ML19320C136
| ML19320C136 | |
| Person / Time | |
|---|---|
| Site: | Perkins, Cherokee  |
| Issue date: | 06/11/1980 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Dail L DUKE POWER CO. |
| References | |
| NUDOCS 8007160230 | |
| Download: ML19320C136 (1) | |
Text
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'o, UNITED STATES 8
NUCLEAR REGULATORY COMMISSION o
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101 MARIETTA ST., N.W., SUITE 3100
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-In Reply Refer To:
N 11 1980 RII:JPO p T,i
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qq 10-493) S0-488 50-489, 50-490 Duke Power Company Attn:
L. C. Dail, Vice President Design Engineering P. O. Box 33189 Charlotte, NC 28242 Gentlemen:
This Information Notice is provided as an early notification of a possible significant matter.
It is expected that recipients will review the information for possible applicability to their facilities. No specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular or Bulletin will be issued to recommend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Of fice.
Sincerely, I
James P. O'Reilly Director
Enclosures:
1.
IE Information Notice No. 80-27 2.
' List of Recently Issued IE Information Notices i
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.r N 11 1980 Duke Power Company s cc w/ encl:
J. T. Moore, Project Manager Post Office Box 422 Gaffney, South Carolina 29340 s
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UNITED STATES 8003050068 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
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IE Information Notice No. 80-27
' DEGRADATION OF REACTOR COOLANT PUMP STUDS Description of Circumstances:
On May 17, 1980, the NRC staff was informed by Omaha Public Power District (OPPD) that severe corrosion damage was found on a number of closure studs in two of the i
four Byron Jackson reactor coolant pumps at Fort Calhoun Unit 1 (PWR).
At the time, the reactor coolant system was undergoing a routine low pressure leak test (180 psig) and visaal inspection prior to plant restart after a four-month outage for refueling, pipe support modifications and scheduled inservice inspection. During the visual inspection, saturated and dripping insulation was observed at one of the Byron Jackson reactor coolant pump flange regions. Upon i
removal of the insulation, evidence of coolant leakage was found emanating from the neating surfaces between the pump casing and the pump cover.
Further i
investigation of the three remaining pumps indicated similar r,31act Aerksge past both inner and outer flange gaskets on two of the three pumps. After complete removal of the nonmetallic insulation, further visual observations revealed three studs located side-by-side on one pump and three studs simils ely located on the 1
other pump had significant corrosion wastigt in the shank ares next to the lower thread section in the pump casing flenge. Wastage of approxf.nately 50% of the original diameter of the stud giving them an " hour-glass" ty;e appearance was observed. The corroded studs were located in the vicinity o:t a component cooling water line on both affected pumps but to direct correlation..f this fact has been established. Although not confirmed by metallurgical analysis, the cause of the stud wastage is thought to be corrosive attack by hot boric acid from the primary coolant.
I The pump cover and casing for these pumps are constructed of ASTM A-351, Grade h
CF8M stainless' steel. Sealing between the cover and casing is achieved by two l
concentric 304 stainless steel flexitallic gaskets. A leak off line installed i
between the gaskets on each pump was plugged and not instrurented. The leak-off line was not in use and therefore, no indication of RCS lettage from the inner seal was available. Each pump has 16 closure studs, consis ing of ASTM A-193 Grade 87 low alloy steel, which are chrome plated in the th2ead area and phosphate coated in the shank area. The studs are approximately 3-1/2 inches in diameter and about 29 inches long.
No maintenance requiring removal of the pump casing studs had been performed on the reactor coolant pumps since initial construction. The studs were covered t
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IE Information Notice No. 80-27 June 11, 1980 Page 2 of 2 L
with block type insulation since construction thereby limiting them from view.
The studs on two~ pumps were ultrasonically inspected in place in accordance with the applicable ASME Section XI code rules. These ultrasonic examinations were intended to locate cracks in bolting and were not effective in revealing wastage of the studs.
The three affected pumps will be disassembled for further cleaning and inspection of the studs and mating surfaces. Prior to reassembly, all studs exhibiting significant corrosion will be replaced. All new, or acceptable used studs, will be subjected to ultrasonic, visual and magnetic particle examinations.
Installation of instrumentation for actively monitoring the leak-off lines between the flexitallic gaskets is being performed. Future inservice inspec-tions, presently limited to ultrasonic examination, will be supplemented with visual examination of the studs installed in the reactor coolant pumps. Replace-ment insulation will be in the form of a removable blanket to facilitate visual examination.
The condition of the studs discovered at Ft. Calhoun raises concerns that such severe corrosion, if undetected, could lead to stud failures which could result in loss of integrity of the reactor coolant pressure boundary. The lack of effectiveness of current ultrasonic examinations in revealing wastage emphasizes
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the need for supplemental visual inspections and use of instrumented leak detec-tion systems to preclude unacceptable stud degradation going undetected. Licensees should consider that the potential for undetected wretage of carbon steel bolting by a similar mechanism could exist in other compcnents such as valves.
This IE Information Fotice is provided as an early notification of a signi-ficant matter that is still under review by the NRC staff.
It is expected that recipients will review the information for possible applicability to their facilities.
No specific action or written response to this IE Information Notice is required. If NRC evaluations so indicate, further licensee actions may be
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IE Information Notice No. 80-27 Enclosure June 11, 1980 RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To Notice No.
Issued 80-27 Degradation of Reactor 6/11/80 All PWR facilities Coolant Pump Studs with an OL or CP 80-26 Evaluation of Contractor 6/10/80 All power reactor QA Programs facilities with an OL or CP, near-term cps and 50 Fuel Facility Licensees 80-25 Treasportation of 5/30/80 Material Licensee in Pyrophoric Uranium Priority / Categories II-A, II-D, III-I and IV-DI; Agreement State Licensees in equivalent categories 80-24 Low Level Radioactive S/30/80 All NRC and Agreement Waste Burial Criteria State Licensees 60-23 Loss of Suction to 5/29/80 All power reactor to Emergency facilities with an OL or CP 80-22 Breakdown In Contamination 5/28/80 All power reactor Control Programs OLs and near term cps 80-21 Anchorage and Support of 5/16/80 All power reactor Safety-Related Electrical facilities with an i
Equipment OL or CP 80-20 Loss of Decay Heat Removal 5/8/80 All light water reactor i
Capability at Davis-Besse facilities holding 5
~ Unit 1 While in a Refueling power reactor OLs or cps 7
Mode 80-19 NIOSH Recall of Recircu-5/6/80 All holders of a power lating-Mode (Closed-Circuit) reactor OL, Research Self-Contained Breathing Reactor License, Fuel Apparatus (Rebreathers)
Cycle Facility License g
2 and Priority I Material l
License 3
80-18 Possible Weapons Smuggling 5/5/80 All power reactor facilities Pouch with an OL, fuel fabrication and processing facilities and Materials Priority I licensees (processors and distributorp)ll'
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