Bulletin 80-11: Masonry Wall Design
SSINS No.: 6820
Accession No.:
7912190695
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
May 8, 1980
IE Bulletin No. 80-11
MASONRY WALL DESIGN
Description of Circumstances:
In the course of conducting inspections pursuant to IE Bulletin Nos. 79-02
and 79-14 at the Trojan Nuclear Plant, Portland General Electric Co. (PGE)
identified a problem with the structural integrity of concrete masonry walls
with Seismic Category I piping attached to them. This problem was briefly
addressed in IE Information Notice No. 79-28, which was sent to all
Construction Permit and operating License holders on November 16, 1979
(Attachment 1).
The problem was that some walls were found which did not have adequate
structural strength to sustain the required piping system support reactions.
These structural deficiencies were at that time reported to be attributable
to two deficiencies:
1) Apparent lack of a final check of certain pipe support locations and
reactions to ensure that the supporting elements possessed adequate
structural integrity to sustain the required loads.
2) Non-conservative design criteria for the reactions from supports
anchored into the face of concrete masonry walls; e.g., relying on the
combined strength of double block walls without substantial positive
connection between the two walls by means other than the bond provided
by a layer of mortar, grout or concrete between them.
Continued investigations into the deficiencies identified at the Trojan
Nuclear Plant, engineered by Bechtel, confirmed the deficiencies to be
attributable to error in engineering judgment, lack of procedures and
procedural detail, and inadequate design criteria (details are in Trojan
Nuclear Plant's LER No. 79-15, and supplements). Because of this and the
generic implications of similar deficiencies with other operating
facilities, we have concerns with regard to the adequacy of design criteria
used for the design of masonry walls and an apparent lack of design
coordination between the structural and piping/equipment design groups.
IE Bulletin 79-02, Revision 2 issued on November 8, 1979 required a review
of pipe supports attached to masonry walls using expansion anchor bolts. For
most pipe supports in this category, the expansion anchor bolts were
replaced by bolting through the wall or the support was relocated to another
structure. Supports that are bolted through masonry walls are also to be
considered in the review for this Bulletin.
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IE Bulletin No. 80-11 May 8, 1980
Page 2 of 4
Action to be taken by all power reactor facilities with an Operating License
(except Trojan, Sequoyah Unit 1, North Anna Unit 2, and Salem Unit 2):
1. Identify all masonry walls in your facility which are in proximity to
or have attachments from safety-related piping or equipment such that
wall failure could affect a safety-related system. Describe the systems
and equipment, both safety and non-safety-related, associated with
these masonry walls. Include in your review, masonry walls that are
intended to resist impact or pressurization loads, such as missiles,
pipe whip, pipe break, jet impingement, or tornado, and fire or water
barriers, or shield walls. Equipment to be considered as attachments or
in proximity to the walls shall include, but is not limited to, pumps,
valves, motors, heat exchangers, cable trays, cable/conduit, HVAC
ductwork, and electrical cabinets, instrumentation and controls. Plant
surveys, if necessary, for areas inaccessible during normal plant
operation shall be performed at the earliest opportunity.
2. Provide a re-evaluation of the design adequacy of the walls identified
in Item 1 above to determine whether the masonry walls will perform
their intended function under all postulated loads and load
combinations. In this regard, the NRC encourages the formation of an
owners' group to establish both appropriate re-evaluation criteria and
where necessary, a later confirmatory masonry test program to quantify
the safety margins established the re-evaluation criteria (this is
discussed further in Item 3 below).
a. Establish a prioritized program for the re-evaluation of the
masonry walls. Provide a description of the program and a detailed
schedule for completion of the re-evaluation for the categories in
the program. The completion date of all re-evaluations should not
be more than 180 days from the date of this Bulletin. A higher
priority should be placed on the wall re-evaluations considering
safety-related piping 2-1/2 inches or greater in diameter, piping
with support loads due to thermal expansion greater than 100
pounds, safety-related equipment weighing 100 pounds or greater,
the safety significance of the potentially affected systems, the
overall loads on the wall, and the opportunity for performing
plant surveys and, if necessary, modifications in areas otherwise
inaccessible. The factors described above are meant to provide
guidance in determining what loads may significantly affect the
masonry wall analyses.
b. Submit a written report upon completion of the re-evaluation
program. The report shall include the following information.
