ML20141M833

Masonry Wall Design,Haddam Neck Plant, Technical Evaluation Rept

ML20141M833
Person / Time
Site:	Haddam Neck, 05000000
Issue date:	02/24/1986
From:	Con V CALSPAN CORP.
To:	Nilesh Chokshi NRC
Shared Package
ML20141D206	List: ML20141D204 ML20141D223 ML20141M833
References
CON-NRC-03-81-130, CON-NRC-3-81-130 TAC-42911, TER-C5506-003, TER-C5506-3, NUDOCS 8602280369
Download: ML20141M833 (59)

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ATTACl#4ENT 1 6

FRANKLIN RESEARCH CENTER .

DIVISION OF ARVIN/CALSPAN r

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TECHNICAL REPORT ,

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l f TECHNICAL EVALUATION REPORT NRC DOCKET NO. 50-213 FRC PROJECTC5506 NRCTACNO. 42911 FPC ASSIGNMENT 6 NRCCONTRACTNO.NRC 03-81 t30 FRCTASK 253 i j MASONRY WALL DESIGN CONNECTICUT YANKEE ATOMIC PCHER COMPANY HADDAM NECK PLANT TER-C5506-003 l -

6 Preparedfor l NuclearRegulatory Commission FRC Group Leader: v. Con

! Washington, D.C. 20555 NRC Lead Engineer: N. C. Chokshi February 24, 1986 I

This report was prepared as an account of work sponsored by an egency of the United States Government. Neither the Unf tod States Government nor any agency thereof, or any of their employees, makes any warranty, expreeted or Impiloti, or assumes arty legal liability or i responsibility for any third party's use, or the results of such use, of any information, appa-ratus, product or process disclosed in thfe nepcrt, or represents that its use by such third party would not Infringe privately omed ryhts.

Prepared by: Revlewed by: Approved by:

b Prinlipal Author Affb mo

'Dspartment D/ectpf l Date: 2~ N- M_ Date: 2~N O Date: 2 -14 'N i

I FRANKLIN RESEARCH CENTER i onnsacN oF ARVIN/CALSPAN aca a eatsimm.p.maenema ca e,es

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I C0tfrENTS

_Section Title Page l 1 INTRODUCTION . . . . . . . . . . . . . I 1.1 Purpose of Review . . . . . . . . . . . 1 !

1.2 Generic Issue Background . . . . , , . . . 1 1.3 Plant-Specific Background , . . . . . . . . 1 2 EVALUATION CRITERIA. . , . . . . . . . , . 4 3 TECHNICAL EVALUATION . . . . .

( . . . . . . 5 3.1 Evaluation of Licensee's Criteria . . . . . . . 5

. 3.2 Evaluation of Licensee's Approach to Wall Modifications . 15

! 4 COffCLUSIONS. . . . . . . . . . . . . . 16

, S REFERENCES . . . . . . . . . . . . . . 18 l

APPENDIX A - SGEB CTsITERIA FOR SAFLTY-REEATED MASONRY WALL EVALUATION (DEVELOPED BY THE STR'JCTURAL AND GEOTHECHNICAL ENGINEERING BRANCH (SGEB] OF THE NRC) i APPENDIX B - SITICH OF A TYPICAL WALL MODIFICATION FOR UNMORTARED WALLS 4

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i FOREWORD This Technical Evaluation Report was prepared by Franklin Research Centec under a contract with the U.S. Nuclear Regulatory Comunission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions. The technical evaluation was conducted in accordance with criteria established by the NRC.

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1. INTRODUCTICN 1 e

t 1.1 PURPOSE OF REVIEW The purpose of this review is to provide technical evaluations of licensee responses to IE Bulletin 80-11 (1]* with respect to compliance with the Nuclear Regulatory Comunission (NRC) masonry wall criteria. In addition, if a licensee has planned repair work on masonry walls, the planned methods and procedures are to be reviewed for acceptability.

1.2 GENERIC ISSUE BACKGROUND In the course of conducting inspections at the Trojan Nuclear Plant, Portland General Electric Company determined that some concrete masonry walls did not have adequate structural strength. Further investigation indicated that the problem resulted from errors in engineering judgment, a lack of 4 established procedures and procedural details, and inadequate design criteria. Because of the implication of similar deficiencies at other operating plants, the NRC issued IE Bulletin 80-11 on May 8, 1980.

IE Bulletin 80-11 required licensees to identify plant, masonry walls and

, their intended functions. Licensees were also required to present reevaluation criteria for the masonry walls with the analyses to justify those criteria.

, If modifications were proposed, licensees were to state the methods and schedules for the modifications.

6 1.3 PLANT-SPECIFIC BACKGROUND In response to IE Bulletin 80-11, Connecticut Yankee Atomic Power Company (CYAPCO) provided NRC with letters plus attachments dated November 4, 1980 (2], March 3, 1981 [3], and June 26, 1981 [4] describing the status of masonry walls at the Haddam Neck plant. These documents were reviewed, and a request ,

for additional information was sent to the Licensee on September 28, 1982, to l which the Licensee has responded [5]. The review of this response revealed I several unresolved issues, so another request for additional information was sent on July 22, 1985. During a site visit on October 28-30, 1985, tne NRC, l

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• Numbers in brackets indicate references, which are cited in Section 5.

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its consultants, and the Licensee discussed responses to the latest requests for infermation and reviewed plant modifications made in response to IE I

Bulletin 80-11. The Licensee subsequently submitted the written responses (6) to the July 22, 1985 requests.

In Reference 6, the Licensee reported 31 masonry walls within the scope of IE Bulletin 80-11. These walls do not support any safety-related piping systems nor were they designed to resist horizontal building inertial forces, j Typically, the masonry walls at this plant function as partitions and shield walls.

l The masonry walls at the Haddam Neck plant are predominantly holicw, single-wythe walls with mortar joints between the masonry wall and adjoining structural elements.

The construction materials used are as follows:

a. Exterior or load-bearing partitions - ASTM C-90, Grade A

b. Non-load-bearing partitions - ASTM C-129

c. Solid units - ASTM C-145, Grade B

d. Lightweight units - ASTM C-90, Grade B i e. Mortar - ASTM C-270, Type N I f. Reinforcement - A-305 and A-15.

(, Three walls, CYCT 1001, CYPAB 102, and CYPAB 103, were made of solid blocks, stacked with to mortar. But these walls have been modified by adding

, decking, supported by circular steel posts, to the entire face of the wall (see Appendix B), thus preventing loose blocks from falling on equipment.

This type of modification was also applied to four mortared walls at the l Haddam Neck plant so that they could be allowed to fail without jeopardizing l safety-related equipment. Other modifications include the addition of steel angles at wall edges to reinforce boundary conditions, the insertion of steel i

posts at the wall face to reduce the wall spans and transfer loads to the boundaries, and the addition of steel bumpers at the top and bottom of the wall to prevent sliding and overturning.

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l TER-C5506-253 The Licensee originally relied upon the arching action technique to

. qualify one masonry wall, CYPAB 101C. However, a reevaluation of this wall determined that it is not in fact safety-related. Further discussion of this subject is provided in Section 3.1.

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3. TECHNICAL EVALUATION t

1 This evaluation is based on the Licensee's earlier responses (2, 3, 4],

{ and subsequent responsec (5, 6] to the NRC requests for additional information. The Licensee's criteria were evaluated with regard to design and g analysis methods, loads and load combinations, allowable stresses, i

construction specifications, materials, and any relevant test data.

3.1 EVALUATION OF LICENSEE'S CRITERIA The Licensee evaluated the masonry walls using the following criteria:

o The stress allowables are based on ACI 531-79.

o Loads and load combinations are consistent with the final design safety analysis (FDSA).

t o The following damping values are used:

4% damping for severe environmental load combinations 7% damping for extreme environmental load combinations.

o The working stress method of analysis was used.

o A typical analytical procedure used in the working stress design method is summarized below:

- determine wall boundary conditions calculate the wall's fundamental frequency using a one-way span assumption

- obtain inertial loading from the floor response spectra

- compare computed stresses with allowable values.

The Licensee's criteria and responses (5, 6] have been reviewed. Other than those areas identified in Section 4, the Licensee's criteria have been found to be adequate and in compliance with the SGEB criteria (Appendix A).

Fc11owing is a review of the Licensee's responses in References 5 and 6.

Questions and responses covering the same topic have been combined:

Question 1 Indicate how equipment loads were considered in the analysis.

f TER-C5506-253 Response 1 j In this response, the Licensee indicated that equipment loads were estimated in the field and included in the model used to analyze wall I

l response. The ways in which these loads were applied to the wall were determined by field inspection of the attachments. In the inertial load calculations, the mass of all the attachments was averaged over the area of the wall and added to the unit mass of the wall. This total mass was used to determine the fundamental frequency of the wall, which was, in turn used with the floor response spectra to obtain the inertial loading.

