit information concerning the programs for monitoring the thickness of pipe walls in high-energy single-phase and two-phase carbon steel piping systems. The Georgia Power Company response is provided in the enclosure to this letter.

Mr. L. T. Gucwa states that he is duly authorized to execute this oath on behalf of Georgia Power Company, and that to the best of his knowledae and belief, the facts set forth in this letter and enclosure are true. {

GEORGIA POWER COMPANY BY: 8 d- '-

L. T. Gucwa  !

Sworn to and subscribed before me this 8th day of September 1987.

au NotaryPublic GINGER CARTEE NOTARY PUBLIC JCJ:LTG:ju GEORGIA RICHMOND COUNTY W N EXPtRES MARCH 29,1991 i Enclosure 1: Response to NRC Bulletin 87-01 /

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Georgia Powerkn U. S. Nuclear Regulatory Commission September 8, 1987 Page Two c: Georaia Power Comoany Mr. J. P. O'Reilly Mr. R. E. Conway Mr. J. T. Beckham, Jr.

Mr. G. Bockhold, Jr.

Mr.. J. F. D'Amico Mr. C. H. Hayes Mr. S. B. Tipps G0-NORMS Southern Comoany Services Mr. R. A. Thomas Mr. J. A. Bailey U. S. Nuclear Regulatory Commission. Washington. D. C.

Mr. L. P. Crocker, Licensing Project Manager - Hatch Ms. M. A. Miller, Licensing Project Manager, NRR (2 Copies)

U., S. Nuclear RfLqulatory Commission. Reaion II Dr. J. N. Grace, Regional Administrator Mr. P. Holmes-Ray, Senior Resident Inspector - Hatch Mr. J. F. Rogge, Senior Resident Inspector-0perations, Vogtle Shaw. Pittman. Potts & Trowbridae Mr. B. H. Churchill, Attorney-at-Law Troutman. Sanders. Lockerman & Ashmore Mr. A. H. Domby, Attorney-at-Law Georaians Aaainst Nuclear Entrav Mr. D. Feig Ms. C. Stangler

/w)Y 700775

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ENCLOSURE 1 GEORGIA POWER COMPANY RESPONSE TO NRC BULLETIN NO. 87-01

" THINNING OF PIPE WALLS HATCH AND V0GTLE NUCLEAR PLANTS" A. OVERVIEW Georgia Power Company (GPC) is committed to maintaining the functional capability of all high energy piping systems for each of our operating nuclear plants. Assuring that pipe walls are maintained within allowable thickness values is a primary concern since several operating plants have experienced degradation of piping components due to a process called Erosion / Corrosion (E/C). The degradation is characterized by pipe wall thinning which can result in catastrophic failure of the pipe when the pipe wall is reduced below minimum Code requirements. The degradation is a function of operating time and system specific parameters including piping configuration, operating pressure and temperature, flowrate, moisture content, and water chemistry. In general, the systems of primary concern are those which GPC would classify as having high energy (i.e., greater than 2000F and 200 PSIG) and significant service hours (30000_). Prior to i:he Surry Event (Dec 1986), GPC was addressing the piping degradation problem as one which related only to two-phase flow (wet steam) systems. Subsequent to the Surry event, GPC has expanded efforts to include single-phase, as well as two-phase flow systems.

B. WHAT GEORGIA POWER COMPANY HAS DONE o Plant Hatch Unit 1 Wall Thickness (UT) Inspections - 176 total components, 70 Surry type.

o Plant Hatch Unit 2 Wall Thickness (UT) Inspections - 88 total components, O Surry type.

o Replaced three elbows in the sixth stage extraction of Plant Hatch Unit 2 in April 1983.

o Replaced one reducer and overlayed two elbows in the sixth stage extraction of Plant Hatch Unit 2 in April 1986 following a failure of the reducer.

o Replaced one tee, three elbows, and two spool pieces in the sixth stage extraction of Plant Hatch Unit 2 in October 1986.

o Replaced one reducer and two spool pieces downstream of MSR drain tank control valves on Plant Hatch Unit 1 in June 1987.

o Installed chrome / moly extraction lines on Plant Vogtle to eliminate E/C due to two-phase ',ow.

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C. WHAT GEORGIA POWER COMPANY HAS FOUND TO DATE o No significant E/C at Surry type locations was found on Plant Hatch Unit 1 during the spring 1987 outage.

o E/C has been found in virtually all areas of two-phase flow.

