NRC Generic Letter 1991-17
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555 October 17, 1991 PERMITS FOR
TO: ALL HOLDERS OF OPERATING LICENSES OR CONSTRUCTION
NUCLEAR POWER PLANTS
SUBJECT: GENERIC SAFETY ISSUE 29, 'BOLTING DEGRADATION OR 91-17)
FAILURE IN NUCLEAR POWER PLANTS" (GENERIC LETTER
Regulatory Comnisslon's This letter provides information on the U.S. Nuclear 29, "Bolting Degradation or (NRC's) resolution of Generic Safety Issue (GSI) GSI-29 includes all Failure in Nuclear- Power Plants." The scope of screws, other special safety-related bolts, studs, embedments, machine/cap and washers.
1 The NRC has threaded fasteners, and all their associated nuts based on licensees resolved this issue without developing any new requirements, to previous NRC guidance and continuing to implement actions taken in response the industry's initiatives in this area. It is expected that recipients will to their facilities and review the information in this letter for applicability However, the suggestions consider whether any further actions are appropriate.requirements; therefore no contained in this letter do not constitute NRC
specific action or written response is required.
initiatives and previous The GSI-29 resolution encompasses a number of industry in the enclosed documented NRC actions. The bases for resolution are further29: Bolting Degradation or NUREG-1339, "Resolution of Generic Safety Issue by NRC in June 1990.
Failure in Nuclear Power Plants,". which was published by the Joint Task Group on The industry's initiatives on bolting include workForum (AIF), the Materials Bolting established by the Atomic Industrial Institute (EPRI).
Properties Council (MPC), and the Electric Power Research two-volume report, in a The Task Group on bolting presented its findings studs are being Additional concerns regarding reactor vessel closure and are addressed under GSI-109, "Reactor Vessel Closure Failure,"
not considered under GSI-29.
9110150302 RETUN TO REGULTORY WIT& FILES
Generic Letter 91-17 - 2 -
"Degradation and Failure of Bolting in Nuclear Power Plants," EPRI
The Institute of Nuclear Power Operations (INPO) performed another NP-5769.
study in which it recommended a number of actions in response to potentially unsafe bolting conditions.
The Nuclear Management and Resources Council (NUMARC) addressed EPRI's work a letter to its members on July 64, 1989, notifying them of the publication in EPRI Reports NP-5769 and NP-5067 , and stating that the reports provide of industry's technical basis for resolving GSI-29. the The letter encouraged members to refer to these reports to perform appropriate root cause analyses and implement proper corrective actions in response to NRC Bulletin 87-02,
"Fastener Testing to Determine Conformance with Applicable Material Specifi- cations."
Since establishing GSI-29 in 1982, the staff has issued a number of bulletins, generic letters, and information notices on bolting events judged to be safety- significant (See NUREG-1339). The bulletins and some of the generic letters required both one-time actions and continuing programs. These actions and continuing programs were considered by the staff in resolving GSI-29.
Backfit Discussion
This generic letter is not coresidered to be a backfit because it does involve any new requirements or staff positions. not The currently applicable requirements, in combination with actions taken in response to industry initiatives, are sufficient tu assure integrity of safety-related However, because safety-related bolting may continue to pose somebolting.
concerns, it is important that all licensees continue their actions safety accordance with commitments made in response to NRC bulletins and generic in letters on bolting events as listed in NUREG-1339.
The NRC staff further believes that licensees can significantly improve and reduce costs by implementing the industry's recommendations delineated safety in
2 EPRI NP-5769 published in April 1988 proposes, among other things, that bolted connections that satisfy certain criteria would exhibit leakage before total failure of the connection occurred and therefore should be subject to less stringent inservice inspection criteria.
American Society of Mechanical Engineers (ASME)Section XI Subcommittee The is reviewing a related proposal to add an ASME code case. If the code case is approved by the ASME, NRC will then consider endorsement. General endorsement of EPRI NP-5769 does nut imply that the NRC endorses the proposed code case.
3 EPRI
NP-5067, "Good Bolting Practices, A Reference Manual for Nuclear Power Plant Maintenance Personnel," volume 1: "Large Bolt Manual,"
1987 and volume 2: "Small Bolts and Threaded Fasteners," 1990.
Generic Letter 91-17 - 3 -
implement these the EPRI reports. The staff suggests that, to efficiently to recommendations, licensees may wish information:
(i) review the following industry-developed a. EPRI NP-5769, volumes 1 and 24 b. EPRI NP-5067, volumes 1 and 2 Bolting Problems,"
c. EPRI videotapes, "Pgessure Boundary parts I, II and III
which
(2) review the NRC staff report, NUREG-1339, of, and exceptions to, discusses the NRC's evaluation EPRI NP-5769.
as means of ensuring bolting reliability, The staff agrees that an effective be to develop and implement plant-specific recommended in EPRI NP-5769, would encompass all safety-related bolting.
bolting integrity programs that and guidelines for the content of a NUREG-1339 includes recommendations EPRI NP-5769 provides additional program.
comprehensive bolting integrity The plant-specific bolting integrity program details on bolting integrity. for continuing actions made in could incorporate licensee's commitmentsNRC bulletins and generic letters listed in response to the previously issued NUREG-1339.
Therefore, not constitute NRC requirements.
The information in this letter does is required. In this generic letter, no specific action or written response safety issue of bolting degradation or the staff considers the broad may be warranted failure resolved. However, additional regulatory actions should occur in the concerning safety-related bolting if specific problems please If you have any questions about the information in this letter, future. listed below.
contact one of the technical contacts and NP-5067 should be
4 Requests for copies of EPRI reports NP-5769 P.O. Box 50490, Palo Alto, CA 94303, directed to Research Reports Center,
(415) 965-4081.
5These videotapes are available from EPRI NDE Center, P.O. Box 217097, Charlotte, NC 28221, (704) 547-6110
- 4- i
This generic letter contains no information collection requirements therefore is not subject to the requirements
1980 (44 U.S.C. 3501 et seq.) of the Paperwork Reduction Act and of Sincerely, Jam ^G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation Enclosure:
NUREG-1339 Technical Contact(s): R. E. Johnson, RES
(301) 492-3909 T. Y. Chang, RES
(301) 492-3922 J. A. Davis, NRR
(301) 492-0713
LIST OF RECENTLY ISSUED GENERIC LETTERS
Generic Date of Letter No. Subject Issuance Issued To
91-16 LICENSEDOPERATQRS'-AND- - - 10/03/91 HOLDERS OP LIC OR
OTHER NUCLEAR FACILITY CONSTR. PERMITS FOR
PERSONNEL FITNESS FOR DUTY NUC PWR/NPRs AND ALL
LICENSED OPERATORS
& SENIOR OPERATORS
91-15 OPERATING EXPERIENCE 09/23/91 ALL POWER REACTOR
FEEDBACK REPORT, SOLENOID- LICENSEES AND
OPERATED VALVE PROBLEMS AT APPLICANTS
US REACTORS
91-14 EMERGENCY TELECOMMUNICA- 09/23/91 ALL HOLDERS OF OP
TIONS LICENSES OR CONST.
PERMITS
91-13 REQUEST FOR INFO RELATED 09/19/91 LICENSEES AND APPLI-
TO RESOLUTION OF G1130, CANTS Braidwood, Byron
"ESSENTIAL SERVICE WATER Catawba, Comanche Peak SYS FAILURES AT MUTLI-UNIT Cook, Diablo, McGuire SITES," PURSUANT TO 10CFR50.54(f)
91-12 OPERATOR LICENSING NAT. 08/27/91 ALL PWR REACTOR
EXAMINATION SCHEDULE AND APPLICANTS FOR
AN OPERATING LICENSE
91-11 RESOLUTION OF GENERIC 07/18/91 ALL HOLDERS OF
ISSUES 48, "LCOs FOR'CLASS OPERATING LICENSES
lE VITAL INSTRUMENT BUSES,"
and 49, "INTERLOCKS AND LCOs FOR CLASS 1E TIE BREAKERS"
PURSUANT TO 10CFR50.54(f)
91-10 EXPLOSIVES SEARCHES AT 07/08/91 TO ALL FUEL CYCLE
PROTECTED AREA PORTALS FACILITY LICENSEES
WHO POSSESS, USE,
IMPORT OR EXPORT
FORMULA QUANTITIES
OF STRATEGIC SPECIAL
NUCLEAR MATERIAL
88-20 INDIVIDUAL PLANT EXAMINATION 06/28/91 ALL HOLDERS OF
SUPP. 4 OF EXTERNAL EVENTS (IPEEE) OLs AND CPs FOR
FOR SEVERE ACCIDENT VULNERA- NUCLEAR POWER
BILITIES - 10 CFR 50.54 (f) REACTORS
91-09 MODIFICATION OF SURVEILLANCE 06/27/91 ALL HOLDERS OF
INTERVAL FOR THE ELECTRICAL OLs FOR BWRs PROTECTIVE ASSEMBLIES IN
POWER SUPPLIES FOR THE
NUREG-1339 Resolution of Generic Safety Issue 29: Bolting Degradation or Failure in Nuclear Power Plants a
U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research Richard E. Johnson Reprinted September 1991
I
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20555
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NUREG-1339 Resolution of Generic Safety Issue 29: Bolting Degradation or Failure in Nuclear Power Plants Manuscript Completed: March 1990
Date Published: June 1990
Richard E. Johnson Division of Safety Issues Resolution Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555
CONTENTS
Page iii Abstract .................................................................................
vii Abbreviations .............................................................................