This response is consistent with the SGEB criteria.

l Question 2 1

Indicate if testing for material properties was used in lieu of the minimum specified. If so, provide a description of the testing program I and the test data.

l Response 2 The Licensee responded that material properties were not determined by testing; all minimum values used were based on ACI S31-79. However, to support these values, random samples of block were tested for unit compressive

, strength in accordance with ASTM C-140. The tests indicated a minimum unit strength of 1260 psi (on the gross area). In Table 4.3 [8], the minimum f'm of 700 psi for Type N mortar corresponds to 1,000 psi (compressive strength of

a block on the net cross-sectional area). This result suggests that the value of 700 psi for f'm, which was used in the analysis, is conservative.

r This response is satisfactory.

Question 3 Indicate how variations in frequency due to uncertainties in mass,

) materials, and other parameters were considered in the analysis.

, Response 3 1

The Licensee indicated that for each wall being analyzed a decision was i

made either to use the peak response spectra or the response spectra i

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i corresponding to the fundamental frequency of the wall. If the latter case was adopted, a broadened spectrum of 85 percent to 115 percent of the fundamental frequency of the wall was used.

I In addition, as indicated in Response 4, a factor of 1.3 was multiplied to the wall acceleration.

This response satisfies the intent of the SGEB criteria.

Question 4 In calculating seismic loads, the Licensee multiplies the wall accele-ration by factors of 1.3 for out-of-plane loads and 1.0 for in-plane f

loads. Justify this difference in factors used for in-plane and out-of-plane loads.

Response 4 The Licensee responded that the wall is rigid for in-plane loads and, therefore, no increase factor need be applied to the in-plane acceleration.

In the out-of-plane direction, however, the wall is flexible and the spectral response associated with the natural frequency must be increased to account for higher modes of vibration. The Licensee has chosen a factor of 1.3 to account for higher modes of vibration. It has been found in many cases at other plants that the first mode contributes 95% or more of the total response. Based on these considerations, it is concluded that the Licensee's approach is satisfactory and complies with the SGEB criteria.

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,t Question 5 During the site walkdown, several cracks were noted in walls CYTB 1009 and CYTB 1010. Indicate the cause of the cracks and what action is required to address this issue.

Response 5 I

During the site visit on October 28-30, 1985, the Licensee indicated actions will be taken to alleviate concerns associated with these cracks. The Licensee is planning to submit an action plan addressing this issue; the NRC staff will review and address the adequacy of this action plan in their Safety Evaluation Report (SER).

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l TER-C5506-253 Question 6 In Appendix A of the final report on the evaluation of masonry walls at the Haddam Neck plant [5], the Licensee indicates that the shear stress

1. - caused by in-plane relative displacements was approximately equal to G/h multiplied by the relative displacement, where G is the masonry shear l modulus and h is the height of the wall. Specify the limits on the value for relative displacement.

Response 6 The Licensee responded that in its analysis of relative displacement, the maximum deflection depended upon the maximum allowable shear strese and, therefore, no limits were placed on the deflection.

I This response is satisfactory and complies with the SGEB criteria.

.[ Question 7 In Section 4.4.1 of Reference 2, the Licensee states that the response of in-filled panels to in-plane relative displacements may be analyzed by t

considering the non-linear composite action of the masonry wall and surrounding frame. The Licensee is requested to identify all walls which

{ were qualified by this technique. Discuss and provide the technical

, , basis for the non-linear composite motion. The Licensee is also requested to provide the results of the analysis along with some sample calculations.

Response 7 The Licensee responded that the method of "non-linear composite action"

, was not used in the reevaluation of any wall at the Haddam Neck plant.

Question 8 t

In Response 8 of Reference 5, CYAPCO stated that one wall at the Haddam Neck plant was analyzed using the " arching action" technique. Identify this wall. The NRC position on this issue states that the use of the I arching action theory to qualify unreinforced masonry walls is not acceptable. These walls should be repaired so they can be qualified based on the SGEB criteria (Appendix A).

Response 8

{ The Licensee indicated that wall CYPAB 101C, which was qualified on the

basis of arching action, has been reanalyzed using a working stress approach

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! TER-C5506-253 that is less conservative than the original working stress criteria. One of the conservatisms that was eliminated is the use of a one-way vertical beam model of the wall when two-way action is more appropriate. The revised calculations used a simply supported plate model. Eliminating conservatisms reduced wall stresses to acceptable SGEB limits when the licensee's floor

response spectra (see Response 18) were used. However, according to Table 1 i

[6], when the SEP response spectra were used, stresses in this wall were as much as 3.18 times the allowable stresses. It must be assumed that the wall fails, but a recent investigation has shown that the failure of wall CYPAB 101C would not endanger any safety-related equipment and that its original i

classification as a safety-related wall was very conservative. Wall CYPAB 101C has, therefore, been removed from the scope of IE Bulletin 80-11.

This response is adequate and consistent with the SGEB criteria.

Question 9 4

Indicate whether the construction practice for masonry walls at the Haddam Neck plant was in conformance with provisions specified for the special inspection category in ACI 531-79 (8). If not, explain and justify the use of allowable stresses.

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Response 9 i

The Licensce indicated that the construction engineers were responsible 4

for inspecting workmanship and monitoring the sequence of construction of masonry walls at the Haddam Neck plant. The inspection was controlled by the l

original drawings and specifications. As part of the reevaluation effort,

?I field engineers surveying the masonry walls found no deviations between the as-ij built conditions and the original specifications. Consequently, it was concluded that the construction practices were consistent with the provisions of the special inspection category of ACI 531-79. In addition, tests performed on block samples indicated that the blocks had higher strengths than the values used to determine f's from Table 4.3 in ACI 531-79 (see Response 2, this report). Therefore, the use of the stress allowables of the special

inspection category of ACI 531-79 is considered justified.

This response is satisfactory and consistent with the SGEB criteria.

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Question 10

) Justify by any existing test data or literature the use of 35 psi for allowable masonry diagonal tension.

Response 10 In this response, the Licensee indicated that the value of 35 psi for allowable diagonal tension was intended for use with the nonlineac composite j action technique; however, this technique was not used in the reevaluation of any wall at the Haddam Neck plant.

I Question 11 With respect to Attachment 5, Section 5.1 (Appendix A) in Reference 5, i

CYAPCO indicates that allowable stresses can be increased by 33 percent for OBE seismic loadings. However, the SGEB criteria, Section 3(a),

expressly forbids the increase of allowable stress when wir.d or seismic f loads (OBE) are involved. CYAPCO should identify the walls that require i

an increase in allowable stress for OBE load combinations in order to be qualified. Also, provide the actual percentage increase in allowable stress that is needed to qualify these walls.

i Response 11 In response, the Licensee indicated that only SSE stresses were considered as a basis for the response to IE Bulletin 80-11. The SSE condition yielded larger actual stress to allowable stress ratios than the OBE condition, even without applying the 33 percent increase to the CBE

{ allowables. Therefore, the 33 percent increase for OBE allowables was not used in qualifying any masonry walls at the Haddam Neck plant.

This response 1u adequate and satisfies the SGEB crit,eria.

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l Provide any increase factors that may have been used for allowable stresses under abnormal conditions. If they are higher than those listed in the SGEB criteria, provide justification. The SGEB factors are listed below by type of stress:

Axial or flexural compression 2.5 l

l Bearing 2.5 i

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Reinforcement stress except shear 2.0 but not to exceed f y Shear reinforcement and/or bolts 1.5 l

Masonry tension parallel to the bed joint 1.5 Shear carried by masonry 1.3 Masonry tension perpendicular to the bed joints 1.5 Reinforced masonry 0 Unreinforced masonry 1.3 f Response 12 The Licensee indicated that all allowable stresses were initially increased by 1.67 for load cases involving SSE loads, although the SGEB criteria permit increase factors of only 1.3 for masonry shear and tension normal to the bed joint and 1.5 for tension parallel to the bed joint.

I However, the Licensee has since compared the expected actual stresses with c

allowables using the SGEB increase factors and SEP loadings where applicable (see Response 18). According to Table 1 of Reference 6,11 walls had stresses in excess of allowable limits. The maximum ratio of actual to allowable

stress using SGEB criteria was 3.19 for wall CYPAB 101E. But this wall has been reevaluated using a more rigorous approach that eliminated some of the conservatisms in the initial analysis. The techniques used to eliminate conservatisms included a modal analysis to determine wall frequency, obviating the application of an increase factor to the fundamental frequency to account for the effects of higher modes and a two-way plate action assumption instead of the much more conservative one-way beam assumption. This reevaluation found that the stress ratio of actual to allowable stress was reduced from 3.19 to 0.76. Based on this result, it can be concluded that conservatisms in the initial analysis offset any exceedance of allowable stress when the SGEB criteria and SEP loadings are applied. Therefore, use of the SGEB increase i factors and SEP response spectra would not affect the Licensee's initial evaluation of masonry walls at the Haddam Neck plant.