However, the only areas with any significant degradation are:

1. Plant Hatch Unit 2 sixth stage extraction l 2. Plant Hatch Unit 1 fifth stage extraction 1 3. Plant Hatch MSR drains with carbon steel piping, downstream of control valves D. EXISTING PROGRAM AND PHILOSOPHY o GPC has monitored and utilized industry experience since 1982 to assist in the selection of components to be inspected and to evaluate two-phase flow E/C.

o GPC utilized EPRI guidelines contained in report NP-3944," Erosion / Corrosion In Nuclear Plant Steam Piping:

Causes And Inspection Program Guidelines", since it's issuance in April 1985.

o GPC has replaced all components found to have erosion / corrosion which had reduced the component's wall to near the minimum acceptable code value, o GPC utilized lessons learned from the Surry feedwater pipe failure report issued in January 1987 in the selection of inspection components for the spring 1987 Plant Hatch Unit 1 outage. That inspection also met the guidelines contained in NUMARC's " Working Group On Piping Erosion / Corrosion Summary Report", June 11, 1987.

o No baseline inspections have been performed on Plant Vogtle Unit

1. As E/C is not believed to be a problem for components with less than 30000 service hours, we foresee no degradation of piping components prior to the August 1988 outage, at which time sample baseline inspections will be performed.

o Piping and components with configurations and service conditions similar to those for Tr.ojan feedwater piping will be included in GPC E/C programs.

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l ENCLOSURE 1 (Con't)

E. CHRONOLOGY OF GPC AND SIGNIFICANT INDUSTRY EROSION / CORROSION ACTIVITIES l DATE DESCRIPTION 1982 o Oconee piping failure o NRC Issued IEN 82-22 concerning Oconee j failure -

o GPC initiated a study of E/C for two-phase flow systems (extraction and heater drains)  !

o 50 components inspected on Plant Hatch Unit 2 o 71 components inspected on Plant Hatch Unit 1  !

1983 o Two elbows replaced in sixth stage extraction on Plant Hatch Unit 2 1985 o Eight components inspected on Plant Hatch Unit 2 I

o EPRI issued report NP-3944,

" Erosion / Corrosion in Nuclear Plant Steam Piping: Causes And Inspection Program Guidelines"  !

4 1986 o Twenty components inspected on Plant Hatch Unit 1 o GPC replaced one reducer and overlayed two elbows in sixth stage extraction on Plant '

Hatch Unit 2. Expanded scope to other extraction lines for both units. I o 31 components inspected on Plant Hatch Unit 2. Three elbows, one tee, and two spool pieces replaced, o Surry feedwater line failure in December 0797n SL-3155 j i

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ENCLOSURE 1 (Con't) 1987 o VEPC0 issued report on Surry failure January 14.

o Twenty Surry type components inspected on Plant Hatch Unit 1. No problems found.

NRC issued Bulletin No. 87-01 concerning the o

Surry event.

o 63 two-phase flow components inspected on Plant Hatch Unit 1. Three components replaced.

o GPC Nuclear Operations initiated development =

of a formal E/C program for Plants Hatch and .

Vogtle, o NRC issued Information Notice No. 87-36 concerning erosion of Trojan feedwater lines. >.

1988 o Planned inspection of 17 Surry type components and 35 two-phase flow components during Plant ;latch Unit 2 January outage.

o Planned sample baseline inspection during Plant Vogtle Unit 1 first refueling outage, including Surry and Trojan type components.

F. SPECIFIC NRC BULLETIN NG 87-01 INFORMATION RE00ESTS

1. Identify the codes or standards to which the piping was designed and fabricated.

Response: High energy piping for safety related systems is ,

constructed in accordance with USAS B31.7 or ASME Section III. Piping of non-safety systems is constructed in accordance with ANSI B31.1.

2. Describe the scope and extent of your programs for ensuring that pipe wall thicknesses are not reduced below the minimum allowable thickness. Include in the description the criteria that you have established for:

a. selecting points at which to make thickness measurements b, determining how frequently to make thickness measurements

c. selecting the methods used to make thickness measurements

d. making replacement / repair decisions 0797n SL-3155 E-4 9/8/87

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ENCLOSURE 1 (Con't)

Response: From 1982 to 1985, GPC utilized industry experience (including GPC experience) for selection and frequency of inspection criteria. Following issuance by EPRI of NP-3944 in April 1985, GPC has utilized the criteria contained therein for two-phase flow. GPC is currently using the Surry Pipe Failure Report for single phase flow systems to assist in defining the scope and extent of our programs. UT is utilized for pipe wall measurement and repair / replacement decisions are based on wear rate and minimum wall considerations.

