ML20106A679
| ML20106A679 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 09/12/1984 |
| From: | Triolo S FRANKLIN INSTITUTE |
| To: | Nilesh Chokshi NRC |
| Shared Package | |
| ML20099D899 | List: |
| References | |
| CON-NRC-03-81-130, CON-NRC-3-81-130 TER-C5506-233, NUDOCS 8410120129 | |
| Download: ML20106A679 (35) | |
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Aedmed i TECHNICAL EVALUATION REPORT MASONRY WALL DESIGN PHILADELPHIA ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION UNITS 2 AND 3 NRC DOCKET NO. 50-277, 50-278 FRC PROJECT C5506 NRC TAC NO.
FRC ASSIGNMENT 6 NRC CONTRACT NO. NRCM-81 130 FRC TASK 233 Preparedby Franklin Research Center Author:
S. Triolo, 7. N. Con 20th and Race Street Philadelphia, PA 19103 FRC Group Leader:
V. N. Con Preparedfor Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer: N. C. Chokshi September 12, 1984 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal flability.or responsibility for any third party's use. or the results of such use, of any infor. nation, 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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TECHNICAL EVALUATION REPORT MASONRY WALL DESIGN PHILADELPHIA ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION UNITS 2 AND 3 NRC DOCKET NO. 50-277, 50-278 FRC PROJECT C5506 NRC TAC NO.
FRC ASSIGNMENT 6 NRC CONTRACT NO. NRC-03-81 130 FRC TASK 233 Preparedby Franklin Research Center Aut"or:
S. Triolo, V. N. Con 20th and Race Street Philaddphia, PA 19103 FRC Group Leader:
V. N. Con Prepared for Nuclear Regulatory Comrnission Washington, D.C. 20555 Lead NRC Engineer:
N. C. Chokshi September 12, 1984 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees. makes any warranty, expressed or implied, or assumes any legal liability or 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.
Prepared by:
Reviewed by:
Approved by:
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TER-C5506-233 CONTENTS Section Title Page 1
~ INTRODUCTION 1
t 1.1 Purpose of Review.
1 1.2 Generic Issue Background 1
1.3 Plant-Specific Background..
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2 EVALUATION CRITERIA.
3 TECHNICAL EVALUATION 6
3.'l Evaluation of Licensee's Criteria.
6 3.2 Evaluation of Licensee's Approach to Wall Modifications.
16 4
. CONCLUSIONS.
17 5
REFERENCES.
18 APPENDIX A - SGEB CRITERIA FOR SAFETY-RELATED MASONRY WALL EVALUATION (DEVELOPED BY THE STRUCTURAL AND GEDTECHNICAL ENGINEERING BRANCH [SGEB] OF THE NRC)
APPENDIX B - SKETCHES OF WALL MODIFICATIONS 1
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TER-C5506-233 FORENORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Couniission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical cassistance in support of NRC operating reactor licensing actions. The 2
technical evaluation was conducted in accordance with criteria established by the NBC.
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INTRODUCTION
' l.1 PURPOSE OF BEVIEW l
The purpose of this review is to provide technical evaluations of the
- i licensee responses to IE Bulletin 80-11 (1]* with respect to compliance with the Nuclear Regulatory Consission (NBC) masonry wall criteria.
In addition, if a licensee plans repair work on masonry walls, the planned methods, procedures, and repair schedules are reviewed for' acceptability.
3 1.2 GENERIC ISSUE BACEGROUND 1
4 In the course of conducting inspections at the Trojan Nuclear Plant, Portland " eneral Electric Company determined that some concrete, masonry walls
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G 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
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operating plants, the NBC issued IE Bulletin 80-ll'on May 8,1980.
1 IE Bulletin 80-11 required licensees to identify plant masonry walls and l
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.
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1.3 PLANT-SPECIFIC BACKGROUND In response to IE Bulletin 80-11, Philadelphia Electric Company provided the NRC with documents describing the status of masonry walls at Peach Bottom 4
Station Units 2 and 3 (2, 3, 4(). These documents were reviewed, and a 1
request for additional information was sent to the Licensee on March 10, 1982. The Licensee responded to this request on May 26, 1982 [9].
Additional t
- Numbers in brackets indicate references, which are cited in Section 5.
