IR 05000315/1997006
| ML17333A929 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 07/02/1997 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML17333A928 | List: |
| References | |
| 50-315-97-06, 50-315-97-6, NUDOCS 9707080033 | |
| Download: ML17333A929 (18) | |
Text
U. S. NUCLEAR REGULATORY COMMISSION
REGION III
Docket No.:
License No.:
50-31 5 DPR-27 Report No.:
50-31 5/97006(DRS)
Licensee:
Indiana Michigan Power Facility Name:
D. C. Cook Nuclear Plant - Unit 1 Location:
Bridgman, Ml Dates:
March 17-20, 26-28, April 2-4, May 29 and June 6, 1997 Inspectors:
J. Schapker, Reactor Inspector K. Green-Bates, Reactor Inspector Approved by:
J. Gavula, Chief Engineering Specialists Branch
Division of Reactor Safety 9707080033 970702 PDR ADOCK 050003i5
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EXECUTIVE SUMMARY D. C. Cook Nuclear Plant
.Inspection Report 50-31 5/97006(DRS)
Maintenance Improvements were noted in the steam generator inspection program, including use of state-of-the-art eddy current procedures and equipment, and oversight of contractors'rocesses and procedures.
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The flow accelerated corrosion program continued to be aggressively implemented.
The licensee identified a deficiency with previous eddy current evaluations, in that a significant number of steam generator tube indications should have been characterized as unacceptable and should have resulted in those tubes being repaired or plugged.
~En ineerin
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The licensee identified a deficiency with a previous engineering evaluation of a piping minimum wall thickness issue, where non-compliance with the design code was not addressed.
The licensee submitted a Code relief to allow the compliance issue to be resolve Re ort Details II. Maintenance M1 Conduct of Maintenance M1.1 Observations of Inservice Ins ection ISI Activities a.
Ins ection Sco e 73753 73052 73755 50002 The inspector observed work, reviewed ISI procedures, personnel certifications and reviewed data associated with the following activities:
Ultrasonic examination of reactor vessel charging system piping.
Eddy current examination (ET) on steam generator (SG) tubes.
Review of ET data in process and previous outage reviews for defective SG tubing.
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In situ pressure testing to assess structural adequacy of degraded tubes
'during normal operation and accident conditions.
Repairs to defective SG tubes.
Review of defective tube selection process for in situ testing, to bound the tube degradation within the SGs.
Review of defective tubes (repair) list and ET indication lists to assure compliance with Technical Specification (TS) requirements.
b.
Observations and Findin s
IS I Activities Ultrasonic test (UT) examinations of reactor vessel charging system piping observed by the inspector were performed in accordance with the applicable procedure requirements.
Indications were recorded and plotted to indicate geometrical reflectors which were recorded in previous examinations with no change in size or amplitude.
Data records were reviewed for accuracy and Code compliance.
Calibratioris and certifications of equipment were verified.
Personnel qualifications complied with the contractors written practice and SNT-TC-1A requirements.
Steam Generator Ins ection and Re airs Framatone Technologies was contracted to perform eddy current examination of the SG tubes.
The inspection program was conservative and followed the guidance of.the Electric Power Research Institutes'uidelines for steam generator inspections.
Site specific analyst training and examinations were performed and observed by licensee staf I Ij
The plus point coil was used this outage for inspection of the row 1 and 2 U-bends and hybrid expansion joint (HEJ).sleeves.
A 0.115 inch diameter Motorized Rotating Pancake Coil (MRPC) probe was used for the tubesheet area inspection.
All open tubes with MRPC indications in the tube support plate, which exceeded the 2-volt alternate plugging criteria, received a 100 percent inspection using bobbin coil ~
A significant number of defective SG tubes were identified this outage.
To quantify degradation growth rates for 10 CFR Part 100 compliance, the licensee performed in situ pressure tests on bounding, degraded tubes and reviewed ET data from the two previous outages for tubes with the most degradation.
In addition to the in situ testing, secondary side hydro testing was performed, to assure adequacy of tubesheet rerolls performed this outage.
Some of the previously installed rerolls had exhibited leakage during the in situ testing.
The licensee performed F" rerolls and tube plugging to repair the defective tubes.
No sleeving was performed during the outage.
A total of 979 tubes were plugged and 699 tubes had rerolls installed to meet the F" criteria.
The SG tube repairs were performed in accordance with the applicable procedure requirements.
