ML20137S112
| ML20137S112 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 02/07/1986 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20137S001 | List: |
| References | |
| NUDOCS 8602130577 | |
| Download: ML20137S112 (4) | |
Text
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Enclosura 6 l
i Safety Evaluation of Confirmatory Item 6 Inservice Inspection Fort St. Vrain (FSV)
Public Service Company of Colorado Docket No. 50-267 I.
Background
SECY-85-370(1) recommended that the requested extension for Fort St. Vrain be authorized to operate at op to 35 percent of full power through May 31, 1986 contingent on a finding that certain confirmatory submittals from the licensee are acceptable.
The statement of the confirmatory items and the licensee's evaluation of the topics are attached to the. licensee's letter dated December 10,1985(2),
l Confirmatory Item 6 states:
l Submit a plan and )erform inservice inspections on several critical areas of tort St. Vrain's high energy piping to verify the integrity of this piping, prior to returning the plant to operation.
Thelicensee'sstatedobjectiveoftheinspectionprogramistoverifythe integrityofthemainsteam(MS),hotreheat(HRH),coldreheat(CRH)le.and feedwater(FW) systems (Reference 2).
The staff reviewed the availab information in the licensee's letter and the updated FSAR relevant to Con-firmatory Item 6 and inservice inspection (ISI) and requested additional information.(3) The licensee responded with a revised 3, 1986(4) proposal and sup-porting information in letters dated January and January 8, 1986(5).
II.
Objectives of the Staff Review and Technical Considerations Theobjectivesofthestaffreviewarethefollowing:
1)
A representative sample of welds and base material should be subjected to nondestructive examination (NDE) to provide reasonable assurance that generic service-induced degradation, if present, is detected.
2)
The NDE procedures and techniques used are effective for the detection of significant flaws, if present.
3)
The NDE personnel are qualified and experienced in the detection of flaws.
As discussed in SECY-85-370, Fort St. Vrain is a unique power plant.
Although rules for inspection and testing of components ofplantsweredescrib as-cool are not applicable because 10 CFR 50.55a does not require compliance with this document at Fort St. Vrain.
Therefore, a special plant-specific U ) References in Paragraph V
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inspection program was needed to resolve this issue.
This program should include inspection of a representative sample of base material and welds from the following locations:
(1) known areas of high design stress, (2) locations where inservice degradation has been experienced and (3) additional locations sufficient to tions of the materials of construction, provide a sample of the combina-fabrication techniques and potential degradation mechanisms.
The intent of Confirmatory Item 6 was to verify the high energy piping integrity through a successful inspection of a limited, but sufficient, sample size considering the proposed rela-tively short period of operation, i.e.
through May 31, 1986.
Establishing objective. gram for periodic inservice Inspection is a separate, longe an ISI Pro III. Licensee's Proposals In Reference 2 the licensee proposed the following action to resolve Confirmatory Item 6:
1)
Perform volumetric examination of three (3) butt welds (8" pipe to fitting, 8" pipe to elbow and 20" pipe to fitting),
2)
Perform volumetric examination of the base metal at the mid point of the 8" elbow and, 3)
Use the inspection methods and analyses of the original plant piping construction Code, ANSI B31.1.
After discussions with the staff, the licensee proposed four additional examinations in the hot and cold reheat systems.
In response to the request for information, the licensee proposed an expanded inspection plan with a total of 35 examination locations in the MS, HRH, CRH and FWsystems(Reference 4).
The licensee selected the representative examination locations by considering the following factors:
1)
High energy service conditions for MS, HRH, CRH and FW systems.
2)
The materials used in the construction of the high energy piping systems.
3)
The various high energy piping fabrication methods, i.e., hollov forged, seamless and welded plate.
4)
High stressed piping areas based on thermal and mechanical analysis.
5)
Areas which in the past have shown evidence of degradation at FSV.
The licensee provided isometric drawings of the locations he proposed to examine and described the material composition and fabrication methods of the selected locations.
The potential degradation phenomena considered were thermal fatigue, mechanical fatigue, corrosion and erosion.
The 35 examination points were chosen by the licensee such thd at least oni l
examination point represents the various possible combinations of the four plant systems, piping fabrication methods, materials of construction and degradation phenomena.
As the asbestos insulation was removed from the examination point, uncovered welds were examined.
The licensee made the conservative estimate that there would be two welds per examination point.
The licensee estimated that the four systems contain a population of about 2000 welds.
A sample of approximately 60 welds identified for inspection results in a confidence level of 95 percent with an error rate of less than 5 percent.
The licensee considers this confidence level adequate to pro-vide reliable detection of flaws.
Historical information was obtained by the licensee through interviews of key Public Service Company of Colorado personnel.
The repairs to the pressure boundary identified by these inter-views were listed and considered by the licensee during the selection of examination points.
ANSI B31.1 is a construction Code and the inspection methods and acceptance criteria may not be effective for the detection of inservice degradation, if present, or the reso M inn of the characteristics of flaw indications.
Therefore, the licensee proposed in Reference 5 to use ultrasonic testing procedures based on Division 1 of Section XI of the ASME Code which is intended for inspection of components of light-water-cooled plants.
IV.
Staff Evaluation The staff has completed the review of the licensee's submittals (Refer-ences 2, 4 and 5) related to Confirmatory Item 6.
The staff evaluated theissueIntwophases: (1) definition of the scope of the inspection program and (2) implementation of the examinations.
Toaccomplishtheseobjectives,aplantsitemeetingwasconductedduring the week of January 13, 1986 between the licensee and his consultants, and the NRC Resident Inspector, a Region IV Inspector, the NRR reviewer and an NRC consultant from Oak Ridge National Laboratories (ORNL).
The NRR re-viewer evaluated the size and location of the examination sample.
The Region IV Inspector evaluated the examination procedures, the qualifi-cation of the NDE personnel, the calibration of the instrumentation, observed inspections in progress and reviewed the inspection data.
The Region IV activities are summarized in the attached Memorandum dated January 22, 1986.
Details of these inspection efforts will be reported in NRC Inspection Report 50-267/86-04 to be issued at a later date.
The NRC consultant from ORNL prepared a Trip Report dated January 22,1986(7).
Based on the above information, the staff concludes that the licensee has completed Confirmato/y Item 6.
The staff has determined that the licensee's letters (References 4 and 5) constitute an acceptable inspection program and the implementation of examinations will be described in NRC Inspection Report 50-267/86-04.
The licensee's actions have provided reasonable assurance of the structural integrity of the high energy piping as recom-mended by SECY-85-370.
4 V.
References 1.
SECY-85-370 "Environme. ital Qualification (EQ) Extension of the November 30, 1985 Deadline for the Fort St. Vrain Nuclear Generating Station."
2.
Licensee's letter dated December 10, 1985 (Serial No. P-85460),
Subject:
Confirmatory Actions in Support of 35 Percent Power Restriction During EQ Scheduled Extension Period.
3.
NRC letter dated December 26, 1985 from Berkow to Walker.
4.
Licensee's letter dated January 3, 1986 (Serial No. P-86004),
Subject:
Confirmatory Action 6, Inspection of High Energy Piping.
5.
Licensee's letter dated January 8,1986 (Serial No. P-86012),
Subject:
Transmittal of NOE Examination Procedures.
6.
ASME Boiler and Pressure Vessel Code,Section XI, Division 2,
" Rules for Inspection and Testing of Com>onents of Gas-Cooled Plants" 1981 Edition including Addenda t1 rough Winter 1981.
7.
ORNL Trip Report dated January 22, 1986 from K. V. Cook to H. F. Conrad.
, Reviewer:, M. Hum I
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