ML13330A119
| ML13330A119 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/23/1980 |
| From: | Baskin K Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-12, REF-GTECI-EQ, TASK-A-12, TASK-OR NUDOCS 8009300377 | |
| Download: ML13330A119 (5) | |
Text
Southern California Edison Company P. 0.
BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 K. P. BASKIN TELEPHONE MANAGER OF NUCLEAR ENGINEERING, September 23, 1980 (213) 572-1401 SAFETY, AND LICENSING Director of Nuclear Reactor Regulation Attention: D. M. Crutchfield Operating Reactors Branch #5 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Fracture Toughness Design San Onofre Unit 1 By letter dated July 23, 1980 you requested additional information regarding the steam generator and reactor coolant pump supports at Unit 1.
The enclosure to this letter responds to your request. It is understood that this information is necessary for the staff's continuing review of the fracture toughness design of the steam generator and reactor coolant pump supports.
If you have any questions regarding this information, please let me know.
Very truly yours, Enclosure 80093003 77'
ADDITIONAL INFORMATION FRACTURE TOUGHNESS DESIGN REACTOR COOLANT PUMP AND STEAM GENERATOR SUPPORTS SAN ONOFRE UNIT 1 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 cannot 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).
RESPONSE
1.1 The reactor coolant pump support design drawings were reviewed to determine if A307 bolts were used to join any principle elements of the structure.
It was found that A307 bolts were used in only two types of connections as described below:
- a. Vertical column to base mat embedment connection for 4 columns on RCP G-2A and 3 columns each on RCP G-2B and RCP G-2C. The embedded bolts are 1" diameter.
- b. RCP upper lateral support bumper-to-frame connections for each of the 3 bumpers per RCP added during the seismic backfit project. These are 1 1/2" diameter bolts.
The load and stress evaluation of these structures shows that both the columns and lateral bumpers are loaded only in compression for both the normal operating condition and a seismic event.
Consequently, the bolts cannot be loaded by the structural members.
The bolts installed during the seismic backfit program were tightened snug tight as stated on Westinghouse drawing 1461F10. They were not required to meet Charpy V-notch requirements.
1.2 The fracture toughness of the A307 bolts on the reactor coolant pump supports is not important for the pump support structural integrity since the bolts aren't required to resist any loads. Hence, a fracture toughness evaluation of the bolts is not necessary.
-2 ITEM 2.0 In order that the fracture-toughness adequacy of such applications may be evaluated, please submit the following information:
- a. Identify all applications where this steel is used in thick sections. An acceptable procedure for making such deteminations is to use the formula:
K 2
t =2.5 ID c
o~yD Where:
oyD is the dynamic yield strength of the steel.
ID is the nominal minimum assured fracture toughness of the steel in accordance with values supplied by NUREG 0577.
tc is the critical thickness. In members thicker than tc, 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 of 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.
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 tensile stress in the flange is of interest. Compare these stresses among all members. Only the results for the member found to be most highly stressed need be reported.
-3
- 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.
RESPONSE
- a. The critical section thickness tc used for determining thick section A36 members was calculated using the relationship given above:
K 2
t ID tc = 2.5 ["']
c MyD A value of KID equal to 35 ksi \\ff Fwas used per NUREG 0577. The dynamic yield strength of the steel was based on the strain rate of the supports for normal and SSE loads and published experimental results regarding the yield strength of mild steel under various loading rates. The resulting minimum thickness for a "thick section" was found to be about 2 inches.
- b. The only A36 SG and RCP support members having thicknesses greater than 2" are some W14 x 398 columns on loop C, which have 3.0 and 2.8 inch flange thicknesses.
As stated in the reply to Request Item 1.0, these columns are always loaded in compression for the normal condition and seismic events, so they never have any tensile stresses.
- c. Since the "thick section" members are always loaded in compression, the fracture toughness of the members isn't important to the support integrity, and a fracture toughness evaluation isn't necessary.
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 feet 7 inches 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 processes,.
welding conditions, and diameter of electrode(s) are used?
How was the heat treatment done (time, temperatures, methods)?
-4
RESPONSE
a & b. Although no specific construction inspection documents have been located at this time, the following standards were applicable at the time of original construction:
Base Material, ASTM A-36 E70 Series Electrodes ASTM A233 (1964)
Manual Shielded Metal-Arc Process AWS Standard Code for Welding in Building Construction (1964)
Visual and Liquid Penetrant Inspection C. It is assumed that this question is related to Table 1-3 in the report "Fracture Toughness and Design Considerations for Addressing Lamellar Tearing of Steam Generator and Reactor Coolant Pump Support Material" dated September 1978. This table was based on the original Bechtel support specification which included all primary equipment supports. The design drawings do not show any A514 steel used for the steam generator and reactor coolant pump supports. A514 plate was used in the reactor support structure. However, since bolted connections were utilized, there was no welding on the A514.
- d. Seismic backfit procurement records show that for shop fabricaton, welds were heat treated in accordance with ASME III Paragraph NF 4600. Welds requiring PWHT are those on material over 1 1/2" thickness except fillet welds with a throat thickness of 3/4" or less and partial penetration welds with a groove depth or preparation 3/4" or less. Weldments were generally furnace heated. The holding temperature ranged from 1100OF to 12500F. The minimum holding times were 30 minutes for 1/2 inch or less nominal thickness, 1 hour/inch for 1/2 to 2 inches, and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> plus 15 minutes for each inch over 2 inches for nominal thicknesses over 2 inches. Below 8000F, rapid heating and air cooling was permissible, but above 8000F, heating and cooling did not exceed 4000F per hour divided by the section thickness. The heating and cooling did not have to be less than 100OF per hour, but could not exceed 400oF per hour.
The maximum temperature variation on any weldment was 2500F.