ML20062M593
| ML20062M593 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 08/11/1982 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| REF-SSINS-6820 IEB-82-02, IEB-82-2, NUDOCS 8208200151 | |
| Download: ML20062M593 (10) | |
Text
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W)SCORSin Electnc me coune 231 ft. MICHIGAN, P.O. BOX 2046. MILWAUKEE, WI 53201 August 11, 1982 Mr. J. G. Keppler, Regional Administrator Office of Inspection and Enforcement, Region III U. S. NUCLEAR REGULATORY COMMISSION 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Keppler:
DOCKETS 50-266 and 50-301 REPLY TO IE BULLETIN 82-02 In IE Balletin 82-02 dated June 2, 1982, the NRC notified PWR Licensees of incidents of severe degradation of threaded fasteners in closures of the reactor coolant pressure boundary of various PWR nuclear plants.
The Bulletin instructed Licensees to perform specific actions concerning threaded fastenors, including an augmented in-service inspection (ISI) of these threaded fasteners, specifically bolting less than, or equal to, two inches in diameter.
Table 1, enclosed, provides a listing of all bolted connections that are included under the scope of IE Bulletin 82-02 at the Point Beach Nuclear Plant, Units 1 and 2.
Reactor pressure vessel studs at Point Beach are excluded from the scope of this Bulletin since the ISI requirements of Regulatory Guide 1.65 are fulfilled.
In accordance with the 1977/ Summer 1979 Edition / Addenda of ASME.Section XI, the following examinations of the reactor pressure vessel. studs are performed:
Percent of Studs Completed by End-of Specific Period Exam Method First Second Third Volumetric 16-34 50-67 100 Surface 16-34 50-67 100 The reactor pressure vessel studs are removed from the vessel for these examinations.
Since both the pressurizer heaters and control rod drive mechanisms at Point Beach are seal-welded, they also are excluded from the scope of this Bulletin.
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Mr. J. G.
Keppler August 11, 1982 Each of the action items of Bulletin 82-02 is addressed specifically in the following paragraphs.
Action Item 1 Mechanic training at Point Beach in the area of bolting practices has in the past consisted almost entirely of on-the-job training.
Junior mechanics are accompanied and supervised, if required, by experienced mechanics and supervisors while conducting maintenance evolutions.
Table 2 provides a summary of the experience levels of mechanics at Point Beach.
The low frequency of significant bolting problems at Point Beach, as indicated in Table 1, can be attributed primarily to experienced, intelligent, and conscientious personnel performing and supervising critical bolting operations.
There are detailed, written procedures for the following critical bolting operations at the Point Beach Nuclear Plant:
1.
Steam generator primary manway removal and installation 2.
Reactor pressure vessel flange bolt-up 3.
Reactor coolant pump assembly and disassembly These procedures provide the necessary details to obtain a leak-tight closure at the appropriate flange or manway.
For bolted closures in valves and miscellaneous flanges within the reactor coolant pressure boundary, bolting operations are conducted in accordance with standard bolting practices and bolting specifications (i.e.,
standard bolt torque tables and manufacturer's specifications).
At the present time, we are developing a training program for maintenance personnel, including mechanics.
The major objectives of this maintenance employe training program will be to provide formal training in maintenance skills, provide on-the-job certification of skills in work-related practical factors, and provide formal training in specific plant systems and components.
This training program is currently in a draft form and is being reviewed and finalized by the plant staff.
Concerning bolting practices, the training program will include either formal classroom training or on-the-job training, or a combination of both.
Quality assurance of lubricants and sealants are handled on a case-by-case basis.
Lubricants and scalants that come into contact with austenitic stainless steel or nickel alloys are tested to verify acceptable levels of chlorine, fluorine, and sulfur.
In most instances, lubricants and sealants are not quality assurance items, but verification of their composition would be required prior to its use on austenitic stainless steel or nickel alloy steels.
Mr. J. G. Keppler August 11, 1982 Action Item 2 1
In an October 6,1981 letter to Mr. Harold R. Denton, Wisconsin Electric informed the NRC that the Units 1 and 2 ISI plan for the second ten-year interval would be conducted in accordance with the 1977/ Summer 1979 Edition / Addenda of ASME Section XI.