This response is adequate and the SGEB criteria are satisfied.  !

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. Question 13 Indicate if block pullout was considered in the analysis. If so, provide sample calculations of block pullout analysis.

Response 13 The Licensee responded that the possibility of attachments pulling out of masonry walls was investigated. Sample calculations in Reference 6 indicated that the pullout shear stress from the attachment bolts was calculated and l

compared with the allowable masonry shear stress. The pullout shear stress i was based on attachment loads and an effective shear area. No problem with h pullout was found.

This response is satisfactory.

I l Question 14 Indicate whether the walls are stacked or running bond. If any stacked bond wall exists, provide sample calculations to obtain stresses of a

\ typical wall.

t Response 14 In this response, the Licensee indicated that all walls, except for a f three unmortared shield walls (CYCT 1001, CYPAB 102, CYPAB 103), are running bond. The stacked, unmortared walls were modified to prevent damage to safety-related equipment by adding metal decking, supported by steel posts, to l the whole face of the wall. See Section 3.2 for the evaluation of the Licensee's modifications.

This response is satisfactory. ,

Question 15 In Reference 4, the Licensee reports that all modifications have been completed except those for wall CYTB-1008 in the turbine building, which were scheduled to be completed by September 1, 1981. Verify the status of the modifications to this wall and other walls in inaccessible areas.

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t-TER-C5506-253 Response 15 i

l The Licensee reported that all modifications have been completed at the Haddam Neck plant.

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Question 16 In Reference 4, a final report was scheduled to be docketed upon completion of the modifications. Provide this report.

Response 16 l The Licensee provided the final report on the masonry well reevaluation, including modifications, in Attachment 5 of Reference S.

Question 17 Provide a description of the modifications and detailed drawings of some sample modifications. In addition, provide a sample calculation to show that the modified walls will be qualified under the working stress design

, method.

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Response 17 In this response, the Licensee provided the following list of the types

, of wall modifications found at the Haddam Neck plant.

o Detachment of the top and sides of the wall from the adjacent boundary supports due to large interstory displacements.

o Insertion of angles at the wall edges to assure pinned boundary conditions.

r o Insertion of steel members across a wall face to transfer wall loads to the boundaries and limit wall span. -

o Insertion of steel bumpers at the top of the wall to prevent overturning and at the base of the wall to prevent slidings, o Shielding so that falling blocks would not hit safety-related equipment.

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, o Removal of the wall.

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, o Rerouting of pipes.

s o Relocation of pipe supports.

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l Appendix 5 contains a sketch of a typical modification for unmortared J walls. See Section 3.2 for evaluation of the Licensee's modifications.

. 'The Licensee's response is adequate.

Question 18

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Since the Haddam Neck plant is part of the systematic evaluation program 1

(SEP), the Licensee is requested to clarify whether the seismic analysis was performed based on SEP loadings. If not, provide justification.

l Response 18 The Licensee indicated that masonry walls at the Haddam Neck plant were initially analyzed using floor response spectra based on the Interim Seismic Design Ground Spectrum.

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The SEP floor response spectra were not used; however, not all the buildings containing safety-related masonry walls were required to have a

floor response spectra developed under the SEP. Table 1 of Reference 6 indicates seven walls located in buildings that were outside the SEP scope of work with respect to the development of floor response spectra (diesel generator, spent fuel, and service buildings). For the rest of the walls, the

,  ; Licensee has estimated the ratios of actual stress to SGEB allowable stress if I

the SEP spectra were used. The maximum ratio was found to be 3.19, but this

!g was shown to be reduced to 0.76 after conservatisms in the Licensee's

l. analytical method were eliminated (see Response 12). It was concluded that all other ratios less than 3.19 would also reduce to less than 1.0 af ter

conservatisme were eliminated. Therefore, the use of the SEP floor response

spectra instead of the Licensee's original floor response spectra would not

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adversely affect the original evaluation of masonry walls at the Haddam Neck plant under IE Bulletin 80-11.

l This response is adequate and in compliance with the SCEB criteria.  ;

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i TER-C5506-253 3.2 EVALUATION OF LICDISEE'S APPROACH TO MODIFICATIONS

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According to the Licensee's final report on the reevaluation of masonry walls (Reference 5, Attachment 5], all walls that did not meet the l reevaluation criteria have been modified. All walls within the scope of IE I

Bulletin 80-11 required some form of modification. The types of modifications l at the Haddam Neck plant include the insertion of steel angles at wall edges to reinforce boundary conditons, the addition of steel posts across the wall face to reduce the wall span and carry wall loads to the boundaries, and the addition of steel bumpers at the top and bottom of the wall to prevent overturning and sliding. Also, solid block walls that were stacked without i

mortar have been modified to prevent loose blocks from falling on equipment.

This type of modification entails the installation of metal decking, supported by steel posts, against an entire wall face to restrain the loose blocks (see Appendix B). Other actions taken to rectify wall deficiencies include the detachment of wall boundary supports from the adjacent structure due to excessive interstory drift, the rerouting of pipes, the relocation of pipe supports, and the removal of the entire wall.

The Licensee has indicated that the modified walls qualify under the

, working stress design method when SGEB criteria and SEP loads are applied and has provided sample calculations and drawings for some modified walls.

I The Licensee's approach to wall modifications has been reviewed and has been found to be adequate and consistent with the SGEB criteria.

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4. CONCLUSIONS

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l A detailed stue was performed to provide a technical evaluation of the j masonry walls at the Haddam Neck plant. Review of the Licensee's criteria and additional information provided by the Licensee led to the conclusions given below, o An increase of 33% in allowable stress was proposed for load combinations containing OBE seismic loads. The SGEB criteria do not permit any increase in allowable stress where OBE or wind loads are involved. However, the CBE condition was not considered in the evaluation of masonry walls under IE Bulletin 80-11. The SSE l condition resulted in larger ratios of actual to allowable stress than the CBE condition, even before increasing the CBE allowables by 33%. Therefore, it is concluded that the 33% increase in allowable stress for OBE or wind loads has no bearing on the evaluation of masonry walls at the Haddam Neck plant.

o An increase factor of 1.67 was applied to the allowable stresses for l, all load combinations containing SSE loads, although the SGEB i

criteria permit increase factors of only 1.3 for masonry shear and tension normal to the bed joint and 1.5 for tension parallel to the bed joint.

However, since its initial evaluation for IE Bulletin 80-11, the Licensee has estimated the ratios of actual stress.to allowable j stress that would be obtained if the SGEB increase factors and SEP loading were used. The results indicate 11 walls with stresses

' larger than SGEB allowables, 3.19 being the maximum ratio of actual to allowable stress. However, the Licensee has also performed an evaluation of the conservatisms in its initial analysis and has found that by eliminating conservatisms, the maximum stress ratio of 3.19 can be reduced to 0.76. Conservatisms were eliminated by using a multi-mode analysis to account for the effects of higher modes instead of applying a factor to the fundamental wall frequency and by using a two-way action assumption instead of one-way action. It is f therefore concluded that the use of SGEB increase factors for allowable stress would not adversely affect the Licensee's initial .

evaluation in which the 1.67 increase factor was used; thus, the walls qualified using the 1.67 factor would also qualify using the SCEB factors and SEP loads, o The Licensee initially relied on arching theory to qualify one wall (CYPAP 101C). As previously discussed in Section 1.3 and Response 8, the NRC does not accept the use of arching action in qualifying masonry walls, and this issue will be addressed in its Safety Evaluation Report. Since its initial evaluation, however, the Licensee has investigated the classification of this wall and found that the failure of this wall would not actually endanger any i

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safety-related equipment the wall was originally classified as

safety-related on a very conservative basis. Therefore, wall CYPAB 101C was removed from the scope of IE Bulletin 80-11. It is concluded that the use of the arching action technique to qualify masonry walls under IE Bulletin 80-11 is not a concern at the Haddam Neck plant.

i o In its seismic analysis, the Licensee did not use the floor response spectra generated by the SEP program. Instead, the masonry walls at this plant were analyzed using estimated floor response spectra, based on the Interim Seismic Design Ground Spectrum.

However, since its initial evaluation for IE Bulletin 80-11, the Licensee has estimated the ratios of actual stress to allowable stress based on the SEP response spectra and the SGES allowables.