(i) Describe, in detail, the function of the masonry walls, the
configurations of these walls, the type and strengths of the
materials of which they are constructed (mortar, grout,
concrete and steel), and the reinforcement details
(horizontal steel, vertical steel, and masonry ties for
multiple wythe
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IE Bulletin No. 80-11 May 8, 1980
Page 3 of 4
construction). A wythe is considered to be (as defined by ACI
Standard 531-1979) "each continuous vertical section of a
wall, one masonry unit or grouted space in thickness and 2
in. minimum in thickness."
(ii) Describe the construction practices employed in the
construction of these walls and, in particular, their
adequacy in preventing significant voids or other weaknesses
in any mortar, grout, or concrete fill.
(iii) The re-evaluation report should include detailed
justification for the criteria used. References to existing
codes or test data may be used if applicable for the plant
conditions. The re-evaluation should specifically address the
following:
(a) All postulated loads and load combinations should be
evaluated against the corresponding re-evaluation
acceptance criteria. The re-evaluation should consider
the loads from safety and non-safety-related
attachments, differential floor displacement and thermal
effects (or detailed justification that these can be
considered self limiting and cannot induce brittle
failures), and the effects of any potential cracking
under dynamic loads. Describe in detail the methods used
to account for these factors in the re-evaluation and
the adequacy of the acceptance criteria for both
in-plane and out-of-plane loads.
(b) The mechanism for load transfer into the masonry walls
and postulated failure modes should be reviewed. For
multiple wythe walls in which composite behavior is
relied upon, describe the methods and acceptance
criteria used to assure that these walls will behave as
composite walls, especially with regard to shear and
tension transfer at the wythe interfaces. With regard to
local loadings such as piping and equipment support
reactions, the acceptance criteria should assure that
the loads are adequately transferred into the wall, such
that any assumptions regarding the behavior of the walls
are appropriate. Include the potential for block pullout
and the necessity for tensile stress transfer through
bond at the wythe interfaces.
3. Existing test data or conservative assumptions may be used to justify
the re-evaluation acceptance criteria if the criteria are shown to be
conservative and applicable for the actual plant conditions. In the
absence of appropriate acceptance criteria a confirmatory masonry wall
test program is required by the NRC in order to quantify the safety
margins inherent in the re-evaluation criteria. Describe in detail the
actions planned and their schedule to justify the re-evaluation
criteria used in Item 2. If a test program is necessary, provide your
commitment for such a program and a schedule for submittal of a
description of the test program and a schedule for completion of the
program. This test program should address all
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IE Bulletin No. 80-11 May 8, 1980
Page 4 of 4
appropriate loads (seismic, tornado, missile, etc,.). It is expected
that the test program will extend beyond the 180 day period allowed for
the other Bulletin actions. Submit the results of the test program upon
its completion.
4. Submit the information requested in Items 1, 2a, and 3 within 60 days
of the date of this Bulletin. Within 180 days of the date of this
Bulletin submit the information requested in Item 2b.
If in the course of the re-evaluation, the operability of any safety related
system is in jeopardy, the licensee is expected to meet the applicable
technical specifications action statement.
This information is requested under the provisions of 10 CFR 50.54(f).
Accordingly, you are requested to provide within the time period specified
in Item 4, written statements of the above information, signed under oath or
affirmation.
Reports should be submitted to the Director of the appropriate NRC Regional
Office and a copy should be forwarded to the NRC Office of Inspection and
Enforcement, Division of Reactor Operations Inspection, Washington, D.C.
20555.
The reporting requirements of this Bulletin do not preclude nor substitute
for the applicable requirements to report as set forth in the regulations
and license.
If you require additional information regarding this matter, please contact
the Director of the appropriate NRC Regional Office.
Approved by GAO, B180255 (R0072); clearance expires 7/31/80. Approval was
given under a blanket clearance specifically for identified generic
problems.
Attachment:
IE Information Notice No. 79-28
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021