All non-exempt Class 1 pressure retaining bolting is examined in accordance with Table IWB-2500-1, Category BG1 for bolting greater than two inches and Category BG2 for bolting less than, or equal to, two inches.
IE Bulletin 82-02 has further directed that Licensees perform a visual and surface exam of all Class 1 bolting under the scope of Bulletin 82-02 whenever the bolted closure is disassembled and the bolting is removed.
It is our opinion that the best method to detect boric acid corrosion wastage of high strength low alloy bolting is by a visual examination of the bolting.
The preferred method would be a visual examination of the bolting when it is removed.
For those-bolted closures in which there is a significant gap between the flangea, and the bolt or stud shank araa is visible, a meaningful visual exam of the stud can be performed in the vicinity where borated water is likely to attack the stud.
Stress corrosion cracking of high strength low alloy bolts and studs can also best be detected by visual or surface examinations.
This type of cracking would most likely occur at a high stress area such as the root of a thread or at a discontinuity i
in the bolt cross-section.
Stress corrosion cracking and fatigue cracking of high strength low alloy steel can be attributed not only to the improper use of lubricants and sealants but also to the following:
1.
Heat treatment 2.
Bolting material 3.
Method of forming threads 4.
Cyclic loads 5.
Bolting practices Items 1, 2, and 3 are factors that could be checked at the time of manufacture or receipt of bolting st site (QA receipt) as opposed to once the component is in service.
Inadequate attention given to reactor coolant system leaks, whether minor or major, is not only a poor housekeeping practice but also may be a challenge to the integrity of bolting subjected to the boric acid environment..At Point Beach routine surveillance by operations personnel and periodic surveillance during in-service
Mr. J. G. Keppler August 11, 1982 testing is conducted to detect signs of reactor coolant system leakage.
In addition, five basic parameters are trended daily on each containment to aid in the early detection of any reactor coolant system leakage to the containment from any source.
These leakage detection and inspection techniques have been successful in minimizing potential problem situations.
As a result, as noted in Table 1, there has been no indication of stress corrosion cracking and very few indications of boric acid corrosion wastage at the Point Beach Nuclear Plant.
For the purposes of compliance with the surveillance recommendations of IE Bulletin 82-02, however, the following threaded fasteners inspections will be performed at Point Beach Nuclear Plant, Units 1 and 2:
1.
For bolting greater than two inches, the requirements of the 1977/ Summer 1979 Edition / Addenda of ASME Section XI, Category BG1 will be met.
2.
For bolting two inches in diameter and less, the following will be met:
a.
The requirements of the 1977/ Summer 1979 Edition / Addenda of ASME Section XI, Category BG2 will be met for all bolting.
A surface exam of bolting will be performed when the bolting is removed to supplement the visual examination required under ASME Section XI.
These exams will be performed at the frequency specified in ASME Section XI to insure proper surveillance throughout the interval.
b.
When bolting is removed for maintenance, and the ASME Section XI exam has been previously completed for the period / interval or does not require an inspection of all the bolting, a visual exam of all the bolting will be performed.
This examination will be performed by experienced maintenance personnel.
They will, however, not l
necessarily be qualified in accordance with IWA-2300 of ASME~Section XI nor will the examination be conducted in accordance with ASME XI.
This has been our standard practice in the past.
c.
Closures will not be disassembled and the bolting removed expressly for the purpose of examination unless bolting degradation is suspected.
Mr. J. G. Keppler August 11, 1982 IE Bulletin 82-02 is unclear as to the circumstances surrounding the instances of bolting failing under the mechanism of stress corrosion cracking.
To provide more insight into the situation, the following additional information would be useful for each case of reported failure under stress corrosion cracking:
1.
Material 2.
Heat treatment 3.
Product tensile strength 4.
Product hardness 5.
Location of cracking on the bolting or studs 6.
Product size This information would allow us to identify specifically which of our bolting is more susceptible to stress corrosion cracking.
Only the bolting susceptible to stress corrosion cracking should require a surface examination.
Thus, instead of an across-the-board type application of increased inspection with its associated time, exposure, and cost, as presently required by the IE Bulletin, a more practical inspection program could be devised.
Action Item 3 Table 1 provides a listing of leaks that occurred at bolted closures at Point Beach Nuclear Plant, Units 1 and 2 within the scope of IE Bulletin 82-02.
