76960 Federal Register / Vol. 69, No. 246 / Thursday, December 23, 2004 / Notices 

NUCLEAR REGULATORY 

COMMISSION 

Proposed Interim Staff Guidance 

(ISG)–17 on; Periodic Inspection of 

Bus Ducts for License Renewal 

Solicitation of Public Comment

AGENCY: Nuclear Regulatory 

Commission (NRC).

ACTION: Solicitation of public comment.

SUMMARY: The NRC is soliciting public 

comment on its proposed interim staff 

guidance (ISG) for license renewal. This 

ISG proposes an acceptable aging 

management program (AMP), ‘‘Periodic 

Inspection of Bus Ducts,’’ to manage the 

effects of aging on bus ducts during the 

period of extended operation. The NRC 

staff issues ISGs to facilitate timely 

implementation of the license renewal 

rule and to review activities associated 

with a license renewal application. 

Upon receiving public comments, the 

NRC staff will evaluate the comments 

and make a determination to 

incorporate the comments, as 

appropriate. Once the NRC staff 

completes the ISG, it will issue the ISG 

for NRC and industry use. The NRC staff 

will also incorporate the approved ISG 

into the next revision of the license 

renewal guidance documents.

DATES: Comments may be submitted by 

February 22, 2005. Comments received 

after this date will be considered, if it 

is practical to do so, but the 

Commission is able to ensure 

consideration only for comments 

received on or before this date.

ADDRESSES: Comments may be 

submitted to: Chief Rules and Directives 

Branch, Office of Administration, U.S. 

Nuclear Regulatory Commission, 

Washington, DC 20555–0001. 

Comments should be delivered to: 

11545 Rockville Pike, Rockville, 

Maryland, Room T–6D59, between 7:30 

a.m. and 4:15 p.m. on Federal workdays. 

Persons may also provide comments via 

e-mail at NRCREP@NRC.GOV. The NRC 

maintains an Agencywide Documents 

Access and Management System 

(ADAMS), which provides text and 

image files of NRC’s public documents. 

These documents may be accessed 

through the NRC’s Public Electronic 

Reading Room on the Internet at

http://www.nrc.gov/reading-rm/

adams.html. Persons who do not have 

access to ADAMS or who encounter 

problems in accessing the documents 

located in ADAMS should contact the 

NRC Public Document Room (PDR) 

reference staff at 1–800–397–4209, (301) 

415–4737, or by e-mail at pdr@nrc.gov.

FOR FURTHER INFORMATION CONTACT: Mr. 

Mark Lintz, License Renewal Project 

Manager, Office of Nuclear Reactor 

Regulation, U.S. Nuclear Regulatory 

Commission, Washington, DC 20555–

0001; telephone (301) 415–4051 or email mpl2@nrc.gov.

SUPPLEMENTARY INFORMATION:

Attachment 1 to this Federal Register

notice, entitled Staff Position and 

Rationale for the Interim Staff Guidance 

(ISG)–17: Proposed Aging Management 

Program (AMP) XI.E4, ‘‘Periodic 

Inspection of Bus Ducts’’ contains the 

NRC staff’s rationale for publishing ISG–

17. Attachment 2 to this Federal 

Register notice, entitled Proposed Aging 

Management Program: Periodic 

Inspection of Bus Ducts, contains the 

proposed AMP required to implement 

ISG–17. 

NRC Information Notice 89–64, 

entitled ‘‘Electrical Bus Bar Failures,’’

and NRC Information Notice 98–36, 

entitled ‘‘Inadequate or Poorly 

Controlled, Non-Safety-Related 

Maintenance Activities Unnecessarily 

Challenged Safety Systems,’’ provide 

examples that illustrate the importance 

of periodic inspection of bus ducts and 

the potential problems that can arise 

from age-related bus duct failures. 

Instances of the loosening of the bus bar 

connecting bolts at several plants due to 

thermal cycling have been reported in 

Sandia National Laboratory Report 

entitled Aging Management Guideline 

for Commercial Nuclear Power Plants 

(Sandia 96–0344; September 1996) and 

in NRC Information Notice 2000–14, 

entitled ‘‘Non-Vital Bus Fault Leads to 

Fire and Loss of Offsite Power.’’ The last 

report identified torque relaxation of 

splice plate connecting bolts as one 

potential cause of a bus duct failure. 

