ML20083H820
| ML20083H820 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 01/04/1984 |
| From: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20083H823 | List:
|
| References | |
| RTR-NUREG-0991, RTR-NUREG-991 NUDOCS 8401090477 | |
| Download: ML20083H820 (28) | |
Text
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PHILADELPHIA ELECTRIC COMPANY 23O1 MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 JAN 041984 JOHN S. KEMPER V IC E-PR ESI D E NT ENG4 NEE RthG AND NESE ARCH Mr. A. Schwencer, Chief Docket Nos.: 50-352 Licensing Branch No. 2 50-353 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Limerick Generating Station, Units 1 and 2 Structural Steel Fire Resistance
References:
(1)
Limerick Safety Evaluation Report (NUREG-0991)
(2) NRC Chemical Engineering Branch Meeting, Held December 13, 1983 (3)
L. S. Kintner to Applicant (PECO) Letter Dated December 23, 1983 File:
GOVT 1-1 (NRC)
Dear Mr. Schwencer:
Reference (1) requires that the applicant provide fire protection for exposed structural steel supporting the floors of safe shutdown areas.
The Reference (2) meeting was held to describe the means for assuring equivalent protection for structural steel in lieu of strict application of protective coating.
The attachments provide the information requested in Reference (2) and documented in Reference (3), to support the program we presented to close out SER Open Item #14, Structural Steel Protection.
I.
The follovring information was requested by Mr.
C.
P.
Tan at the Reference (2) meeting:
A.
Mechanical Properties of Steel at Elevated Temperatures The curves contained in Attachment I were published by the U. S.
Steel Corporation and illustrate the effect of temperature on yield strength, tensile strength and modulus of elasticity.
Similar curves published by the American Iron and Steel Institute (AISI) are contained in Attachment II.
The structural steel used at Limerick conforms to ASTM Specification A36.
(O 8401090477 840104 PDR ADOCK 05000352 ljl }
E PDR k.
The steel behavior predicted by these curves is based on tension tests of small uniformly heated test specimens.
While the curves provide an indication of the effect of temperature on the properties of steel, they are not considered to accurately represent the totally different stress condition existing in flexural members that are both end restrained and constructed compositely with the concrete slab.
In the reference material submitted with the structural steel methodology, the behavior of structural members subjected to elevated temperatures is discussed in greater detail.
B.
Typical Construction Details Floor framing systems are typically composite construction utilizing steel studs to resist shear between the cteel beam and the concrete slab. In many cases, the top flange of the beam is encased in concrete with the steel deck being supported by ledge angles welded to the web of the beam.
In all cases the deck is welded to the supporting member, a type of construction that has been verified by testing to provide a degree of composite action.
In accordance with standard structural theory, the effect of constructing the steel beam integrally with the concrete slab is to increase the section modulus of the assembly and thus increase its load-carrying capacity. When subjected to elevated temperatures, a composite beam / slab assembly can withstand higher temperatures than a non-composite member of the same size prior to reaching the point at which the assembly can no longer support the applied loading.
Loading considered in the design of the steel framing is contained in Section 3.0 of the Limerick FSAR.
The primary concern is with floor support beams since exposed steel columns occur in few fire areas.
Column members are typically W14 rolled sections or built-up members consisting of a W14 section with flange plates. Exposed columns in identified problem areas will be evaluated similarly to the beam / slab assemblies.
Typical framing details are contained in Attachment III.
r
- C.
Acceptance Criteria The structural steel acceptance temperatures presented in the analysis methodology are specified by ASTM as end-point criteria for determining a fire endurance rating.
Therefore, if the actual steel temperatures do not exceed the criteria during a defined fire in the area, the steel is acceptable as a fire barrier having a fire rating equal to the fire resistance required of the barrier.
The conservatism inherent in the ASTM end-point temperatures for beams is that these acceptance temperatures are applied uniformly to beams that are:
1.
both end-restrained and free to move-2.
individually acting versus one member of a multi-member floor system.
It is stated by AISI in Attachment II that test experience and research clearly show a significant improvement in fire endurance when the ends of a test specimen are restrained against expansion and that even minimal restraint will improve fire endurance.
