ML13322A936
| ML13322A936 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/23/1980 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Dietch R Southern California Edison Co |
| References | |
| NUDOCS 8008140112 | |
| Download: ML13322A936 (7) | |
Text
09 DISTRIBUTION
-JFair NRC PDR Local PDR ORB Reading Docket No. 50-206 NRR Reading JUL 2 9OELD OI&E (3)
DCrutchfiel d GLainas Mr. R. Dietch SNowicki Vice President HSmith Nuclear Engineering and Operations NSIC Southern California Edison Company TERA 2244 Walnut Grove Avenue ACRS (16)
Post Office Box 800 Rosemead, California 91770 TAC 10150
Dear Mr. Dietch:
SUBJECT:
FRACTURE TOUGHNESS DESIGN We are continuing our review of the fracture toughness design of the steam generator and reactor coolant pump supports at San Onofre Unit 1 and have found that additional information described in the enclosure to this letter is needed.
We request your response within 30 days of your receipt of this letter.
Sincerely, ELD DniM. Crutchfield, Chief Operating Reactors Branch #5 ivision of Licensing
Enclosure:
Request for Additional Information "0081,40 \\2 OFFICEDL 45 D
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 July 23, 1980 Docket No. 50-206 Mr. R. Dietch Vice President Nuclear Engineering and Operations Southern California Edison Company 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770
Dear Mr. Dietch:
SUBJECT:
FRACTURE TOUGHNESS DESIGN We are continuing our review of the fracture toughness design of the steam generator and reactor coolant pump supports at San Onofre Unit 1 and have found that additional information described in the enclosure to this letter is needed.
We request your response within 30 days of your receipt of this letter.
Sincerely, Dennis M. Crutchfield Cie Operating Reactors Branch #5 Division of Licensing
Enclosure:
Request for Additional Information
1r. R. Dietch Juy-23, 1980 cc Charles R. Kocher, Assistant Director, Technical Assessment General Counsel Division Southern California Edison Company Office of Radiation Programs Post Office Box 800 (AW-459)
Rosemead, California 91770 U. S. Environmental Protection Agency David R. Pigott Crystal Mall #2 SSarmuel B. Casey Arlington, Virginia 20460 Chickering & Gregory Three Embarcadero Center U. S. Environmental Protection Twenty-Third Floor Agency San Francisco, California 94111 Region IX Office ATTN:
EIS COORDINATOR Jack E. Thomas 215 Freemont Street Harry B. Stoehr San Francisco, California 94111 San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector c/o U. S. NRC P. 0. Box AA Oceanside, California 92054 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676 Mayor City of San Clemente San Clemente, California 92672 Chai rman Board of Supervisors County of San Diego San Diego, California 92101 California Department of Health ATTN:
Chief, Environmental Radiation Control Unit Radiological Health Section 714 P Street, Room 498 Sacramento, California 95814
S EST FOR ADDITIONAL INFORMATION SW FRACTURE TOUGHNESS DESIGN SAN ONOFRE UNIT 1 ITFM 1.0 CONCERN The fracture-toughness status of bolting used in the RCP supports is riot clear. From SCE's response of Sept. 15, 1978, it appears that:
a)
Some bolts ordered to ASTM A-307 are used.
ASTM A-307 does not ensure good fracture toughness and is classified by NUREG 0577 as a Group I material (i.e., one of relatively poor fracture toughness).
Design drawings do not unequivocally show that such usage is confined to connections which are not important to structural integrity.
Note, for example, the use of such bolts to support lateral bumper guides.
b)
At least some bolts installed during seismic backfit were required to meet Charpy V-notch requirements.
On the other hand, none of the originally installed bolting was procured to such requirements.
The concern is that some members important to structural integrity may have bolted connections of poor fracture toughness.
REQUEST, ITEM 1.0 1.1 Please list all bolting connections used to join or support principle elements of the RCP structure, where bolts were ordered to ASTM A-307.
