United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 80-11: Masonry Wall Design

                                                            SSINS No.: 6820 
                                                            Accession No.: 

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                                 May 8, 1980

                                                      IE Bulletin No. 80-11 


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. 

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 

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 

               (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 

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

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. 

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 

IE Information Notice No. 79-28 
Page Last Reviewed/Updated Friday, May 22, 2015