( These ratios were found to be as high as 3.19, but after an evaluation and elimination of conservatisms in the anslysis, the maximum ratio was reduced to 0.76, indicating the a'eceptability of the actual stress. The techniques used to eliminate conservatisms included a modal analysis instead of an increase factor to determine the effect of higher modes on the fundamental frequency of the wall and a two-way action assumption instead of a one-way action assumption. Therefore, it is concluded that, although the SEP response spectra were not used in the evaluation of maconry walls at the Haddam Neck plant, the walls that qualified under the Licensee's loading criteria would also qualify using the SEP loading criteria and SGEG allowables, g o During a site visit on October 28 through 30, 1985, the Licensee e

' indicated that actions will be taken to alleviate concerns associated with existing cracks on a number of walls. The Licensee is planning

, to submit an action plan addressing this issues the NRC staff will review and address the adequacy of this action plan in their SER.

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5. REFERENCES 1 IE Bulletin 80-11 Masonry Wall Design NRC, May 8, 1981 i

2. W. C. Counsil Letter to B. H. Grier, NRC.

Subject:

Haddam Neck Plant - IE Bulletin 80-11 Masonry Wall Design Connecticut Yankee Atomic Power Co. , November 4,1980 i ,

A01021

3. W. C. Counsil Letter to B. H. Grier, NRC.

Subject:

Haddam Neck Plant, Millstone l Nuclear Power Station, Unit Nos.1 and 2 - Masonry Wall Design Northeast Utilities, March 3, 1981 A01021

' 4. W. C. Counsil Letter to B. H. Grier, NRC.

Subject:

Haddam Neck Plant - Masonry Wall Design Northeast Utilities, June 26, 1981 A01021 l

5. W. C. Counsil Letter with Enclosures to R. A. Clark, NRC.

Subject:

Request for Additional Information on IE Bulletin 80-11, Masonry Wall Design Northeast Utilities, December 3,1982 Enclosure I

6. J. F. Opeka Letter with Enclosure to C. I. Grimes, NkC.

Subject:

Response to Request for Additional Information on IE Bulletin 80-11, Masonry Wall Design j Northeast Utilities, December 31, 1985

7. Uniform Building Code International Conference of Building Officials, 1979 f

8. Building Code Requirements for Concrete Masonry Structures Detroit: American Concrete Institute, 1979 ACI 531-79 and ACI 531-R-79 e

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., APPENDIX A i i

SGEB CRITERIA FOR SAFETY-RELATED MASONRY WALL EVALUATION .

(DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BRANCH f (SGEB) OF THE NRC) l f

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Section Title Page 1 GENERAL REQUIREMurrS . . . . . . . . . . . A-1 1 2 LOADS AND LOAD COMBINATIONS. . . . . . . . . . A-1

a. Service Load Combinations

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b. Extreme Environmental, Abnormal, Abnormal / Severe Environmental, and Abnormal / Extreme Environmental Conditions . . . . . . . . . . . . . A-2 3 ALLONABLE STRESSES . . . . . . . . . . . . A-2 4

DESIGN AND ANALYSIS CONSIDERATIONS . . . . . . . . A-3 5 REFEREleCES . . . . . . . . . . . . . . A-4 l

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, 1. General Requirements The materials, testing, analysis, design, construction, and inspection  :

related to the design and construction of safety-related concrete masonry walls should conform to the applicable requirerents contained in Uniform Building Code - 1979, unless specified otherwise, by the provisions in this criteria.

The use of other standards or codes, such as ACI-531, ATC-3, or McMA, is also acceptable. However, when the provisions of these codes are less I

censervative than the corresponding provisions of the criteria, their use should be justified on a case-by-case basis.

In new construction, no unreinforced masonry walls will be permitted. For operating plants, existing unreinforced walls will be evaluated by the provisions of these criteria.

Plants which are applying for an operating license and which have already built unreinforced masonry walls.will be evaluated on a case-by-case basis.

2. Loads and Load Combinations The loads and load combinations shall include consideration of normal loads, severe environmental loads, extreme environmental loads, and

abnormal loads. Specifically, for operating plants, the load combinations i

provided in the plant's FSAR shall govern. For operating license applications, the following load combinations shall apply (for definition of load terms, see SRP Section 3.8.4II-3).

(a) Service Load Conditions (1) D + L (2) D + L + E (3) D+L+W If thermal stresses due to To and Ro are present, they should be f included in the above combinations as follows:

(la) D + L + To + Ro (2a) D + L + To + Ro + E (3a) D + L + To + Ro + W Check load combination for controlling condition for maximum 'L' and for no 'L'.

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l (b) Extreme Environmental, Abnormal, Abnormal / Severe Invironmental, and Abnormal / Extreme Environmental Conditions (4) D + L + To + Ro + E (5) D + L + To + Ro+Wt (6) D+L+Ta + Ra + 1.5 Pa (7) D + L + T + Ra + 1.25 Pa + 1.0 (Y g + Yj + Ya) + 1.25 E ,

(8) D + L + Ta + R, + 1.0 P, + 1.0 (Yr+Tj+Y)m+ 1. 0 E '

l In combinations (6), (7), and (8) the maximum values of Pa , T.,

Ra

• Tj' Y r, and Y , including an appropriate dynamic load factor, should be used unless a time-history analysis is performed to justify otherwise. Combinations (5), (7), and (8) and the corresponding structural acceptance criteria should be satisfied first without the tornado missile load in (5) and without Yr

• T is '

and Ya in (7) and (8) . When considering these loads, local secEton

• strength capacities may be exceeded under these concentrated loads, provided there will be no loss of function of any safety-related system.

Both cases of L having its full value or being completely absent should be checked.

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3. Allowable Stresses

• Allowable stresses provided in ACI-531-79, as supplemented by the following modifications / exceptions, shall apply. ,

(a) When wind or seismic loads (OBE) are considered in the loading

{ combinations, no increase in the allowable stresses is permitted.

(b) Use of allowable stresses corresponding to special inspection category shall be substantiated by demonstration of compliance with the inspection requirements of the SEB criteria.

(c) When tension perpendicular to bed ioints is used in qualifying the J unreinforced masonry walls, the allowable value will be justified by test program or other means pertinent to the plant and loading conditions. Por reinforced masonry walls, all the tensile stresses will be resisted by reinforcement.

1 (d) For load conditions which represent extreme environmental, abnormal, abnormal / severe environmental, and abnormal / extreme environmental conditions, the allowable working stress may be multiplied by the factors shown in the following tables i

A-2

a Of TER-C5506-253 Type of stress rector 1

Axial or Flexural Co gression 2.5 Bearing 2.5 Reinforcement stress except shear 2.0 but not to exceed 0.9 fy Shear reinforcement and/or bolts 1.5 I

Masonry tension parallel to bed joint 1.5 Shear c . cried by masonry 1.3 l

Masonry tension perpendicular to bed joint for reinforced masonry 0 for unreinforced assonry2 1,3 Notes

[ (1) When anchor bolts are veed, design should prevent facial spelling of mesonry unit.

(2) See 3(c).

4. Desien and Analysis Considerations (a) Se analysis should follow established principles of engineering mechanics and take into account sound engineering practices.

l (b) Assumptions and modeling techniques used shall give proper I

considerations to boundary conditions, cracking of sections, if any, and the dynamic behavior of masonry walls.

(c) Damping values to be used for dynamic analysis shall be those for reinforced concrete given in Regulatory Guide 1.61.

(d) In general, for operating plants, the seismic analysis and Category I structural requirements of FSAR shall apply. For other plants, corroeponding SRP requirements shall apply. The seismic analysis shall account for the variations and uncertainties in mass, materials, and other pertinent parameters used.

(e) S e analysis should consider both in-plane and out-of-plane loads.

(f) Interstory drift effects should be considered.

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I TER-C5506-253 l (g) In new construction, grout in concrete masonry walls, whenever used, shall be compacted by vibration.

(h) For masonry shear walls, the minimum reinforcement requirements of ACI-531 shall apply.

(i) Special constructions (e.g., multiwythe, composite) or other items not covered by the code shall be reviewed on a case-by-case basis for their acceptance.

(j) Licensees or applicants shall submit QA/QC information, if available, for staff's review.

, In the event QA/QC information is not available, a field survey and a test program reviewed and approved by the staff shall be implemented to ascertain the conformance of masonry construction to design drawings and specifications (e.g., robar and grouting).

(k) For masonry walls requiring protection from spalling and scabbing due to accident pipe reaction (Yr ), jet impingement (Yj), and missile impact (Ym), the requirements similar to those of SRP 3.5.3 shall apply. However, actual review will be conducted on a case-by-case basis.

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! 5. Peferences (a) Uniform Building Code - 1979 Edition.

(b) Building Code Requirements for Concrete Masonry Structures ACI-531-79 and Commentary ACI-531R-79.

(c) Tentative Provisions for the Development of Seismic Regulations for Buildings - Applied Technology Council ATC 3-06.

, (d) Specification for the Design and Construction of Load-Beating Concrete Masonry - NCMA August, 1979.

l (e) Trojan Nuclear Plant Concrete Masonry Design Criteria Safety Evaluation Report Supplement - November, 1980.

