ML20076B989
| ML20076B989 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Point Beach |
| Issue date: | 08/10/1982 |
| From: | Noonan V Office of Nuclear Reactor Regulation |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19302F297 | List:
|
| References | |
| FOIA-82-309 NUDOCS 8210070228 | |
| Download: ML20076B989 (2) | |
Text
-
UNITED STATES g_
NUCLEAR REGULATORY COMMISSION
- e
- WASHWGTON, D. C. 20555
,) 1 4
)
MEMORANDUM FOR:
A. Schwencer, Chief Operating Reactors Branch No. 1 Division of Operating Reactors i
FROM:
V. S. Noonan, Chief Engineering Branch Division of Operating Reactors I
THRU:
L. C. Shao, Acting Assistant Director for Engineering Programs
(.
Division of Operating Reactors
SUBJECT:
POINT BEACH UNIT 1 - PROPOSED STEAM GENERATOR INSPECTION i
AND TUBE PULLING The Engineering Branch, Division of Operating Reactors, has reviewed Wisconsin Electric Power Company's submittal dated February 26, 1980 regarding its pro-
. posed eddy current inspection program and plans for pulling of defective tube samples during the upcoming outage for steam generator inspection and hydrostatic-
. testing at Point Beach Unit 1.
It is our recommendation that the licensee's program be revised-to reflect the following comments:
~ ~ -- -
1.
Eddy current inspection of the cold leg tubes should not be limited to the peripheral tubes, but should also include additional tubes in the high heat flux areas of the tube bundles which experience has 'shown to be most susceptable to the deep crevice phenomenon.
2.
Three (3) of the five (5) tubes found in October 1979 to contain defects at or above the top of the tubesheet should be removed for laboratory examinations.
3.
If additional tubes are found defective at or within one inch of the l
top of the tubesheet, the number of such tubes to be pulled should be based upon considerations such as the number of tubes involved and the locations of-the tubes within the tube bundle.
(
Our evaluation is enclosed.
f.
2++
V. S.-
nan, Chief Engineering Branch Division of Operating Reactors
Contact:
J. Strosnider X27356 f
cc: Next page l
imwp
== ~
cLON082-309 PDR
--_.._~:--
=,
.2 2 - -
z~a:T 2
- ='
T
,+
POINT BEACH UNIT 3 EVALUATION OF PROPOSED STEAM GENERATOR INSPECTION AND TUBE PULLING ENGINEERING BRANCH DIVISION 0F OPERATING REACTORS INTRODUCTION In accordance with the November 30,~ 1979 Confirmatory Order, Wisconsin Electric
~
Power Company submitted, by letter dated February 26, 1980, its eddy current inspection program to be conducted at Point Beach Unit 1 during the upcoming outage.
This submittal also describes the licensee's plans regarding removal of defective tube samples for laboratory examinations.
EVALUATION l
The licensee's proposed eddy current inspection program bounds those areas in both l
steam generators where deep crevice corrosion has previously been found.
In addition.
a random 3% sample of the un-plugged hot leg tubes outside these areas will be con-l ducted and cold leg inspection from the hot leg of 20 selected peripheral tubes in each steam generator has been proposed. With the exception of the proposed cold leg inspection we have concluded that the proposed inspection program prov1 des an adequate initial sample for evaluating the condition of the steam generators. Re-garding the cold leg inspection, the initial sample size should include a minimum I
of 3% of the cold leg tubes.
Since these inspections are being performed by driving l
. the ECT probe from the hot leg through the U-bend to the cold leg, difficulties can occur in inspecting inner row tubes which have small radius U-bends. However these inspections should not be limited to. peripheral tubes but should be expanded to the _._
extent practicable, to those high heat flux areas of the bundle which experience has shown to be most susceptible to the deep crevice corrosion phenomona. Requirements for, additional inspections, based on the results of the initial sample inspection will be dctermined in close cooperation with the NRC and the inspection will not be considered complete without NRC concurrence. The proposed inspection will be per-formed using multifrequency ECT. Of those ECT techniques currently available, this technique provides the best sensitivity to tube degradation in the tubesheet and at~
the tube sheet surface. We therefore find this technique acceptable.
With respect to the licensee's proposal not to pull any of the five (5) tubes which were found during the October 1979 inspection to contain defects at or above the tubesheet, we find it not acceptable.
It is our conclusion that the pulling and laboratory examination of at least three (3) of these five (5) tubes is necessary to confirm previous conclusions, based upon an evaluation of eddy current data, that the defects are wastage and not related to the general intergranular corrosion occurring within the tubesheet crevices. The occurrence of general intergranular corrosion above the tubesheet would represent a significant safety concern and it is, therefore, our conclusion that the man-rem exposure associated with the tube pulling operation is justified. We also do not agree with the licensee's proposal,to pull only one (1) tube if one or more tubes are found during the upcoming inspection with dete ts at or within one inch of the top of the tubesheet.
It is cur conclusion that the nu & r of tubes pulled must be based upon considerations such as the number of tubes inv @ ed and the locations of the tube within the tube bundle.
_