I
1 Introduction ..........................................................................
1
1.1 The Bolting Safety Issue ............................................................ 1
1.2 Problem ......................................................................... 2
1.3 Plan for Resolution .................................................................
2
2 Industry Resolution .....................................................................
2
2.1 Planned Program ..................................................................
3
2.1.1 General Bolting Tasks ........................................................ 3
2.1.2 Pressure Boundary Bolting Tasks ............................................... 4
2.1.3 Tasks Associated with Internals Bolting .........................................
4
2.2 Technical Findings .................................................................
4
2.2.1 Basis for the Resolution .......................................................
7
2.2.2 Supporting Data for the Resolution .............................................
11
3 Conclusions ...........................................................................
15
4 References .........................................................................
ABBREVIATIONS
Advisory Committee on Reactor Safeguards LAQT low-alloy quenched and tempered (steel)
Atomic Industrial Forum LOCA loss-of-coolant accident AIF
AISC American Institute of Steel Construction MPC Materials Properties Council ANSI American National Standards Institute ASME American Society of Mechanical Engineers NDE nondestructive examination ASTM American Society for Testing and Materials NRC Nuclear Regulatory Commission NRR (Office of) Nuclear Reactor Regulation BTC Bolting Technology Council (NRC)
B&W Babcock and Wilcox NSSS nuclear steam supply system BWR boiling-water reactor PWR pressurized-water reactor CGWT cylindrically guided wave technique RCPB reactor coolant pressure boundary EPRI Electric Power Research Institute SCC stress-corrosion cracking GSI generic safety issue SRP Standard Review Plan SOER Significant Operating Event Report HSLA high-strength, low-alloy (steel)
USI unresolved safety issue IE (Office of) Inspection and Enforcement UT ultrasonic test (NRC) UTS ultimate tensile strength IGSCC intergranular stress-corrosion cracking ISI inservice inspection WOG Westinghouse Owners' Group vii NUREG-1339
1 INTRODUCTION When the NRC prioritized generic issues in November
1982, GSI 29 was assigned a high priority (Ref. 3).
1.1 The Bolting Safety Issue 1.2 Problem The bolting safety issue originally was an integral part of The NRC noted (Ref. 4) that from 1964 to the early 1980s the Nuclear Regulatory Commission's (NRC's) Unre- the incidence of reported failures in high-strength bolting solved Safety Issue (USI) A-12, "Fracture Toughness of in Class 1 component supports and other safety-related Steam Generator and Reactor Coolant Pump Supports." equipment increased. Common characteristics among the Recognizing that the types and variety of failure mecha- reported incidents included materials that were subjected nisms active in bolting safety problems were distinctly to high sustained tensile stresses, out-of-specification different from those to be addressed in structural steel pretorquing, an aqueous environment caused by high hu- supports, the NRC staff separated the bolting safety issue midity, primary and borated water leakage, and materials from USI A-12 (Ref. 1) and identified it as Generic that were overly hard and out of specification. The most Safety Issue (GSI) 29, "Bolting Degradation or Failure in frequently observed failure mode for the structural bolt- Nuclear Power Plants." The identification of bolting in- ing was SCC. Both low-alloy quenched and tempered tegrity as a separate issue received impetus from the (LAQT) steels and maraging steels were degraded by Advisory Committee on Reactor Safeguards (ACRS) in SCC. A small number of overstress failures was traced to October 1981. The ACRS recommended that the NRC improper heat treatment or low-strength material. Pres- staff expand its concerns about stress-corrosion cracking sure-retaining bolts failed from corrosion wastage*. In- (SCC) of high-strength, low-alloy (HSLA) steel bolts to cluded in the RCPB components were steam generator include a more comprehensive approach to the degrada- manway closures, reactor coolant pumps, pressurizer tion and failure of bolting and threaded fasteners. Sepa- manway closures, reactor vessel closures, chemical and rating the bolting issue from USI A-12 created no conflict volume control system isolation valves, check valves in with the other USI A-12 goals. No structural materials the emergency core cooling system that form part of the were liable to the same kinds of degradation mechanisms RCPB, and other check valves. Some reactor vessel inter- as bolting materials, and adequate fracture toughness nal components, mainly the lower thermal shield bolts criteria for bolting materials were available within the and upper core barrel bolts, were degraded, requiring American Society of Mechanical Engineers Boiler and extensive and expensive replacement of bolts in some Pressure Vessel Code (ASME Code). plants.
The safety aspects of GSI 29 can be summarized as fol- Millions of threaded fasteners, including nuts, bolts, lows. Critical bolting applications in nuclear power plants studs, and capscrews, are used in a nuclear power plant.
constitute an integral part of the reactor coolant pressure The most important application of these fasteners is their boundary (RCPB) and include closure studs or bolts on use as an integral part of the RCPB, such as in pressure- reactorvessels, reactor coolant pumps, and steam genera- retaining closures on reactor vessels, pressurizers, reactor tors. Failure of these bolts or studs could result in the loss coolant pumps, and steam generators. The NRC received of reactor coolant and jeopardize safe operation of the reports of a number of degraded threaded-fastener inci- plant. Bolting also is an integral part of the pressure dents that involved the RCPB and major component sup- boundary and other safety-related systems, such as com- ports. Although none of the reported incidents resulted ponent supports and embedded anchor bolts or studs. In in an accident,they do reflect an undesirable level of June 1982, the NRC staff issued Office of Inspection and degradation in operating nuclear power plants by impair- Enforcement (IE) Bulletin No. 82-02 (Ref. 2). The bulle- ing the integrity of the RCPB or component supports.
tin required responsive actions by all pressurized-water- Most of the reported bolting degradations were discov- reactor (PWR) licensees because threaded fastener fail- ered either during refueling outages or scheduled inser- ures had shown an increasing frequency of occurrence vice inspections (ISIs) or maintenance and repair out- and a variety of underlying mechanisms. Motivated by the ages.Thus far, bolting degradation has not caused an acci- issuance of NRC requirements regarding fastener integ- dent, and has not produced any immediate adverse effect rity, the Atomic Industrial Forum (AIF) joined with the on public health and safety. However, NRC is somewhat Materials Properties Council (MPC) to form the Joint concerned that inadequate ISI of fasteners, either be- AIF/MPC Task Group on Bolting, also in June 1982. This cause of ineffective nondestructive examination (NDE)
task group was composed of representatives from AIF methods or failure to include fasteners in the ISI pro- member organizations-utilities, vendors, and architect- gram, could contribute to the potential for reduction in engineers-plus representatives from the Electric Power the integrity of the RCPB and structural supports. Expe- Research Institute (EPRI). The coordinated industry re- rience has shown that either wastage from borated-water sponses to Bulletin 82-02 and, earlier, to the "For Com- corrosion or SCC can go undetected. Furthermore, such ment" version of NUREG-0577 (issued in October 1979)
gave added emphasis to the importance of GSI 29. 'See Ref. 2 for a description of the wastage problem.
degradation in bolting important to the RCPB integrity 2 INDUSTRY RESOLUTION
could lead to a loss-of-coolant accident (LOCA) because of bolting failures.
2.1 Planned Program
1.3 Plan for Resolution The technical program eventually formulated by the AIF/
MPC Task Group on Bolting was a comprehensive, 19- The NRC considered possible solutions to GSI 29 as part task action plan aimed at resolving GSI 29. The Electric of the process for prioritizing generic issues. The NRC Power Research Institute (EPRI) organized a matrix- noted in Ref. 3 that bolting has a wide range of applica- managed Generic Bolted Joint Integrity Program to carry tion in nuclear power plants and that no single solution to out the research. The results, to the extent that they the problem is known. Therefore, to minimize potential provide relevant technical findings, are summarized in bolting problems in new power plants, improvements in Section 2.2 of this report.
one or all of the five following areas could be recom- mended: design, materials, fabrication, installation, and Early in its existence, the task group reviewed informa- inservice inspection. The NRC suggested that the effi- tion on fastener service failures and categorized them into ciency and adequacy of the ISI program be emphasized. four basic groups:
The NRC action plan for GSI 29, as it finally evolved, Degradation or Failure of Pressure Group I -
included four tasks in its scope of work: Boundary Bolting Caused by General Borated Water Corrosion (Wastage or
(1) Develop the technical bases for bolting application Erosion/Corrosion)
requirements by the NRC staff through a technical assistance contractor at the Brookhaven National Laboratory. Group I - Degradation or Failure of Pressure Boundary Bolting Caused by Stress-
(2) Review licensees' responses to IE Bulletin No. Corrosion Cracking
82-02, "Degradation of Threaded Fasteners in the Reactor Coolant Pressure Boundary of PWR Group III - Degradation or Failure of Internals Plants." Bolting Caused by Fatigue and Stress- Corrosion Cracking
(3) Draft staff recommendations for proposed criteria and guidelines to be incorporated into the NRC Group IV - Degradation or Failure of Supports and Standard Review Plan (SRP). Embedment Bolting Caused by Stress- Corrosion Cracking, with Two Sub-
(4) Develop a proposed plan for implementing bolting Classes Separated at the Minimum Speci- application requirements. fied Yield Strength Level of 150,000 psi Meanwhile, the Joint AIF/MPC Task Group on Bolting Three of these groups (Group HI was excluded) formed became more active. The original charter of the task the basis for what was called the Generic Bolting Pro- group was oriented toward a coordinated industry re- gram. EPRI assumed the lead for technical integration sponse to IE Bulletin No. 82-02 and to the bolting aspects and research support in this generic program. Work re- of the related document, NUREG-0577, issued in 1979 lated to Group III (internals bolting) failures was assigned as the "For Comment" version. The industry response to individual vendor owners' groups. Resolution of the was to emphasize (1) a bolting survey, (2) stress-corro- fastener integrity issue involved many disciplines. Input sion-cracking susceptibility criteria, and (3) corrective ac- was needed from the areas of metallurgy, fracture me- tions to deal with the problem. However, through meet- chanics, nondestructive examination, design, specifica- ings of the task group, by itself and with NRC staff, a more tions and standards, quality assurance, manufacturing or comprehensive industry program evolved. The 19-task quality control, corrosion engineering, joint design, and Generic Bolting Program was presented for review and tensioning control. The AIF/MPC task group considered comment to the parent AIF Subcommittee on Material all of these disciplines. Assessment of priorities related to Requirements in February 1983; the program was offi- fastener applications led to the focus of action on primary cially transmitted by the AIF to the NRC in July 1983. pressure boundary components. The action plan designed The basic objective, which was attractive to the NRC staff, by the task group encompassed the following 19 tasks was that the nuclear industry itself would provide the (several of which were divided into sub-tasks). These 19 technical basis for resolution of GSI 29; therefore, NRC's tasks were grouped under 3 headings: General Bolting activities regarding this generic issue were delayed until Tasks, Pressure Boundary Bolting Tasks, and Tasks Asso- the NRC received industry's findings. ciated with Internals Bolting.