Operating experience has shown that 

electrical buses in bus ducts have failed 

due to cracked insulation in the 

presence of moisture, debris buildup, 

and loosening of bus connecting bolts. 

These failures could lead to loss of 

power to electrical loads connected to 

the buses and could cause unnecessary 

challenges to plant safety systems. To 

prevent such failures, NRC has 

developed ISG–17 to ensure that: 

(1) Internal portions of bus duct 

assemblies are free of corrosion, debris, 

excessive dust buildup, and moisture 

intrusion; 

(2) Electrical buses and their supports 

are free of insulation cracking; and 

(3) Bolted connections of the buses 

are secure. 

Additionally, the external portions of 

bus ducts and structural supports will 

also be inspected in accordance with a 

plant-specific structural monitoring 

program.

Dated at Rockville, Maryland, this 16th day 

of December 2004.

For the Nuclear Regulatory Commission. 

Pao-Tsin Kuo, 

Program Director, License Renewal and 

Environmental Impacts Program, Division of 

Regulatory Improvement Programs, Office of 

Nuclear Reactor Regulation.

Attachment 1: Staff Position and 

Rationale for the Interim Staff 

Guidance (ISG)–17: Proposed Aging 

Management Program (AMP) XI.E4, 

‘‘Periodic Inspection of Bus Ducts’’

Staff Position 

Consistent with the requirements 

specified in 10 CFR 54.4(a), bus ducts 

(non-segregated phase bus and isolated 

phase buses) support safety-related and 

non-safety-related functions in that the 

failure of the bus ducts precludes a 

safety function from being 

accomplished [10 CFR 54.4(a)(1) and 

(a)(2)]. 

Thermal cycling of bus ducts can 

result in torque relaxation of connecting 

bolts, causing loose connections that 

lead to arcing, overheating, and 

explosive damage. Bus insulation 

material may experience a significant 

temperature rise during operation that 

may cause age-related degradation 

during the period of extended operation. 

Insulation failure, along with the 

presence of moisture or debris, may 

provide phase-to-phase or phase-toground electrical tracking paths that 

eventually result in catastrophic failure 

of the bus ducts. These bus ducts, 

therefore, need to be inspected 

periodically during the period of 

extended operation to preclude their 

failure. 

In order to prevent such occurrences, 

the staff has developed an aging 

management program for periodic 

inspection of bus ducts for license 

renewal to ensure that; 

(1) Internal portions of bus duct 

assemblies are free of corrosion, debris, 

excessive dust buildup, and moisture 

intrusion; and 

(2) Electrical buses and their supports 

are free of insulation cracking; and 

(3) Bolted connections of the buses 

are secure. 

Additionally, the external portions of 

bus ducts and structural supports will 

also be inspected in accordance with a 

plant-specific structural monitoring 

program. 

Rationale 

An electrical bus is an assembly of 

bus conductors with the associated 

connections, joints, and insulating 

supports. Bus ducts are electrical buses 

installed on electrically insulated 

supports and are constructed with all 

Federal Register / Vol. 69, No. 246 / Thursday, December 23, 2004 / Notices 76961

phase conductors enclosed in either a 

separate metal enclosure or a common 

metal enclosure. The conductors are 

separated and insulated from each other 

and from the ground by insulating bus 

supports. Also, the conductors in the 

non-segregated bus are insulated 

throughout to reduce corona and 

electrical tracking. The bus ducts are 

used in power systems that connect 

various elements of electric power 

circuits, such as switchgears, 

transformers, main generators, and 

diesel generators. 

Industry operating experience 

indicates that the failure of bus ducts is 

caused by the cracking of bus bar 

insulation (bus sleeving) combined with 

the accumulation of moisture or debris. 

Cracked insulation results from high 

ambient temperatures and 

contamination from bus bar joint 

compound. Cracked insulation in the 

presence of moisture or debris provides 

phase-to-phase or phase-to-ground 

electrical tracking paths, which results 

in catastrophic failure of the buses. Bus 

failure leads to loss of power to 

electrical loads connected to the buses, 

causes subsequent reactor trips, and 

initiates unnecessary challenges to plant 

safety systems. 