3. For liquid-phase systems, state specifically whether the following factors have been considered in establishing your criteria for selecting points at which to nonitor piping thickness (Item 2a):

a. piping material (e.g., chromium content)

b. piping configuration (e.g., fittings less than 10 pipe diameters apart)

c. ph of water in the system (e.g., ph less than 10)

d. system temperature (e.g., between 190 and 5000 F)

e. fluid bulk velocity (e.g., greater than 10 ft./sec.)

f. Oxygen content in the system (e.g., oxygen content less than 50 ppb)

Response: The factors listed above are utilized in assisting in the determination of the systems / components to be inspected.

GPC samples components with the extreme-combinations of factors to-determine if there are any E/C problems for single-phase flow systems. The sample of 20 components on Plant Hatch Unit 1 during the spring 1987 outage revealed no significant.E/C problems.

4. Chronologically list and summarize the results of all inspections that have been perforned, which were specifically conducted for the purpose of identifying pipe wall thinning, whether or not pipe wall thinning was discovered, and any other inspections where pipe wall thinning was discovered even though that was not the purpose of that inspection.

a. 'I Briefly describe the inspection program and indicate whether I it was specifically intended to measure wall thickness or whether wall thickness measurements were an incidental determination,

b. Describe what piping was examined and how (e.g., describe .

the inspection instrument (s), test method, reference i thickness, locations examined, means for locating measurement point (s) in subsequent inspections).

0797n SL-3155 E-5 9/8/87

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ENCLOSURE 1 (Con't)

c. Report thickness measurement results and note those that were identified as unacceptable and why.

d. Describe actions already taken or planned for piaing that has been found to have a nonconforming wall thic(ness. If you have performed a failure analysis, include the results of that analysis. Indicate whether the actions involve -

repair or replacement, including any change of materials.

Response: Records of Inspections performed to date are maintained at the GPC plants and are available for NRC Review.

Parts A thru E of this report address GPC's program, how many components have been inspected per this program, and the results of the inspections.

5. Describe any plans either for revising the present or for developing new or additional programs for monitoring pipe wall thickness. _

Response: GPC plans are as follows:

o Continue to monitor industry activity and modify the GPC program to comply with selected industry guidelines. -

o Continue the GPC inspection program utilizing Plant Hatch procedure 42IT-N36-001-0N thru the January 1988 Plant Hatch Unit 2 outage. Inspections performed per this program during that outage will meet the significant EPRI and NUMARC guidelines, including 17 Surry type components.

o Develop formalized program docu.nents for each nuclear unit and implement the formalized program during the August 1988 Plant Vogtle Unit 1 outage.

These programs will document and enhance the already existing plant procedure being utilized at Plant Hatch. The schedule for issuance of these formal programs is as follows:

• PLANT HATCH UNIT 1 NOV 1, 1987 PLANT HATCH UNIT 2 MAY 1, 1988 PLANT V0GTLE UNIT 1 MAY 1, 1988 PLANT V0GTLE UNIT 2 MAY 1, 1988 Until these formal programs are officially in place, the program at Plant Hatch , utilizing procedure 421T-N36-001-0N, will continue to be implemented.

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.z ENCLOSURE 1 (Con't) o Share with industry groups the program details and summary inspection results.

o Evaluate the need for noisture preseparator in MSR crossunder which could reduce two-phase E/C problems.

G.

SUMMARY

1. Georgia Power Company has inspected two-phase flow systems since 1982 on both Plant Hatch Units. Plant Hatch Procedure 42IT-N36-001-0N currently sets the program. ,

2. Components found with excessive degradation during inspections are evaluated per EPRI Guidelines and replaced or repaired when necessary to assure safe operation of the units.

3. All GPC inspections for piping degradation were restricted to two-phase flow systems prior to the Surry event in December 1986.

4. GPC inspections at Plant Hatch revealed that the components were within the guidelines.

5. GPC has adhered to industry (EPRI) Guidelines for the E/C Inspection Program, and will continue its use in the future. Until EPRI Guidelines are available for single-phase flow, GPC will utilize the Surry Feedwater Pipe Failure Report and Trojan Feedwater Line Erosion Reports in conjunction with EPRI Guidelines for the formal single-phase flow program development.

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