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TER-C5506-233 questions were sent on February 7, 1984 (10], to which the Licensee has also responded [11].
A total of 86 walls have been identified as safety-related. All of them are reinforced. The functions of the masonry walls at Peach Botton Units 2 and 3 and the number of walls in each category are indicated in Reference 2 as follows:
I Shielding 35 walls i
Partition 2 walls Fire resistance 49 walls s
Total 86 walls These walls are located in the radwaste building, turbine building, reactor building, emergency cooling tower, and circulating water pump structure.
Priorities for wall reevaluation were determined based on the following factors (2):
a.
the number of safety-related systems on the walls or in their i
proximity i
b.
the weight of the loadings to which.the walls are subject J
c.
the criticality of the walls in terms of height, length, and thickness.
Concrete masonry walls are not used as shear walls at Peach Bottom Atomic j
Power Station. Wall thickness range from 8 in to 48 in.
Vertical l
reinforcements have been placed in single wythe walls and in the exterior wythes of multiple wythe walls.
In shield walls, all cells are grouted, whereas in partition and fire walls, only the cells containing reinforcement are grouted. Horizontal reinforcements and bond beams are provided at intervals. At the base of the walls, restraint is provided by steel angles bolted to the floor or by expansion bolts projecting into the block cells at 1
the same spacing as the vertical reinforcing.
In addition, where required,
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horizontal restraints are provided at the sides and tops of the walls. There are four safety-related walls that required modification. Modifications 1
typically consist of improvements to the restraints at the top of walls.
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The materials used in the construction of the masonry walls were
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specified as follows:
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o Concrete block ASTM Specification C90-66, Grade U-l o Mortar ASTM Specification C-270,-type N, minimum compressive strength 750 psi at 28 days 4
. o Grout (concrete)
Minimum compressive strength 2000 psi
.at 28 days e
o Reinforcing steel ASTM Specification A-615, Grades 40 and 60 a.
vertical reinforcing Deformed bars from 64 to 48, spaced l
at 24 in tc 32 in.
b.
horizontal reinforcing Bond beam reinforcing with 64 or 95 deformed bars spaced at 40 in (2 or 4 bars per beam). Also, ladder-type reinforcing is placed in horizontal joints, spaced at 16 in.
o Masonry ties In multiple wythe walls, #10 gage.
ties placed at a spacing of 48 in
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prisontallyandvertically.
Adequate inspection was performed during construction. Documentation of 4
j the tests and inspection is maintained in the project file. Test of materials conducted during construction confirmed that the values used for concrete l
block, mortar, grout, and rebar were conservative (31 The Licensee has relied upon the energy balance technique to qualify some masonry walls.
NRC, FRC, and FRC's cor}sultants (Drs. H. Harris and A. Hamid of Drexel University) have conducted an exhaustive review of this subject based on submittals provided by the Licensee and published literature and have I
l concluded that the available data in the literature do not give enough insight for understanding the. mechanics and performance of reinforced masonry walls under cyclic, fully reversed dynamic loading. As a result, a meeting with representatives of the affected plants was held at the NRC on November 3, 1982 so that the NRC and FRC's staff and consultants could explain why the applicability of the energy balance technique to masonry walls in nuclear power plants is questionable [12).
In a subsequent meeting, consultants of I
utility companies presented their rebuttals [13] and requested that they be treated on a plant-by-plant basis.
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TER-C5506-233 In accordance with the above request, NRC, FRC, and consultants visited several nucl ear power plants to examine the field conditions of masonry walls in the plant and to gain first-hand knowledge of how the energy balance technique is applied to actual walls. Further discussion on this subject is provided in Section 3.1.
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TER-C5506-233 2.
EVALUATION CRITERIA The basic documents used for guidance in this review were the criteria developed by the Structural and Geotechnical Engineering Branch (SGEB) of the NRC (attached as Appendix A to this report), the Uniform Suilding Code (6],
and ACI 531-79 (7].
In materials, testing, analysis, design, construction, and inspection of safety-related concrete masonry structures should conform to the SGEB criteria. For operating plants, the Iraads and load combina? ions for qualifying the 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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TECHNICAL EVALUATION s
This evaluation is based on the Licensee's earlier responses [2, 3, 4]
t-and subsequent responses (9, 11] to the request for additional information.