2.1.1 General Bolting Tasks (Tasks 1 sible for structural bolting) to revise sampling require- Through 9) ments in new and existing specifications to be more con- sistent with end-product expectations.
Task 1 - Assessment of Priorities and Safety Significance Task 63 - To prepare a draft ASTM standard entitled,
"Standard Test Method for Leeb Hardness Testing of Task 1.1. - To monitor bolting priority ranking and to Metallic Materials,' based on Equotip hardness test ex- assess the failure and success history for each of the four perience.
degradation orfailure groups listed previously. (See Sec- tion 2.1 of this report.) Task 7 - ASME Code Bolting Requirements Task 1.2. - To conduct a pilot scoping study, under EPRI Task 7.1 - To prepare a critique regarding ASME Code direction, on the use of decision analysis for bolting aimed bolting requirements, particularly as related to preten- at developing a methodology for determining the techni- sioning of both pressure boundary and structural bolting cal parameters that influence the likelihood of bolt fail- joints.
ure.
Task 7.2 - To review ASME Code Section III bolting requirements to determine the need for revising or im- Task 2 - Literature Survey of Fastener Corrosion proving.
To perform a literature survey of carbon and alloy steel fastener corrosion in PWRs. Task 8 - Develop Field NDE Techniques to Detect Wastage and Stress-Corrosion Cracking Task 3 - Stress-Corrosion Cracking To focus pilot studies that were under way on the devel- opment of field techniques, utilizing advanced ultrasonic To study and evaluate the effects of water environments techniques to detect wastage or stress-corrosion cracking on quenched and tempered low-alloy steel bolting mate- in pressure boundary and support fasteners.
rials.
Task 3.1 - Fracture Mechanics Analysis. To develop Task 9 - Information Exchange stress intensity factors for realistic flaw shapes and load- Task 9.1 - To hold bolting workshops to exchange infor- ing conditions in bolts. mation on industry efforts regarding bolting integrity.
Task 3.2 - Data Review. To obtain detailed descriptions Task 9.2 - To produce and distribute to utilities video- of failures involving stress-corrosion of HSLA material tapes on the behavior and maintenance of flanged pres- from previously unpublished accounts. sure boundary connections as aids to improving bolting design, installation, and maintenance.
Task 4 - Include Hardness Test Data into the Bolting Database Task 93 - To produce a videotape on design, behavior, and tensioning practices as applicable to structural joints To include data obtained by utilities from hardness sur- if warranted from the Task 16 results.
veys of installed and spare bolting in a bolting database and to assess impact of these data on the issue. 2.1.2 Pressure Boundary Bolting Tasks (Tasks 10 Through 17)
Task 5 - Bolting Database Task 10 - Screening Strategy and Corrective Action To maintain a database containing hardness data and for Pressure Boundary Bolting other properties of bolting materials and to update the database as necessary to support industry efforts. To develop a strategy for identifying bolts in pressure boundary applications that may be susceptible to boric Task 6 - Development of Bolting Specifications and acid corrosion or stress-corrosion cracking and recom- Standards for Nuclear Power Plant mend corrective actions.
Applications Task 11 - Recommend ASME Code Section XI
Task 6.1 - To develop a general specification for bolting Changes requirements that eventually could be adopted by nuclear utilities. To review ASME Code Section XI requirements and send comments and recommendations to the code com- Task 6.2 - To initiate action in American Society for mittees for action, including (1) appropriateness of Testing and Materials (ASTM) Committee F-16 (respon- Section XI size limits for inspection requirements;
(2) provisions to ensure adequate visual inspection; and 2.13 Tasks Associated with Internals Bolting
(3) assurance that NDE inspections are effective in de- tecting corrosion wastage and stress-corrosion cracking. (Tasks 18 and 19)
Task 18 - High-Strength Bolting Task 12 - Recommend Research Programs to EPRI on To conduct research to improve the stress-corrosion re- Degradation of Fasteners sistance of high-strength, age-hardenable, Ni-Cr-Fe al- loys and A 453 Gr. 660 (A286) bolting materials and to To recommend three projects to EPRI that would in- investigate the influence of irradiation and stress and crease the understanding of (1) accelerated boric acid strain on the behavior of structural materials.
attack of carbon and alloy steel fasteners, (2) the effect of MoS2 , and (3) sealants for PWR primary system compo- Task 19 - Owners' Groups Liaison nents (the impact of the recommendations on the con- tracted work under Task 3 also was evaluated). To maintain liaison with owners' groups to ensure that duplication of effort is minimized and that pertinent in- formation on the efforts of the task group is exchanged.
Task 13 - Alternative Materials and Coatings The 19 tasks were modified during the progress of the To recommend alternative materials and coatings and program. Redistribution of effort reflecting reassessment provide guidance regarding selection criteria for the pur- of relative priorities among the tasks occurred.
pose of eliminating borated water corrosion concerns (this task was included in the contracted work under 2.2 Technical Findings Task 3).
The results of the Joint AIF/MPC Task Group on Bolting Program, described in this section, constitute a recom- Task 14 - Component Support Bolting Screening mended technical basis for resolution of GSI 29 by the Criteria nuclear industry. The program, outlined in Section 2.1 of To develop a strategy for identifying component support this report, was presented in detail along with the results bolts that may be susceptible to stress-corrosion cracking from the executed tasks in a two-volume report, EPRI
and recommend plant-specific methods for resolving NP-5769, "Degradation and Failure of Bolting in Nuclear findings regarding materials that require review. Power Plants" (Ref. 5). The report was published in two volumes to make the results of the research easy to review and to aid utility engineers in addressing plant-specific Task 15 - Assess Fastener Integrity Based on Fracture bolting and fastener problems with a single source docu- Mechanics ment. Volume 1 included the background information, a description of the action plan for the AIF/MPC Task To develop a technique to evaluate the integrity of bolting Group on Bolting, the approach to resolution of the bolt- material in component support fasteners. ing issue and the basis for this resolution, summaries of the findings from the 19 action plan tasks (Section 2.1.1),
Task 16 - Preload Technology Assessment and the conclusions and recommendations.
Volume 2 included more complete supporting references To evaluate the need for high preloads, to identify poten- and data. Publication of the two-volume report com- tial relief in preload requirements, to investigate preload pleted a comprehensive, generic review and analysis pro- application techniques and resulting preload variability, gram. A major finding indicated that the design of critical and to recommend optimum techniques. Also, to discuss closure joint bolting involves enough redundancy to en- methodologies for estimating existing preloads based on sure that there is virtually no pressing cause for concern knowledge of the tensioning techniques, sampling, or regarding bolting integrity. A brief review of the EPRI
some combination of information and to discuss risks of report by volume and section follows.
detensioning existing joints.
2.2.1 Basis for the Resolution Task 17 - Develop UT Procedures for Inspection of Ultra-High-Strength Low-Alloy Maraging EPRI NP-5769, Volume 1.
Steels
- Section 1, "Introduction," provided an historical re- To develop a field procedure for ultrasonic test (UWI) view and the planned tasks (i.e., those given in Sec- inspection of ultra-high-strength bolts in the lower sup- tion 2.1 of this report).
port feet of the Westinghouse-designed steam generator, * Section 2, "Industry Resolution of the Bolting Is- using Westinghouse Owners' Group (WOG) funding. - sue," presented additional detail on the Joint Task NUREG-1339 4
Group approach to the problem, the results ob- (3) Catalogue service experiences for primary tained from research according to the task action boundary -closures, and identify service-sensi- plan, and brief discussions of two principal contribu- tive closures based on utility input.
tions of the work-development (1) of a generalized closure integrity model and (2) of joint leak-tight- (4) Follow the AIF/MPC bolting programs, pro- ness criteria. The resulting information led to the vide liaison for the WOG plants, and prevent conclusion that the technical basis for resolution of any duplication of effort.
the generic bolting issue was reached.
(5) Develop nondestructive methods for bolting
- Section 3, "Pressure Boundary Bolting," concluded for primary boundary closures.
that closure integrity can be ensured through appli- cation of a leak-before-break criterion and provides (6) Prepare specifications for primary boundary three analyses (primary manway cover, reactor cool- bolting, including quality assurance require- ant pump main flange, and check valve flange) to ments for procurement, receipt, and preinstal- illustrate the methods. The work led to a proposed lation inspections.
ASME Code Section XI code case (see the discus- (7) Evaluate and qualify sealants for primary sion of Section 6, Volume 1, EPRI NP-5769, in this boundary closures.
report) on inspection of bolted closures with ob- served or detected leakage. (8) Evaluate and qualify lubricants for primary boundary closure.