In addition, Table 1 provides a listing of the lubricants for each bolted closure.
As you will observe from this table, there has been no evidence of stress corrosion cracking for bolting within the reactor coolant pressure boundary at Point Beach.
Only one recordable indication of boric acid wastage has been observed.
This occurred during an ASME Section XI visual examination of the body-to-cap bolting of check valve 1SI-853A, in which one stud was found to have a 3/4xl/2xl/8" deep area of localized corrosion on the stud thread.
None of the other studs from the valve showed any indications of corrosion, nor was there any obvious signs of borated water leakage.
The affected stud was replaced.
Furmanite has been used in two instances at the plant.
In 1977 a Unit 2 pressurizer manway leak was sealed temporarily by injecting Furmanite into the gasket area.
A second similar temporary fix was made on a body-to-bonnet leak on the Unit 1 spray valve 1-431B in 1981.
Note, however, that Valve 1-431B is not within the scope of IE Bulletin 82-02 since it is a three-inch valve.
As previously stated, we have utilized several bolting lubricants and sealants.
Table 3 provides data concerning the r'ollowing lubricants and sealants used at Point Beach Nuclear Plant:
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Mr. J. G. Keppler August 11, 1982 1.
Neolube No. 2 by Huron Industries, Inc.
2.
Antiseize by Loctite Corporation 3.
Furmanite F-500 (nuclear grade) 4.
Furmanite F-77N (nuclear grade) 5.
Furmanite F-77N2 (nuclear grade)
Items 1, 3, 4, and 5 are nuclear grade materials.
Item 2 is being evaluated currently for chlorine, fluorine, and sulfur content.
Preliminary tests performed at the plant on Antiseize thread lubricant indicate acceptable leachable levels of chlorine and fluorine.
We intend to follow the actions specified in this letter to satisfy the concerns of the NRC as identified in IE Bulletin 82-02.
Based on our past history of few bolting problems and our associated good maintenance and housekeeping practices, we believe that these actions should satisfy the NRC's concerns.
Very truly yours, d2d i Assistant Vic ~ President C. W. Fay Subscribe and sworn to before me this /
day of August 1982.
WY = ^
Notary PyfTic, State of Wisconsin My Commission expires L A J,/ g.
v-gr-Copies to NRC Resident Inspector Director, Office of Inspection and Enforcement, Washington, D.C.
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Table 1 Page 2 PAST
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CLOSURE LEAKAGE BOLT BOUT MATL MATL SIZE USED FURMANITE WASTAGE OR SCC p
Check Valve SI-842C SA-193 SA-194 16 1-5/8" AS Body-to-Cap GR-B7 GR-211 Check Valve SI-842D
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n su showed 12 1-5/8" AS Body-to-Cap GR-B7 GR-211 evidence of localized corrosion wastage.
Check Valve SI-853B SA-193 SA-194 12 1-5/8" AS Body-to-Cap GR-B7 GR-211 Check Valve SI-853C SA-193 SA-194 12 1-5/8" AS Body-to-Cap GR-B7 GR-211 Chick valve SI-853D sA~193 SA~194 12 1-5/8" AS Body-to-Cap GR-B7 GR-211 NOTES; NL ~ Neolube No. 2 lubricant AS - Loctite Antiseize lubricant (1)
Westinghouse specification !!O. BDS70041AL (2)
Replaced gasket (3)
Seal welded body-to-bonnet connection and lubricated and retightened the bolting.
(4)
For each case of leakage, a visual exam was performed of connection af ter repairs to verify leaktight integrity at nornal operating pressure.
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TABLE 3 LUBRICANTS Total (ppm)
Imachable (ppm)
Chlorine Fluorine Sulfur Chlorine Fluorine Sulfur Neolube No. 2
<100
<100
<100 Typical
- Anti Seize
.14 5.04 LGc No. 21%5 SEALANTS Total (ppm)
Icachable (ppm)
Chlorine-Fluorine Sulfur Chlorine Fluorine Sulfur Furmanite F-500-58 19 70 510 5.2 5.17 Lot 504 Furmanite F-77N 164 112 1.4 1.4 6.0 Lot 145 Furmanite.F-77N2-150, 90 260 5100 Lot 101
- This' analysis performed at PBNP.
Further analysis for total halogens and sulfur will be performed.
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