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a l APPENDIX D SKETCH OF A TYPICAL WALL MODIFICATION FOR UNMORTARED WALLS l

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO HASONRY WALL DESIGN, IE BULLETIN 80-11 MILLSTONE UNIT 1 DOCKET NO. 50-245

1.0 BACKGROUND

IE Bulletin 80-11 required licensees to identify plant masonry walls and their intended functions. Licensees were also required to present reevaluation criteria for the masonry walls with the analyses to justify those criteria. If modifications were proposed, licensees were to state the methods and scht:dules for the modifications.

In response to IE Bulletin 80-11, Northeast Nuclear Energy Company (NNECO) provided NRC with 'etters plus attachments dated November 4, 1980 and September 29, 1981 describing the status of masonry walls at Millstone Unit 1. These documents were reviewed, and a request for additional information was sent to the Licensee on September 28, 1982, to which the Licensee has responded by letter dated December 3, 1982. The review of this response revealed several unresolved issues, so another request for additional information was sent on July 22, 1985. During a site visit on October 28-30, 1985, the NRC, its consultants, and the Licensee discussed responses to the latest requests for information and reviewed plant modifications made in response to IE Bulletin 80-11. The Licensee subsequently submitted the written responses by letter dated Decem5er 31, 1985.

2.0 EVALUATION The findings reported in this Safety Evaluation Report (SER) are based on the attached Technical Evaluation Report (TER), Attachment 1, prepared by Franklin Research Center (FRC) as a contractor to NRC. This TER contains the details of construction techniques used, technical information

I j reviewed, acceptance criteria, and technical findings with respect to masonry wall construction at Millstone Unit 1. The staff has reviewed this TER and concurs with its technical findings. The following is our sumary of the major technical findings:

1. The licensee has identified 199 safety related masonry walls at Millstone 1. The licensee's reevaluation criteria, as applied in the evaluation of Millstone I walls, comply with the intent of the staff acceptance criteria delineated in Appendix A of the TER.

Initially,-the licensee had relied on the arching action theory to qualify 39 unreinforced walls. However, a subsequent reanalysis of these walls using refined modeling and SEP seismic loading indicated that these walls can be qualified using the working stress approach consistent with the staff acceptance criteria. Therefore, it is concluded that the reevaluation of all safety related masonry walls at Millstone I complies with the intent of the staff acceptance criteria.

2. The licensee has also demonstrated that the Millstone 1 masonry walls can withstand the seismic loading resulting from the review under Systematic Evaluation Program (SEP).

3. The licensee has modified 140 masonry walls using the following approaches.

l Insertion of angles or plates at the wall edges to assure pinned boundary conditions; Insertion of steel members across a wall face to transfer wall loads to the boundaries and limit wall span; Shielding so that falling blocks would not hit safety-related equipment; Rerouting of pipes; and i

Relocation of pipe supports.

The licensee's modification approaches are found to be adequate as the modified walls comply with the intent of staff acceptance criteria.

3.0 CONCLUSION

Based on the above findings, the staff concludes that, Items 2(b) and 3-of the IE Bulletin 80-11 have been fully implemented at Millstone 1 and that there is a reasonable assurance that the safety-related masonry walls .

at Millstone I will withstand the specified design load conditions without I impairment of (a) wall integrity or (b) the performance of the required safety functions.

4.0 ACKNOWLEDGEMENT Principal Contributor: N. Chokshi, RRAB, DSRO

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FRANKLIN RESEARCH CENTER DIVISION OF ARVIN/CALSPAN i

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TECHNICAL REPORT i

1 20TH & RACE STREETS PHR.ADELMMA, PA 19103 TWX 7146701889 TEL (2151448-1000

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TECHNICAL EVALUATION REPORT l

NRC DOCKET NO. 50-245 FRC PROJECT C5506 NRCTACNO. 42913 FRC ASSIGNMENT 6 N RC CONTRACT NO. NRC-03-81-130 FRC TASK 254 MASONRY WALL DESIGN

, NORTHEAST NUCLEAR ENERGY COMPANY F

MILLSTONE POINT NUCLEAR POWER STATION UNIT 1 TER-C5506-254 l

Preparedfor l Nuclear Regulatory Commission FRC Group Leader: V. Con Washington, D.C. 20555 NRC Lead Engineer: N. Chokshi l March 7, 1986 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Govemment nor any agency thereof, or any of their employees, makes any warranty, expressed or impiled, or assumes any legal liability or i

responsibility for any third party's use, or the results of such use, of any information, appa-ratus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.

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( Prepared by: Reviewed by: Approved by:

4 M&T b ' SFC -

Prindpal Atkhor /epartment Directo'r Date: !Ob Date: 3!7,l b Date: 7!7! I*

FRANKLIN RESEARCH CENTER OtVISION OF ARVIN/CALSPAN sorn a ence steests.matAcetana.pa etics

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.TER-C5506-254 i CONTENTS e

l Section Title Page 1 INTRODUCTION . . . . . . . . . . . . . 1 1.1 Purpose of Review . . . . . . . . . . . I 1.2 Generic Issue Background . . . . . . . . . I 1.3 Plant-Specific Background . . . . . . . . . I 2 EVALUATION CRITERIA. . . . . . . . . . . . 4 l 3 TECHNICAL EVALUATION . . . . . . . . . . . 5 3.1 Evaluation of Licensee's Criteria . . . . . . . 5 i 3.2 Evaluation of Licensee's Approach to Wall Modifications . 11 i

4 CONCLUSIONS. . . . . . . . . . . . . . 14 5 REFERENCES . . . . . . . . . . . . . . 16 APPENDIX A - SGEB CRITERIA FOR SAFETY-RELATED MASCNRY WALL EVALUATION l (DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BRANCH (SGEB] OF THE NRC)

APPENDIX B - SKETCH OF WALL MODIFICATION 5

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, TER-C5506-254 FOREWORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Comission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions. The i

technical evaluation was conducted in accordance with criteria established by the NRC. '

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1. INTRODUCTION 1.1 PURPOSE OF REVIEW The purpose of this review is to provide technical evaluations of licensee responses to IE Bulletin 80-11 (1]* with respect to compliance with the Nuclear Regulatory Commission (NRC) masonry wall criteria. In addition, if a licensee has planned repair work on masonry walls, the planned methods '

and procedures are to be reviewed for acceptability.

1.2 GENERIC ISSUE BACKGROUND In the course of conducting inspections at the Trojan Nuclear Plant.

Portland General Electric Company determined that some concrete masonry walls did not have adequate structural strength. Further investigation indicated that the problem resulted from errors in engineering judgment, a lack of established procedures and procedural details, and inadequate design criteria. Because of the implication of similar deficiencies at other operating plants, the NRC issued IE Bulletin 80-11 on May 8, 1980.

IE Bulletin 80-11 required licensees to identify plant masonry walls and their intended functions. Licensees were also required to present reevaluation criteria for the masonry walls with the analyses to justify those criteria.

If modifications were proposed, licensees were to state the methodJ and schedules for the modifications.

1.3 PLANT-SPECIFIC BACKGROUND In response to IE Bulletin 80-11, Northeast Nuclear Energy Company (NNECO) provided NRC with letters plus attachments dated November 4, 1980 (2) and September 29, 1981 [3] describing the status of masonry walls at Millstone Point Nuclear Power Station Unit 1. These documents were reviewed, and a request for additional information was sent to the Licensee on September 28, 1982, to which the Licensee responded (4). The review of this response revealed several unresolved issues, so another request for additional information was sent on July 22, 1985. During a meeting on October 28-30, CNumbers in brackets indicate references, which are cited in Section 5.

s .

l TER-C5506-254 of this subject based on submittals provided by the Licensee and published literature; they have concluded that the available data in the literature do i .not give enough insight for understanding the mechanics and performance of

} unreinforced masonry walls under cyclic, fully reversed dynamic loading. The Structural and Geotechnical Engineering Branch (SGEB) had issued a position statement regarding this subject which will be addressed in the Safety Evaluation Report. The Licensee, however, has conducted a review of all its initial calculations for IE Bulletin 80-11, using the SGEB criteria and SEP loadings as the basis. It found that all 39 walls will qualify without j relying on the arching action technique. Further discussion on this subject is provided in Section 3.1.

The Licensee has modified a total of 140 walls that did not meet its reevaluation criteria. These modifications include the insertion of angles or plates at the wall edges to reinforce boundary conditions, the addition of steel members across a wall face to reduce the wall span and carry loads to the boundaries, and the addition of shielding to prevent loose blocks from striking safety-related equipment.

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2. EVALUATION CRITERIA I

, The basic documents used for guidance in this review were the criteria l developed by the Structural and Geotechnical Engineering Branch (SGEB) of the NRC (attached as Appendix A to this report), the Uniform Building Code (6),

and ACI 531-79 (7].