- Section 4, "Structural and Component Support Bolting," presented results from Task 14 of the ac- (9) Establish the number of "failed" bolts in clo- tion plan. Component support bolting that may be sures resulting in one-gallon-per-minute leak- susceptible to SCC was identified, and both generic age (or limits set by technical specifications),
and plant-specific review procedures were recom- and determine margins of safety for bolting in mended. It was concluded that application by licen- primary boundary closures.
sees of the proposed screening and disposition (of materials which failed to pass the screen) steps (10) Establish feasibility of having an inventory of would be an adequate bolting integrity program and bolting (considering Task 3) for primary bound- would serve to resolve GSI 29 with regard to compo- ary closures.
nent support bolting.
Of the original 10 tasks, the WOG actually spon-
- Section 5, "Owners' Groups Summary," presented sored the first 4 tasks; the other tasks were judged to results from the Babcock and Wilcox (B&W) and be adequately covered by separate efforts sponsored Westinghouse Owners' Group programs on primary by EPRI, ASTM bolting standards committees, pressure boundary bolting. The B&W program lent ASME Code committees, or other MPC activities.
further support to findings by others (see the discus- The WOG did assume responsibility for Task 17 (see sion of Section 3, Volume 1, EPRI NP-5769, in this Section 2.1.2 of this report), the development of an report) that a leak-before-break approach and con- ultrasonic field procedure applicable to ultra-high- servative failure criteria can be used to ensure the strength bolts.
integrity of bolted closures. Failure mechanisms in- cluded SCC and chemical wastage. A steam genera- A discussion of the first 4 of the 10 tasks for the tor manway closure with SCC and a reactor main WOG's program on bolting follows (Ref. 6):
coolant pump closure with wastage were analyzed as - Task 1 supported a leak-before-break ap- examples to demonstrate the adequacy of this ap- proach and these criteria. The WOG program origi- proach to closure integrity by addressing the nally included the following 10 tasks (Ref.6) (see complete bolted closure rather than individual Table 5-1, Vol. 1, EPRI NP-5769): fasteners and resulted in publication of a user's manual.
(1) Determine the bolting material, number of - Task 2 investigations resulted in recommended bolts, bolt dimensions, and gasket material installation procedures. To arrive at these pro- used for primary boundary closures (i.e., cedures, the WOG compared several preload pumps, valves, steam generators, and pres- measurement techniques, including those for surizers). torque wrenches, stud heaters, stud tensioners, and the Bolt Gage (a Raymond Engineering,
(2) Provide installation procedures for bolting for Inc., development). The Bolt Gage was the primary boundary closures. preferred technique.
5s NUREG-1339
- Under Task 3, from available data, the WOG assembly methods, and quality control, even though listed and analyzed primary boundary closure additional aspects of fastener preload could have leakage. It was concluded that (1) the available been considered.
information useful in determining service- sensitive closures is limited, (2) the leak-
- Section 7, "NDE of Bolting," presented the results of studies designed to attain the goal of developing , 1.
before-break approach recommended by the AIF/MPC Task Group on Bolting is a sound field techniques as stated in Task 8 of the AIF/MPC
engineering attack, and (3) the ASME Code bolting action plan (see Section 2.1 of this report).
should be changed to address bolt/stud flaw Conventional UT methods were evaluated and their limits based on closure integrity and fastener limitations determined. EPRI funded three separate redundancy. contracts and asked the contractors to develop and evaluate new techniques that lend themselves to
- Task 4 provided for liaison with others in the field application and that are capable of detecting AIF/MPC task group. both SCC and wastage. One contractor developed acoustic resonance and reverberation techniques for An NDE field procedure was developed for bolts detection of wastage, another contractor further de- under AIFIMPC Task 17 that provided in situ tech- veloped the acoustic resonance technique to detect niques for inspection of Westinghouse PWR steam SCC, and the third contractor developed the generator support bolts. The procedure can obviate cylindrically guided wave technique (CGWT) for de- costs previously borne by utilities for removal and tection of SCC as well as wastage.
surface examination.
The reverberation technique used a spectrum ana-
- Section 6, "ASME & ASTM Codes and Standards," lyzer to quantify the frequency content of a pulse- included the results of Tasks 6 and 7 of the action echo envelope and detect characteristic time spacing plan (Section 2.1 of this report). Subtask 6.1 was changes and then compared the reverberation spec- completed with the preparation of "Utility Recom- trum of a target bolt to that of an unflawed bolt to mendations and Guidelines for the Purchase Speci- detect degradation.
fication and Receipt/Installation Inspection Re- quirements for ASME Section III, American The CGWT provided an inspection method applica- Institute of Steel Construction (AISC), American ble to most studs or bolts over a range of 16 in. to 112 National Standards Institute ANSI/ASME B31.1, in. (406 mm to 2,844 mm) in length and 1 in. to 4.5 in.
and ANSI B31.5 Bolts and Threaded Fasteners." (25.4 mm to 114 mm) in diameter. The technique The report is published in its entirety as Section 1 of could be used to detect cracklike defects as small as Vol. 2, EPRI NP-5769. Subtask 6.2 addressed the 0.05 in. (1.27 mm) deep in the threaded region of the advisability of changing the sampling requirements bolt. In addition, the CGWT could be used to detect for structural bolting specifications under the corrosion wastage greater than 25% of the bolt di- jurisdiction of ASTM Subcommittee F16.02, and, at ameter.
the time of publication of EPRI NP-5769, approval
- Section 8, "Lubricants and Sealants," included three of the proposed changes was still pending. Subtask sub-tasks as part of Task 12 in the AIF/MPC task
6.3 resulted in preparation of the draft standard, plan (Section 2.1.2 of this report). Several projects
"Standard Test Method for Equotip Hardness Test- and studies, described in EPRI NP-5769, provided ing of Metallic Materials," its submittal to ASTM useful data. The text of Section 8 was adapted from a Subcommittee E28.06, and its publication as Section more detailed report (Ref. 7). The influence of sev-
2, Vol. 2, of EPRI NP-5769. Task 7 resulted in two eral lubricants on boric acid wastage was studied products: First, the many places in the ASME Code with results too varied to review in detail here. How- where rules are given for the design and construc- ever, one result reported was the detrimental influ- tion of bolted joints, scattered among voluminous ence of MoS 2 and the difficulty of removing it from rules for welding and other fabrication methods, fasteners that have been exposed to service condi- were listed and explained in Section 9, Vol. 2, EPRI tions. The studies of leak sealants and concerns de- NP-5769. Until such time as changes in the ASME rived from them led to several recommendations;
Code make the Section 9, EPRI NP-5769, listing principal among them was that the responsible de- obsolete, it will serve as a useful single reference sign organization (e.g., ASME) should establish source. Second, the results of a review of ASME standards for leak sealants.
Code bolting requirements were published as Sec- tion 10, "Critique of Bolt Preload Aspects of ASME
- Section 9, "Alternative Materials," the task identi- and AISC Codes," Volume 2, EPRI NP-5769. The fied as number 13 in Section 2.1.2 of this report, was material in this section was limited to ASME Code drawn from the more detailed reports of "Stress- treatment of bolt preload with respect to design, Corrosion Cracking of Alternative Bolting Alloys,"
EPRI RP-2058-12 (Ref. 8) and Section 3, Vol. 2, Section III, AISC, ANSI/ASME B31.1, and ANSI
EPRI NP-5769. This work also is related to Task 3 of B31.5 Bolts and Threaded Fasteners," presented the action plan. The resulting four conclusions can recommended guidelines for utilities constructing or be restated briefly as follows: (1) whereas low alloy operating nuclear power plants, including certifica- steels are vulnerable to boric acid corrosion, other tion, identification, NDE, and storage requirements alloy steels generally are resistant; (2) galvanic cor- for bolting material (bolts, studs, and nuts) to be rosion, depending on specifics of the material com- used in permanent features. It also included recom- position and environmental chemistry, can occur, mended guidelines for receipt or preinstallation in- but data are needed for each combination if sensible spection designed to help ensure fastener integrity.
decisions are to be made; (3) MoS 2 lubricant was Recommended guidelines were given for tightening shown to be a factor in laboratory corrosion testing fasteners when neither preloading, torquing, nor when conditions favored the liberation of hydrogen both are specified by other documents. The guide- sulfide, but its role in service-related failures re- lines were written specifically for ASME Code Sec- mains to be clarified; (4) more Klscc data are tion m Code-of-Record plants. They were given as needed if a damage-tolerant methodology is to be adequate for pre-ASME Code Section m Code-of- adopted. Record plants (i.e., ANSI B31.1 and B31.7), but, for plants of such vintage, the user was cautioned to
- Section 10, 'Training Package," consisted of a brief consider the safety class of the system in which the description of two EPRI-sponsored actions aimed at bolting is used and to provide a commensurate level information exchange. First, a workshop was held of quality. For instance, a plant having ANSI B31.1 November 2 through 4, 1983, at Knoxville, Tennes- as the code of record may choose to use ASME
see. Participants included representatives from the Section HI Class 1 requirements for systems classi- U. S. Nuclear Regulatory Commission, the Atomic fied American Nuclear Society Safety Class 1.