The Licensee's criteria (4, 9] were evaluated with regard to design and analysis methods, loads and load cimasinations, allowable stresses, construction specifications, and materials. The' Licensee's response to the
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request for additional information was also reviewed.
4 3.1 EVALUATION OF LICENSEE'S CRITERIA o The design allowables are based on ACI 531-79 [7], and the stresses are also checked against Uniform Building Code 1967.
o The load combinations considered are based on the project FSAR.
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o Proper construction practices were conclucted in building the walls.
Appropriate tests were also performed to verify the strength 2
requirements of the walls. Test results indicated that the values used for concrete block, mortar, grout, and rebar were conservative (3].
o The following damping values are used:
a.
for uncracked sections, 24 for both OBE and safe shutdown earthquake (SSR) b.
for cracked sections, 44 for OBE and 7% for SSE.
o Collar joint tension and shear strengths have been conservatively assumed to be zero.
I o Joint reinforcement is not relied upon to resist tension.
o The typical analytical procedure is summarized below:
determine wall boundary conditions calculate the wall's natural frequency assuming either one-way or
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two-way action j
obtain inertial loading from the floor response spectra compare computed stresses with the allowable values in ACI 531-79 l
[7] and the Uniform Building Code 1967.
3 o Both working stress and energy balance techniques were used in the j
analysis. Of 86 total walls, 5 were qualified by the energy balance l
technique.
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a TER-C5506-233 Other than those areas identified in Section 4, the Licensee's criteria have been reviewed and found to be technically adequate and in compliance with the SGER criteria. The review of the Licensee's responses to the requests for additional information follows.
Question 1 With reference to Section 3, Appendix I, part 1 (4], justify the basis for load combinations 7, 8, and 9 which contain dead load (D), jet impingement (P), pressurization load due to line break (P'), and accident temperature load (Ta): 7) 1.05D + 1.25P, 8) 1.05D + 1.0P', 9) 1.0 5D +
1.0 Ta.
Response 1 (Reference 91 5
The load combination 8 (FSAR) considers the combined effect of dead load (D), jet impingement (P), and pressurization (P') due a to high energy line break (HELB). The Licensee stated that one term (1.0P) was inadvertently omitted and the report was revised to reflect the load combination (1.05D +
1.0P' + 1.0P).
The load combination 7 (1.05D + 1.25P) recognizes the impulsive nature of jet impingement load by using a dynamic load factor of 25%. Since the peak pressure in a compartment due to a HELB does not occur at the instant of this impact, the pressurization load is not included in this combination.
The load combination 9 (1.05D + 1.0Ta) considers the accidental temperature stresses. The thermal effects are relatively long term and, by the time the final temperature gradients are established across the wall thickness, the jet impingement and pressurization effects become negligible, and thus are not combined directly.
The Licensee's response is considered adequate and consistent with the SGEB criteria.
Question 2 With reference to Table 1, Appendix I, part 1 (4], justify the increase factors of 1.67 applied to allowable stresses in shear, bond, tension
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5 TER-C5506-233 normal to the bed joint, and tension parallel to the bed joint. The SES Criteria (5] allow increase factors of only 1.5 for tension parallel to the bed joint and shear in the reinforcement and 1.3 for tension normal to the bed joint and masonry shear.
Response 2 (Reference 9]
The Licensee stated that the reevaluation of block walls has been based on steel tension reinforcement resisting all tension normal and parallel to the bed joint, and that the increase factor of 1.67 was not used for tension, shear, or bond.
The Licensee's response is considered adequate and satisfies the SGER criteria.
Question 3 with reference to section 5.2.4, Appendix I, part 1 (4], justify the increase factor of 1.67 proposed for allowable in-plane strains.
Response 3 (Reference 9]
The Licensee stated that the allowable strain foe a confined wall was based on the equivalent compression strut model with a factor of safety of 3.0 against crushing.
The increase factor of 1.67 has been used for abnormal and/or extreme environcent conditions, which are credible but highly improbable. The effect is to reduce the factor of safety against crushing from 3.0 to 1.8, which is considered sufficient for such conditions.
It has been found in other plants that this increase factor is judged to be reasonable based on various test programs performed at the Earthquake Engineering Research Center, University of California, Berkeley. The response is adequate and satisfactory.
