ML19320C161
| ML19320C161 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 06/11/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Woolever E DUQUESNE LIGHT CO. |
| References | |
| NUDOCS 8007160345 | |
| Download: ML19320C161 (1) | |
Text
_ _
UNITED STATES y
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NUCLEAR REGULATORY COMMISSION
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xiNo or enuss: A, PENNSYLVANI A 19406 Docket No. 50-412 June 11, 1980 Duquesne Light Company ATTN:
Mr. E. J. Woolever Vice President 435 Sixth Avenue Pittsburgh, Pennsylvania 15219 Gentlemen:
The enclosed IE Information Notice No. 80-27, " Degradation of Reactor Coolant Pump Studs", is forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, M. A/
oyce H. Grier Director
Enclosures:
1.
4E Information Notice No. 80-27 2.
List of Recently Issued IE Information Notices CONTACT:
L. E. Tripp (215-337-5282) cc w/encls:
R. J. Washabaugh, Quality Assurance Manager 80071603 %
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l ENCLOSURE 1 4
i SSINS No.:
6835 Accession No.:
UNITED STATES 8005050068
. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT TD' %
"P WASHINGTON, D.C.
20555 IE Information Notice No. 80-27 Date: June 11, 1980 Page 1 of 2 l
DEGRADATION OF REACTOR COOLANT PUMP STUDS i
- Description of Circumstances:
[
1 i
On May 17, 1980, the NRC staff was informed by Omaha Public Power District-(0 PPD) that severe corrosion damage was found on a number of closure studs in two of the four Byron Jackson reactcr 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 visual 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 i
observed at one of the Byron Jackson reactor coolant pump flange regions.
Upon removal of the insulation, evidence of coolant leakage was found emanatir.g from the seating surfaces.between the pump casing and the pump cover.
Further
. investigation of the three remaining pumps indicated similar coolant leakage 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 i
studs located side-by-side on one pump and three studs similarly located on the i
other pump had significant corrosion wastage in the shank area next to the lower thread section in the pump casing flange.
Wastage of apgroximately 50% of the original diameter of the stud giving them an " hour glass type appearance was observed.
The corroded studs were located i~n the vicinity of a component cooling water line on both affect'ed pumps but no direct correlation of 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.
l The pump cover and casing for these pumps are constructed of ASTM A-351, Grade CF8M stainless steel.
Sealing between the cover and casing is achieved by two concentric 304 stainless steel flexitallic gaskets.
A leak-off line' installed between the gaskets on each pump was plugged and not instrumented.
The leak-off line was not in use and therefore, no indication of RCS leakage from the inner
. seal was available.
Each pump has.16 closure studs, consisting of ASTM A-193 l
Grade B7 low alloy steel, which are chrome plated in the thread 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 perforned on the reactor coolant pumps since initial. construction.
The studs were covered j
... n
IE Information Notice No. 80-27 June 11, 1980 Page 2 of 2 with block type insulation since construction thereby limiting them from view.
The studs on two pumps were ultrasonically inspected in place in acccrdance with the applicable ASME Secticn 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.
Pcior 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 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 wastage of carbon steel bolting by a similar mechanism could exist in other components such as valves.
This IE Information Notice 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 required.
+
IE Information Notice No. 80-27 June 11, 1980 RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To Notice No.
Issued 80-26 Evaluation of Contractor 6/10/80 All Part 50 Licensees QAPrograms 80-25
-Transportationof 5/30/80 Material Licensee in Pyropnoric Uranium Priority / Categories II-A, II-0, III-I and IV-DI; Agreement State Licensees in equivalent categorits 80-24 Low Level Radioactive 5/30/80 All NRC and Agreement Waste Burial Criteria State Licecrees 80-23 Loss of Suction to 5/29/80 All power reactor to Emergency Feedwater facilities with an Pumps 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 Equipment OL cr CP 80-20 Loss of Decay Heat Removal 5/8/80 All light water reactor Capability at Davis-Besse facilities holding Unit 1 While in a Refueling power reactor OLs or cps Mode 80-19 NIOSH Recall of Recircu-5/6/80 All holders of a power lating-Mode (Closed-Circuit) reactor OL, Research Self-Contained Breathin Reactor License, Fuel Apparatus (Rebreathers)g Cycle Facility License and Priority I Material License 80-18 Possible Weapons Smuggling 5/5/80 All power reactor Pouch facilities with an OL, fuel fabrication and processing facilities and Materials Priority I licensees (processors and distributors)
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