ML20095B466
| ML20095B466 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/31/1984 |
| From: | Oprea G HOUSTON LIGHTING & POWER CO. |
| To: | Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| ST-HL-AE-1121, NUDOCS 8408220130 | |
| Download: ML20095B466 (5) | |
Text
4 The Light Company ii.,1,si,,, ugisig u,,m m ii.,mo,
ii.,,,si,,,,. i_,,oni oimmii ST-HL-AE-1121 File Number: G12.168
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~i Mr. John T. Collins t
U. S. Nuclear Regulatory Comiission t
AUG 1 31984 !i t
Director, Region IV 1
611 Ryan Plaza Drive, Suite 1000 l
Arlington, Texas 76102 u-
Dear Mr. Collins:
South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Third Interim Report Concerning Corrosion in a Safety Injection System Weld On October 20, 1983, pursuant to 10CFR50.55(e), Houston Lighting & Power Company (HL&P) notified your office of an item concerning corrosion in a pipe weld at the South Texas Project (STP). Attached is the third interim report concei'ning this item. The next report will be submitted to your office by November 16, 1984. As previously stated, the final report will address recurrence control and safety analysis aspects.
If you should have any questions concerning this matter, please contact Mr. Michael E. Powell at (713) 993-1328.
Very truly yours, G. W. Oprea, Jr.
Executive Vice President MEP/mg
Attachment:
3rd Interim Report Concerning Corrosion in a Safety Injection System Weld 8408220130 840731 PDR ADOCK 05000498 S
PDR W2/NRC2/d LE-)] gjg
Ilouston Lighting & Power Company ST-HL-AE-1121 File Number: G12.168 Page 2 cc:
Darrell G. Eisenhut, Director Brian E. Berwick, Esquire Division of Licensing Assistant Attorney General for Office of Nuclear Reactor Regulation the State of Texas U.S. ' Nuclear Regulatory Comission P. O. Box 12548, Capitol Station Washington, DC 20555 Austin, TX 78711
~ Victor Nerses, Project Manager Lanny Sinkin U.S. Nuclear Regulatory Comission Citizens Concerned About Nuclear Power 7920 Norfolk Avenue 114 W. 7th, Suite 220
~Bethesda, MD 20016 Austin, TX 78701 D.-P. Tomlinson Robert G. Perlis, Esquire Resident Inspector / South Texas Project Hearing Attorney c/o U.S. Nuclear Regulatory Comission Office of the Executive Legal Director P. O. Box 910 U.S. Nuclear Regulatory Comission Bay City,.TX 77414 Washington, DC 20555 1
M. D. Schwarz, Jr.. Esquire Charles Bechhoefer, Esquire Baker & Botts Chainnan, Atomic Safety & Licensing Board One Shell Plaza U.S. Nuclear Regulatory Comission Houston, TX 77002 Washington, DC 20555 J.: R. Newman, Esquire Dr. James C. Lamb, III Newman & Holtzinger,.P.C.
313 Woodhaven Road 1025 Connecticut Avenue, N.W.
Chapel Hill, NC 27514 Washington, DC 20036 Judge Ernest E. Hill Director, Office of Inspection Hill Associetes and Enforcement 210 Montego Drive U.S. Nuclear Regulatory Comission Danville, CA 94526 Washington, DC 20555 E. R. Brooks /R. L. Range William S. Jordan, III. Esquire Central Power & Light Company Harmon & Weiss P. 0. Box 2121 1725 I Street, N.W.
Corpus Christi, TX 78403 Suite 506 Washington, DC 20006
- 11. L. Peterson/G. Pokorny City.of Austin Citizens for Equitable Utilities, Inc.
P. O. Box 1088 c/o Ms. Peggy Buchorn Austin,-TX 78767 Route 1, Box 1684 Brazoria, TX 77422
-J. B. Poston/A. vonRosenberg City Public Service Board P. O. Box 1771
-San Antonio, TX 78296 Revised 07/31/84 l-
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s Attachment' ST-HL-AE-1121 Page 1 of 3
-South Texas Project Units 1-and 2 Third-Interim Report Concerning
- Corrosion in a Safety Injection System Weld
-I.-
Summary Voids,have been discovered in two welds in the portion of-the Safety
- (RWST)'and the'SI pumps located in the Fuel Handling Building-(ge Tank Injection System ~(SIS) piping between the Refueling Water Stora FHB). A
=
. portion of one weld was removed for analysis to determine the extent of
- the defects and-the cause.
Investigations of the defects showed through-wall penetration.= - Analysis of the physical appearance of the Epipe section and microscopic analysis of samples taken from defects
-indicated the presence of microbiologically influenced corrosion (MIC).
'. Inspections _-and investigations have been initiated and completed as described below.
,An expert in the field of microbiologically influenced corrosion has been retained to' determine the source of the bacteria and assist in the
. formulation of a recurrence control program. A closed circuit television-inspection ' program to investigate the interior of installed and laydown area piping has been completed for a-sample population. The T
. inspection / investigation concluded that-the majority of the subject piping has not been-affected by MIC; however, a few isolated areas did
- show evidence of potential MIC presence.
