Information Notice 1988-25, Minimum Edge Distance for Expansion Anchor Bolts
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
May 16, 1988
NRC INFORMATION NOTICE NO. 88-25: MINIMUM EDGE DISTANCE FOR EXPANSION
ANCHOR BOLTS
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
This Information notice is being provided to alert addressees to test results
indicating that the recommended minimum edge distance for the design and instal- lation of expansion anchor bolts may be unconservative with respect to effectively
resisting the shear forces imposed on anchor bolts during a design-basis event
such as a safe-shutdown earthquake. It is expected that recipients will review
the information for applicability to their facilities and consider actions, as
appropriate, to avoid similar problems. However, suggestions contained in this
information notice do not constitute NRC requirements; therefore, no specific
action or written response is required.
Description of Circumstances
On March 18, 1988, Hilti, Inc., informed the Nuclear Regulatory Commission (NRC),
in accordance with 10 CFR Part 21, of recent tests of Hilti Kwik-Bolts that indi- cate that the previously recommended minimum distance from an anchor bolt to an
unsupported concrete edge may be insufficient to develop 100% of the recommended
anchor capacity. In view of the foregoing, the NRC staff met with representatives
of Hilti, Inc. (Hilti) to discuss the notification.
During the meeting, the NRC staff was informed that prior to November 1985, the
edge-distance guidelines provided by Hilti for the installation of Hilti Kwik- Bolts were those of the Expansion Anchor Manufacturers Institute (EAMI). The
EAMI guidelines are used throughout the United States and recommend an edge
distance, the distance from the center of an expansion anchor bolt to an un- supported edge of a concrete support, of five anchor diameters to achieve 100%
of the recommended anchor capacity. In November 1985, Hilti revised its design
and installation guidelines and recommended a greater edge distance than the
EAMI guidelines. These conservative guidelines were adopted based on infor- mation and broader technical knowledge and experience gained as a result of
marketing Hilti bolts to foreign customers. Consequently, Hilti initiated a
testing program in 1986 to support their revised edge-distance guidelines.
8805100246 ZA-
IN 88-25 May 16, 1988 The 10 CFR Part 21 notification documents the results of this testing program
and indicates that Hilti Kwik-Bolts installed In accordance with the EAMI guide- lines have only 30% of the recommended anchor shear capacity and 78% of the, recommended tensile capacity.
HIlti further Indicated that the test results
are believed to be applicable to other expansion anchor bolts that use the same
type of anchor mechanism as Hilti Kwik-Bolts.
Discussion:
The NRC staff considers the test results indicating a 70% reduction in shear
capacity to be significant and to indicate that there is a potential safety
concern that will require further NRC review.
However, the test results do
not indicate an imminent safety concern for expansion anchor bolts installed
in nuclear power facilities for the reasons given below.
(1) The purpose of the Hilti edge-distance test program was to establish
design recommendations for the resistance capacity of a single bolt
as a function of edge distance.
The test anchorage consisted of only
one bolt anchored to a concrete block that was not reinforced.
Equip- ment or system anchorage arrangements at nuclear power facilities usually
use more than one anchor bolt and a steel bearing plate or base assembly.
Installation pretensioning torque loads applied to the anchor bolt nuts
create compressive loads and frictional resistance forces between the
bearing plate and the concrete that tend to make the anchorage and con-
-crete-support-act asrarthrgle unit and11ltigate-the-severtty-of-the sfngle- bolt edge-distance problem.
If the frictional resistance forces between
the concrete support and the bearing plate are reduced due to the creep
of concrete and the relaxation of anchor bolts, the bearing plate can
still redistribute the additional shear forces, which cannot be resisted
by the edge bolts with reduced capacity, to other bolts that have no
capacity reduction due to the edge-distance problems.
(2) The test results are an acceptable basis for establishing design recommen- dations; however, they should be viewed as conservative for the installation
of bolts. The presence of steel reinforcement between the bolt and an un- supported concrete edge should increase the bolt shear capacity, depending
on the amount of reinforcement and the type of placement, and also mitigate
the consequences of the edge-distance problem. This is particularly true
for large diameter expansion bolts (greater than 3/4-inch bolts).
Based on the NRC staff assessment of the information that has been provided
since the submittal of the 10 CFR Part 21 notification, it appears that 1) most
anchor bolts in nuclear power facilities were installed using the EAMI recom- mended guidelines and 2) the potential failure of these bolts to perform their'
intended function during a design-basis event, such as a seismic event, could
jeopardize the integrity of safety-related systems and equipment.
Therefore, the NRC will continue to evaluate this issue and take appropriate regulatory
action if It is determined that a significant safety hazard exists at nuclear
power facilities. However, addressees may wish to review the information and
consider appropriate actions if this information Indicates that a significant
safety hazard exists at their facility.
