ML19345B556
| ML19345B556 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/22/1980 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-1778, NUDOCS 8012020031 | |
| Download: ML19345B556 (12) | |
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SEP.2 91980 MINUTES OF THE ACRS SUBCOMMITTEE ON STRUCTURAL ENGINttKING
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WASHINGTON, DC SEPTEMBER 2, 1980 L
A meeting of the ACRS Subcommittee on Structural Engineering was held in Room l
- 1046, 1717 H Street, NW, Washington, DC on September 2, 1980. The purpose of
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the meeting was to determine the capacity of the Sequoyah containment when subjected to static or quasi-static unifonn internal pressure caused by i
hydrogen burn.
-A copy of the schedule and attendee list are att ted.
There were no oral presentations nor written statements received fr om any members of the public.
The entire meeting was held in open session. Handouts at the meeting are attached to the office copy of the minutes.
Mr. Denton, TVA, investigated various locations of tht! Sequoyah containment 'in order to determine the critical sections.
Some of the locations investigated and found structurally adequate were anchorage, piping penetrations, personnel x
The critical section of the containment was found to be in N locks, and seals.
the cylindrical shell-near the spring line. Using specified code stresses and the Tresca's yield stress criterion resulted in a critical pressure of 23.2 psig. This value is 38.2 psig if actual yield stress and the ion Misis yield i
stress criteria are used. The personnel lock seems to be structurally adequate l
but the Subcommittee. requested that the NRC Staff look into this matter.
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Dr. Griemann, Ames Laboratory, performed structural analysis of the containment at the request of the NRC Staff.
The shell, penetrations, and anchor bolts were investigated. The shell was found to be the area of maximum stresses.
The result of the analysis using the finite element analysis code (ANSYS) and using the actual value for yield stre.s Dr. Griemann calculated a static s
limit pressure of 47.psig.
Mr. Parry, Research and Development Associates, at the request of Commissioner Gilinsky, performed an independent stress analysis on the containment.
In his analysis, Mr. Parry attempted.to establish the lower bounds for the containment integrity. No comprehensive computer analysis, such as finite element methods, were performed.
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STRUCTURAL ENGINEERING September 2,1980 In an open caucus, the Subcommittee agreed on the following items.
Uniform static pressure will be considered.
Local yielding in flexure can be neglected.
Yield strain can be exceeded-by a moderate amount without detrimental effects.
Ultimate strength is not meaningful because of large deflections.
Contaimnent penetra-.ns do not control at moderate strains.
Anchor bolts and knuckle joints do not control the containment design.
Base slab is not a -critical item.
Actual test yeild strength values should be used in this case.
von Mises instead of Trescas yield criterion should be used.
Dr. Siess, Subcommittee Chairman, summarized the meeting by presenting the table below, listing the containment pressure capacities based on actual values of yield stress.
SEQU0YAH CONTAINMENT PRESSURE CAPACITY (psig)
BASIS 33 NRC Staff - Tresca - 1st yield 38 NRC Staff - von Mises - 1st yield 38 R&D Ass. - single panel - full yielding 46 Bagchi - 1st yield 47 Zudans - 1st yield 50 TVA-0PS - full yielding, 9.5 ft. panel 56 Ames - full yielding, smeared (equivalent thickness) 57 TVA-0PS - full yielding, 6.5 ft. panel 60 Bagchi - full yielding (+30%)
60 Ames - 1.0 inch displacement curve 64
' Ames - 2.0 inches displacement curve The meeting was adjourned at 3:30 p.m.
NOTE: For additional details, a complete transcript of the meeting is avail-able in the NRC Public Document Room,1717 H St., NW, Washington, DC 20555 or from Alderson Reporters, 300 7th St., SW, Washington, DC, (202)554-2345).
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' totember 2,1980 STRUCTURAL ENGINEERING a.
Mr. Parry ' stated that the results vary significantly depending on the initial effectiveness of the shell/ ring-longeron stiffener interactions. Encastre plate and membrane (aircraft fuselage type analysis)-models were assumed.
Mr. Parry's calculations resulted in a yield pressure of 27 psig. This was based on fy = 32 ksi. Mr. Parry recommended that detailed elastic / plastic analysis by computer code and full scale or model testing be performed.
- Dr. Bagchi, NRC-Research, performed a containment structural analysis assuming an equilibrium of force model for visualizing load redistribution following gross yielding. The result of his analysis using actual yield values is 34 psig.
Dr. Orr, Offshore Power Systems, at TVA's request, performed a finite element structural analysis of the containment.
In his analysis, the containment yield -
pressure was calculated to be about 52 psig. This value is based on actual yield stress, von Mises criterion, and two-way stiffening effects of the shell/
ring-longeron geometry.
Dr. Tan, NRC, stated that based on analysis by TVA, Staff's consultants and others 'and taking -into consideration all the factors, the Staff concluded that the yield pressure is 33 psig.
Dr. Zudans, consultant to the ACRS, reviewed and performed stress analysis on the Sequoyah containment, at the Subcommittee's request. Dr. Zudans stated that the results of Ames and R&D Associates analyses were not supported with adequate rigor. To offer a rational estimate of the containment strength, Dr. Zudans performed independent analysis using a reduced finite element model of the containment. His analysis of the 5/8 inch thick shell resulted in a pressure of 34.3 psig for full yielding of the shell to occur and 38.6 psi for the entire panel to yield. Non-linearities will stiffen the structure and higher pressure will be required to produce gross distortion.