Industrial Forum, the Electric Power Research In- stitute, its contractors and consultants, and the nu- clear power generating industry. The stated objec-
- Section 2, "Standard Test Method for Equotip tives included alerting industry to the NRC's generic Hardness Testing of Metallic Materials," covered bolting safety issue and the regulator's perspective the use of the Equotip Hardness Tester to deter- of the issue. Also, speakers reviewed the AIF pro- mine the Leeb hardness of metal components. The gram and the EPRI efforts toward resolution, in- discussion included definitions, test procedures, in- c'uding bolting design criteria, codes and standards, strument verification, test-block calibration, and a specifications, fabrication, quality control, tools, table of hardness conversion. As previously noted procedures, and general bolting problems. Second, a under Section 6, Vol. 1, EPRI NP-5769, the text of set of three videotapes was produced and made Section 2, Vol. 2, was a draft ASTM standard, sub- available to any interested party. They are identified mitted to ASTM Subcommittee E 28.06. As will be as "Electric Power Research Institute Pressure explained in Section 3 of this report, the NRC un- Boundary Bolting Problems; Part I: The Basics; Part derstands the need for in situ hardness measurement U: Engineering Problems; Part III: The Mechanic as part of a program by licensees to ensure confor- and Bolting." Although they were aimed at the mity to codes and standards, and the NRC agrees manager, the engineer, and the mechanic, respec- that properly conducted Leeb hardness tests can be tively, viewed together, they constitute a rather com- part of that program. However, Section 2 of EPRI
plete tutorial on bolting. NP-5769 contained what appear to be technical er- rors because tabulated hardness conversion values
- Section 11, "Conclusions and Recommendations," disagree with published ASTM Standards. The ap- summarized the many conclusions derived from parent disagreements must be clarified, presumably completion of the Joint AIF/MPC Task Group on by ASTM Subcommittee E 28.06.
Bolting 19-task program. The diverse disciplines and the many activities were joined and integrated to
- Section 3, "Evaluation of Bolting Experiences in provide what the industry believed to be a basis for Primary Pressure Boundary Closures," presented resolution of the NRC GSI 29. the results of compiling and analyzing 125 incidents of bolting failure reported by nuclear utilities. The
2.2.2 Supporting Data for the Resolution principal failure mechanisms, in order of decreasing importance, were boric acid corrosion (wastage),
EPRI NP-5769, Volume 2. maintenance damage, corrosion pitting, and stress- corrosion cracking. Not included in the analysis were
- Section 1, "Utility Recommendations and Guide- a number of flange bolt problems in the control rod lines for the Purchase Specification and Receipt/ drive mechanism that were judged to be related Preinstallation Inspection Requirements for ASME mainly to one nuclear steam supply system (NSSS).
Although the fastener rejection rate* varied with criteria, load relief, preload range acceptability, the component and generally was small (not more preload estimation, and preload accuracy.
than about 10%), the rate was sufficient to justify ranking NRC GSI 29 as a high priority task.
- Section 6, "The Bolting Database: An Example of a Numeric Database Application in the Nuclear
- Section 4, "Sampling Inspection and Acceptance Power Industry," briefly discussed the nature of the Criteria for Bolted Connections," provided a statis- database, the stored information and classification tical evaluation of fastener loads. The evaluation scheme, access, software, and applications.
addressed the main concerns in highly stressed high- strength fasteners, that is, failures that were due * Section 7, "Assessment of Field Hardness Meas- either to the external load exceeding the preload urements on Low-Alloy Quenched and Tem- across the joint (overload) or to stress-corrosion pered (LAQT) Bolting Materials at Midland," pre- cracking. If the preload of a given fastener were sented the collection (from four nuclear sites) and known, then one could decide about preload ade- analysis of LAQT fastener steels. Significant devia- quacy simply by checking whether the preload is tion from specification requirements was observed.
inside or outside the acceptable design range for that It was estimated that the portion of bolts at one site fastener. Because uncertainties exist about the ac- (Midland) with a hardness indicating a susceptibility tual value of preload, the deterministic checking for SCC was less that 1% of the total population; not procedure must be replaced with a probabilistic cri- a serious concern.
terion.
- Section 8, "Good Bolting Practices," briefly re- Ideally, standards for bolted connections susceptible viewed the two reference manuals for nuclear power to overload and stress-corrosion cracking should be plant maintenance personnel that were developed set by establishing maximum acceptable probabili- under EPRI sponsorship and were intended for ties for the occurrence of each failure mode, based rapid-access field or office use by utility staff who on the severity of the consequences. To apply such must disassemble and assemble bolted joints in nu- standards, uncertainties on the external loads, the clear power plants. This section described bolting state of preload, and the maximum flaw size should practices that should help staff members identify, be quantified. Unfortunately, the state of knowledge understand, and solve (or minimize) bolted joint (e.g., about SCC) and current deterministic practice problems such as leaks, vibration loosening, fatigue, make it impossible to fully implement probabilistic and stress-corrosion cracking.
standards. A semi-probabilistic format, explicitly The first of the manuals was entitled, "Good Bolting recognizing uncertainties on fastener preload, but Practices: Large Bolt Manual;" the second was enti- avoiding failure probability calculations, was pro- tled, "Good Bolting Practices: Small Bolt Manual."
posed. The uncertainty is changed by sampling in- The manuals described the problem-reducing steps spection, for which a simple method of sample size in order of increasing complexity and cost, recogniz- determination and uncertainty updating was pro- ing that the options available to maintenance per- posed, consistent with the format of the acceptance sonnel are generally limited.
criteria.
The manuals were not intended for use by designers;
- Section 5, "Nuclear Structural Bolting Preload therefore, the theories behind the recommended Evaluation," reported on the results of completing procedures were not discussed at any length. The Task 16 (see Section 2.1.2 of this report). The task encyclopedia format for the manuals was intended consisted of evaluating the need for high preloads, to make the topics easy to locate. Topics were listed identifying potential relief in preload requirements, alphabetically and identified by legends printed in and investigating preload application techniques bold face. Each topic was described briefly, with and variability. Section 4 of EPRI NP-5769 provided typical data, if pertinent, and with cross-references the statistical nature of the preloading process, and to related topics, also in bold-face type.
Section 5 evaluated existing preload design require- ments, the relationship of the specified joint preload * Section 9, "Bolting Rules of the ASME Boiler and to the minimum preload required to carry design Pressure Vessel Code," presented a detailed, point- loads, and the effect of potential loading relief on by-point, review of the ASME Code with explana- minimum preload requirements for one heavy com- tions, interpretations, and suggestions for improve- ponent support structural joint. The report dis- ment. The many scattered bolting requirements cussed conclusions that were reached about design were collected in this one section of the EPRI report to provide a source document for reference. This
'Rejection rate was the relative number of failures, degradations, in- was noted in the discussion of Section 6, Vol. 1, spection call-outs, etc., as a percent of the total fasteners inservice. EPRI NP-5769.
- Section 10, "Critique of Bolt Preload Aspects deal with materials that require some evaluation of ASME and AISC Codes," is a companion piece under the generic issue.
to Section 9, Vol. 2 (and was cited in Section 6, Vol.
1) of the EPRI report. The stated assignment was "to The primary objective was to present the procedural critique existing preload sections of the ASME steps and required information to determine allow- Code." The Joint AIF/MPC Task Group on Bolting able bolt loads to avoid SCC under steady-state or posed two questions to guide this effort: long-term normal operating conditions. Allowable bolt stress as a function of material hardness, bolt
(1) Do provisions of the ASME Code contribute size, and thread pitch could be determined with the to the types of bolting failure experienced in procedures. The allowable bolt stress then could be the last decade or so by the nuclear industry? compared with actual bolt stresses calculated for the design. A requirement of the procedure was that
(2) Do omissions in the ASME Code contribute to hardness testing be performed on the population of the types of bolting failure experienced by the bolts so that hardness limits could be statistically nuclear industry? determined. Also, as part of the evaluation objec- tive, allowable bolt stresses to prevent fracture un- The investigators were directed to limit the re- der short-term (accident) loads must be established sponses to preload aspects of bolting problems. The when low toughness was implied by the hardness review identified several provisions of the AISC and data.
ASME Codes that could be troublesome. The points raised and the rectifications suggested were too nu-
- Section 12, "Alternate Alloys," consisted of brief merous to be reported here, but are described in reports on five separate research projects, all spon- EPRI NP-5769. In addition to general observations sored by EPRI and dealing with steel corrosion in concerning the ASME Code, preload philosophy, nuclear reactor environments. Each project had preload and installation method codification, educa- been reported in more detail elsewhere; the five tion, quality control, and the role of the mechanic, published documents were cited in the EPRI
five specific problems were cited and solutions of- NP-5769, Volume 2, reference list.
fered. Four appendices completed the section; they went into greater detail on specific problems and The Combustion Engineering Project grew out of gave support to the conclusions and recommenda- interest in fastener corrosion and is entitled, "Lit- tions stated in the text of Section 10. The titles of the erature Survey of Carbon and Alloy Steel Fastener appendices follow: Corrosion in the PWR Plants." The objective of this project was to determine the extent of low-alloy
(1.) Appendix 10A, "AISC Specification for Struc- steel fastener corrosion problems in the domestic tural Joints Using ASTM A325 or A490 Bolts" PWR industry and to review available data in the literature on boric acid corrosion and stress-corro-
(2.) Appendix lOB, "ASME Boiler and Pressure sion cracking of fasteners. Service failures from both Vessel Code,Section III, Division 1, Subsec- mechanisms were collected and analyzed. A com- tion NF" mon factor in six SCC events involving steam gen- erator primary manway closure studs, which pose a
(3.) Appendix 10C, "ASME Boiler and Pressure potential for a LOCA, was the use of MoS 2 lubri- Vessel Code,Section VIII, Division 1" cant. Decomposition at high temperatures can yield hydrogen, which can induce SCC in HSLA steels
(4.) Appendix lOD, "Comparison of ASME Codes even at low concentrations.
on Pressure Boundary Bolting"
The Battelle, Columbus, Laboratories Project was
- Section 11, "Evaluation Procedure for Assuring closely allied to the Combustion Engineering Pro- Integrity of Bolting Material in Component Sup- ject. It involved a review of joint failures in nuclear port Applications," is the companion piece on struc- components from either boric acid wastage or SCC.
