ML17306A537
| ML17306A537 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/04/1992 |
| From: | Trammell C Office of Nuclear Reactor Regulation |
| To: | Conway W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| References | |
| GL-89-08, GL-89-8, IEB-87-001, IEB-87-1, IEIN-82-22, IEIN-83-55, IEIN-86-106, IEIN-87-036, IEIN-87-36, IEIN-88-017, IEIN-88-17, IEIN-91-018, IEIN-91-18, IEIN-92-007, IEIN-92-7, NUDOCS 9203120350 | |
| Download: ML17306A537 (14) | |
Text
March 4, 1992 Docket Nos.
50-528, 50-529 and 50-530 Mr. William F.
Conway Executive Vice President, Nuclear Arizona Public Service Company P.O.
Box 53999
- Phoenix, Arizona 85072-3999
Dear Mr. Conway:
SUBJECT'UDIT REPORT OF THE EROSION/CORROSION PROGRAM AT PALO VERDE NUCLEAR GENERATING STATION, UNIT NO.
2 On January 13-17, 1992, representatives of the Office of Nuclear Reactor Regulation and NRC Region V conducted an audit of the erosion/corrosion program at Palo Verde which was developed in response to NRC Generic Letter 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning."
The enclosed report was prepared jointly by the audit team members, and is forwarded to you for your information.
Sincerely, Original signed bi Charles M. Trammell, Sr. Project Manager Project Directorate V
Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation
Enclosure:
Audit Report cc w/enclosure:
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 March 4, 1992 Docket Nos.
50-528, 50-529 and 50-530 Mr. William F.
Conway Executive Vice President, Nuclear Arizona Public Service Company P.OS Box 53999
- Phoenix, Arizona 85072-3999
Dear Mr. Conway:
SUBJECT:
AUDIT REPORT OF THE EROSION/CORROSION PROGRAM AT PALO VERDE NUCLEAR GENERATING STATION> UNIT NO.
2 On January 13-17,
- 1992, representatives of the Office of Nuclear Reactor Regulation and NRC Region V conducted an audit of the erosion/corrosion program at Palo Verde which was developed in response to NRC Generic Letter 89-08, "Erosion/Corrosion-Induced Pipe Wall Thinning."
The enclosed report was prepared jointly by the audit team members, and is forwarded to you for your information.
Sincerely, V
Charles M. Trammell, Sr. Project Manager Project Directorate V
Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation
Enclosure:
Audit Report cc w/enclosure:
See next page
Mr. William F.
Conway Arizona Public Service Company Palo Verde CC:
Nancy C. Loftin, Esq.
Corporate Secretary
& Counsel Arizona Public Service Company P.
O.
Box 53999, Mail Station 9068
- Phoenix, Arizona 85072-3999 Jack R.
- Newman, Esq.
Newman 8 Holtzinger, P.C.
1615 L Street, N.W., Suite 1000 Washington, D.C.
20036 James A. Beoletto, Esq.
Southern California Edison Company P. 0.
Box 800
- Rosemead, California 91770 Senior Resident Inspector U.S. Nuclear Regulatory Commission HC-03 Box 293-NR
- Buckeye, Arizona 85326 Regional Administrator, Region V
U ~
S. Nuclear Regulatory Commission 1450 Maria Lane Suite 210 Walnut Creek, California 94596 Ignacio R. Troncoso Senior Vice President El Paso Electric Company Post Office Box 982 El Paso, Texas 79960 Roy P.
Lessey, Jr.,
Esq.
Bradley W. Jones, Esq.
Arkin, Gump, Strauss, Hauer and Feld El Paso Electric Company 1333 New Hampshire Ave., Suite 400 Washington, D.C.