In the 1/2 inch thick shell, Dr. Zudans calculated a yield pressure of 30.3 psig and full panel yielding pressure of 34.7 psig. These values are based on a yeild strength of 34 ksi and assuming Tresca yield criterion.
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UNITED STATES 8'
NUCLEAR REGULATORY COMMISSION
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ADVISORY COMMITTEE ON REACTOR SAFEGUARDS k
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.a September 3, 1980 MEMORANDUM FOR: ACRS Members FROM:
C. P. Siess, Subcomittee Chairman Structural Engineering
SUBJECT:
REPORT OF SUBCOMMITTEE ON STRUCTURAL ENGINEERING -
INTERNAL PRESSURE CAPACITY OF SEQUOYAH CONTAINMENT The Subcomittee met on 2 September 1980. Those present included:
ACRS Members ACRS Consultants H. Etherington M. P. White J. Ebersole Z. Zudans C. P. Siess Presentations were made by representatives of the following:
TVA Ames Research Laboratory Research and Development Associates NRC - RES NRC - NRR All presented results of calculations of the internal pressure capacity of the Sequoyah containment structure. The calculations ranged from relatively crude approximations to relatively sophisticated finite element analyses.
Calculations not previously submitted were presented by Ames and by TVA.
Major variables entering into the calculations include:
a) The effects of longitudinal stiffeners.
b) The use of specified minimum yield strength for the shell plau (32,000 psi) vs. the minimum yield strength obtained from mill tests on the actual material (about 45,000 psi).
c) The " theory of failure" used to determine first yielding of the plate caterial:
Tresca: maximum shear stress Von Mises: maximum shear strain energy
ACRS Members The Von Mises criterien gives a yield stress about 15", greater than the Tresca criterion for the cases considered.
The Subcommittee agreed on the following bases for detennining the capacity of the containment und<
uniform internal static pressure:
- 1) The capacity will be governed by stresses and deformations in the stiffened shell at the location of the minimum shell thickness at the upper _end of the cylindrical portion.
- 2) The capacity will not be limited by stress or deformation of the hold-down bolts attaching the cylinder to the concrete base mat or by the " knuckle joint" at the bottom of the cylinder.
- 3) There is reasonable assurance that the capacity will not be limited by the penetrations or hatch openings, but this should be checked by the Staff for any penetrations through the upper portion of the containment in the region of concern.
- 4) Local yielding in flexure can be neglected.
- 5) Yield strain in the material can be exceeded by a moderate amount in determining the limiting capacity. A moderate amount means a few times the strain at first yield, which is about 0.0015 for the actual material.
- 6) Calculations involving the ultimate tensile capacity of the material should not be considered because of the excessive strains and dis-placements involved.
7)
It is appropriate to use the tensile properties of the actual mate-rial as determined from tests.
8)
It is appropriate to use the Von Mises yield criterion rather than the Tresca criterion for the shell plate.
If the foregoing criteris are accepted, the following valtes of pressure capacity seem to be reasonable. They are all based on a tensile yield strength of 45,000 psi. The actual minimum to be used may be 1,000 to 2,000 psi lower depending on the confidence level or probability level de-si red.
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ACRS Members -
38 psig Conservative lower bound based on neglecting the effects of the longitudinal (meridional) stiffeners.
46 psig Reasonable value for first yielding other than local yielding in flexure.
50 psig Reasonable lower bound for the limit capacity based on general yielding, but at still limited deformations.
55 psig Best estimate of limit capacity.
The NRC-NRR Staff has concluded that 33 psig is an acceptable value.
This value is based on neglect of stiffener effects, use of actual yield
' strength (45,000 psi), and use of the Tresca yield crit >rion.
For the same assumptions, but using the Von Mises criterion. This value would become 38 psig, the lowest value presented in the table above.
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o TENTATfVE MEETING SCHEDULE ACRS Str3 COMMITTEE ON STRUCTURAL ENGINEERING September 2,1980 Washington, D. C.
8:30 A.M.
I.
Chairman's Opening Remarks C. Siess 9:00 A.M.
II. TVA Presentation Introductory Statement Technical Presentation Description of containment assembly Design Criteria Stress Analysis Methodology including computer code description, a.
verification Penetrations, containment - base mat attachment, o.
and/or other high stress locations Design loads and temperatures used in analysis c.
Material properties of containment, design values, test data, weld properties, etc.
Design margins, based on yield strength,' ultimate strength at locations of a.sh stresses Conclusion and Recommendations 11 :30
~..M.
III. Ames Presentation Dr. Griemann LUNCH 12:30 - 1:30 P.M.
1:30 P.M.
IV. Research and Development Associates Frank Parry 2:30 P.M.
V. NRC Research G. Bagchi
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.3:00 P.M.
.VI', NRC Presentation J
. Intfoductory Statement
- Technical Presentation Detail Structural Evaluations of Containment
- Structure.
C. P. Tan
- Conclusions and Recomendations 5:00 P.M.
VII. -CAUCUS
~5:30 P.M.
~ VIII. ADJOURNMENT i
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