IN 88-25 May 16, 1988 No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate
regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
John Ma, NRR
(301) 492-1376
Jaime Guillen, NRR
(301) 492-1153 Attachment:
List of Recently Issued NRC Information Notices
Attachment
May 16, 1988
Page I of 1
- In nr
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1
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LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
88-24
88-23
88-22
88-21
88-20
88-19
88-18 Failures of Air-Operated
Valves Affecting Safety-
Related Systems
Potential for Gas Binding
of High-Pressure Safety
Injection Pumps During a
Loss-of-Coolant Accident
Disposal of Sludge from
Onsite Sewage Treatment
Facilities at Nuclear
Power Stations
Inadvertent Criticality
Events at Oskarshamn
and at U.S. Nuclear
Power Plants
Unauthorized Individuals
Manipulating Controls and
Performing Control Room
Activities
Questionable Certification
of Class IE Components
Malfunction of Lockbox on
Radiography Device
5/13/88
5/12/88
5/12/88
5/9/88
5/5/88
4/26/88
4/25/88
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power, test and
research reactors.
and all licensed
operators.
All holders of OLs
or CPs for nuclear
power reactors.
All NRC licensees
authorized to
manufacture, distribute, and/or operate radio- graphic exposure
devices.
- Operating License
- Construction Permit
IN 88-25 May 16, 1988 No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate
regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
John Ma, NRR
(301) 492-1376
Jaime Guillen, NRR
(301) 492-1153 Attachment:
List of Recently Issued NRC Information Notices
Transmitted by memorandum to
dated 4/20/88
- SEE PREVIOUS CONCURRENCES
- OGCB:DOEA:NRR*ESGB:DEST:NRR
JGuillen
JMa
05/03/88
05/03/88
Charles E. Rossi from Lawrence C. Shao
~
R*C/OGCB: DOEA:NRR
CHBerl inger
05/0/88
05/09/88
- SC/ESGB:DEST:NRR*C/ESGB:DEST:NRR *PPMB:ARM
DJeng
GBagchl
TechEd
05/03/88
05/03/88
04/28/88
IN 88-XX
May xx, 1988 No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate
regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
John Ma, NRR
(301) 492-1376
Jaime Guillen, NRR
(301) 492-1153 Attachment:
List of Recently Issued NRC Information Notices
Transmitted by memorandum to
dated 4/20/88
Charles E. Rossi from Lawrence C. Shao
- SEE PREVIOUS CONCURRENCES
- OGCB: DOEA:NRR*ESGB:DEST:NRR
JGuillen
JMa
05/03/88
05/03/88 D/DOEA:NRR
CERossi
05/ /88
- SC/ESGB:DEST:NRR*C/ESGB:DEST:NRR
DJeng
GBagchi
05/03/88
05/03/88 C/O B
C
EA:NRR
CHBerlinger
05/f /88
- PPMB:ARM
TechEd
04/28/88
IN 88-XX
May xx, 1988 can still redistribute the extra shear force (which cannot
the edge bolts with reduced shear capacity) to other bolts
capacity reduction resulting from edge-distance problems.
be resisted by
that have no
(2) Since the anchor bolts were tested in concrete that was not reinforced, the test results should be viewed as the most conservative value for
design.
Steel reinforcement Is typically present in concrete supports in
structures at nuclear power facilities.
The presence of steel reinforce- ment between the bolt and unsupported concrete edge should increase the
bolt shear capacity. This is particularly true for large diameter
expansion bolts (greater than 3/4-inch bolts). The amount of increase
depends on the amount of reinforcement and the type of placement.
The NRC is in the process of collecting more Information that would constitute
the basis for further action and provision of regulatory guidance. The NRC
staff will issue appropriate guidelines and criteria to ensure that all sup- ports Installed in nuclear power facilities with expansion anchor bolts have
acceptable margins of safety.
However, addressees are expected to review the
information and consider appropriate actions if this information indicates that
a significant safety hazard exists at their facility.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact listed below or the Regional Administrator of the appropriate regional
office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
John Ma, NRR
(301) 492-1376
David Jeng, NRR
(301) 492-0842
Jaime Guillen, NRR
(301) 492-1153 Attachment:
List of Recently Issued NRC Information Notices
Transmitted by memorandum to Charles E. Rossi from Lawrence C. Shao
dated 4/20/88
, . I 2 OG
JGiTn en
05/. J88 ESGB:DEST:NRR
JMaj
d'
05/3 /88 SC/ESG 1U[ST:NRR
DJeng
05/' /.
D/DOEA:NRR
CERossi
05/ /88 C/E G jDEST:NRR
GBa56R/
05/ %7/88 C/09L tEA: NRR
CHBe linger
05/ 1/88 PPMB:ARM
TechEd
04/28/88
The NRC is in the process of collecting more information that would constitute
the basis for further action and provision of regulatory guidance.
The NRC
will issue appropriate guidelines and criteria to ensure that all supports
installed in nuclear power facilities with expansion anchor bolts have
acceptable margins of safety.
Ever, addressees are expected to review the
information and consider appr =a% actions if this information indicates that
a significant safety hazard exias at their facility.
Charles E. Rossi, Director
DOEA
Technical Contacts: John Ma, NRR
(301) 492-1376
David Jeng, NRR
(301) 492-0842
Jaime Guillen, NRR
(301) 492-1153 OGCB:DOEA:NRR
JGuillen
4/ /88 PRMB:AF41 TechEdU
4 /88 SC/ESGB:DEST:NRR
DJeng
4/ /88 C/ESGB:DEST:NRR
GBagchi
4/ /88 C/OGCB:DOEA:NRR
CHBerlinger
4/ /88 D/DOEA:NRR
CERossi
4/ /88