Question 4 In Section 5.4, Appendix I (4), two approaches are given for determining the modulus of ruptures the first used 6 f'e or 0.8 times modulus of rupture as determined by test; the second used 2.4 times the code-allowsble flexural tensile stress. Justify these two approaches.
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TER-C5506-233 Response 4 (Reference 91 The Licensee stated that, in the first method, a 204 variation in modulus of rupture was assumed and a lower bound modulus of rupture was obtained by applying a reduction, factor of 0.80 to the ACI Code Value of 7.5 The Licensee stated that the second approach, given in Section 5.4, was not used in the masonry wall reevaluation. It this approach, the modulus of
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rupture is obtained by applying a factor of safety of 3 to the code allowable flemural tensile stress, and then reducing it by 204 to arrive at a lower
.i bound value.
The Licensee's response is satisfactory and consistent with the SGEE criteria.
Question 5 Justify the use of alternative acceptance criteria of Section 6.0, 3
Appendix 1, part 1, since it is the NBC's position that energy balance 1
techniques and the arching theory should not be used in the absence of conclusive evidence of their applicability to masonry structures in i
nuclear power plants.
Response 5 (Reference 91 The Licensee gave a theoretical justification for the energy balance technique and used it to qualify five walls with an alternative acceptance
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criteria (see Response 13). According to Reference 9, the following walls were qualified by the energy balance technique 68.2, 68.3, 532.1, 532.2, and 532.3.
NRC staff, FRC, and FRC's consultants have conducted an exhaustive review of available information on this subject and of licensees' responses to determine the technical adequacy of the methodology. FRC and its consultants have issued their evaluation and assessment of the use of the energy balance technique for masonry walls (121. The Structural and Geotechnical Engineering Branch (SCEB) has issued a position statement regarding this subject which will be addressed in its Safety Evaluation Report.
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TER-C5506-233 Question 6 with reference to section 7.1.2, Appendix I, part 1 [41, provide sample calculations to indicate how the effects of higher modes of vibration are accounted for.
Response 6 (Reference 91 The Licensee showed analytically that the contribution of higher modes to the seismic response of the masonry walls is ses11 relative to the fundamental mode, and can be neglected in the evaluation of wall deflections, moments, shears, etc.
The above is demonstrated with an example of an undamped simply supported beam. Using the square root of the sum of the squares (SRSS) method of combining sodal responses, the contribution of higher modes to the response is less than in of the fundamental mode response. Using the more conservative absolute sum (ABS) method of combining responses, the contribution of higher
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modes is less than about 54.
3 The Licensee's response is considered adequate and in compliance with the SGER criteria.
Question 7 with reference to Section 7.1.4, Appendix I, part 1 (4), justify the use of average ficer acceleration instead of the envelope of the floor response spectra.
Response 7 (Reference 91 The Licensee showed analytically that the use of the average response spectra is more appropriate than the conservative approach of using the envelope of the floor response cpectra. Using an example of an undamped simply supported beam, it is shown that the absolute maximum modal displace-ment response is less than or equal to the value obtained by using the average of spectral values corresponding to the two supports. Also, the use of the average response spectra is considered satisfactory in view of the conservative
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TER-C5506-233 method of determining responses the peak acceleration is used if the lower bound frequency falls on the low frequency side of the peak and, if the lower bound frequency falls on the high frequency side, its corresponding accelera-tion is used. The Licensee's response is satisfactory and adequate.
Question 8 In Section 7.2, Appendix I, part 2 [4], the following formulae were given to estimate the localized moment per unit length in a plate due to concentrated loads:
Mt = 0.4P and, for loads close to an unsupported edge ML = 1.2P where P is the concentrated load.
Justify the application of these formulae to masonry walls and indicate how walls with openings were analyzed.
Response 8 (Reference 91 The Licensee stated that computer programs using finite element models were employed for the analysis of walls with. concentrated loads and openings and that the formulae in question were not used in the reevaluation of masonry walls.
Since these formulae were not used, this question is considered to be resolved.
Question 9 Provide brief descriptions for the analytical approaches used for single wythe and multiple wythe walls.
Response 9 [ Reference 9]
The Licensee outlined the analytical approach as follows:
1.
The single wythe concrete masonry walls are first evaluated by considering one-way action.
2.
