ML17306A917
| ML17306A917 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/17/1992 |
| From: | Trammell C Office of Nuclear Reactor Regulation |
| To: | Conway W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| References | |
| GL-89-09, GL-89-9, NUDOCS 9208250221 | |
| Download: ML17306A917 (15) | |
Text
August 17, 1992 Docket Nos.
50-528, 50-529 and 50-530 Hr. William F.
Conway Executive Vice President, Nuclear Arizona Public Service Company P.O.
Box 53999
- Phoenix, Arizona 85072-3999
Dear Hr. Conway:
SUBJECT:
REVISED AUDIT REPORT OF THE EROSION/CORROSION
- PROGRAM, PALO VERDE NUCLEAR GENERATING STATION By letter dated March 4,
- 1992, we enclosed an NRC audit report of the erosion/corrosion program at Palo Verde.
This program was developed in response to NRC Generic Letter 89-09, "Erosion/Corrosion-Induced Pipe Wall Thinning."
Following the issuance of this report and discussions with representatives of Arizona Public Service and the NRC staff, it was decided that some sections of the report should be clarified.
The revised report is enclosed.
The changes are printed in italics.
Sincerely,
Enclosure:
Revised Audit Report Original Signed By:
Charles H. Trammell, Sr. Project Manager Project Directorate V
Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation cc w/enclosure:
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 August 17, 1992 Docket Nos.
50-528, 50-529 and 50-530 Hr. William F.
Conway Executive Vice President, Nuclear Arizona Public Service Company P.O.
Box 53999
- Phoenix, Arizona 85072-3999
Dear Hr. Conway:
SUBJECT:
REVISED AUDIT REPORT OF THE EROSION/CORROSION
- PROGRAM, PALO VERDE NUCLEAR GENERATING STATION By letter dated Harch 4,
- 1992, we enclosed an NRC audit report of the erosion/corrosion program at Palo Verde.
This program was developed in response to NRC Generic Letter 89-09, "Erosion/Corrosion-Induced Pipe Wall Thinning."
Following the issuance of this report and discussions with representatives of Arizona Public Service and the NRC staff, it was decided that some sections of the report should be clarified.
The revised report is enclosed.
The changes are printed in italics.
Sincerely,
Enclosure:
Revised Audit Report cc w/enclosure:
See next page
- 4. /~
Charles H. Trammell, Sr. Project Hanager Project Directorate V
Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation
Nr. William F.
Conway Arizona Public Service Company Palo Verde CC:
Nancy C. Loftin, Esq.
Corporate Secretary
& Counsel Arizona Public Service Company P. 0.
Box 53999, Mail Station 9068
- Phoenix, Arizona 85072-3999 James A. Beoletto, Esq.
Southern California Edison Company P. 0.
Box 800
- Rosemead, California 91770 Senior Resident Inspector U.ST 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 Nr. Charles B. Brinkman, Manager Washington Nuclear Operations ABB Combustion Engineering Nuclear Power 12300 Twinbrook Parkway, Suite 330 Rockville, Maryland 20852 Hr. William A. Wright, Acting Director Arizona Radiation Regulatory Agency 4814 South 40 Street
- Phoenix, Arizona 85040 Chairman Naricopa County Board of Supervisors 111 South Third Avenue
- Phoenix, Arizona 85003 Jack R.
- Newman, Esq.
Newman
& Holtzinger, P.C.
1615 L Street, N.W., Suite 1000 Washington, D.C.
20036 Curtis Hoskins Executive Vice President and Chief Operating Officer Palo Verde Services 2025 N. 3rd Street, Suite 220
- Phoenix, Arizona 85004 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
ENCLOSURE NRC AUDIT OF EROSION/CORROSION PROGRAM AT PALO VERDE NUCLEAR GENERATING STATION AUDIT DATES:
January 13-17, 1992 NRC AUDIT PARTICIPANTS:
S.
S. Koscielny, NRR*¹ P.
P. Narbut, Region V¹ K. I. Parczewski, NRR*¹ H. J.
- Royack, Region V*¹ J.
A. Sloan, Resident Inspector¹ LICENSEE PERSONNEL:
J.
A. Bailey, NED, Director Nuc. Eng.*¹ R. Badsgard, SNL, Supervisor¹ J.
N. Bailey, NS 8 L, VP¹ M. Benac, El Paso Electric¹ T.
P. Bradish, Compliance, Manager¹ J. Bergstedt, QAM/QA, 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, QA 8 H, Manager¹ S. Guthrie, QA, Director¹ D.B. Hansen, ISI, Supervisor*¹ W. Himanpour, Tech.
- Data, Engineer*
H. Hodge, Nuc.Eng.Mech.,
Manager*
L. Johnson, Chemistry, Hanager*
D. A. Johnson, Compliance, Supervisor*
D. Kanitz, Compliance, Engineer*¹ A. K. Krainik, NED - H/C, Supervisor*¹ J.
H. Levine, Nuc. Prod.,
VP¹ J.L. HcGath, QA, Engineer¹ W. S.
- Payne, NED - M/C, Engineer*
B. Simpson, Eng.
8 Constr.,
VP*
J.
M. Ritchie, NED - H/C, Engineer*¹ D. Webb, QA, Tech. Spec.¹
- Present at entrance meeting.
¹ Present at exit meeting.
r)
BACKGROUND Erosion/Corrosion (E/C) of carbon steel piping systems occurs in the turbine cycle of both fossil and nuclear power plants.
The catastrophic failure of a main feedwater elbow in December 1986 at Virginia Power's Surry Power Station prompted the NRC to request the 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:
o Information Notices 82-22 o
Information Notice 86-106 and Supplements 1, 2, 3
Information Notice 91-18 and Supplement 1
o Information'Notice 92-07 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 audits.