The materials, testing, analysis, design, construction, and inspection of safety-related concrete masonry structure should conform to the SGEB criteria.

For operating plants, the loads and load combinations for qualifying the f masonry walls should conform to the appropriate specifications in the Final Safety Analysis Report (FSAR) for the plant. Allowable stresses are specified in Reference 7 and the appropriate increase factors for abnormal and extreme environmental loads are given in the SGEB criteria (Appendix A).

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, 3. TECHNICAL EVALUATION i

This evaluation is based on the Licensee's earlier responses (2, 3] and subsequent responses (4, 5] to the NRC requests for additional information.

The Licensee's criteria were evaluated with regard to design and analysis I

methods, loads and load combinations, allowable stresses, construction specifications, materials, and any relevant test data.

3.1 EVALUATICN OF LICENSEE'S CRITERIA The Licensee evaluated the masonry walls using the following criteria:

o Loads and load combinations are based on the Final Safety Analysis Report (FSAR) requirements for Class I structures.

o Allowable stresses are consistent with the Uniform Building Code, 1979 (6] and ACI 531-79 [7].

I o All unreinforced walls were designed to be in the rigid range, i.e.,

natural frequency is at least 20 cps.

( o The working stress method of analysis is used; initially, arching action was used for 39 walls. However, these walls were reanaly:ed using the working stress method, t

i o A typical analytical procedure used in the working stress design method is summarized below.

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- determine wall boundary conditions

- calculate the natural frequency using either a one-way or two-way 1

action assumption j - obtain inertial loading from the floor acceleration calculated in the original design, multiplied by an amplification factor of 5 for

, reinforced walls and 1.3 for unreinforced walls

- compare computed stresses with allowable values, f The Licensee's criteria and responses (2, 3, 4, 5] have been reviewed.

With the exception of those areas identified in Section 4, the Licensee's r criteria have been found to be adequate and in compliance with the SGEB criteria (Appendix A),

Following is a review of the Licensee's responses (4, 5] to the NRC's September 28, 1982 and July 22, 1985 requests for additional information.

Questions and responses covering the same topic have been combined in the review that follows.

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Question 1 Indicate whether walls are stacked or running bond. If any stack bond

, wall exists, provide sample calculations of the stresses for a typical wall.

l Response 1 t

The Licensee responded that all walls were laid in a running bond.

Question 2 t

Explain and justify the difference (if any) between the load combinations provided in the plant FSAR and the load combinations used in the reevaluation of the masonry walls.

Response 2 In this response, the Licensee indicated that the final reevaluation of masonry walls considered all loads and load combinations outlined in the Millstone Unit 1 FSAR for Class I structures. Discussion on the SEP loadings is given in Response 7.

j This response is satisfactory and is consistent with the SGEB criteria.

t Question 3 Indicate how earthquake forces in three directions were considered in the analysis.

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Response 3 i

The Licensee responded that the stresses caused by the vertical seismic

, load were combined absolutely with the stresses caused by the horizontal

{ seismic load acting in the most severe direction. The most severe horizontal t

direction is normal to the wall face because none of the walls are shear walls and the in-plane seismic effects are insignificant in walls that do not carry building shear loads.

The Licensee's method is adequate and satisfactory.

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, Question 4a i

I Justify the use of an increase factor of 1.5 for allowable masonry 4

tension normal to the bed joint (Exhibit C-1. Reference 4).

k Response 4a i

The Licensee .3tated that unreinforced masonry walls were modeled as one-way horizontal spans. This means that the increase factor for allowable tension normal to the bed joint is not applicable because the allowable masonry tension normal to the bed joint in a one-way horizontal span is zero.

This increase factor was used only for tension parallel to bed joint, which is consistent with the SGEB criteria.

Question 4b i

Exhibit C-2 in attachment 6 of Reference 4 indicated that an increase factor of 1.5 for allowable masonry shear stress was used for reinforced walls.

If a basic allowable of 1.5 6 was used (as suggested by Exhibit C-2 [4)) and an increase factor 1.5 was applied to it, that would be

"~{

equivalent to applying an increase factor of about 2 to the basic '

allowables found in ACI 531-79, which is 1.1 6 m. The SGEB criteria j

(Appendix A), however, allow an increase factor of only 1.3 for masonry shear.

4 l' Indicate whether the maximum shear stress in the reinforced walls still meets the SGEB criteria, which is based on ACI 531-79. If any 2 walls would not qualify, provide the percentages by which the SGEB

, allowables are exceeded.

, Response 4b

i Regarding masonry shear, the Licensee responded that flexural shear stress is insignificant compared to flexural tensile stress. However, the ,

i shear at the wall boundaries was still checked using an allowable of 1.5 6 and an increase factor of 1.5. The Licensee has since conducted a complete review of its initial IE Bulletin 80-11 calculations for reinforced and unreinforced walls, considering the SGEB criteria and the SEp loadings. The I

results indicated a maximum boundary shear for unreinforced walls of 17.1 psi (due to tornado pressure), which is about 48% of the SGEB allowable of 35.9 psi. For reinforced walls, the maximum shear was 31.4 psi, which is about 60%

!L of the SGEB allowable of 52.5 psi. With respect to shear, therefore, all

}, walls which met the Licensee's original evaluation criteria would also meet the SGEB criteria.

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7 TER-C5506-254 This. response is satisfactory and is consistent with the SGEB criteria.

Question 5 l Provide sample calculations for block pullout of attachments analysis and tornado analysis.

Response 5 The Licensee responded that masonry walls at Millstone Unit 1 do not support any equipment of significant weight, so the block pullout capacity is not an important consideration. Nevertheless, Se Licensee provided sample calculations for block pullout capacities. Pullout. capacities range from 1604 lb for 4-in-thick walls to 4606 lb for 12-in-thick walls. These capacities, according to the Licensee, are well in excess of the loads due to the attacnments found on these walls.

I I This response is satisfactory.

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, Question 6 Regulatory Guide 1.61 allows 4% damping for operating basis earthquake j (OBE) and 7% damping for safe shutdown earthquake (SSE). Provide the damping values used in the analysis and justify them if they are higher than those allowed by Regulatory Guide 1.61.

Response 6 In this response, the Licensee indicated that damping factors were not r

used in the initial seismic analysis of masonry walls under IE Bulletin 80-11.

All unreinforced walls were designed to be rigid, i.e., the minimum allowable natural frequency is 20 cps. The floor acceleration calculated in the original design and amplified by a factor of 1.3 was used to determine the inertial load for unreinforced walls. Reinforced walls were not designed to

, be rigid. Their inertial load was determined by applying an amplification factor of 5 to the floor acceleration calculated in the original design.

The Licensee has since conducted a complete review of its initial IE Bulletin 80-11 calculations for reinforced and unreinforced walls. This review used the SEP loadings to assess the integrity of each wall relative to the SGEB criteria. The seismic acceleration for each wall was based on the I

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TER-C5506-254 l

c SEP floor response spectra at 7% damping. See Response 7 for the results of the comparison of wall stresses with SGEB allowables.

l Question 7

, Since Millstone Unit 1 is a part of the systematic evaluation program i

' (SEP), the Licensee is requested to clarify whether SEP loadings for seismic analysis have been used. If not, provide justification.

Response 7 As stated in Response 6, the initial seismic analysis of masonry walls under IE Bulletin 80-11 was based on the floor accelerations that were calculated in the original plant design. The Licensee has since conducted a

, complete review of its initial IE Bulletin 80-11 calculations. This review used the SEP loadings to assess the integrity of each wall relative to the SGEB criteria. As a result of this review, wall T-18 is the only masonry wall that does not meet the SGEB allowable stresses when the SEP response spectra are considered. The tensile stress for this wall under seismic loads was found to be acceptable at 15.8 psi when compared with an allowable of 63.6 psi (based on ACI 531-79); but under tornado pressure the tensile stress was 80 psi. Consequently, a detailed analysis was performed on this wall (this wall

, was already modified), and it showed that the addition of the structural steel j modifications assured the wall's overall stability even though there remained localized overstressing. This is the only wall in which the calculated stress f exceeded the SGEB allowable by 26%; with the addition of the structural steel modifications, the percentage of exceedance will be smaller. Therefore, wall T-18 was considered acceptable and no further modifications were required.

This response is adequate and satisfactory.

Question 8 r

j Identify the 24 walls that have been qualified by arching action. The NRC position on this issue states that the use of the arching action theory to qualify unreinforced masonry walls is not acceptable. These

(' walls should be repaired so that they can be qualified based on the SGEB criteria.