For the cases found inadequate in (1), a more refined analysis considering plate action is performed using available plate theories.
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TER-C5506-233 3.
For boundary conditions and for loading not covered by available plate theories, and for walls with openings, analysis is, performed using. finite element computer programs.
4.
Neglecting collar shear strength, the multiple wythe walls are treated as an assemblaae of single wythe walls and analyzed accordingly.
5.
For seismic analysis of suitiple wythe walls, additional inertia due to the unreinforced' interior wythes is imposed on the reinforced t
exterior wythes.
6.
Alternate acceptance criteria (energy balance technique) are used to demonstrate functional capability of walls that have stresses in excess of the allowablu limits.
Except for the use of alternate acceptance criteria in item 6, the Licensee's analytical approach is considered adequate and in compliance with the SGEB criteria.
Response 5 addresses the use of alternate acceptance criteria.
Question 10 With regard to seismic analysis, indicate how the equipment loads were accounted for and how the earthquake forces in horizontal and vertical directions were considered.
Response 10 (Reference 91 I
The Licensee stated that the weights of equipment and pipes were considered distributed over the wall height, but the seismic reactions of Class I pipes were considered as concentrated loads. Since the masonry walls j
are nonbearing, vertical seismic effects are insignificant except for the I
pipes and equipment on brackets causing local moments. These local moments were combined with out-of-plane inertia effects. The Licensee's response is considered adequate and in compliance with the SGEB criteria.
I Questic., 11 l
Provide details of proposed wall modifications and indicate,,,uning sample calculations, how these modifications will correct the wall deficiencies.
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TER-C5506-233 Response 11 (Reference 9]
According to the Licensee response, the wall modification improves the support condition at the top of the wall by connecting the two wythos. Before wall modification, mechanical connection of the top 6 x 4 angle was only to a 4-in wythe through 1/2-in diameter expansion bolts. A 1/2-in plate has been welded to the top angle and anchored to the 8-in wythe with 5/8-in diameter expansion bolts. The details of the wall modifications are given in Appendix B.
The Licensee's response is considered adequate and satisfies the SGEB criteria.
Question 12 Provide a status report of the proposed wall modifications.
Response 12 (Reference 91
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In this response, the Licensee stated that all modifications have been comple'ted.
Question 13 Provide the results of the wall analysis indicating the walls that do not qualify under the working stress criteria.
Response 13 (Reference 9]
The Licensee stated that the energy balance technique was used to qualify five walls (68.2, 68.3, 532.1, 532.2, 532.3). Alternate acceptance criteria were used, making certain that a displacement of 2 times the calculated value would not affect the function of the safety-related system attached to the walls. As previously discussed in Response 5, the Structural and Geotechnical Engineering Branch (SGEB) of the NBC has issued a position statement regarding this subject which will be addressed in its safety Evaluation Report.
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TER-C5506-233 Question 14 Indicate whether the door modifications and vent installations recommended by Bechtel [4] pertain to walls 68.1 to 64.4; if they do not, provide a complete description of the problem, including wall identification and proposed modification.
Response 14 (Reference 9}
The Licensee affirmed that the door modifications and vent installations recommended by Bechtel [4] to alleviate the effects of tornado depressuri-zation inside the computer room pertained to the walls 68.1 to 68.4.
Further details concerning this subject are given is Section 3.2 of this report.
The response is satisfactory.
REVIEW OF ADDITIONAL REQUESTS [10] AND RESPONSES [11]
Question 1 with regard to Response No. 2 of Reference 9, it is noted that the SGEB criteria (developed by the Structural and Geotechnical Engineering Branch of the NRC) specify that no increase factor is allowed for load combinations including OBE loads.
In view of this, the Licensee is requested to provide the following information:
a.
If no increase factor is used, indicate whether the walls can still be qualified for load combinations including OBE loads. It is recommended that some worst cases could be reviewed to obtain this information.
b.
If the walls cannot be qualified, the Licensee is advised to explain all conservative measures used in the analysis to justify the proposed increase factor and also to identify all affected j
walls and the actual increase factor used in each wall.
i Response 1 (Reference 11]
In response to this request, the Licensee stated that for worst cases the walls can be qualified for load combinations containing OBE loads without using the 1.3 increase factor.
This response is satisfactory and in compliance with the SGEB criteria.