tural bolting to the RCPB discussion, Section 3, Vol. The primary objective was to determine if austenitic,
2, EPRI NP-5769. The Section 11 presentation de- age-hardenable materials could be used for bolting scribes an evaluation procedure for general applica- applications. A secondary objective was to review tion to bolting products used in component supports the boric acid corrosion and stress-corrosion crack- and fabricated from steels commonly used for sup- ing behavior of currently used low-alloy steels and port bolting. The evaluation procedure could be issues relating to lubricants and sealants. Based on used to justify serviceability of questionable materi- the review, recommendations were made for further als. It was anticipated that this section would be work to improve the industry's capability for dealing useful to a utility as part of a plant-specific plan to with the bolting problem. It was concluded that
austenitic materials seem to be resistant to boric acid processing. The project included detailed micro- wastage but vulnerable to SCC. The report pre- structural characterization and corrosion testing of sented so many qualifications regarding the use of the alloys subjected to 15 different combinations of high-strength high-alloy steels that Battelle could melting practice and thermomechanical processing.
hardly be accused of recommending them. Much of As in the Westinghouse study, preliminary findings the report discussed conditions that can lead to fail- indicated that Alloy X-750 had the best resistance to ure of low-alloy steels without recommending alter- SCC when in a particular metallurgical condition.
native resistant materials. As in the companion study, the conclusions were not solid and unambiguous except for recommending The Materials Engineering Associates Project was further studies.
part of a failure analysis of Type 410 stainless steel valve studs purchased to ASTM specification A 193, * Section 13, "Standard Specification for Supplemen- Grade B6, with a supplemental requirement of 125 tal Requirements for Structural Fasteners for Nu- ksi tensile strength specified by the utility. The utili- clear Applications," consisted of some background ty's investigation focused on improper heat treat- and introductory material and the proposed ASTM
ment of the studs, resulting in temper embrittle- standard: *F XXX-"Standard Specification for ment. The embrittlement permitted SCC, with stud Quality Assurance and Inspection Requirements for failure occurring once the critical flaw size was Structural Fasteners for Nuclear and Other Special achieved. Mechanical property tests confirmed that Applications." Experience with fasteners has cre- the material exhibited low fracture toughness. In ated several concerns. The draft specification in- combination with the experimentally determined cludes requirements for nuclear fasteners as follows:
rather high tensile strength and somewhat reduced ductility (less than 50% reduction in area in three of - Establish sampling and quality levels for all six specimens), the studs would be vulnerable to series of structural fasteners on a uniform SCC. basis.
- Establish mandatory lot control and trace- The Westinghouse Electric Project sought a solu- tion to the cracking of age-hardenable Ni-Cr-Fe al- ability of fasteners. By maintaining such con- loys in PWRs and boiling-water reactors (BWRs). trol, prevent mixing and possible contamina- Several instances of stress corrosion or, in some tion of parts intended for nuclear systems.
cases, corrosion fatigue in bolts, beams, and pins - Require positive identification and source of were observed in reactors using Alloys X-750, fasteners intended for nuclear system as evi-
1-718, and A 286. The object was to examine the dence of adherence to required quality level.
three alloys in different heat-treated conditions. Al- loy X-750 with increased amounts of zirconium, - Require preferential full-scale testing of fin- which previously had been shown to be beneficial, ished fasteners in lieu of reliance on possible also was included. Stress-corrosion cracking studies, machined coupons from fasteners. Actual full- involving both crack initiation and crack propagation scale testing is designed to confirm integrity of specimens in PWR and BWR conditions, were con- finished fastener not possible by coupon evalu- ducted on alloy X-750 in 11 conditions, alloy 1-718 ation.
in 2 conditions, and alloy A 286 in 2 conditions. The - Permit utilization of state-of-the-art technol- operating conditions of BWRs were shown to be ogy and beneficial effects of heading and more detrimental to the alloys than operating condi- thread rolling by specific callout. Such other tions of the PWRs. Alloy X-750 exhibited the most major industries as automotive and aerospace resistance to cracking (or propagation) in one of the have similarly mandated such requirements.
several heat treatments that were applied, but, in a different condition, it was the least resistant. Long- - Recognizing the potential long-term degrada- term (more than 10,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />) tests are continuing. tion resulting from the presence of discontinui- ties such as cracks and seams, establish specific The Babcock and Wilcox Project was a companion requirements to define acceptable and rejec- to the Westinghouse project, using the same high- table criteria for nuclear system use.
strength, age-hardenable Ni-Cr-Fe alloys, X-750, This very important standard, now in the hands of
1-718, and A 286. Service failures were attributed to the cognizant ASTM committee, was supported by fatigue, corrosion fatigue, and intergranular stress- the Joint AIF/MPC Task Group on Bolting.
corrosion cracking (IGSCC). Susceptibility to failure by these mechanisms depended strongly on the met-
- This standard is being developed; the number will be assigned after it allurgical condition produced by thermo-mechanical is completed and approved.
NUREG-1339 10
- Section 14, "lhe Bolting Technology Council" tions of fasteners. The Institute of Nuclear Power Opera- (BTC), provided a brief description of the Council, tions can be expected to act in response to potentially its activities, and its makeup. The BTC is affiliated unsafe conditions as in the past when Significant Operat- with the Materials Properties Council, Inc., formerly ing Event Report (SOER) No. 84-5 on bolting (Ref. 9)
the Metals Properties Council, which provides was issued. Further refinement in codes and standards administrative services as required. The BTC was will be provided by the responsible committees in ASME
formed to provide opportunities for threaded fas- and ASTM (e.g., Committee F16 on Fasteners).
tener and tool users to engage in a variety of coop- erative activities. As stated in its bylaws, the purpose During the period in which GSI 29 was being resolved, the of the Council is "to sponsor research; to recom- NRC took several additional steps that must be factored mend practices; to act as a clearing house for infor- into the resolution of the issue. Incidents of threaded mation; and to provide education concerning the art fastener degradation and failure from October 1969 to and science of the installation and behavior of me- March 1982 were identified and analyzed (see Ref. 4).
chanical fasteners and their interaction with the Five documents were prepared based on results of techni- joints they are used in." As anyone who has at- cal assistance contracts in support of the bolting generic tempted to understand bolted joint behavior win issue (Refs. 10 through 14). In addition, action items realize, the task selected by the BTC is not a simple included the following NRC notices, bulletins, and ge- one, nor will the effort be inexpensive. Because of neric letters:
the magnitude of the job, members felt that it would be desirable to pool a portion of their technical and * IE Bulletin 74-03, "Failure of Structural or Seismic financial resources and attack the problems jointly. Support Bolts on Class 1 Components," April 29, Results achieved by cooperative efforts, further- 1974.
more, often have greater credibility, are more widely accepted, and are most economically achieved. The * IE Bulletin 79-02, "Pipe Support Base Plate De- Council expects to provide benefits to industry signs Using Concrete Expansion Anchor Bolts,"
through interaction with recognized experts in March 8, 1979.
bolting technology, opportunities to participate in seminars and symposia, opportunities to share in * IE Bulletin 79-07, "Seismic Analysis of Safety- cooperatively funded research to be planned, moni- Related Piping," April 14, 1979.
tored, and directed by BTC groups, and opportuni- ties to review publications and research results well a IE Bulletin 79-14, "Seismic Analysis for As-Built before general release. It is anticipated that the BTC Safety-Related Piping Systems," July 2, 1979, will identify unresolved bolting problems recognized (also: Revision 1 of page 2 of 3, July 18, 1979;
now and as they arise from experience in the future. Supplement 1, August 15, 1979; Supplement 2, Through its resources in personal expertise and in September 7, 1979).
financial assistance, the BTC will be instrumental in developing solutions to generic bolting issues. * IE Bulletin 82-02 (Ref. 2), which resulted in W.
Anderson and P. Sterner, "Evaluation of Responses to IE Bulletin 82-02," NUREG-1095, May 1985.
3 CONCLUSIONS * NRC Compliance Bulletin 87-02, "FastenerTesting The NRC staff has reviewed the technical findings devel- to Determine Conformance with Applicable Mate- oped by the industry and presented in EPRI NP-5769 rial Specifications," November 6, 1987 (later: Sup- (Ref. 5) as well as other relevant industry-generated in- plements 1 and 2).
formation. The staff has concluded that the technical basis for resolution of GSI 29 is available. * NRC Bulletin 89-02, "Stress Corrosion Cracking of High-Hardness Tlpe 410 Stainless Steel Internal The conclusion that GSI 29 can be resolved is based on Preloaded Bolting in Anchor Darling Model S35OW
the availability of several relevant documents. Actions Swing Check Valves or Valves of Similar Design,"
taken by the Joint AIF/MPC Task Group on Bolting July 19, 1989.
resulted in EPRI NP-5769, three video training films (see Section 10, Vol. 1, Ref. 5) and the Good Bolting Practices * NRC Generic Letter 88-05, 'Boric Acid Corrosion reference manuals, Vols. 1 and 2 (see Section 8, Vol. 2, of Carbon Steel Reactor Pressure Boundary Com- Ref. 5). Industry representatives established the Bolting ponents in PWR Plants," March 17, 1988.
Technology Council (an MPC affiliate) to take the lead in sponsoring bolting research, recommending practices, * NRC Generic Letter 89-02, "Actions to Improve gathering and providing information, and promoting edu- the Detection of Counterfeit and Fraudulently Mar- cation on installation, application, behavior, and interac- keted Products," March 21, 1989.