An inspection procedure has been developed
( Inspection Procedure 49001) which provides guidance for the NRC inspectors.
The purpose of the pilot audit of five plants is twofold: (1) it provides some indication of how well the E/C programs are implemented by the industry, and (2) it helps to refine the inspection procedure.
AUDIT PLAN 1)
Using Draft Inspection Procedure 49001 to review the licensee's Erosion/Corrosion Program in the following areas:
o Organization o
Analysis o
Implementation of Inspection and NDE o
Data Management o
Management Commitment
2)
Review the implementation of EPRI "CHEC/CHECMATE" computer programs used to analyze components for the effects of E/C in four systems:
o Feedwater o
Moisture Separator Drains 3)
Review erosion/ corrosion inspection
- program, including inspection data, inspector qualification and conduct a plant walkdown through the Unit 2 balance of plant areas containing repaired/replaced piping/components.
4)
Review of repair/replacement program for erosion/corrosion damaged components.
5)
Monitoring the licensee conference call of 1/15/92 with NRC Region V
concerning Information Notice 92-07, "Rapid Flow-Induced Erosion/Corrosion of Feedwater Piping."
GENERAL REMARKS ON EROSION/CORROSION PROGRAM The licensee has establish an erosion/corrosion control program which in its general scope meets the guidelines 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 operational experience.
The output from the codes was then used to develop a
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 drains and condensate systems were analyzed using the EPRI CHEC computer code.
However, contrary to the EPRI's preferred methodology, 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 recommend a complete analysis, including all components, and then to select for inspection the ten most susceptible components determined by the analysis and additional five based on engineering
- judgment, The licensee is planning to perform a complete analysis of these lines using the CHECMATE code and following the NUMARC guidelines.
0
These analyses will be performed in two stages:
the first stage will include class "Q" lines and will be completed in the October/November 1992 time frame and the second stage will include non-Q lines
("NQR") and will be completed in the Harch/April 1993 time frame.
Subsequent to these initial CHEC analyses, the licensee extended the program to include several other two phase high energy lines, such as extraction steam.
These analyses were performed with the CHECHATE code.
The licensee is planning to continuously upgrade and expand the program to include the components which could be subjected to erosion/corrosion degradation.
REVIEW OF CHEC/CHECHATE DATA AND ANALYSIS The CHEC analysis for the Palo Verde plant was performed by the licensee using an early version of CHEC.
This analysis is in need of upgrading to the current version of CHEC or CHECHATE.
The licensee prepared the input to the CHECHATE code and contracted an outside organization to run the code.
The contractor used Version l.l of the CHECHATE.
Also, there was a dedicated individual with EPRI training 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 us with isometric drawings for the analyzed systems and the tabulated 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 the CHEC code input inaccuracies:
In modeling the main feedwater lines, elbow geometry code used (geometry code 3 for 45 deg elbow and geometry code 4 for 90 deg elbow) corresponded to an elbow with 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 CHEC results.
In the same line, material codes used in the input for elbows,
- tees, reducers and a check valve corresponded 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 model,ing 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 predictions, they indicate that data input into the computer code was not as precise as it should be and there is a need for a second person check of the input data.
The selection of the components to be analyzed was based on several criteria.
In general the licensee's procedure 13-HS-A-025 allows elimination of systems based on one parameter (e.g.,
temp. greater than or equal to 250 deg.
F) and does not consider the effect of chemistry (e.g.,
pH control agent or dissolved oxygen).
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 chemistry, velocity, steam quality, temperature and geometry).
All of them should be, therefore, considered.
Some departures from the existing requirements were also noted in the quoted procedure which specified as a selection criterion for CHEC/CHECMATE analysis a velocity of 14 fps and a temperature 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.
The licensee's procedure also states that Condensate and Feedwater Systems will be analyzed using CHEC.
The current licensee position is to conduct these analyses using CHECHATE.
The procedure should be revised to resolve this inconsistency.
The procedure in Section 3.1, "Single Phase Systems Analyzed", states that the main steam system will be analyzed using the CHEC code.
The CHEC code cannot analyze steam systems, it is designed to analyze single phase liquid systems only.
The procedure also does not specifically mention that the Hoisture Separator Reheater Drains or the Feedwater Heater Drains are to be included in the systems to be analyzed.
These two drain systems are highly susceptible to Erosion/Corrosion damage.
In the case of two similar trains within a system the licensee was initially modeling only one train which is usually conservatively chosen to be the one with more tortuous path.
Our review of, the licensee's data input to the CHEC/CHECMATE codes, results of the code analyses and general approach to the management of analytical work indicated that, except for discrepancies in the CHEC analysis, 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 in 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 the methods used are in compliance with the EPRI recommendations, 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 methodology).
This incompatibility of data acquired by different methods causes difficulty
in determining erosion/corrosion wear rates using CHEC/CHECMATE.
However, the licensee is considering to use the UT grid pattern technique as a preferential method in taking future NDE measurements.
During the plant walkdown the audit team had opportunity 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.
We found that the reviewed documents were carefully prepared and clearly identified the components which 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 generators 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 analyzed in early 1988 using an early version of the CHEC code.
As it was pointed out in the earlier section of this report, these analyses were not performed using the preferred methodology and the licensee is planning 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 line is needed.
REVIEW OF MANAGEMENT INVOLVEMENT During our discussion with the licensee's management we were assured that they recognize importance of the erosion/corrosion program and will actively support it by providing proper staffing and 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.
4
CONCLUSIONS The licensee responded to the NRC guidelines specified in IE Bulletin 87-01 and Generic Le'tter 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.