20036 Mr. Charles B. Brinkman, Manager Washington Nuclear Operations ABB Combustion Engineering Nuclear Power 12300 Twinbrook Parkway, Suite 330 Rockville, Maryland 20852 Mr. William A. Wright, Acting Director Arizona Radiation Regulatory Agency 4814 South 40 Street
- Phoenix, Arizona 85040 Chairman Maricopa County Board of Supervisors 111 South Third Avenue
- Phoenix, Arizona 85003
ENCLOSURE NRC AUDIT OF EROSION/CORROSION PRGGRAM AT PALO VERDE NUCLEAR GENERATING STATION AUDIT DATES:
January 13-17, 1992 t<fiC A40iT PAR1ICIPANTS:
S. S. Koscielny, NRR*¹ P.
P. Narbut, Region V¹ K. I. Pare"ewski, hhh"'¹ M. J.
- Royack, Region V*¹ J.
A. Sloan, Resident Inspector¹ LICENSEE PERSGlit<EL:
J. A. Bailey, NED, Director Nuc. Eng.*¹ R. Badsgard, SNL, Supervisor¹ J.
h;. Bailey, NS 8 L, VP¹ hl. Benac, El Paso Electric¹ T. P. Bradish, Compliance, Manager¹ J. Bergstedt,
/AH/gA, Technical Specialist*
R. Bernier, Compliance, Supervisor*
C. Clapper, SED/BOP, Supervisor*
C. Churchman, Site Nuclear Eng., Manager*
P. J. Coffin, Compliance, Engineer¹ W. F. Conway, APS, Exec.
VP¹ B. Ecklund, Tech. Data, Supervisor*
Z. Elanar, Nuc.Safety Dept., Sr. Engineer*
R.
C. Fullmer, gA 8 M, Manager¹ S. Guthrie, gA, Director¹ D.E. Mansen, ISI, Supervisor*¹ W. Mimanpour, Tech. Data, Engineer*
H. Modge, Nuc.Eng.Hech.,
Manager*
L. Johnson, Chemistry, Manager*
D; A. Johnson, Compliance, Supervisor*
D. Kanitz, Compliance, Engineer*d A. K. Kraini k, NED - M/C, Supervisor*¹ J.
H. Levine, Nuc. Prod.,
YP¹ J.L. McGath, gA, Engineer¹ W. S.
- Payne, NED - M/C, Engineer*
B. Simpson, Eng.
& Constr.,
VP*
J.
M. Ritchie, NED - M/C, Engineer*¹ D. Webb, QA, Tech. Spec.¹
- Present at entrance nieetirg.
¹ Present at ex",t reating.
uaCkbk(,LhL Eros>on/Corrvsion
',E/C) of carbon steel piping systems occurs in the turbine cycle of both fossil and nuclear power plants for a number of years.
The catastrophic failure of a main feedwater elbow in December 1986 at Virginia Power's Surry Power Station prompted the NRC to request all licensees to institute special programs for controlling erosion/corrosion of carbon steel components in their plants.
The NRC has issued the following generic communications related to erosion/corrosion:
Information Notice 86-106 and Supplements 1, 2, 3
Information Notice 91-18 and Supplement 1
o Informa ion Notice 92-07 o
I E Bul Ietin 87-01 o
Generic Letter 89-08 In 1988 ten plants were audited on their response to the IE Bulletin 87-01 and a program was established for E/C.
As a result of these audits, NRC issued Generic Letter 89-08.
In this Generic Letter NRC specifically requested the licensees to develop programs consisting of systematic measures to ensure that erosion/corrosion does not lead to degradation of single phase or two phase high-energy carbon steel systems.
The NRC intends to verify how well these programs are implemented in individual plants by performing auaits.
An inspection procedure has been developed (Inspection Procedure 49001) which provides guidance for NRC inspectors.
The purpose of the piiot audits of five plants is twofold:
( 1) it provides some indication of how well E/C programs are being implemented by the industry, and (2) it helps to refine the inspection procedure.
AUDIT PLAN 1)
Using Inspection Procedure 49001 to review the licensee's Erosion/Corrosion Program in the following areas:
o Organization o
Analysi s o
Implementation of Inspection and NDE.
o Data Management o
Management Commitment 2)
Review the implemenxation of EPRI "CHEC/CHECHATE" computer programs used to analyze components for the effects of E/C in four systems:
o Feedwater o
t>ioisture Separator Drains
3)
Review the licensee erosion/corrosion inspection program, including inspection data, inspector qualification and conducted a plant walkdown through the Unit 2 balance of plant areas containing 'repaired/replaced piping/components, 4)
Review of the repair/replacement program for erosion/corrosion damaged components.