11 NUREG-1339
- IE Circular 78-14, "HPCI Turbine Reversing It must be understood that although the NRC staff recog- Chamber Hold Down Bolting," July 12, 1978. nized the value of the several products of the industry effort (the work of the Joint AIF/MPC Task Group on
- IE Information Notice 80-27, "Degradation of Re- Bolting) in helping to resolve GSI 29, that recognition actor Coolant Pump Studs," June 11, 1980. does not constitute unqualified endorsement of their technical content. The NRC staff found technical dis-
- IE Information Notice 80-29, "Broken Studs on agreement with several specific discussions in EPRI
Terry Turbine Steam Inlet Flange," August 7, 1980. NP-5769, the three videotapes on training, and the Good Bolting Practices reference manuals. The technical dis-
- IE Information Notice 80-36, "Failure of Steam agreements, except for the following, however, generally Generator Support Bolting," October 10, 1980. were not important enough to mention.
- IE Information Notice 82-06, "Failure of Steam First, the staff notes that a general plan for evaluation of Generator Privacy Side Manway Closure Studs," bolting integrity can be derived from Section 11, Vol. 2, March 12, 1982. EPRI NP-5769. Section 11, "Evaluation Procedure for Assuring Integrity of Bolting Material in Component
- IE Information Notice 86-25, "Traceability and Ma- Support Applications," was written to fulfill a specific terial Control of Material and Equipment, Particu- assignment for the Joint AIF/MPC Task Group on Bolt- larly Fasteners," April 11, 1986. ing. With appropriate modifications, the procedure could serve for other than component-support bolting. The
- IE Information Notice 86-108, "Degradation of Re- screening process should use fastener material properties and fracture mechanics analyses to ensure that actor Coolant System Pressure Boundary Resulting safety-related fasteners are unlikely to be susceptible to from Boric Acid Corrosion," November 1986 stress-corrosion cracking. Material properties should be (ater: Supplements 1 and 2). experimentally verified rather than assumed to be as specified.
- NRC Information Notice 87-56, "Improper Hy- draulic Control Unit Installation at BWR Plants," Second, and closely related to the first comment, incon- November 4, 1987. sistencies found in EPRI NP-5769 regarding the criteria for categorizing bolting steels according to strength must
- NRC Information Notice 88-11, "Potential Loss of be reconciled. Categorization should be based only on the Motor Control Center and/or Switchboard Function actual measured yield strength, Sy, of the material Due to Faulty Tie Bolts," April 7, 1988. (or Sy determined by conversion of measured hardness values) and not on the specified minimum yield strength.
- NRC Information Notice 89-22, "Questionable The justification for this position is that high-strength Certification of Fasteners," March 3, 1989. steels are vulnerable to SCC. A bolt made of high- strength steels may be obtained through an order which
- NRC Information Notice 89-59 and Supplement 1, specifies a relatively low-yield strength, but by improper
"Suppliers of Potentially Misrepresented Fasten- heat treatment, for example, the bolt may develop an ers," August 16 and December 6, 1989. actual strength far in excess of the minimum specified.
Specifically, that high-strength bolts should be those
- NRC Information Notice 89-70, "Possible Indica- with Sy 2 150 ksi; medium-strength bolts should be tions of Misrepresented Vendor Products, Octo- those with 120 ksi < Sy < 150 ksi The following por- ber 11, 1989. tions of EPRI NP-5769 need to be modified in order to make them consistent with the above definitions:
In various ways, these NRC notices, bulletins, letters, and circular will influence actions that the NRC or licensees * In Vol. 1, Section 4, page 4-3, bolting steels are will need to take in the wake of the resolution of GSI 29. categorized as "high strength" if: " Sy > 150 ksi, Although they do not, individually or collectively, form a where Sy is the yield strength" (compare the basis for the resolution, neither will these documents nor greater-than symbol to the greater-than-or-equal-to the responses made to them change as a result of the symbol recommended). At the same location, me- resolution of GSI 29. dium-strength materials are identified as those with
120 ksi < Sy < 150 ksi which would be consistent The NRC staff concludes that all of the available informa- except for the explanatory text that follows on page tion that has been discussed in this report (from industry 4-4: "Therefore, it seems appropriate for the indus- and regulatory sources combined) provide a sufficient try to examine the use of materials with speci- technical basis to resolve GSI 29. fled minimum yield strengths greater than 150 ksi"
NUREG-1339 12
(emphasis added). The same words are used on page MoS2 is a potential contributor to SCC, especially when
4-5 at two places. applied to high-strength bolting steels. One of the prob- lems posed by MoS2 -difficulty in removing it from parts
- On page 4-4, a proposed category is defined by "the that have been in service (see page 8-3, Vol. 1., Ref.
range of 120 ksi to 150 ksi specified minimum yield 5)-may be close to being resolved. Whereas Czajkowski strength" showing that the use of Sy on page 4-3 (Ref. 12) found that CS2 will remove MoS 2 , handling CS 2 was not to be taken literally. poses some problems. More recently, tests by Czajkowski of samples of "citrus-based cleaners" were subjected to a cleaning task similar to that reported in Ref. 12, and it was
- In Vol. 1, Section 11, "Conclusions and Recommen- evident that the sulfur component (the active SCC ingre- dations," page 11-5, the words "minimum specified" dient) had been effectively removed (Ref. 15). Providing are used again.
that the citrus-based cleaners, themselves, are not SCC
promoters, an answer to the MoS2 cleaning problem may
- On the next page (p. 11-6) one finds "specified yield be at hand.
strength." An inconsistency arises in EPRI
NP-5769, Vol. 2, Section 1, page 1-17 because the Fifth, although the fracture mechanics analyses by reader is advised to consider materials vulnerable to Cipolla cited in Section 9, Vol. I, EPRI NP-5769, are SCC if the minimum specified ultimate tensile useful and could well be employed in engineering prob- strength (UTS) is greater than 150 ksi or if the actual lems where values for the stress intensity factor, K1, are UTS is greater than 170 ksi. needed, other more recent results are available. In a report published in 1988, "Review and Synthesis of Stress
- Then, in NP-5769 Vol. 2, Section 7, page 7-2, we Intensity Factor Solutions Applicable to Cracks in Bolts"
find: ". ..the proposed screening limit of Sy
- 150 (Ref. 16), values for Kg for cracks in round bars, both ksi (1034 MPa)" although in the preceding para- threaded and unthreaded, subject to either tension or graph the words "specified minimum yield strength" bending, were reviewed. Available solutions were synthe- were used to describe the strength range of 120-150 sized into forms appropriate to analyses of bolts and ksi (827-1034 MPa). studs. The K,solutions published in Reference 16 should be used in fracture mechanics analyses of threaded A more careful reading might reveal more discrepancies fasteners.
or inconsistencies. For the reasons previously given, the criterion of actual yield strength, Sy 2 150 ksi should be The importance of maintaining adequate traceability*
used as the level for consideration of SCC vulnerability. and control of material of fasteners at nuclear power plants was set forth in IE Information Notice No. 86-25 Third, the data listed in Table 2-1, Vol.2, EPRI NP-5769 (Ref. 17). Because plant-specific bolting integrity pro- are questionable. Indexing off the values of Rockwell grams should include steps to ensure bolting traceability C-scale hardness as given, the corresponding values of and material control and to prevent introduction of incor- Vickers hardness numbers do not agree with those given rect or defective materials or components, the central in the ASTM Standard E 140. From the same Rc start, ideas from this notice follow:
the corresponding values of tensile strength do not agree with values given in the ASTM Standard A 370. Such Awareness of 10 CFR Part 50, Appendix B, Criterion errors (there are typographical mistakes, as well) also VIII, "Identification and Control of Materials, Parts, and make the hardness conversions listed in Table 11A-1 of Components," and applicable codes and specifications is EPRI NP-5769 suspect; they should be audited. Accept- important. Measures have been established and imple- ing the ASTM standards as the authority, the hardness mented by the NRC for identification and control of conversions and hardness-tensile conversions in EPRI materials, parts, and components and for traceability both NP-5769 should be treated skeptically. Since Table 2-1 to the approved design basis and to the source. It is impor- was to be part of a draft ASTM standard, the responsible tant that required identification of items be maintained by ASTM committee can be expected to make such correc- heat number, part number, serial number, or other ap- tions as may be necessary. Until Leeb hardness values and propriate means, either on the item itself or on records conversion tables have been incorporated in a standard traceable to the item as required, and that required mark- test method by the ASTM, they should be used "for ings be on the item.
information only" and not be accepted as evidence in licensing actions or in safety evaluations. 'in Attachment 2 to NRC Bulletin No. 88-10, November 22, 1988, verifiable traceability was defined as (with minor editing for this re- Fourth, the indictment against MoS2 as a lubricant (found port): Documented evidence such as a certificate of compliance that establishes traceability of purchased equipment to the manufacturer. If on page 3-5 of EPRI NP-5769, Vol. 2) deserves more the certificate of compliance is provided by any party other than the emphasis. Facts gleaned from some service failures and manufacturer, the validity of the certificate must be verified by the li- from laboratory examinations (Ref. 12) clearly show that censee or permit holder through an audit or other appropriate means.
13 NUREG-1339
It is the licensee's responsibility to use qualified individu- NP-5769 (Ref. 5). Specifically, the NRC staff concurred als to examine markings on material and equipment and with the recommendations and guidelines provided in to verify that the markings represent material and equip- Section 1, Vol. 2, of EPRI NP-5769. The recommenda- ment as specified by the design drawings and specifica- tions and guidelines apply to threaded fasteners with re- tions. In the case of fasteners, compliance with the appli- gard to certification, identification, nondestructive exami- cable material specification (e.g., ASTM or ASME mate- nation, storage and tightening procedures, except when rial and grade) is verified by required markings on bolts storage and tightening procedures are specified in other and nuts and certified material test reports or certificates design documents or drawings. Implementing Section 1 of conformance as required by procurement drawings and and other technical guidelines in the EPRI report would orders and by applicable codes and specifications. When help ensure fastener integrity.
vendor-supplied equipment assemblies contain fasteners, it is important to verify compliance with approved vendor A comprehensive bolting integrity program for a nuclear drawings and specifications and such other information power plant would include all safety-related bolting, es- as materials used for equipment qualification tests analy- pecially bolting used to close the primary pressure bound- ses. The required markings on material and equipment, ary and used for component support.
including fasteners, not only must exist, but the markings must indicate the correct material and grade as specified. Of particular importance to safety are component sup- port fasteners in the onsite power distribution system, The NRC staff resolved GSI 29 based on the findings including those power sources, distribution systems, and presented herein, including the following three condi- vital supporting systems provided to supply power to tions. safety-related equipment and capable of operating inde- pendently of the offsite power system. The onsite power First, all earlier NRC notices, bulletins, and generic let- system includes an ac distribution system, a dc power ters that bear on the issues involved in bolting, degrada- system, an uninterruptible ac power system, and the tion or failure, some of which were noted earlier in this emergency (diesel generator) power system. Fasteners in section, should remain in effect. the auxiliary feedwater system and its support systems are also important to safe operation of a plant.
