ML18227C666
| ML18227C666 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 12/14/1976 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Goller K Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18227C666 (3) | |
Text
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D4 4~*~4 UNITEDSTATES NUCLEAR REGULATORYCOMMISSION WASHINGTON, D. C. 20555 MEMORANDUM FOR:
K. R. Goller, Assistant Director for OR, DOR FROM:
SUBJECT:
D.
G. Eisenhut, Assistant Director for OT, DOR REQUEST FOR INFORMATION ON STEAM GENERATOR TUBE INTEGRITY Attached herewith is a list of questions regarding the PWR steam generator tube integrity, specifically for tubes in the U-bend region.
These questions are applicable to the following plants:
Surry Unit 1
(Docket No. 50-280)
Turkey Point Units 3
8 4 (Docket Nos. 50-250/251)
San Onofre Unit 1
(Docket No. 50-206)
For San Onofre Unit 1, this list of questions may be revised, de-pending upon the results of the inspections currently being per-formed.
Enclosures:
As stated
\\
D.
G. Eisenhut, Assistant Director for Operational Technology Division of Operating Reactors cc w/encl:
V. Stello, Jr.,
DOR L. C. Shao, OT R. Reid, OR G. Lear, OR A. Schwencer, OR R. Stuart, OT W. Hazelton, OT M. Fairtile, OR F. Burger, OR D. Elliott, OR B. Liaw, OT F. Almeter, OT
12/8/76 ENGINEERING BRANCH DIVISION OF OPERATING REACTORS INFORMATION REQUIRED FOR SAFETY EVALUATION OF STEAM GENERATOR TUBE INTEGRITY 1.
Provide a tabulation summary of the total strains in the circum-ferential, longitudinal and radial direction at the U-bend apex for tubes at flow slot locations in rows 1 to 4.
The summary should indicate the effects due to manufacturing, service induced ovality (hourglassing),
change in U-bend radius, operating thermal and pressure loads and accident loads.
Also compute the effective strains at the U-bend apex.
2.
Estimate the error band and specify the degree of confidence in the strain data provided in response to question 1, i.e. specify the tolerances in the manufacturing strain.
3.
Indicate whether all tubes within the bundle are from the same heat and if possible provide information of what effect heat-to-heat variations would have on susceptibility to intergranular cracking at the U-bend apex of tubes in rows 1 to 4.
4.
Provide a quantitative analysis of the effect of flow slot closure at the top and bottom support plate on thermal hydraulics, flow
- patterns, vortices and tube vibration, support plate and tubes in the dented regions, support plate wedges, subsequent wrapper defor-mati.ons, and vessel shell integrity.
5.
Describe the anticipated extent of cracking of any support plate after the flow slot has closed.
Estimate the amount of operating time required for such closure.
Describe the subsequent effect on the tubes, wrapper shell, etc.
6.
When all flow slots completely close, the support plates will have a tendency to buckle but are restrained by the tubes.
Provde an assessment of it's effect (the tendency to buckle) on the tube integrity.
7.
As originally designed the support plates did not restrain the tubes during the heat-up and cooldown axial thermal expansion of the tubes.
With corrosion particle buildup in the annulus between each tube and the support plate, restraint to thermal expansion is pro-vided.
guantify the effect of such restraint upon the tubes and the support plates.
8.
How many tubes have been examined at the U-bend apex?" Describe the methods of examination, the degree of confidence and the results.
9.
What magnitude of service induced and/or total effective threshold strain is required to initiate intergranular cracking on either the extradose or intradose ID surfaces at the U-bend apex, and how is it affected by the change in the U-bend radius and thus the pre-strain or ovality in rows 1 to 4?
10.
Since ovality and U-bend radius is strictly a geometrical
- measure, what are the kinetical relationships between ovality or strain with total stresses at the U-bend apex.
11.
Indicate the number of EFPD between the advent of tube denting and flow slot hourglassing.
12.
Indicate the effects of frequent heat-up and cooldown cycles on the support plate hourglassing and cracking due to thermal induced strains.