The reviews of previous ET data identified that a number of the defective tubes had various degrees of degradation present during the previous outage.
The 1995 outage ET utilized the CECCO probe for inspection of the HEJ sleeves, and tubesheet area of the SG tubes.
The 1994 data contained MRPC ET data using a 0.080 inch diameter coil.
Conclusions Licensee and contractor personnel were conscientious of procedural requirements, readily responded to the inspector's inquiry, and demonstrated knowledge and skills necessary for the task performed.
The contractor utilized state-of-the-art equipment and procedures to inspect the SG tubes.
Management involvement was appropriate and demonstrated conservative decision making during the inspection, testing and repairs to the steam generator tubes.
Although improved technology and higher resolution ET probes were utilized this outage, it appeared that some of the indications should have been identified as defective the previous outages and repaired or removed from service.
The licensee reported this finding per the requirements of 10 CFR 50.73(a)(2)(1) in Licensee Event Report (LER) 97-008-00.
The NRC inspector reviewed and concurred with the LER assessment and corrective actions.
The NRC review of the ET graphics of previous outages confirmed some tubes with indications should have been analyzed as defective in accordance with applicable ET guidelines.
The review by the licensee contractors identified additional indications in all four SGs which had various degree of degradation of which some were identified by the CECCO probe the previous outage with confirmation of degradation with the MRPC 0.080 inch coil in 1994.
A significant number of these indications were difficultto analyze due to deposit influences, relative indication size, and the ET technology and analyst guidelines used at that time.
Improvements in ET software and probes have
enabled the analyst to be more accurate in assessing the indications in today'
technology.
This non-repetitive licensee-identified and corrected violation is being treated as a Non-Cited Violation, consistent with Section VII.B.1 of the NRC Enforcement Policy. The licensee's corrective action was complete and conservative (NCV 50-31 5/97006-01).
IVI3 Maintenance Procedures and Documentation M3.1 Flow Accelerated Corrosion Pro ram Review a.
Ins ection Sco e 49001 Inspectors reviewed portions of the licensee's Flow Accelerated Corrosion (FAC)
Program and selected UT data reports from the 1995 and 1997 refueling outages.
b.
Observations and Findin s
During the 1995 Unit 1 refueling outage, UT was performed on a main steam, 30-inch diameter vertical elbow and at two extension locations.
These extensions were 1-inch and 4-inch, respectively, from the weld at the elbow and the sweep bend interface.
The UT data on the elbow was acceptable; however, an area on the second extension line was found to have wall thickness of 0.893 inches which was less than the system design minimum wall thickness of 0.907 inches.
An engineering evaluation was performed to assess the structural adequacy for continued operation.
(See Section E7.1 of this report for additional discussion.)
After further examination in 1997, the licensee concluded that wall thinning was not due to FAC, but rather to an "As Received" condition of the pipe.
Licensee personnel were conscientious of procedural requirements, readily responded to inquiry, and demonstrated knowledge and skills necessary for the overview and nondestructive examination of areas susceptible to FAC. The aggressive number of components selected and areas selected for FAC examination demonstrated a conservative approach and a commitment to safety.
The latest industry FAC computer analysis software edition of "CHECWORKS" was in the process of being reviewed for incorporation into future FAC Program use.
c.
Conclusions The licensee demonstrated a commitment to safety with the continued implementation of an aggressive FAC UT program during refueling outages.
The FAC program was implemented in accordance with the licensee's program as part of the implementation of Generic Letter 89-08 "Erosion/Corrosion Induced Pipe Wall Thinning."
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M8 Miscellaneous Maintenance Issues (92700)
M8.1 Closed LER 97-008-00:
SGs Outside TS Tube Degradation Acceptance Criteria Due to Inadequate Analysis of ET Data.
Review of previous outage ET data to determine growth rates of indications identified a number of defective tubes which were not repaired in accordance with TS 4.4.5.4.a.6 and 4.4.5.4.b.
The cause and corrective action are discussed in Section M1.1.b of this report.
III. En ineerin E7 Quality Assurance in Engineering Activities E7.1 Review of En ineerin Calculations Ins ection Sco e 49001 Inspectors reviewed Engineering Calculation No. DCCNECPOIEC78N, dated September 7, 1995, which evaluated a 30-inch main steam pipe that did not meet the required minimum wall thickness for American Nuclear Standards Institute (ANSI)/American Society of Mechanical Engineers (ASME) B31.1 Piping Code. As discussed in Section M3.1, this condition was discovered by the licensee's FAC program.
b.
