ML20054E117
| ML20054E117 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/25/1982 |
| From: | Hunnicutt D, Tapia J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20054E115 | List: |
| References | |
| 50-482-82-05, 50-482-82-5, NUDOCS 8204260154 | |
| Download: ML20054E117 (3) | |
See also: IR 05000482/1982005
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APPENDIX
U. S. NUCLEAR REGULATORY COMMISSION
REGION IV
Report:
STN 50-482/82-05
Docket:
STN 50-482
Category A2
Licensee:
Kansas Gas and Electric Company
Post Office Box 208
Wichita, Kansas 67201
Facility Name: Wolf Creek, Unit 1
Inspection at:
Bechtel Power Corporation, Gaithersburg, Maryland
Inspection Conducted: March 12, 1982
Inspector:
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3-25 -82.
J
. Thpi'a, R6Jctor Inspector, Engineering Section
Date
Approved:
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3/2.5/8.2
D. M. Hunnicutt, Chief, Engineering Section
Dhte '
Inspection Summary
Inspection on March 12, 1982 (Report STN 50-482/82-05)
Area Inspected: Special, announced inspection of structural steel calculations
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performed by Bechtel in response to concerns expressed by'a. contract employee
at Wolf Creek dealing with the torsional loading of open section structural
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steel.
The inspection involved six inspector-hours by one NRC inspector.
Results:
No violations or deviations were identified.
Expressed concerns
were not substantiated.
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DETAILS
1.
Persons Contacted
Bechtel Power Corporation - Gaithersburg, Maryland
B. Meyers, Project Manager
L. Rotondo, Project Engineer
E. W. Thomas, Civil Group Supervisor
G. Goddard, Assistant Civil Group Supervisor
B. Shah, Plant Design Engineering Group Supervisor
B. Hsu, Civil Group Leader, Reactor Building
2.
Concerns Related to Piping Support Load on Structural Steel
By letter to the NRC Region IV Office dated February 17, 1982, a contract
employee at Wolf Creek expressed concerns related to: (1) using open sections
of steel to resist torsional loading and (2) to an apparent lack of coordi-
nation between structural engineering and pipe support engineering personnel.
The letter specifically identified five structural steel beams which the
contract employee felt were overstressed due to torsional loading.
In
response to the expressed concerr.s, a special inspection was performed at
the SNUPPS Project Design Office of Bechtel Power Corporation.
The follow-
ing items were reviewed during the inspection:
a.
Torsional Loading of Structural Steel Members
The Bechtel Power Corporation application of engineering principles
for the accountability of torsional stresses on structural steel
members which support pipe hanger loads was evaluated by the NRC
inspector.
This evaluation consisted of: reviewing the design
calculations for the beams in question (Calculation No. 02-194-F,
Revision 0, " Torsion Analysis on Platforms at Elevation 2000' - 0",
Azimuth 315 and 210 - 30'"); reviewing Specification No. 10466-C-0(Q),
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Revision 9, " Civil and Structural Design Criteria for SNUPPS"; and
conducting interviews with the engineering discipline supervisory
personnel concerning the design philosophies followed in addressing
torsional loads.
The contract employee's letter contained one example calculation which
the employee felt demonstrated that allowable shear stresses had been
exceeded due to torsion.
That calculation was based on formulas con-
tained in a Lincoln Arc Welding Foundation publication entitled " Design
of Welded Structures." The formulas used address the pure torsional
shear stresses which vary linearly across the thickness of an element
of the cross-section.
This distribution of shear stress is known as
" pure" or "St. Venant" torsion and assumes that a cross-section remains
plane and that only rotation of the cross-section occurs.
However,
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structural steel beam cross-sections not only rotate but also deform
or warp and do not remain plane after torsional loading.
Structural
steel members, therefore, resist torsion through a combination of
"St. Venant" and " warping" torsion and because of the open cross-section,
" warping torsion" generally dominates.
Since the translation producing
lateral bending is restrained for the beams in question, the " warping"
shear stresses are superimposed on the "St. Venant" shear stresses and
add effectively to the torsional resistance of the beams.
Failure to
recognize the warping effect in addition to the pure twisting effect in
the contract employee's calculation renders that stress analysis
incomplete.
The NRC inspector reviewed the calculations performed by
Bechtel Power Corporation and found that the allowable stresses of the
American Institute of Steel Construction (AISC) Specification for the
Design, Fabrication and Erection of Structural Steel for Buildings have
not been exceeded.
A review of the Bechtel Structural Design Criteria
showed that all structural members are reviewed for structural adequacy
after all loads are fully established.
The Bechtel Pipe Hanger
Accountability Program was also reviewed.
This computer program eval-
uates the cummulative effect of all pipe support loads on structural
steel beams and includes a calculation of the imposed torque using the
conservative computational method described as the flexural analogy of
torsion.
b.
Coordination Between Structural and Piping Engineering
The contract employee perceived a lack of coordination between the
structural and piping engineering disciplines which he felt resulted
in torsional loads not being taken into account.
A review of the
Bechtel Engineering Department Project Instruction No. 4.46-01,
Revision 16, " Project Engineering Drawings," disclosed a formalized
system of reviews and approvals required prior to the issuance of
drawings for construction.
This system requires that the piping
support group transmit to the structural group all pipe support loads
in excess of 500 pounds which result from pipes 2-1/2" or larger in
diameter.
The memorandum transmitting the loads used in the analysis
of the beams in question was reviewed by the NRC inspector.
As a result of this special inspection, the concerns expressed by the
contract employee could not be substantiated.
There can, therefore, be
no merit given to the statement that, "the subject problem would result
in loss of control for Safe Shutdown."
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