ML20112D301
| ML20112D301 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 01/10/1985 |
| From: | Jens W DETROIT EDISON CO. |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| EF2-72041, NUDOCS 8501140187 | |
| Download: ML20112D301 (3) | |
Text
a Warne H. Jena Vice Presasent Nuclear Operatx>ns Ferma-2 Edison =400 North Dixie dighway 6
= ' " - -
Januery 10, 1985 EF2-72041 Director of Nuclear Reactor Regulation Attention:
Mr.
B. J.
Youngblood, Chief Licensing Branch No. 1 Division of Licensing U. S.
Nuclear Regulatory Conmission Washington, D.C.
20555
Dear Mr. Youngblood:
Reference:
(1)
Fermi 2 NRC Docket No. 50-341 (2)
Detroit Edison letter to NRC, " Purge Valve Operability", EF2-72272, dated October 11, 1984 (3)
Detroit Edison letter to NRC, " Purge Valve Operability Audit", EF2-55538, dated November 18, 1981 (4)
AISC code, Seventh Edition, Article 1.5.1.2 (5)
ASME Code,Section III, 19 71 Edition, Article NB-3227.2 (6)
J.
E. Shigley, " Mechanical Engineering Design", Third Edition, Section 5-6 (page 170)
Subject:
Purge Valves - Additional Information Subsequent to conversations with Mr. R. Wright ( NRR-EQ B ),
Edison agreed to submit additional information concerning the purge valve operability issue.
Mr. Wright requested additional information on two specific questions which are delineated below.
[The information presented below was provided to Mr. Wright in a December 19 telecon with Edison.]
8501140187 850110 go}
PDR ADOCK 05000341 A
PDR is
d Mr.
B. J. Youngblood January 10, 1985 EF2-72041 Page 2 1.
Mr. Wright:
Verify that the bracket bolt material was SA-19 3 B7.
Edison:
As reflected in Attachment 2 to Reference 2, the purge valve bracket bolts were fabricated of SA-19 3 B7.
2.
Mr. Wright:
Define which industry code was used (and why) to define the bracket bolt shear allowable values.
[There is an apparent conflict between the AISC Code value (i.e.,
40% of tensile yield) used by John Henry Assoc. (Reference 3) and the value reflected in Reference 2 (i.e.,
60% of tensile yield).]
Edison:
In performing a stress analysis on the purge valves subjected to LOCA conditions, the allow-able stress limits were taken as the yield point of each valve component.
Since the yield point in shear for structural steel is considerably lower than the yield point in tension, only 60% of the tensile yield stress was used as the allowable shear stress (i.e.,
shear yield = 60% of tensile yield).
References 4, 5, and 6 support the use of this 60% factor.
(The attach-ment provides pertinent excerpts from References 4 and 5.)
In regards to the allowable stress value used by John Henry Assoc. of 40% tensile yield, it should be noted that this value represents the design allowable shear stress specified by the AISC code.
Furthermore, the AISC code specifies an allowable tensile stress of 66%
tensile yield.
These allowables are consistent with those specified by the ASME Section III code for the normal operating condition; however, the ASME code allows stresses to reach (and even exceed) the material yield strength for the emergency and faulted conditions.
Please direct any questions to Mr. O. K.
Earle at (313) 5d6-4211.
Sincerely, l
cc:
Mr. P. M.
Byron j h
.Mr. M.
D. Lynch
/
Mr. R. J. Wright
- f U. S. NRC, Document Control Desk l
Washington, DC 20555
- With Attachment L
Attachment to EF2-72041 Excerpt from AISC Code (Reference 4):
"While the shear yield stress of structural steel has been variously estimated as between one-half and five-eighths of the tension and compression yield stress and is fre-quently taken as F /U, it will be noted that the permis-y sible working value is given as two-thirds the recommended basic allowable tensile stress, substantially an it has been since the first edition of the AISC Specification, published in 1923.
This apparent reduction in factor of safety is justified by the minor consequences of shear yielding, as compared with those associated with tension and compression yielding, and by the effect of strain hardening."
Excerpt from ASME Code (Reference 5):
"(a) The average primary shear stress across a section loaded in pure shear, experienced as a result of design conditions or of any of the Operating or Testing Conditions, other than Faulted Conditions (for example, keys, shear rings, screw threads), shall be limited to 0.6Sm "