5)
Review of the licensee response to Information Notice 92-07, "Rapid Flow-Induced Erosion/Corrosion of Feedwater Piping."
GENERAL REMARKS ON EROSION/CORROSION PROGRAM The licensee has established an erosion/corrosion control program which in its general scope meets the requirements of Generic Letter 89-08.
To determine erosion/corrosion wear of the carbon steel components, the licensee uses the CHEC/CHECMATE computer codes developed by EPRI.
The initial selection of the components to be included in the analysis was obtained from PRA studies and from operational experience.
The output from the codes was then used to develop an NDE inspection plan and the data from the inspections served to validate the computer codes.
The erosion/corrosion wear rates for the affected components were then predicted using these codes.
The E/C. program was instituted in 1988.
Initially, only portions of the feedwater, heater arain and condensate systems were analysed using the EPRI CHEC computer code.
However, contrary to EPRI's recommendations, not all the components in these systems were included in the CHEC analysis.
This methodology does not meet, therefore, the requirements of the NUMARC guidelines referenced in Generic Letter., 89-08.
These guidelines specifically recomnend performance of a complete analysis, including all components, and then to select for inspection the ten most susceptible components determined by the analysis and an additional five based on engineering judgment.
The licensee has committed to a complete analyses of these lines using the CHECMATE code and following the NUMARC guidelines.
These analyses will be performed in two stages:
the first stage will include class "g" lines and will be completed by October 31,
- 1992, and the second stage which would include non-g lines
("NgR") will be completed by March 31, 1993.
Subsequent to these initial CHEC analyses, the licensee extended the program to include several two-phase high energy lines, such as extraction steam.
These analyses were performed with the CHECMATE code.
The licensee is committed to continuously upgrade and expand the program until the CHECMATE analyses includes all the components which could be subjected to erosion/corrosion degradation.
REVIEW OF CHEC/CHECMATE DATA AND ANALYSIS The CHEC/CHECMATE analysis for the Palo Verde plant was performed by a contractor using CHEC Version 2.0 and CHECMATE Version l.l and following the licensee's procedures.
However, the input for the codes was prepared by the licensee's personnel.
Also, there was a dedicated individual with EPRI training
-4 responsible for monitoring the program.
One single program covered all three units at the Palo Verde site.
The audit was limited to the four systems listed in the audit plan.
The licensee provided isometric drawings for the analysed systems and the i.abulated input data.
The audit team found that although in general the input data were correctly prepared, there were a few inaccuracies in identifying geometries and materials of certain components.
The following are the few examples of these computer code input inaccuracies:
In modeling the main feedwater lines, the elbow geometry code used (geometry code 3 for 45 deg elbow and geometry code 4 for 90 deg elbow) corresponded to an elbow with an upstream fitting within one diameter when in actuality there was a straight pipe upstream of the elbow.
Although this inaccuracy was in a conservative direction, it unnecessarily biased the CHEC results.
!'n the same feedwater line, material codes used in the input for elbows, tees, reducers and a check valve correspond to ANSI Spec.
A106 Gr.B or C (material codes 5 and 6), which are specified for pipe materials, instead of ANSI Spec.
A234 Gr.WPB or WPC (material codes 21 and 22) which are the specific materials of these components.
in modeling the feedwater heater drain line and extraction steam
- systems, gate valve material was identified as A106 Gr.B (material code 5) instead of A234 Gr.WPB (material code 21) which is the correct material for this component.
Although these inaccuracies in themselves would not produce significant differences in CHEC/CHECMATE predictions, they indicate that aata input into the computer coae was not as precise as it should be, or that a second person check of the data was not performed.
The selection of the components to be analyzed was based on several criteria.
In general, velocity of flow and fluid temperature were considered to be the two dominant parameters and were used by the licensee as selection criteria.
This is inconsistent with the EPRI model of erosion/corrosion which considers the erosion corrosion mechanism as controlled by seven synergistic variables (i.e.,
pH, dissolved oxygen, material chem)stry, velocity, steam quality, temperature and geometry).