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• i TER-C5506-254 Response 8 The Licensee provided clarification that arching action was used to i qualify 39 safety-related blockouts in its initial response to IE Bulletin i 80-11. The Licensee has since performed a complete review of its initial IE Bulletin 80-11 calculations. This review used the SEP loadings to assess the I

l integrity of each wall relative to the SGEB criteria. All of the 39 walls initially qualified by arching analysis were solid multi-wythe walls. In the Licensee's review, multi-wythe walls were assumed to act compositely if the collar joint shear was low.

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The results of the reanalysis indicate a maximum l tensile stress of 19.9 psi, which is acceptable when compared with the SGEB allowable of 63.6 psi. Although, the maximum collar joint shear, 4 psi, was l_

low, an additional analysis was performed without taking advantage of qI composite action, and the results indicate a maximum tensile stress of $2.2

, psi compared with an allowable of 63.6 psi. 'It was concluded that 39 walls initially qualified by arching analysis have adequate reserve strength to qualify under the SGEB criteria without relying on arching or composite action.

This response satisfies the SGEB criteria.

i Question 9 Provide a description of the required modifications and explain by sample I calculation how they rectify wall deficiencies. In addition, provide detailed drawings of some sar.ple modifications.

f Response 9

, In this response, the Licensee indicated that 140 walls required

,l_ modification under the initial IE Bulletin 80-11 evaluation. The following is a list ot' the types of wall modifications found at Millstone Unit 1.

,f o The insertion of angles or plates at the wall edges to assure pinned

! boundary conditions.

o The insertion of steel members across a wall face to reduce wall spans.

' o Shielding so that falling blocks would not hit safety-related equipment.

'f o Rerouting of pipes.

, o Relocation of pipe supports.

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i TER-C5506-254 h

e An example of a modification that decreases the unsupported vertical span of a wall by adding angles hori=ontally across the wall face is illustrated in .

f Appendix B.

I This response is adequate.

Question 10 Indicate whether any walls at the Millstone Unit I were built without mortar. If so, the walls must be modified so that loose blocks do not impact safety-related equipment. Provide some sample sketches or drawings of this type of modification if applicable to this plant.

Response 10

, There were no safety-related walls built without mortar at the Millstone

, Unit 1 plant.

Question 11 Identify whether any QA/QC records are available to ensure conformance of masonry construction to design drawings and specifications.

Response 11

! The Licensee indicated that the construction engineers were responsible for inspecting workmanship and monitoring the sequence of construction of masonry walls at the Millstone Unit 1 plant. The inspection was controlled by the original drawings and specifications. As part of the reevaluation effort, l

, t field engineers surveying the masonry walls found no deviations between the as-built conditions and the original specifications. Consequently, it was

(

i concluded that the construction practices were consistent with the provisions of the special inspection category of ACI 531-79. In addition, tests performed cn block samples according to the requirements of ASTM C-140 indicated that the blocks had higher compressive strengths than the values i

used in the analyses. The tested compressive strengths were 1625 psi on gross

, area for hollow units and 4101 psi for solid units. The maximum f'm used in the s.nalyses was 1350 psi. The values of f'm used in the analysis are in

, accordance with the ACI 531-79 specified values. Therefore, the use of the i stress allowables of the special inspection category of ACI 531-79 is considered justified.

i .

7 TER-C5506-254 f This response is satisfactory and consistent with the SGEB criteria.

l Question 12 i

Provide a survey of masonry walls at Millstone Unit 1 plant to identify any signs of cracking.

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Response 12 In this response, the Licensee stated that a walkdown was conducted to survey almost all walls included in the IE 80-11 Bulletin except a small l number of walls which were inaccessible due to high radiation levels. The walkdown revealed no indications of cracking or other signs of distress.

Subsequent to the walkdown, a total of 33 walls were randomly selected for review of their original design drawings and analysis. This review showed 20 walls that were noted as having some form of cracking prior to modifications.

Most cracking was along the boundaries. A resurvey of these 20 walls was performed, and the resultt showed that in all cases, modifications were installed to eliminate any adverse effects on the walls' structural integrity.

These modifications included installation of plates or angles along the

boundary.

i The Licensee's response is reasonably adequate and has resolved concerns associated with wall cracks.

3.2 EVALUATION OF LICENSEE'S APPROACH TO WALL MODIFICATIONS The Licensee has found it necessary to modify 140 masonry walls at

{i Millstone Unit 1. These modifications include the addition of angles or plates at wall edges to reinforce boundary condition, the insertion of steel i

members across a wall face to reduce the wall span, and the addition of I shielding to prevent falling blocks from striking equipment. In Reference 4,

, the Licensee provided sample calculations of the modification of a wall due to tornado effects. This modification basically consists of a series of I

horizontal angles, bolted at one leg to the wall face and welded at the other l leg to existing building' steel (see Appendix B). The effect is to reduce the unsupported vertical span of this wall. Reference 4 also gives an example of a modification that provides shear restraint at the boundaries. In this design, a continuous vertical plate is bolted to an existing concrete wall so that,part of the plate overlaps the vertical edge of the masonry wall.

s. .

. TER-C5506-254 Other actions taken to rectify wall deficiencies at this plant include

-l the rerouting of pipes and the relocation of pipe supports.

, The Licensee's approach to wall modifications has been reviewed and found to be adequate.

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TER-C5506-254 i

4. CONCLUSIONS l

A detailed study was performed to provide a technical evaluation of the j masonry walls at the Millstone Point Nuclear Power Station Unit 1. Review of the Licensee's criteria and additional information provided by the Licensee led to the conclusions given below.

The Licensee's criteria have been found technically adequate and in compliance with the SGEB criteria except for the following areas:

o, The Licensee used an increase factor of 1.5 for allowable masonry l

shear and tension normal to the bed joint, whereas the SGEB criteria allow an increase factor of only 1.3. For unreinforced walls, the Licensee stated in Response 4 (4) that the walls were analyzed using one-way horizontal spans governed by tension parallel to the bed j

joint. Therefore, the increase factor for tension normal to the bed joint was not used. Regarding shear stress, the Licensee initially used an out-of-plane shear allowable for 1.56 in contrast to the f shear allowable of 1.lyf*m given in ACI 531-79. When an increase factor of 1.5 is applied to the Licensee's allowable for extreme loads, that is equivalent to applying an increase factor of about 2 to the basic allowable in ACI 531-79 (further exceeding the SGEB factor of 1.3). However, the Licensee has since conducted a complete review of its initial IE Bulletin 80-11 calculations for reinforced

, and unreinforced walls. This review used the SEP loadings to assess

the integrity of each wall relative to the SGEB criteria. The

, results (see Response 4b) indicated that all actual shear stresses

, are within the SGEB limits. It is concluded, therefore, that all i masonry walls that qualified with respect to shear stress under the Licensee's initial evaluation criteria would also qualify under the SGEB criteria.

! o The Licensee relied on arching theory to qualify 39 safety-related walls in its initial response to IE Bulletin 60-11. The NRC does not t

accept the use of arching action to qualify masonry walls (this position will be addressed in the NRC's Safety Evaluation Report).

However, the Licensee has since performed a review of its initial IE Bulletin 80-11 calculations. The review used the SEP loadings to assess the integrity of each wall relative to the SGEB criteria. The results (see Response 8) indicated that all 39 walls have adequate

' reserve capacity to qualify under the SGEB criteria without relying on arching action. It is therefore concluded that the Licensee's initial evaluation of these walls under IE Bulletin 80-11 would not be adversely affected by precluding the arching action technique.

k o In its initial seismic analysis for IE Bulletin 80-11, the Licensee did not use the floor response spectra generated by the SEP program.

i Instead, the inertial loads for unreinforced walls, which were designed to be rigid, were based on the floor accelerations TER-C5506-254 calculated in the original plant design. The inertial loads for reinforced walls, which were not intended to be rigid, were based on i

the original floor acclerations multiplied by an amplification factor -

of 5.

f The Licensee has since conducted a review of all its initial IE Bulletin 80-11 calculations. The review used the SEP loadings to

} assess the integrity of each wall relative to the SGEB criteria.

According to the results (see Response 7), only one wall, T-18, does not meet the SGEB allowable (tornado prassure tensile stress) when the SEP loadings are applied. However, a detailed analysis was subsequently performed on this wall, and it showed that the addition of the structural steel modifications assured the overall stability

{ of the wall even though localized overstressing remained. This is the only wall in which the calculated stress exceeded the SGEB allowable by 26% with the addition of the structural steel modifica-( ' tions, the percentage of exceedance will be smaller. It is concluded i

that all walls that were acceptable using the Licensee's loading criteria are also acceptable using the SEP loading criteria.