Bus ducts exposed to appreciable 

ohmic heating during operation may 

experience loosening of bolted 

connections because of the repeated 

cycling of connected loads. This 

phenomenon can occur in heavily 

loaded circuits, i.e., those exposed to 

appreciable ohmic heating. A Sandia 

National Laboratory Report entitled, 

Aging Management Guideline for 

Commercial Nuclear Power Plants 

(Sandia 96–0344; September 1996) 

documents instances of bolted 

connection loosening at several plants 

due to thermal cycling. NRC 

Information Notice 2000–14, entitled 

Non-Vital Bus Fault Leads to Fire and 

Loss of Offsite Power, identified torque 

relaxation of splice plate connecting 

bolts as one potential cause of a bus 

duct fault. 

In addition to NRC Information Notice 

2004–14, NRC Information Notice 89–

64, entitled Electrical Bus Bar Failures, 

and NRC Information Notice 98–36, 

entitled Inadequate or Poorly 

Controlled, Non-Safety-Related 

Maintenance Activities Unnecessary 

Challenged Safety Systems, also provide 

examples that underscore the safety 

significance of bus ducts and the 

potential problems that can arise from 

age-related bus duct failures.

Attachment 2: Proposed Aging 

Management Program: Periodic 

Inspection of Bus Ducts 

XI.E4 Periodic Inspection of Bus Ducts 

Program Description 

An electrical bus is an assembly of 

bus conductors with the associated 

connections, joints, and insulating 

supports. Bus ducts are electrical buses 

installed on electrically insulated 

supports and are constructed with all 

phase conductors enclosed in either a 

separate metal enclosure or a common 

metal enclosure. The conductors are 

separated and insulated from each other 

and from the ground by insulating 

supports. Also, the conductors in the 

non-segregated bus are insulated 

throughout to reduce corona and 

electrical tracking. The bus ducts are 

used in power systems that connect 

various elements of electric power 

circuits, such as switchgears, 

transformers, main generators, and 

diesel generators. 

Industry operating experience 

indicates that the failure of bus ducts is 

caused by the cracking of bus bar 

insulation (bus sleeving) combined with 

the accumulation of moisture or debris. 

Cracked insulation results from high 

ambient temperatures and 

contamination from bus bar joint 

compound. Cracked insulation in the 

presence of moisture or debris provides 

phase-to-phase or phase-to-ground 

electrical tracking paths, which results 

in catastrophic failure of the buses. Bus 

failure leads to loss of power to 

electrical loads connected to the buses, 

causes subsequent reactor trips, and 

initiates unnecessary challenges to plant 

systems. 

Bus ducts exposed to appreciable 

ohmic heating during operation may 

experience loosening of bolted 

connections because of the repeated 

cycling of connected loads. This 

phenomenon can occur in heavily 

loaded circuits, i.e., those exposed to 

appreciable ohmic heating. Sandia 96–

0344 identified instances of bolted 

connection loosening at several plants 

due to thermal cycling. NRC 

Information Notice 2000–14 identified 

torque relaxation of splice plate 

connecting bolts as one potential cause 

of a bus duct fault. 

One objective of the aging 

management program is to provide an 

inspection of bus ducts. In managing 

this aspect of the aging management 

program, bolted connections at sample 

sections of the buses in the bus ducts 

will be checked for proper torque, or the 

bolted joints will be checked for low 

resistance. This activity will include 

visual inspection of interior portions of 

bus ducts to identify aging degradation 

of insulating and metallic components 

and water/debris intrusion. The external 

portions of bus ducts and structural 

supports will be inspected in 

accordance with a plant-specific 

structural monitoring program. 

Evaluation and Technical Basis 

1. Scope of Program: This program 

applies to all bus ducts within the scope 

of license renewal. 

2. Preventive Actions: This is an 

inspection program and no actions are 

taken as part of this program to prevent 

or mitigate aging degradation. 

3. Parameters Monitored/Inspected: A 

sample of accessible bolted connections 

(bus joints and ending devices) will be 

checked for proper torque, or the 

resistance of bolted joints will be 

checked using a micro-ohm meter of 

sufficient current capacity that is 

suitable for checking bus bar 

connections. This program will also 

inspect the internal portions of 

accessible bus ducts for cracks, 

corrosion, foreign debris, dust buildup, 

and moisture intrusion. The bus 

insulating system will be inspected for 

signs of embrittlement, cracking, 

melting, swelling, or discoloration, 

which may indicate overheating or 

aging degradation. The bus supports 

will be inspected for structural integrity 

and cracking. 