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TER-C5506c23J Question 2 Indicate whether acy well is subjected to tornado and other impulsive loads (i.e., jet impingement).
If so, provide a typical calculation for each case (with necessary explanation to make the calculation understandable).
Response 2 (Reference ill The Licensee responded that some walls are subjected to tornado and/or jet impingement loads and has provided a sample calculation for such a wall (wall 406.9) illustrating the analytical approach for these loads. Basically, a static, finite element computer analysis (STRUDL) was used to calculate horizontal and vertical moments in the well and well reactions for each load combination. The loads considered included tornado depressurisation, jet impingement (with a 1.25 dynamic load factor). This approach is adequate and satisfactory.
Question 3 With reference to the reinforcement in masonry walls, the ACI-531-79 Code
[7] specifies that the minimum area of reinforcement in a well in either direction, vertical or horisontal, shall be 0.0007 (0.07%) times the gross cross-sectional area of the wall and that the minimum total area of steel, vertical and horizonal, shall not be less than 0.002 (0.2%) times the gross cross-sectional area.
In view of this, clarify whether the reinforced walls at this plant meet the above requirements.
It should be noted that the horisontal reinforcement is installed to satisfy the minimum reinforcement requirement for a reinforced wall.
If the joint reinforcement is used to resist tension, it should follow the working stress design method which limits its allowable to 30 ksi.
The Licensee is requested to clarify if this requirement has been satisfied.
If this requirement is not satisfied, identify all affected walls along with the calculated stress value for each wall.
Response 3 (Reference 111 In this response, the Licensee stated that the minimum reinforcement requirements of the ACI-531-79 Code [7] have been met and that joint reinforcement has not been used to resist tension.
This response satisfies the SGEB criteria.
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3.2 EVALuhTION OF LICENSEB'S APPRDACE TO ISEL MODIFICATIONS 1
The Licensee indicated (91 that 77 walls were qualified in accordance 4
with the conventional working strees criteria. In addition, five walls were t
qualified by the alternative asoeytance criteria (energy balance technique).
The remaining four walls required some minor meditisation since the collar t
i joint tensile strength and shear strength were conservatively assumed to be i
sero. The modified walls ares t
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Modification Status
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11-418.10 completed f
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11 418.11 completed i
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11 102.s completed j
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11 102.9 completed The Licensee indicated that the purpose of the modifications to these walls was to improve support conditions at the top of the walls by connecting the two wythos. This was accomplished by welding ses11 1/2-in plates at regular t
i intervals to the existing restraint (a 4 x 4 angle), which was already bolted 1_
to the top of one wythe. The new plates were then bolted to the top of the j
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second wythe, thus connecting the wythes. Refer to Appendix 3 for stetches of i
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a typical modification.
l In a letter dated June 4, 1981 (8], the Licensee indicated that four j
walls (68.1 to 48.4) were identified as unstable under the effects of tornado j
depressurisation and cardon injection. These are the computer room walls in the cable spreading room. To prevent well failure due to tornado, the j
l computer room walls have been blocked open. A permanent design modification
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to install vents in the walls at each end of the computer room was to be i
completed as soon as possible. According to the response to Question 12 in 1
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Reference 9, all well modifications have been completed.
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Through an analysis performed on the modified walls, the Licensee verified that the modified walls satisfy the SGES criteria. The Licensee's modification methods have been reviewed and are judged to be adequate.
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TRENC5506-233 4.
CONCLUSIONS A detailed study was performed to provide a technical evaluation of the assonry walls at Peach Bottom Atomic Power Station. Review of the Licensee's j
criteria and additional information provided by the Licensee led to the conclusions given below.
8 The criteria used for reevaluation of the masonry walls, along with the
[
additional information provided by the Licensee, indicate that the Licensee's criteria are in compliance with the SGES criteria except for the use of the energy balance technique to qualify five walls in which stress due to out-of-plane loads exceeded the allowable working stresar the five walls are 64.2, l
68.3, 532.1, 532.2, and 532.3. As stated in Response 5, FDC and its con-I J
sultants have issued an evaluation of this technique (121 The sGas has also i
I issued a positi,on statement which will be addressed in its safety Evaluation Report.
section 3.2 indicated that four walls have been structurally modified, that the Licensee's approach to well modifications is judged to be satisfactory, and that the modified walls were structurally adequate and in compliance with the 8G33 criteria.
