ML19294C285
| ML19294C285 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 11/21/1979 |
| From: | Goodwin C PORTLAND GENERAL ELECTRIC CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| IEB-79-17, NUDOCS 8003100055 | |
| Download: ML19294C285 (7) | |
Text
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November 21, 1979 Trojan Nuclear Plant Docket 50-344 License NPF-1 Mr. R. H. Engelken, Director U. S. Nuclear Regulatory Commission Region V Suite 202, Walnut Creek Plaza 1990 N. California Blvd.
Walnut Creek, CA 94596
Dear Sir:
In IE Bulletin 79-17, PGE was made aware of potential intergranular stress corrosion cracking problems with stainless steel piping in por-tions of systems which contain stagnant, borated, oxygenated water.
Required inspections have been completed at Trojan and have identified no evidence of stress corrosion cracking in safety-related stainless steel piping. The attached report is a complete response to both the original and Revision 1 of IE Bulletin 79-17.
Sincerely, s
C. Goodwin, Jr.
Assistant Vice President Thermal Plant Operation and Maintenance CG/JLT/4sa5A13 Attachment c:
Mr. Lynn Frank, Director State of Oregon Department of Enci, -
Director Of fice of Inspection and Enforcement U. S. Nuclear Regulatorf Commission a C, a n %<.
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TROJAN NUCLEAR PLANT Portland General Electric Company IE Bulletin 79-17, Dated July 26, 1979 Revision 1, Dated October 29, 1979 Pipe Cracks in Stagnant Borated Water Systems at PWR Plants 4
Final Report
FINAL REPORT I.
Introduction NRC IE Bulletin 79-17, dated July 26, 1979, required that all licensees of pressurized water reactors inspect portions of safety-related stainless steel systems which contain stagnant, oxygenated, borated water. The inspections, outlined in Sec-tion II of this report, were completed at Trojan in accordance with the original IE Bulletin prior to receiving Revision 1 issued October 29, 1979.
Section III of the report addresses our compliance with Revision 1 of this Bulletin.
No case of stress corrosion cracking was identified during the extensive inspection program.
II.
Original "illetin (Item 2)
Facilities at which ISI examinations have not been performed (ie, visual and volumetric UT) on stagnant portions of systems identified in Item 1 above shall complete the following actions at the earliest practical date, but not later than 90 days after the date of the Bulletin.
A.
Item 2(a)
Perform ASME Section XI visual examination (IWA 2210) of normally accessible welds of all engineered safety systems at service pressure to verify system integrity.
Response
PGE has completed system pressure tests of accessible safety-related stainless steel systems which are capable of being tested at service pressure'which contain stagnant, borated, oxygenated water.
Some portions of systems were not tested due to current operating conditions. The testing was done in accordance with IWA-5241 and IWA-5242. The test personnel, although not documented to be qualified for visual examinations in accordance with the Code, were experienced Plant personnel. For insulated piping, the examination was conducted at service pressure without removal of insulation. During the examination, attention was given to both insulated and noninsulated piping for evidence of leakage and/or boric acid residues.
No evidence of abnormal leakage or boric acid residue was detected at locations other than those normally expected, such as at valve stems and pump seals.
B.
Item 2(b)
Conduct ultrascnic and liquid penetrant examinations on a representative number of circumferential welds in normally accessible portions of systems identified by Section I above.
It is intended that the sample number of welds include all pipe diameters in the 2-1/2-in. to 24-in. rarge with no less than 10 percent sample by
system and pipe wall thickness.
It is also intended that the ultrasonic examinations cover the weld fusion zone and a minimum of 1/2-in. on each side of the weld at the pipe I.D.
The examination shall be in accor-dance with the provisions of ASME Code Section XI -
Appendix III and supplements of the 1975 winter addenda, except all signal responses shall be evaluated as to the nature of the indications.
These code methods, alternative examination methods, combination of methods, or newly developed techniques may be used provided the procedures yield a demonstrated effectiveness in detect-ing stress corrosion cracking in austenitic stainless steel piping.
Response
Ultrasonic and liquid penetrant examinations were performed on approximately 13 percent of all accessible welds on piping 2-1/2 in. and larger on safety-related stainless steel systems containing stagnant, borated, oxygenated water. Attachment I identifies the number of welds inspected and the number of accessible welds by system.
One hundred and fourteen welds were examined. All were examined using liquid penetrants and all except two were ultrasonically examined.
Two welds in 3-in. diameter pipes with 0.120-in. wall thickness were radiographed because a satisfactory ultrasonic procedure could not be developed. Ne cracks were detected by any of the methods used. Seven indications were reported. Three were surface roughness which were removed by filing. One was ground out of the OD and repaired.
The remaining three met Code requirements and no repair was necessary.
None of these indica-tions were evaluated to be related to stress corrosion cracking.
The procedure used is basically in accordance with ASME Sec-tion XI, Appendix III and supplements of the 1975 winter addenda.
However, 5 percent notches rather than 10 percent were used and it was necessary to modify the technique for virtually each diameter and thickness.
