IR 05000269/1982013
| ML20053D827 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/12/1982 |
| From: | Economos N, Herdt A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20053D817 | List: |
| References | |
| 50-269-82-13, 50-270-82-13, 50-287-82-13, NUDOCS 8206070360 | |
| Download: ML20053D827 (4) | |
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UNITED STATES
NUCLEAR REGULATORY COMMISSION
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a REGION 11
o 101 MARIETTA ST., N.W., SUITE 3100 ATLANTA, GEORGIA 30303 o
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Report Nos. 50-269/82-13, 50-270/82-13, 50-287/82-13 Licensee: Duke Power Company 422 South Church Street Charlotte, North Carolina 28242 Facility Name: Oconee Nuclear Station Docket Nos. 50-269, 50-270, 50-287 License Nos. DPR-38, OPR-37, DPR-55 Inspection at Oco ea eneca, South Carolina Inspecto :
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Date Signed j
Approved byv
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A. R'. 'ilerdt, Sect'WChief
/Date' Signed Engineering Inspection Branch s
Division of Engineering and Technical Programs SUMMARY
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Inspection on April 29-30, 1992 Areas Inspected This special unannounced inspection involved 16 inspector-hours on site to observe once through steam generator (OTSG) auxiliary feedwater ring header distortion damage inspection (Unit 3); secondary shield wall vertical tendon failure (Unit 2).
Results No violations or deviations were identified.
8206070360 820513 PDR ADOCK 05000269 G
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REPORT DETAILS 1.
Persons Contacted Licensee Employees J. E. Smith, Station Manager R. J. Brackett, Station Senior QA Engineer
- J. N. Pope, Superintendent of Operations D. M. Thomson, Mechanical Maintenance Engineer W. Gallman, Asst. Mechanical Maintenance Engineer R. Rettew, Asst. Mechanical Maintenance Engineer Other Organizations Babcock & Wilcox - Nuclear Power Generation Division (NPGD)
W. W. Foster, Site Representative C. Gray, Site Representative W. Rossfeld, Backshift Manager NRC Resident Inspector W. Orders
- Attended exit interview
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2.
Exit Interview The inspection scope and findings were summarized on April 30, 1982, with those persons indicated in paragraph 1 above.
3.
Licensee Action on Previous Inspection Findings Not inspected.
4.
Unresolved Items Unresolved items were not identified during this inspection.
5.
Damage To Auxiliary Feedwater Header, Unit 3 On April 23, 1982 the inspector attended a meeting at the NRC headquarters in Bethesda, Maryland between Babcock and Wilcox (B&W), B&W Licensees and NRC staff in order to discuss the auxiliary feedwater header (AFWH) distor-tion that was discovered at Rancho Seco and Davis-Besse. The problem was identified when eddy current inspection of OTSG outer periphery tubes showed denting (dings) near the location of the AFWH. Both licensees described the extent of the damage which included header distortion, support bracket distortion and weld cracking, dowel pin disengagement / separation. The
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licensees stated that, except for the amount of distortion / damage observed in both plants, the nature of the problem appeared to be similar. The Duke Power Company representative expressed concern over Oconee-3 having the same problem and stated that the unit began cooling down in preparation for an inspection of the AFWH and for the scheduled ten year refueling outage, eighteen days earlier than planned.
On April 29, 1982 the licensee inspected 0TSG(s) "A" and "B" headers and reported the following findings:
"A" -
Header shows light to moderate warpage; of the. four dowel pins inspected, all have moved inward toward the tube bundle.
Tack welds on the dowel pin brackets are broken and the brackets are bent. Three dowel pins are present and one is missing.
AFW nozzle is in place in header.
The nozzle backup ring to header gap is wider than normal.
OTSG "B" Header shows moderate to heavy warpage. All four dowel pins
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inspected are missing. Outer dowel pin brackets bent out-ward, toward 0TSG shell but appear flush with baffle. Nozzle is inplace in header. Nozzle backup ring to header gap is much wider than normal.
This inspection was perfortred through the manway at the 15th tube support plate and was limited to about 30% of the AFWH.
B&W has provided the licensee w.ith several repair options. The option given se-tous consideration and most likely to be used, proposes the stabilization of the existing header and the installation of an external header similar to that used in Oconee units-1 and -2.
6.
Secondary Shield Wall Vertical Tendon Failure (Units 2 & 3)
On April 29, 1982 the licensee reported that on April 28, 1982, during reactor building closeout inspection of unit-2 prior to startup following (
refueling, the licensee's inspection team observed that a tendon cover and anchorhead from a vertical tendon on the secondary shield wall (D ring)
surrounding the
"A" steam generator cavity, was resting on the floor.
Further investigation disclosed that the anchor head of a tendon on the other side of the same cavity had some severed wire strands. A subsequent l
inspection of Oconee units-2 and -3 disclosed the following:
Unit - 2:
OTSG Cavity "A" One of the four tendons had all the wire strands severed i
at the base of the anchorhead and another, had only a
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portion of the strands severed at the same location.
One tendon had dry rusted buttonheads and anchorhead.
i One tendon had rusted anchorhead and buttonheads along
with moisture accumulatio. _
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OTSG Cavity "B" All four tendons were found with moisture accumulated inside the tendon covers. Rusting was observed on the anchorheads and on the wire strands near the base of the anchorheads.
The stands in all four tendons were intact.
Unit - 3:
OTSG Cavity "A" All four tendons intact no evidence of rust or moisture.
OTSG Cavity "B" Two tendons had dry rusted anchorheads and buttonheads.
One tendon had significant rust on the anchorhead and buttonhead along with moisture accumulation. One tendon had moisture and some rust on the aforementioned areas.
The licensee has ordered new tendons to replace all eight tendons in Unit-2 and thereby allow the unit to resume operation as soon as possible.
A failure analysis is being performed on the severed strands to verify the cause and of the mechanism failure. Bechtel is performing seismic event calculations to justify continued operation for Unit-1. Because Unit-1 is operating, the licensee observed / inspected the bottom covers on those vertical tendons which were readily visible from the basement floor of the reactor building and found them intact. A more detail inspection is planned next time Unit-1 is shut down. The inspector, accompanied by the senior resident inspector, observed the broken tendons in Unit-2 prior to and following their removal from the shield wall. The inspector noted that only the strands at the base of the anchorheads exhibited degradation from corrosion. The rest of the stands were rust-free and coated with grease.
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Within the areas inspected no violations or deviations were identified.