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TER-C5504-233 5.
REFERENCES 1.
- Masonry Wall Design" USNRC, 08-May-80
/
S. L. Daltroff Letter to 3. M. Grier, NRC.
Subject:
Response to IE Bulletin 80-11, Peach Bottom Atomic Power Station Philadelphia Electric Co., 02-Jul-80 3.
- 8. L. Daltroff Letter to 3. N. Grier, NRC. Subjects Interio Response to Item 2b of IE Bulletin 80 Peach Botton Atomic Power Station Philadelphia Electric Co., 03-Nov-80 4.
S. L. Daltroff Letter with attachment to 3. M. Grier, Nac.
Subject:
IE Bulletin 80 Reevaluation of Concrete Masonry Walls for Peach Bottom Atomic Power Station Philadelphia Electric Co., 04-May-81 5.
Interim Criteria for safety-Related Masonry Wall Evaluation USNac, 00-July-81 SRP 3.4.4 6.
Uniform Building Code International Conference of Building Officia'is, 1979 7.
Building Code Requirements for concrete Masonry structures Detroit: American Concrete Institute, 1979 ACI $31-79 and ACI 531-R-79 8.
M. J. Cooney Letter to B. !!. Grier, MRC. Subject Licensee T, vent Report Narrative Description and Transmittal of LER Philadelpnia Electric Co., 04-June-81 LER 2-81-32/17-0 9.
J. W. Gallagher Letter with Attachment to J. F. Stols (NRC)
Subjects IE Bulletin 80-11 for Peach Bottom Atomic Power Station Units 2 and 3 Philadelphia Electric Co., 26-May-82 10.
J. F. Stols Letter to E. G. Bauer, Jr. (PECO)
Subject Masonry Wall Design, IE Dulletin 80-11 7-Feb-84
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i TER-C5506-233
- 11. Letter with Attachment to J. F. Stols (NBC)
Subject II Bulletin No. 80-11, Masonry Wall Design for Peach Bottom Ateele Power Station Unita 2 and 3 Philadelphia Electric Co., 21-Mar-44 12.
E. G. Barris and A. A. Easid
' Applicability of Energy Balance Technique Reinforced Masonry Walls" 2
Departoont of Civil Engineering, Dromel University 8
i August 1982
- 13. Computech Engineering Services, Inc., URS/Blume and Associates, and sechtal Power Corporation
" Rebuttal to ' Applicability of Energy Balance Technique to Reinforced Masonry Walls' by Barris and Easid" February 1983 i
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I APPENDIX A SEB CRITERIA FOR SAFETY-RELATED MASONRY WALL EVALUATION (DEVELOPED BY THE STRUCTURAL AND GEOTECHNICAL ENGINEERING BRANCH (SGEB] OF THE NRC)
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1 GENERAL REQUIRDIElrrs..
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LOADS AND LOAD COIGBINATICIIS.
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DESIGN AND ANALYSIS CGtISIDERATIOltS.
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General Requirements 4
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 coatained 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 NCMA, is also acceptable. However, when the provisions of these codes are less -
conservative than the corresponding provisions of tho' 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 provisior.s 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 i
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 operating license applications, the following load combinations shall apply (for definition
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of load terms, see SRP Section 3.8.4II-3).
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(a)
Service Load Conditions 1
(1) D+L (2) D+L+2 (3) D+L+W If thermal stresses due to To and R are present, they should be o
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included in the above combinations as follows:
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(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
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Extreme Environmental, Abnormal, Abnormal / Severe Environmental, and.
Abnormal / Extreme Environmental Conditions (4) D + L + To + Ro + E (5) D + L + To + Ro + Nt l
(6) D + L + Ta + Ra + 1.5 Pa t
(7) D + L + Ta + Ra + 1.25 Pa + 1.0 (Yr + Yj + Ym) + 1.25 E
+ 1.0 E' (8) D + L + Ta + Ra + 1.0 Pa + 1.0 (Yr + Yj + Ym)
In combinations-(6), (7), and (8) the maximum values of P, T e a
a Re Yja Tr, and Ya, including an appropriate dynamic load a
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* Yja and Ys in (7) and (8).