Frequencies of 2.25, 3.5 and 5 MHz were used and a 45 degree shear angle was found to be the "ost useful.
For many configurations, only tuo ID and two OD notch reflections could be utilized for preparing the distance amplitude ct.rve.
The procedures were qualified on two EPRI supplied pipe sections which contain stress corrosion crac:.s artificially induced by Battelle Northwest Laboratory. Qualification was witnessed by our Factory Mutual Engineering Authorized Nuclear Inspector.
Selection of welds for examination were not limited by wall thickness nor insulation. Accessible welds were selected for examination on the basis of highest carbon content, then by system importance, mixture of pipe diameters, pipe wall thick-nesses, vertical runs, horizontal runs, elbows, and fittings.
The examinations identified no stress corrosion cracking.
C.
Item 2(c)
If cracking is identified during Item (a) and (b) examina-tions, all welds of safety-related piping systems and asso-ciated subsystems where dynamic flow conditions do not exist during normal operations (Item 1) shall be subject to volumetric examination and repair, including piping in areas which are normally inaccessible.
Response
Since stress corrosion cracking has not been identified in 2(a) or 2(b), additional inspections are not planned at Trojan.
III.
Bulletin Revision 1 A.
Items 1 and 5 Item 1 - For this review, the term " stagnant, oxygenated, borated water systems" refers to those systems serving as engineered safeguards having no normal operating functions and contain essentially air-saturated borated water where dynamic flow conditions do not exist on a continuous basis.
However, these systems must be main-tained ready for actuation during normal power opera-tions.
Where your definition of stagnant differs from the one given above, please supplement your previous response within 30 days of this Bulletin revision.
Item 5 - Provid$ a written report to the director of the appropriate NRC regional office within 30 days of the date of this Bulletin revision addressing the results of your review if required by Item 1.
Provide a sched-ule of your inspection plans and response to Item 2(b) in those cases in which the inspections have not been completed.
Response
PCE's original definition of " stagnant" excluded some portions of systems which were periodically flushed as required by our Tech-nical Specifications.
Portions of systems originally excluded include:
a) Piping from the refueling water atorage tank to the safety injection pumps then back to the refuel-ing water storage tank.
Safety injection pumps are on recirculation once per month.
b) Piping from the refueling water storage tank to the Containment spray pump and ba.k to the refueling water storage tank.
Containment spray is on recir-culation once per month.
PCE does not plan to perform additional inspection of these por-tions of systems which were excluded originally since:
- 1) inspec-tion of 19 and 39 percent respectively of all accessible welds on the noncirculated portions of these systems was performed with no indication of stress corrosion cracking; 2) visual examina-tion of the noncirculated portions of these systems identified non indications of leaks; 3) four welds were inspected on a branch line off the main line from the refueling water storage tank with no indication of stress corrosion cracking; and 4) piping is periodically flushed.
B.
Item 2 All operating pressurized water reactor facilities shall complete the following inspection on the stagnant piping systems identified in Item 1 at the earliest practical date and not later than 12 months from the date of this Bulletin revision. Facilities which have been inspected in accor-dance with the original Bulletin, Sections 2(a) and 2(b) satisfy the requirements of this revision.
Response
PCE has completed the required inspections in accordance with the original Bulletin therefore Sections 2(a) and 2(b) of Revi-sion 1 of the Bulletin do not apply to Trojan. Although Trojan inspections were completed prior to receiving Revision 1, PGE considered carbon content, pipe size and thickness, and system importance in making weld selections. Therefore, our criteria meets the three cri'teria for weld selection identified in Revision 1.
C.
Item 6 Provide a written report to the director of the appropriate NRC regional office within 30 days of the date of completion of the examinations require] by Items 2(a) and 2(b) or 2(c) describing the inspection results and any correct ive actions taken.
Response
Our response in Section II of this report completes this requirement.
JLT/4sa5A14 ATTACHMENT I IE BULLETIN 79-17 INFORMATION Welds Accessible P&ID FSAR Figure System Title Inspected Welds Percent M-201 5.101 Reactor Coolant 2
12 17 M-202 9.3-14 Chemical and. Volume Control, Sheet 1 19 172 11 M-203 9.3-15 Chemical and Volume Control, Sheet 2 i
M-204 9.3-16 Chemical and Volume' Control, Sheet 3 M-205 5.5 7 Residual Heat Removal 6
24 25 M-206 6.3-1 Safety Injection 45 239 19 M-207 6.4-1 Containment Spray 32 82 39 M-220 11.2-9 Clean Radioactive Waste Treatment 0
2 0
M-221 11.2-14 Dirty Radioactive Waste Treatment 0
5 0
M-227 9.1-4 Spent Fuel Pool Cooling and Demineralizer 10 353
_j[
TOTAL 114 889 13
- 1 welds inspected had base material on at least one side with content NOTE:
.05 percent or greater.
2.
The Spent Fuel Pool Cooling System at Trojan is not safety-related.
RJW/JLT/sa/4kk3A22