4. Detection of Aging Effects: Visual 

inspection of internal portions of bus 

ducts detects cracks, corrosion, debris, 

dust and moisture. Visual inspection of 

the bus insulating system detects 

embrittlement, cracking, melting, 

swelling and discoloration. Visual 

inspection of bus supports detects 

cracking and lack of structural integrity. 

Internal portions of bus ducts, the bus 

insulating system, and the bus supports 

are visually inspected at least once 

every 10 years. 

A torque test or a resistance test of a 

sample of accessible bolted connections 

is performed at least once every 10 

years. This program will be completed 

before the end of the initial 40-year 

license term and every 10 years 

thereafter. This is an adequate period to 

identify failures of the bus ducts since 

experience has shown that aging 

degradation is a slow process. A 10-year 

inspection frequency will provide two 

data points during a 20-year period, 

which can be used to characterize the 

degradation rate. 

5. Monitoring and Trending: Trending 

actions are not included as part of this 

program because the ability to trend 

inspection results is limited. Although 

not a requirement, trending would 

76962 Federal Register / Vol. 69, No. 246 / Thursday, December 23, 2004 / Notices 

provide additional information on the 

rate of degradation. 

6. Acceptance Criteria: Bolted 

connections must meet the 

manufacturer’s minimum torque 

specifications, or the resistance of 

bolted joints must meet required 

specifications. Bus ducts are to be free 

from any surface anomalies that suggest 

that conductor insulation degradation 

exists. An additional acceptance 

criterion includes no indication of 

unacceptable corrosion, cracking, 

foreign debris, dust buildup, or moisture 

intrusion. Any condition or situation 

that, if not corrected, could lead to a 

loss of intended function is considered 

unacceptable. 

7. Corrective Actions: Further 

investigation and evaluation is 

performed when the acceptance 

criterion is not met. Corrective actions 

may include but are not limited to 

sample expansion, increased inspection 

frequency, and replacement or repair of 

the affected bus duct insulation 

components. When an unacceptable or 

situation is identified, a determination 

shall be made as to whether the same 

condition or situation is applicable to 

other areas, and sample expansion shall 

include those areas. As discussed in the 

appendix to this report, the staff finds 

the requirements of 10 CFR part 50, 

appendix B, acceptable to address 

corrective actions. 

8. Confirmation Process: As discussed 

in the appendix to this report, the staff 

finds the requirements of 10 CFR part 

50, appendix B, acceptable to address 

the confirmation process. 

9. Administrative Controls: As 

discussed in the appendix to this report, 

the staff finds the requirements of 10 

CFR part 50, appendix B, acceptable to 

address administrative controls. 

10. Operating experience: Industry 

operating experience has demonstrated 

that the failures of bus ducts are caused 

by cracked insulation of the bus 

combined with moisture or debris 

buildup internal to the bus ducts. It has 

also been shown that bus duct internals 

exposed to appreciable ohmic heating 

during operation may experience 

loosening of bolted connections related 

to repeated cycling of connected loads.

References 

1. IEEE Std. P1205–2000, IEEE Guide for 

Assessing, Monitoring and Mitigating Aging 

Effects on Class 1E Equipment Used in 

Nuclear Power Generating Stations. 

2. SAND 96–0344, Aging Management 

Guideline for Commercial Nuclear Power 

Plants—Electrical Cable and Terminations, 

prepared by Sandia National Laboratories for 

the U.S. Department of Energy, September 

1996. 

3. EPRI TR–109619, Guideline for the 

Management of Adverse Localized 

Equipment Environments, Electric Power 

Research Institute, Palo Alto, CA, June 1999. 

4. EPRI TR–104213, Bolted Joint 

Maintenance & Application Guide, Electric 

Power Research Institute, Palo Alto, CA, 

December 1995. 

5. NRC Information Notice 89–64, 

‘‘Electrical Bus Bar Failures.’’