All of them should be, therefore, considered.
Some departures from the existing requirements were also noted in the licensee's procedure I3-MS-A-025 which specified as a selection criterion for CHEC/CHECMATE analysis a velocity of 14 fps and a temperature of 250 or 200 deg.
F.
The NRC in IE Bulletin 87-01 and Generic letter 89-08 endorsed the referenced value of 10 fps for velocity and 190 deg.
F for temperature.
In the case of two similar lines the licensee was initially modeling only one line which is usually conservatively chosen to be the one with the more tortuous path.
Our review of the licensee's data input to the CHEC/CHECMATE codes, results of the code analyses ana general approach to the management of analytical work indicated that, except for discrepancies mentioned
- above, the licensee has a
well functioning program.
REVIEW OF INSPECTION RESULTS The review of the inspection results consisted of verifying the methodology used by the licensee is performing Ultrasonic Testing (UT) inspections, evaluating how the data are processed and recorded and how the information on defective components is forwarded to the departments responsible for plant maintenance.
The audit team found that although current UT measurements are performed by the inspectors certified in the NDE techniques and ihe methods used are in compliance with the EPRI recomendations, early NDE data were not compatible with the current NDE data because of different data-taking methodology (UT scan instead of the current UT grid pattern methoaology).
This incompatibility of data acquired by different methods causes difficulty in determining erosion/corrosion wear rates using CHEC/CHECMATE.
However, the licensee coiira>tted to take all future NDE measurements using the UT grid pattern method.
During the plant walkdown the audit team had the oppor tunity to assess how components are prepared for the UT inspection (grid markings) and found it to be compatible with the EPRI recommendations.
REVIEW OF COMPONENTS REPAIR/REPLACEMENT PROGRAM In this part of the audit the audit team inspected Engineering Evaluation Requests (EER) prepared for the components which were found to be damaged by erosion/corrosion.
The following EERs were reviewed:
90-ED-024, Extraction Steam and 91-ED-039, FW Heater Extraction Steam Dump System.
Also, the audit team reviewed stainless steel replacement packages for extraction steam lines.
The audit team founa that the documents were carefully prepared and clearly identified the components that were damaged by erosion/corrosion and needed engineering evaluation and eventual replacement.
REVIEW OF SPLIT FEEDWATER LINE ISSUE (IN 92-07)
The licensee considered the applicability of the information provided in Information Notice 92-07, "Rapid flow-Induced Erosion/Corrosion of Feedwater Piping," to the plant.
The Information Notice specifically addressed high erosion/corrosion wear rates in the Westinghouse steam generator feedwater lines used to "split feed" in Model D-4, D-5 and E steam generators.
Although Palo Verde is a Combustion Engineering plant, the problem of possible high wear rate induced by high flow velocities could exist because of the split flow feedwater feature used at Palo Verde.
These lines were analysed in early 1988 usiiig the CHEC code.
As it was pointed out earlier in this report, these analyses were riot adequately performed and the licensee has coiimiitted to include these lines as a high priority item in the updated CHECMATE analyses.
The licensee has indicated that although some wear was noted during erosion/corrosion inspections of these lines at Unit 2, no ASME Code wall thickness limit was approached.
To completely analyze the information in the Information Notice, a complete CHECMATE model of the feedwater piping used to "split feed" is needed.
REVIEW OF MANAGEMENT INVOLVEMENT During our discussion with the licensee's management we were assured that they recognize the importance of the erosion/corrosion program and wi 11 actively support it by providing proper staffing, funding and by creating opportunities for the personnel involved in the program to attend the EPRI sponsored
'CHEC/CHECMATE training courses.
The licensee is a member of the CHEC/CHECMATE Users Group (CHUG) which provides a forum for information exchange among the utilities involved in the resolution of erosion/corrosion issues.
CONCLUSIONS The licensee responded to the NRC guidelines specified in IE Bulletin 87-01 and Generic Letter 89-08 and established a viable erosion/corrosion program.
After auditing the program, we have found that, with a few minor exceptions, it is well managed and there is a strong management commitment to continue it at its present level of activity.