When considereing these loads, local section strength capacities.may be exceeded under these concentrated loads, provided there will be no loss of function of r.ny safety-related system.
Both cases.of L having its full value or being completely absent should be checked.
3.
Allowable Strer,ses 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 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 table:
A-2 A
MJ ~ eserxh Center nklia R
TER-C5506-233 Type of Stress Factor Axial or Flexural Compression 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 Masonry tension parallel to bed joint 1.5 Shear carried by masonry 1.3 Masonry tension perpendicular to bed joint for reinforced masonry 0
2 1.3 for unreinforced masonry Notes (1)
When anchor bolts are used, design should prevent facial spalling of aasonry unit.
(2)
See 3(c).
4.
Design and Analysis Considerations (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.
j (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, corresponding SRP requirements shall apply. The seismic analysis shall account for the variations and uncertainties in mass, materials, and other pertinent parameters us.ed.
(e)
The analysis should consider both in-plane and out-of-plane loads.
(f)
Interstory drift effects should be considered.
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4-TER-C5506-233 (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,g 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 i
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 (Y ), jet impingement (Y ), and missile 3
r impact (Y ), 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 (a)
Uniform Building Code - 1979 Edition.
(b) Building Code Requirements for Concrete Maso'nry 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-Bearing Concrete Masonry - NCMA August, 1979.
(e) Trojan Nuclear Plant Concrete Masonry Design Criteria Safety Evaluation Report Supplement - November,1980.
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O ENCLOSURE 2 4
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SGEB STAFF POSIT 0N ON USE OF ENERGY BALANCE TECHNIQUE TO QUALIFY REINFORCED MASONRY WALLS IN NUCLEAR POWER PLANTS INTRODUCTION Under seismic loads, strain energy tr'ansfer through elastic response is very small compared to the inelastic response for energy dissipation. Therefore, inelastic non-linear analysis of reinforced masonry walls is an attractive approach.
Some of the licensees have relied on a non-linear analysis aporoach known as " energy-balance technique" to qualify some of the reinforced masonry walls in their plants.
The staff and their consultants have reviewed the basis provided by licensees to justify the use of energy-balance technique to qualify the reinforcd masonry walls. The staff met with a group of licesees representing approximately ten utilities on November 3,1982 nd January 20, 1983 to discuss this issue.
Further, site visits and detailed review of design calculations were conducted by the staff and their consultants to gain first-hand knowledge of field conditions and the application of energy-balance technique in qualifying in place masonry walls.
Based on the information gained through the above activities, the staff has formulated the following position on the accept-ability of the use of energy-balance technique to qualify reinforced masonry walls in operating nuclear power plants.
The staff's technical basis for the position is discussed in the attached report.
POSITION The use of energy-balance technique or any other non-linear analysis approach is not acceptable to the staff without further confirmation by an adequate test d
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program.
Therefore, the staff position consists of the following three options.
Adoption.of any one of the option and successful implementation will constitute a resolution of the issue regarding the qualification of reinforced masonry walls by energy balance technique or other non-linear techniques.
1.
Reanalyse walls qualified by the energy-balance technique by linear elastic working ' stress approach as recommended in the staff acceptance criteria (SRP Section 3.8.4, Appendix A) and implement modifications
.m to walls as needed.
Develop rigorous non-linear time-his. tory analysis techniques capable of 2.
capturing"~th'emechanijmofthewallsundercyclicloads.
Different stages
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of behavior should be accurately modeled; elastic uncracked, elastic cr$cked"in'dinelasticcrackedwithyieldingofthecentralrebars.
- Then, i limited nember of dynamic tests (realistic design earthquake motion
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__. inputs.at top and bottom of the wall) Should b.e conducted.to demonstate the overall conservatism of the analysis results.
In this case,."as built" walls should be~constr~cted to duplicate the construction details u
of a specific plant.
3.
For walls qualified by energy-balance technique, conduct a comprehensive test program to establish the basic non-linear behavioral characteristics of masonry walls (i.e. load-deflection hysteretic benavior, ductility ratios, energy absorption and post yield envelopes) for material properties and construction details pertaining to masonry walls in question.
The W.
behavior revealed from tests should then be compared with that of elastic-
-perfectly plastic materials for which the energy balance technique was originally developed.
If there are significant differences, then the energy balance technique should be modified to reflect the actual wall behavior.
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