6. NRC Information Notice 98–36, 

‘‘Inadequate or Poorly Controlled, NonSafety-Related Maintenance Activities 

Unnecessary Challenged Safety Systems.’’

7. NRC Information Notice 2000–14, ‘‘NonVital Bus Fault Leads to Fire and Loss of 

Offsite Power.’’

[FR Doc. 04–28067 Filed 12–22–04; 8:45 am] 

BILLING CODE 7590–01–P

PENSION BENEFIT GUARANTY 

CORPORATION 

Submission of Information Collection 

for OMB Review; Comment Request; 

Liability for Termination of SingleEmployer Plans

AGENCY: Pension Benefit Guaranty 

Corporation.

ACTION: Notice of request for extension 

of OMB approval. 

SUMMARY: The Pension Benefit Guaranty 

Corporation (‘‘PBGC’’) is requesting that 

the Office of Management and Budget 

(‘‘OMB’’) extend approval, under the 

Paperwork Reduction Act, of a 

collection of information in its 

regulation on Liability for Termination 

of Single-Employer Plans, 29 CFR Part 

4062 (OMB control number 1212–0017; 

expires January 31, 2005). This notice 

informs the public of the PBGC’s request 

and solicits public comment on the 

collection of information.

DATES: Comments should be submitted 

by January 24, 2005.

ADDRESSES: Comments should be 

mailed to the Office of Information and 

Regulatory Affairs of the Office of 

Management and Budget, Attention: 

Desk Officer for Pension Benefit 

Guaranty Corporation, Washington, DC 

20503. Copies of the request for 

extension (including the collection of 

information) may be obtained without 

charge by writing to or visiting the 

PBGC’s Communications and Public 

Affairs Department, suite 240, 1200 K 

Street, NW., Washington, DC 20005–

4026, or calling (202) 326–4040. (TTY 

and TDD users may call (800) 877–8339 

and request connection to (202) 326–

4040). The regulation on Employer 

Liability can be accessed on the PBGC’s 

Web site at http://www.pbgc.gov.

FOR FURTHER INFORMATION CONTACT:

Thomas H. Gabriel, Attorney, Office of 

the General Counsel, Pension Benefit 

Guaranty Corporation, 1200 K Street, 

NW., Washington, DC 20005–4026, 

(202) 326–4024. (For TTY and TDD, call 

(800) 877–8339 and request connection 

to (202) 326–4024).

SUPPLEMENTARY INFORMATION: Section 

4062 of the Employee Retirement 

Income Security Act of 1974 provides 

that the contributing sponsor of a singleemployer pension plan and members of 

the sponsor’s controlled group (‘‘the 

employer’’) incur liability (‘‘employer 

liability’’) if the plan terminates with 

assets insufficient to pay benefit 

liabilities under the plan. The PBGC’s 

statutory lien for employer liability and 

the payment terms for employer liability 

are affected by whether and to what 

extent employer liability exceeds 30 

percent of the employer’s net worth. 

Section 4062.6 of the PBGC’s 

employer liability regulation (29 CFR 

4062.6) requires a contributing sponsor 

or member of the contributing sponsor’s 

controlled group who believes employer 

liability upon plan termination exceeds 

30 percent of the employer’s net worth 

to so notify the PBGC and to submit net 

worth information. This information is 

necessary to enable the PBGC to 

determine whether and to what extent 

employer liability exceeds 30 percent of 

the employer’s net worth. 

The collection of information under 

the regulation has been approved by 

OMB under control number 1212–0017 

(expires January 31, 2005). The PBGC is 

requesting that OMB extend its approval 

for three years. An agency may not 

conduct or sponsor, and a person is not 

required to respond to, a collection of 

information unless it displays a 

currently valid OMB control number. 

The PBGC estimates that an average of 

5 contributing sponsors or controlled 

group members per year will respond to 

this collection of information. The 

PBGC further estimates that the average 

annual burden of this collection of 

information will be 12 hours and $3,300 

per respondent, with an average total 

annual burden of 60 hours and $16,500.

Issued in Washington, DC, this 20th day of 

December, 2004. 

Stuart A. Sirkin, 

Director, Corporate Policy and Research 

Department, Pension Benefit Guaranty 

Corporation.

[FR Doc. 04–28115 Filed 12–22–04; 8:45 am] 

BILLING CODE 7708–01–P