Second, it was concluded that an effective means of en- suring bolting reliability, as recommended in Ref. 5, The work done to resolve GSI 29 has shown that (1)
would be through development and implementation of existing requirements, (2) the implementation of leak- plant-specific bolting-integrity programs. These pro- before-break criteria for RCPB joints (proposed in EPRI
grams should be comprehensive and include all relevant NP-5769, Volume 1, Section 3), and (3) the ongoing pro- NRC requirements and guidance and the recommended grams (e.g., implementation of USI A-46 and the devel- positions of the industry-sponsored programs. opment of individual plant examinations for external events) should adequately limit the risk resulting from, Third, it is recommended that a new section of the Stan- and minimize the severity of, the failure of safety-related dard Review Plan (SRP) be prepared to provide guidance bolting in current plants. However, licensees with operat- to the staff for the review of future plants. The elements ing plants could avoid many of the problems recorded in of the review would include all safety-related joint design, the past by developing and implementing plant-specific threaded fastener material selection, and programatic bolting-integrity programs that include current require- aspects dealing with bolting integrity during construction, ments and reflect the information and recommendations operation, and maintenance, except for closure studs made by the industry-sponsored program managed by which are addressed in SRP Sections 5.3.1 and 5.2.3. EPRI (with NRC staff exceptions as discussed in Section 3 of this report). New plant licensees, however, could meet In light of the facts that many safety-related systems and stringent bolting requirements with only a very small cost components rely in large measure on fastener integrity increase if established before they begin operating their and that there have been numerous reported instances of plants.
degradation or failure of threaded fasteners, completion of the studies under GSI 29 has led to the conclusion that Guidance regarding bolting for staff reviewers in the fastener integrity needs to be procedurally controlled. NRC Office of Nuclear Reactor Regulation (NRR) per- The information reviewed in this report showed that the forming safety reviews of all new nuclear power plants safety issue related to fastener integrity involves a very could be provided by a new section in the NRC Standard large number of parts in each plant, a number of potential Review Plan. Such a section, entitled, for example, failure mechanisms (therefore, a corresponding number "Safety-Related Bolting," would expand the limited cov- of protective or corrective actions), and several technical erage on fasteners now included in the SRP and provide a and engineering disciplines. Although the resolution of 'The Section 1 title is: "Utility Recommendations and Guidelines for GSI 29 was found to be rather complex, sufficient guid- the Purchase Specification and Receipt/P'reinstallation Inspection Re- ance is available to resolve this issue, mainly from EPRI quirements for ASME Section 111, AISC, ANSI/ASME B31.1, and ANSI B31.5 Bolts and Threaded Fasteners."
NUREG-1339 14
M
systematic method for implementation of the staff posi- 8. R. Rungta and B. S. Majumdar, "Stress-Corrosion tion regarding the basis for resolution of GSI 29. As part Cracking of Alternative Bolting Alloys," Final Re- of the resolution of GSI 29, the staff noted the absence of port RP 2058-12, Electric Power Research Institute, an SRP section on general reviews of bolting and recom- Palo Alto, California, March 1986.
mended that one be prepared and issued.
9. The Institute of Nuclear Power Operations, "Bolt- ing Degradation or Failure in Nuclear Power
4 REFERENCES Plants," SOER No. 84-5, September 20, 1984. Pro- prietary Information. Not Publicly Available.
1. U.S. Nuclear Regulatory Commission, "Potential for Low Fracture Toughness and Lamellar Tearing 10. U.S. Nuclear Regulatory Commission, "Lower- in PWR Steam Generator and Reactor Coolant Bound Kscc Values for Bolting Materials-A Lit- Pump Supports," NUREG-0577, October 1983. erature Study," NUREG/CR-2467, February 1982.
2. U.S. Nuclear Regulatory Commission, Office of 11. U.S. Nuclear Regulatory Commission, "Examina- Inspection and Enforcement, "Degradation of tion of Failed Studs From No.2 Steam Generator at Threaded Fasteners in the Reactor Coolant Pres- the' Maine Yankee Nuclear Power Station,"
sure Boundary of PWR Plants," IE Bulletin No. NUREG/CR-2793, February 1983.
82-02, June 2, 1982.
12. U.S. Nuclear Regulatory Commission, "Testing of
3. U.S. Nuclear Regulatory Commission, "A Prioriti- Nuclear Grade Lubricants and Their Effect on A540
zation of Generic Safety Issues," NUREG-0933, B24 and A193 B7 Bolting Materials," NUREG/
Rev. 0, November 10, 1982. CR-3766, March 1984.
4. U.S. Nuclear Regulatory Commission, "Threaded- 13. U.S. Nuclear Regulatory Commission, "Bolting Ap- Fastener Experience in Nuclear Power Plants," plications," NUREG/CR-3604, May 1984.
NUREG-0943, January 1983.
14. U.S. Nuclear Regulatory Commission, "Preloading
5. The Electric Power Research Institute, R. E. Nick- of Bolted Connections in Nuclear Reactor Compo- ell, Principal Investigator, "Degradation and Failure nent Supports," NUREG/CR-3853, October 1984.
of Bolting in Nuclear Power Plants," EPRI
NP-5769, Vols. 1 and 2, Palo Alto, California, 15. C. J. Czajkowski, Brookhaven National Laboratory, April 1988. letter to Richard E. Johnson, U.S. Nuclear Regula- tory Commission, August 4, 1988.
6. E. I. Landerman et al., "Assurance of Primary Boundary Bolting and Closure Integrity," Westing- 16. L A. James and W. J. Mills, "Review and Synthesis house Owners' Group, Material Subcommittee, of Stress Intensity Factor Solutions Applicable to Program MUHN 1072, December 1985. Cracks in Bolts," EngineeringFractureMechanics, Vol. 30 (No. 5), pp. 641-654, 1988.
7. R. Rungta and B. S. Majumdar, "Materials Behavior Related Issues for Bolting Applications in the Nu- 17. U.S. Nuclear Regulatory Commission, Office of In- clear Industry," in Improved Technology for Critical spection and Enforcement, "Traceability and Mate- Bolting Applications, E. A. Merrick and M. Prager, rial Control of Material and Equipment, Particularly eds., MPC-Vol. 26, pp. 3948, American Society of Fasteners," IE Information Notice No. 86-25, Mechanical Engineers, New York, 1986. April 11, 1986.
is NUREG-1339
1. REPORT NUMBER
U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER
NRC FORM 335 (AssIgned by NRC, Add Vol.,
(2-89) upp., Rev., and Addendum Num- NRCM 1102, bers, If any.)
3201, 3202 BIBLIOGRAPHIC DATA SHEET
(See Instructions on the reverse) NUREG-1339
2. TITLE AND SUBTITLE 3. DATE REPORT PUBLISHED
Resolution of Generic Safety Issue 29: Bolting Degradation or Failure in MONTH YEAR
Nuclear Power Plants June 1990
N/A
6. TYPE OF REPORT
6. AUTHOR(S)
Richard E. Johnson Technical
7. PERIOD COVERED (Inclusive Dates)
N/A
Division, Office or Region, U.S. Nuclear Regulatory Commission, and
8. PERFORMING ORGANIZATION - NAME AND ADDRESS (It NRC. provide mailing address; It contractor, provide name and mailing address.)
Division of Safety Issue Resolution Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555 as above'; if contractor, provide NRC Division, Office or Region,
9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC, type 'Same U.S. Nuclear Regulatory Commission, and mailing address.)
Same as above
10. SUPPLEMENTARY NOTES
11. ABSTRACT (200 words or less)
29, "Bolting Degra- This report describes the U.S. Nuclear Regulatory Commission's (NRC's) Generic Safety Issueits historical highlights.
dation or Failure in Nuclear Power Plants," including the bases for establishing the issue and including its co- The report also describes the activities of the Atomic Industrial Forum (AIF) relevant to this issue, the issue. The Elec- operation with the Materials Properties Council (MPC) to organize a task group to help resolve by the AIF/MPC task group, prepared and issued a two-volume document tric Power Research Institute, supported the NRC's re- that provides, in part, the technical basis for resolving Generic Safety Issue 29. This report presents conjunction with view and evaluation of the two-volume document and NRC's conclusion that this document, in other information from both industry and NRC, provides the bases for resolving this issue.
In locating the report.) 13. AVAILABILITY StATEMENT
12. KEY WORDSIDESCRIPTORS (List words or phrases that will assist researchers Unlimited
14. SECURITY CLASSIFICATION
Bolting; Degradation; Failure; Generic safety issue;
(This Page)
Resolution; Fastener integrity, Fracture; Fracture mechanics;
Corrosion; Stress-corrosion cracking; Nuclear power plants. Unclassified (This Report)
Unclassified
15. NUMBER OF PAGES
16. PRICE
NRC FORM 335 (2-89)