With regard to the modification methods, Section 3.2 indicated that the modifications include the addition of angles or plates at wall edges to i reinforce boundary conditions, the insertion of steel members across a wall face to reduce the wall span, and the addition of shielding to prevent falling

(

{ blocks from striking equipment. Appendix B provides an example of modifications. The modification methods have been reviewed and judged to be adequate and satisfactory.

f TER-C5506-254 1

5. REFERENCES I \

i l

1. IE Bulletin 80-11 l Masonry Wall Design

• NRC, May 8, 1981

2. W. G. Counsi1

, Letter to B. H. Grier, NRC.

Subject:

Millstone Nuclear Power Station.

Unit 1 - IE Bulletin 80-11, Masonry Wall Design Northeast Utilities, November 4,1980 ,

A01021

3. W. G. Counsil Letter to R. C. Haynes, NRC.

Subject:

Millstone Nuclear Power Station, Unit 1 - IE Bulletin 80-11, Masonry Wall Design Northeast Utilities, September 29, 1981 B10313

4. W. G. Council Letter with Enclosures to R. A. Clark, NRC.

Subject:

Request for

( Additional Information on IE Bulletin 80-11, Masonry Wall Design

( Northeast Utilities, December 3, 1982 Enclosure II

5. J. F. Opeka l

Letter with attachment to C. I. Grimes, NRC.

Subject:

Request for Additional Information on IE Bulletin 80-11, Masonry Wall Design l Northeast Utilities, December 31, 1985

6. Uniform Building Code International Conference of Building Officials, 1979

7. Building Code Requirements for Concrete Masonry Structures

, . Detroit: American Concrete Institute, 1979 ACI 531-73 and ACI 531-R-79 l

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APPENDIX A ,

d SGEB CRITERI A FOR SAFETY-RELATED MASONRY WALL EVALUATION 1

(DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BRANCH

[SCEB) OF THE NRC) l I

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l FRANKUN RESEARCH CENTER DMSION OF ARVIN/CALSPAN 20th & RACE STREETS.PHilAOfLPHIA,PA 19103

1 g e CONTENTS

Section Title Page

.g i GENERAL REQUIREMENTS . . . . . . . . . . . A-1 2 LOADS AND LOAD COMBINATIONS. '

. . . . . . . . . A-1 f a. Service Load Combinations . . . . . . . . . A-1 ,

b. Extreme Environmental, Abnormal, Abnormal / Severe

Environmental, and Abnormal / Extreme Environmental

, Conditions . . . . . . . . . . . . . A-2 r 3 ALLOWABLE STRESSES . . . . . . . . . . . . A-2 4 DESIGN AND ANALYSIS CONSIDERATIONS . . . . . . . . A-3 5 REFERENCES . . . . . . . . . . . . . . A-4 i

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1. General Requirements The materials, testing, analysis, design, construction, and inspection related to the design and construction of safety-related concrete masonry ,

walls should conform to the applicable requirements contained in Uniform j Building Code - 1979, unless specified otherwise, by the provisions in

, this criteri.e.

g The use of other standards or codes, such as ACI-531, ATC-3, or NCMA, is l

also acceptable. However, when the provisions of these codes are less conservative than the corresponding provisions of the criteria, their use should be justified on a case-by-case basis.

In new construction, no unreinforced masonry walls will be permitted. For operating plants, existing unreinforced walls will be evaluated by.the r

provisions of these criteria. Plants which are applying for an operating r license and which have already built unreinforced masonry walls will be evaluated on a case-by-case basis.

i 2. Loads and Load Combinations The loads and load combinations shall include consideration of normal loads, severe environmental loads, extreme environmental loads, and abnormal loads. Specifically, for operating plants, the load combinations provided in the plant's FSAR shall govern. For cperating license j . applications, the following load combinations shall apply (for definition

( of load terms, see SRP Section 3.8.4II-3) .

(a) Service Load Conditions j

i (1) D+L f (2) D + L + E (3) D+L+W

) If thermal stresses due to To and Ro are present, they should be included in the above combinations as follows:

(la) D+L+To + Ro (2a) D+L+To+Ro+E (3a) D+L+To+Ro+W Check load combination for controlling condition for maximum 'L' and for no 'L'.

A-1 1

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(b) Extreme Environmental, Abnormal, Abnormal / Severe Environmental, and Abnormal / Extreme Environmental Conditions (4 ) D + L + To + Ro+E i (5) D+L+To+Ro*Wt (6) D+L+Ta+Ra + 1.5 P a (7) D+L+Ta+Ra + 1.25 Pa + 1.0 (Yr + Yj + Ym) + 1.25 E (8) D+L+Ta+Ra + 1.0 Pa + 1.0 (Yr + Yj + Ym) + 1.0 E' i In combinations (6) , (7) , and (8) the maximum values of Pa, Tae Ra

• Yje Yr , and Ym, including an appropriate dynamic load 7 factor, should be used unless a time-history analysis is performed to justify otherwise. Combinations (5), (7) , and (8) and the corresponding structural acceptance criteria should be satisfied first without the tornado missile load in (5) and without Yr* Yje and Ya in (7) and (8) . When considering these loads, local section strength capacities may be exceeded under these concentrated loads, provided there will be no loss of function of any safety-related system.

Both cases of L having its full value or being completely absent g should be checked.

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3. Allowable Stresses

Allowable stresses provided in ACI-531-79, as supplemented by the ,

I following modifications / exceptions, sha1.1 apply.

i (a) when wind or seismic loads (Ots) are considered in the loading combinations, no increase ir. the allowable stresses is permitted.

(b) Use of allowable stresses corresponding to special inspection category shall be substantiated by demonstration of compliance with the inspection requirements of the SEB criteria.

(c) When tension perpendicular to bed joints is used in qualifying the unreinforced masonry walls, the allowable value will be justified by test program or other means pertinent to the plant and loading conditions. For reinforced masonry walls, all the tensile stresses

.[ will be resisted by reinforcement.

(d) For load conditions which represent extreme environmental, abnormal, abnormal / severe environmental, and abnormal / extreme environmental conditions, the allowable working stress may be multiplied by the factors shown in the following tablet A-2

4 o

Type of Stress Factor Axial or Flexural Compression 2.5 Bearing 2.5 i

Reinforcement stress except shear 2.0 but not to exceed 0.9 fy Shear reinforcement and/or bolts 1.5 Masonry tension parallel to bed joint 1.5 Shear carried by masonry 1.3 Masonry tension perpendi:ular to bed ; !.r.t for reinforced masonry 0 for unreinforced masonry 2 1,3 Notes i- (1) When anchor bolts are used, design should prevent facial spalling of masonry unit.

I 4

(2) See 3(c).

4. Design and Analysis Considerations I (a) The analysis should follow established principles of engineering mechanics and take into account sound engineering practices.

(b) Assumptions and modeling techniques used shall give proper considerations to boundary conditions, cracking of sections, if any, and the dynamic behavior of masonry walls.

(c) Damping values to be used for dynamic analysis shall be those *or reinforced concrete given in Regulatory Guide 1.61.

(d) In general, for operating plants, the seismic analysis and Category I structural requirements of FSAR shall apply. For other plants, corresponding SRP requirements shall apply. The seismic analysis shall account for the variations and uncertainties in mass, materials, and other pertinent parameters used.

(e) The analysis should consider both in-plane and out-of-plane loads.

(f) Interstory drift effects should be considered.

A-3

- e (g)

In new construction, grout in concrete masonry walls, whenever used, shall be compacted by vibration.

(h) For masonry shear walls, the minimum reinforcement requirements of ACI-531 shall apply.

(i) Special constructions (e.g. , multiwythe, composite) or other items not covered by the code shall be reviewed on a case-by-case basis for their acceptance.

($) , Licensees or applicants shall submit QA/QC information, if available, for staff's review.

In the event QA/QC information is not available, a field survey and a test program reviewed and approved by the staff shall be implemented to ascertain the conformance of mar.onry construction to design drawings and specifications (e.g., rebar and grouting).

(k)

For masonry walls requiring protection from spalling and scabbing due to accident pipe reaction (Yr), jet impingement (Y ) , and missile 3

impact (Ym), the requirements similar to those of SRP 3.5.3 shall apply. However, actual review will be conducted on a case-by-case basis.

5. References

{

l (a) Uniform Building Code - 1979 Edition.

(b) Building Code Requirements for Concrete Masonry Structures ACI-531-79 and Commentary ACI-531R-79.

(c) Tentative Provisions for the Development of Seismic Regulations for

{ Buildings - Applied Technology Council ATC 3-06.

(d) Specification for the Design and Construction of Load-Dearing Concrete Masonry - NCMA August, 1979.

(e) Trojan Nuclear Plant Concrete Masonry Design Criteria Safety Evaluation Report Supplement - November, 1980.

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i APPENDIX B 4

SKETCH OF WALL MODIFICATION l

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I I FRANKUN RESEARCH CENTER DMSION OF ARVIN/CALSPAN 20th & NACE STREETS, PHILADELPHI A.PA 19103 l

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