It is therefore conservative to apply end-point temperature criteria for an unrestrained beam to a restrained beam.
Similarly, a beam that is constructed so as to act integrally with the concrete slab has greater load carrying capacity than an individual, non-composite beam of the same size.
In additien to greater load carrying capacity, composite beams have continuous lateral support of the top flange which, according to Appendix X4 of ASTM E119, provides substantial restraint against thermal expansion.
This is neglected in the end-point temperature criteria.
Finally, the steel temperature of 1100*F can be correlated to the temperature vs.
strength curves given in Attachments I and II.
It is commonly accepted that, at 1100*F, the yield stress of steel has decreased to approximately 60% of the room temperature value which is the normal design stress level.
This criteria is reiterated in the NRC Generic Letter 83-33 dated October 19, 1983.
As previously discussed, the application of this criteria to restrained, composite beams is, if ariything, conservative.
Therefore, by adhering to the ASTM criteria, the structural integrity of the structural steel is assured.
-6
- II. Structural Steel Exposure to the E-119 Time Temperature Curve In Attachment IV, we have shown the.results of exposing the beams (indicated as having a " local effects" problem) in the Control Enclosure, El. 217-Switchgear Area to' the extreme fire condition depicted by ' the E-119 time-temperature furnace condition.
They indicate that:
~1.
The time period for these beams reaching critical temperatures
_ range - from twenty to fc.rty minutes, whereas the furnace
~~
temperature reached 1100*F in seven minutes.
2.
There ~is a significant lagging effect of the structural steel temperature to'the average compartment gas temperature.
III. In Attachment V, we have provided a comparison between the results of the NRC sponsored tests performed at Underwriters Laboratories as published in NUREG/CR-3192 and the results of Limerick structural steel survivability calculational methodology as applied to the Underwriters Laboratc, ries fire tests.
Our ' efforts have been limited to evaluating the results of Experiment #3 and Test #1.because of the limited data in.the NUREG.
The data required to -complete the comparisons for the remaining experiments and tests was received from Sandia National Laboratories on January 4, 1984.
We expect to submit the additional' comparison calculations by January 13, 1984.
IV.
Structural Steel Analysis In Attachment VI,- we have included the results'of our structural steel analysis calculations for an additional thirty-four plant areas
. hich contain safe shutdown equipment and exposed structural steel w
- sembers. Three areas; the Unit 1-Refueling Floor, the Spray Pond Pump Structure, and a ' Unit 1 Reactor Enclosure pipe chase remain to be completed.
The. calculations for these areas will be available for submittal by the end of January, 1984.
Sincerely, IM DMO /GMM/GJR/DMG/gra/122983415
________________i.._
o cc: Judge Iawrence Brenner (w/ enclosure)
Judge Peter A. Morris (w/ enclosure)
Judge Richard F. Cole (w/ enclosure)
Troy B. Conner, Jr., Esq.
(w/ enclosure)
Ann P. Ibdgdon, Esq.
(w/ enclosure)
Mr. Frank R. Romano (w/ enclosure)
Mr. Ibbert L. Anthony.
(w/ enclosure)
Mr. Marvin I. Lewis (w/ enclosure)
Ms. Phyllis Zitzer (w/ enclosure)
Charles W. Elliott, Esq.
(w/ enclosure)
Zori G. Ferkin, Esq.
(w/ enclosure)
Mr. Thmas Gerusky (w/ enclosure)
Director, Pennsylvania Energency Managenent AJency (w/ enclosure)
Mr. Steven P. Hershey (w/ enclosure)
Angus Love, Esq.
(w/ enclosure)
~ Mr. Joseph H. White, III (w/ enclosure) i David Wersan, Esq.
(w/ enclosure)
Robert J. Sugarman, Esq.
(w/ enclosure)
Martha W. Bush, Esq.
(w/ enclosure)
Spence W. Perry, Esq.
(w/ enclosure)
Jay M. Gutierrez, Esq.
(w/ enclosure)
Atanic Safety and Licensing Appeal Board (w/ enclosure)
Atanic Safety and Licensing Board Panel (w/ enclosure)
Docket and Service Section (w/ enclosure)
James Wiggins (w/ enclosure) s
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