Observations and Findin s During the 1995 Unit 1 Refueling Outage (July - Oct. 1995), the FAC program identified that the pipe wall thickness of elbow sweep bend component 1-MS-001-1-M-9E, between the No.
1 Steam Generator and containment penetration, had an area of pipe. wall thickness that was 0.843 inches.
The minimum wall thickness required by ANSI/ASME B31.1 Piping Code was 0.907 inches.
The nominal wall thickness was 1 inch.
Engineering performed the referenced calculation and determined that the pipe section was acceptable for its intended service, and scheduled it for reexamination in the next refueling outage.
The inspectors reviewed calculation No. DCCNECPOIEC78N and noted that it only considered the longitudinal stress requirements and did not address the noncompliance with the design code for hoop stresses.
The calculation's Design Verification Checklist incorrectly stated that the requirements for the applicable design codes were met.
Concurrent with the NRC's review, the licensee independently reviewed this calculation, concluded that it lacked the proper technical bases, and documented this deficiency in Condition Report No. 97-0908.
A new calculation, No.
DC-D-01-MSC-66, "Hoop Stresses in the Sweep Bend," dated April 2, 1997, was generated to verify the structural integrity of the affected component.
By using higher tensile strengths as shown in the material's mill test reports, the calculation concluded that the design intent and/or requirements of 831.1 were met.
The NRC and the licensee held conference calls on April 14, and 25, 1997, to the discuss the validity of the bases for the revised calculation.
As a result, the
licensee submitted a Code relief request on June 5, 1997, to operate Unit 1 for one fuel cycle with a section of the main steam piping having a wall thickness less than that allowed by B31.1.
Although the piping may be eventually shown to be acceptable, the original calculation did not address the noncompliance with the design code.
This non-repetitive licensee-identified and corrected violation is being treated as a Non-Cited Violation consistent with Section VII.B.1 of the NRC Enforcement Policy. (50-31 5/97006-02)
Conclusions Design verification activities for the initial minimum wall thickness evaluation did not assure that applicable design requirements were met.
This was treated as a Non-Cited Violation. The adequacy of the bases for the revised calculation was questioned by the NRC, and the licensee submitted a Code relief request to allow the issue of Code compliance to be resolved.
V. Mana ement Meetln s
X1 Exit Meeting Summary At the conclusion of the inspection on April 4, and teleconference on June 6, 1997, the inspector met with licensee representatives and summarized the scope and findings of the inspection activities.
The inspector questioned licensee personnel as to the potential for proprietary information in the likely inspection report material discussed at the exit.
No proprietary information was identified.
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PARTIAL LIST OF PERSONS CONTACTED Licensee M. Akerman, Nuclear Licensing K. Baker, Production Engineering Superintendent M. Duepaunt, Nuclear Licensing J. Jensen, Engineering Projects F. Pisarsky, Mechanical Engineering Superintendent R. Ptacek, Nuclear Licensing J. Sampson, Plant Manager M. Schartzwalder, Mechanical Engineering L. Smart, Nuclear Licensing K. Worthinton, Mechanical Engineering Framatone Technolo ies M. Chambers, Lead Analyst, LIII ET J. Fleck, Engineer NRC B. Bartlett, Senior Resident Inspector INSPECTION PROCEDURES USED IP 50002:
IP 73753:
IP 73755:
IP 73051:
IP 73052:
IP 49001:
- Maintenance Inservice Inspection - Observation of Work Inservice Inspection - Data Review and Evaluation Inservice Inspection - Program Review Inservice Inspection - Procedure Review Erosion/Corrosion
- Program Review
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ITEMS OPENED, CLOSED, AND DISCUSSED Closed 97-008-00 LER Cycle 15 operation of SGs outside TS tube degradation acceptance criteria due to inadequate analysis of eddy current data.
50-315/97006-01 NCV Licensee identified violation of previous defective tubing not repaired or plugged 50-315/97006-02 NCV Licensee identified violation of previous engineering evaluation inadequacies.
LIST OF ACRONYMS USED ANSI ASME ET HEJ LER MRPC SG TS NCV UT American Nuclear Standards Institute American Society of Mechanical Engineers Eddy Current Examination Hybrid Expansion Point Licensee Event Report Motorized Rotating Pancake Coil Steam Generator Technical Specification Non-Cited Violation-Ultrasonic Examination