For each, indicate bolt diameter, critical loading combination, maximum tensile load in the most severely stressed bolt, and bolt prestress.
Identify which bolting was supplied for original construction and for seismic backfit. If bolting was ordered for seismic backfit, clarify whether or not it was required to meet provisions of paragraph NF 2333 of Section III of the ASME code. If tested, provide test reports.
1.2 If the fracture-toughness adequacy of all ASTM A-307 bolting important to RCP support integrity can not be directly demonstrated from data provided in Item 1.1, please provide a fracture-toughness evaluation for the A-307 bolt found to be most highly stressed in tension. In making such evaluations, general guidance as to methods acceptable to NRC is provided by NUREG 0577 (Draft).
ITEM 2.0 CONCERN NUREG 0577 ranks steel specifications according to the fracture toughness of products typically supplied under each specification when no additional material requirements are included in the procurement order. A Group II rating is assigned to specifications governing steel of intermediate fracture toughness.
NUREG 0577 also establishes NDT criteria to screen steels for their suitability for use in S/G and RCP supports. Certain Group II steels meet these screening criteria in applications where members are thin, but fail them if members are thick.
Thus, although use of these steels in thin sections is acceptable, no outright sanction for thick section use is granted. In such cases fracture-toughness adequacy must be evaluated for each specific application.
Guidance as to methods, acceptable to NRC, for making such evaluations is also supplied by NUREG 0577.
The design of the supports for the San Onofre Unit 1 nuclear power station, incorporates thick section use of ASTM A-36 steel which does not meet the NDT screening criteria.
REQUEST, ITEM 2.0 In order that the fracture-toughness adequacy of such applications may be evaluated, please sutmit the following information:
a)
Identify all applications where this steel is used in thick sections. An acceptable procedure for making such determinations is to use the formula:
K 2 t 25[-ID tc
- 2.
D Where:
yD ayD is the dynamic yield strength of the steel.
KID is the nominal minimum assured fracture toughness of the steel in accordance with values supplied by NUREG 0577.
t is the critical thickness.
In members thicker than t c, brittle (i.e., plane strain) behavior may be expected.
If adequately documented, other procedures may be employed in making this determination. For example, if other KID values specific to the steel used in the application are known from mill or other tests; these may be used in lieu of values taken from NUREG 0577.
b)
For structural members found to be thick, please submit the following information:
- 1.
Mill test records, along with any additional available information which may be indicative of.fracture toughness (e.g., supplementary material specification requirements, or other test results).
- 2.
Identify which of the thick members is most highly stressed in tension on the thick section.*
Report the most severe primary stresses and the most severe primary-plus-secondary stress found, the station at which these occur, and the loading combination(s) that produces them.
c)
Please furnish a fracture-toughness adequacy evaluation of the condition identified in Item (b, 2) above. Guidance as to acceptable means for making this evaluation is provided by NUREG 0577.
- In making this determination, consider each thick member individually.
For each, identify the loading combination which most highly stresses the thick material at its most critical station. For example, if the member is a thick flange I-Beam, the highest tensil stress in the flange is of interest. Compare these stresses among all members.
Only the results for the member found to most highly stressed need be reported.
ITEM 3.0 CONCERN Additional information is necessary to help evaluate the fracture-toughness adequacy of S/G and RCP welding.
REQUEST, ITEM 3.0 a) Which welding processes (SMAW or SAW) were used for joints of the S/G hanger support frames such as that shown at elevation 31 ft 7 in on Bechtel Drawing No. 568101-8? What electrodes (type and diameter) and what welding conditions were used for these and similar RCP support frames weldments?
b) What inspection techniques were used for S/G and RCP weldments in the original construction?
Specify inspection methods and frequency of visual inspection of weld passes.
c)
Which ASTM A-514 elements are welded?
What welding prdcesses, welding conditions, and diameter of electrode(s) are used?
d) Which welds for seismic backfit were given post weld heat treatment?
How was the heat treatment done (time, temperatures, methods)?