In addition, visual _ inspection of six (6) safety-related carbon steel tanks indicates no evidence of_ MIC. An inspection of stainless steel tanks has been initiated.
.II.
Description
^
On October.20, 1983, pursuant'to 10CFR50.55(e), Houston Lighting & Power Company (HL&P) notified the NRC Region IV of an item concerning corrosion in an SIS mld. ~ During a re-examination and repair program of ASME safety-related welding,'certain field welds in the SI piping from the RWST were being repaired to eliminate defects identified in the radiographs taken by Brown & Root, Inc. (B&R). During examination of T
the weld metal in two welds, voids were found that exhibited' signs of corrosion. From comparison of recent radiographs to the original b.
radiographs, it is evident that the indications present in the new radiographs were not present in the original films. One weld was "e
LW2/NRC2/d
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Attachment ST-HL-AE-1121 Page 2 of 3 sectioned and a sample sent for laboratory analysis. After metallographic examination and microscopic analysis of scrapings from the corrosion sites, MIC resulting from the action of bacteria (including Gallionella) was determined to be the probable cause of corrosion. This determination was further substantiated by the fact that the SI pipe had been observed to be partially filled with standing water, thus providing a suitable growth medium for bacteria.
III. Investigative Measures An expert in the field of MIC has been retained to determine the source of the bacteria and assist in the formulation of a recurrence control program. The sampling program indicates corrosion causing bacteria are present in both the well water and soil at the plant site.
The low points of the buried 30" diameter aluminum-bronze essential cooling water system piping have been visually examined for MIC. Four small deposits have been discovered at one backing ring which had contained standing water-for several months. The inspection of the deposits at the one backing ring in the essential cooling water piping has been completed. A portion of the backing ring adjacent to three of the four deposits was removed. This was accomplished without disturbing either the weld or pipe base material. The area underneath the backing ring as well'as the backside of the backing ring was visually inspected, wire-brushed and probed with a sharp instrument for pitting. No significant pitting was observed. No other evidence of MIC was found in these ECW lines.
The MIC consultant has been attempting to grow bacteria nodules on test specimens of aluminum-bronze piping since January of this year. To date, the bacteria have developed only small deposits on the test specimens. These deposits were scraped away and no significant corrosion was found.
. Based on the laboratory testing and the field investigation noted above, HL8P has determined that bacteria caused corrosion is not a significant concern for the essential cooling water aluminum-bronze components.
The inspection program using a closed circuit television and direct visual examination to investigate the interior of installed and laydown area piping has been completed. Approximately fifteen percent of laydown area piping with indications that dirt or water could have been introduced.have been examined for indications of MIC. The laydown area stainless steel and aluminum-bronze piping evraination has been completed and no indications of MIC have been found. Approximately fifteen percent of installed safety-related staialess steel piping low points have been examined. Stainless steel pip 11g examination in the
. reactor containment building has been comple+.ed and no indications of MIC have been found. Stainless steel and carbon steel piping investigation in the mechanical auxiliary building has been completed W2/NRC2/d-L
Attachment ST-HL-AE-1121 o
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Page 3 of 3 and no indicaticns of MIC have been found in safety-related systems.
Evidence of possible MIC'in the nonsafety-related stainless steel equipment drain system has been discovered, and is mentioned here only for information completeness.
Stainless steel safety-related auxiliary feedwater system piping embedded in the slab of the isolation valve cubicle has also been found to contain indications of possible MIC in several welds. Two additional
" suspect" welds have been identified in two Containment Spray System (CSS) lines, which are located in the same area in the Fuel Handling _
Building as the SIS line discussed in Section II above.
Visual inspection of the six (6) safety-related carbon steel standby diesel fuel oil storage tanks has been completed. No evidence of MIC was found. Some degree of MIC pitting has been identified in the field erected stainless steel tanks. Measures for detailed inspection of these tanks for location and disposition of MIC pitting are currently being developed, but have not yet been implemented.
In sumary, the areas that show evidence of potential MIC are as follows:
1.
Three stainless steel lines in the Safety Injection (SI) and Containment Spray (CS) systems, located in the lower elevations of the Unit 1 Fuel Handling Building (FHB).
'2.
Stainless steel lines in the Auxiliary Feed (AF) system, located in the lowest elevation of the Isolation Valve Cubicle (IVC) rooms in both Units 1 and 2.
3.
Stainless steel lines in the nonsafety-related Equipment Drain (ED) system, located in the Mechanical Electrical Auxiliary Building (MEAB), Unit 1 that have been and are currently being used as construction drains.
4.
One aluminum bronze ECW line lo'cated immedi tely east of the Unit 1 MEAB. The area of interest is the lo. point of the system.
5.
Field erected stainless steel tanks.
W2/NRC2/d a