ML17296A995
| ML17296A995 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/18/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| References | |
| NUDOCS 8009290307 | |
| Download: ML17296A995 (7) | |
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0 UNITED STATES NUCLEAR REGULATORY COMMISSION REGION V 1990 N. CALIFORNIABOULEVARD SUITE 202, WALNUTCREEK PLAZA WALNUTCREEK, CALIFORNIA94696 August 18, 1980 Docket Nos
. 50-528, 50-529, 50-530 Arizona Public Service Company P. 0.
Box 21666 Phoenix, Arizona 85036 Attention:
Mr. E. E. Van Brunt, Jr.
Vice Pr sident, Nuclear Projects Gentlemen:
The enclosed-Information Notice, which provides information regarding Degradation of Reactor Coolant Pump Studs, may not, according to our records, have been sent to you on June 11, 1980, when it was sent to other NRC licensees and construction permit holders.
Therefore, the enclosed copy is being submitted to assure you are aware of this significant matter which is under review by the NRC staff.
Sincerely, R.
H. Engelken Director
Enclosures:
1.
IE Information Notice No. 80-27 2.
List of Recently Issued IE Information Notices cc w/enclosures:
F. M. Hartley, APS 8009 99 0 303
UNITED STATES NUCLEAR REGULATORY COMMISSION
'FFICE OF INSPECTION AND ENFORCEHENT WASHINGTON, D.C.
20555 June 11, 1980 SSINS No.:
6835 Accession No.:
8005050068 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 four Byron Jackson reactor coolant pumps at Fort Calhoun Unit 1 (PMR).
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 observed at one of the Byron Jackson reactor coolant pump flange regions.
Upon removal of the insulation, evidence of coo'lant leakage was found emanating 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 studs located side"by-side on one pump and three studs similarly located on the other pump had significant corrosion wastage in the shank area next to the lower thread section in the pump casing flange.
Mastage of approximately 5(C of the'riginal diameter of the stud giving them an "hour glass" type appearance was observed.
The corroded studs were located in the vicinity of a component cooling water line on both affected 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.
The pump cover and casing for these pumps are constructed of ASTM A-351, Grade CFBM 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'as available.
Each pump has 16 closure studs, consisting of ASTH A-193 Grade 87 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 diamete~
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
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IE Information Notice Ho. 80-27 June ll, 1980 Page 2 of 2 with block type insulation since construction thereby limiting them froar 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 wer e 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 su~faces.
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 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 stee'I 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 Enclosure Information Subject Notice No.
RECENTLY ISSUED IE INFORMATION NOTICES Date issued Issued To 80-26 80"25 80-24 80-23 80"22 80-21 80"20 80"19-Evaluation of Contractor gA Programs Transportation of Pyrophoric Uranium Low Level Radioactive Waste Burial Criteria Loss of Suction to to Emergency Feedwater Pumps Breakdown In Contamination Control Programs Anchorage and Support of Safety-Related Electrical Equipment Loss of Decay Heat Removal Capability at Davis-Besse Unit 1 While in a Refueling Mode HIOSH Recall of Recircu-1 ating-Mode (Closed-Circui t)
Self-Contained Breathing Apparatus (Rebreathers) 6/10/80 5/30/80 5/30/80 5/29/80 5/28/80 5/16/80 5/8/80 5/6/80 All Part 50 Licensees Material Licensee in Priority/Categories II-A, II-O, III-I and IV"DI; Agreement State Licensees in equivalent categories All NRC and Agreement State Licensees All power reactor facilities with an OL or CP All power reactor OLs and near term CPs All power reactor facilities with an OL or CP All light water reactor facilities holding power reactor OLs or CPs All holders of a power reactor OL, Research Reactor
- License, Fuel Cycle Facility License and Priority I Material License 80-18 Possible Meapons Smuggl ing 5/5/80 Pouch All power reactor facilities with an OL, fuel fabrication and processing facilities and Materials Priority I licensees (processors and distributors)
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