ML20236E947
| ML20236E947 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 10/26/1987 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 87-474F, NUDOCS 8710300076 | |
| Download: ML20236E947 (3) | |
Text
- - _ _ - -
I l
VIRGINIA ELECTRIC AND Powen COMPANY RicItxown, VIRGINIA 20061 W,L STEWANT i
Vaca Passinawr
.Nuctman Orn aATIONN October 26, 1987 I
United States Nuclear Regulatory Commission Serial No.
87-474F Attention: Document. Control Desk N0/RCB:jmj Washington, D.C.
20555-Docket No.
50-338 License No. NPF-4 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 1 STEAM GENERATOR TUBE STABILIZATION On September 15, 1987, Virginia Electric and Power Company submitted Revision 1 to the Steam Generator Tube Rupture Report.
Sections of this revised report (VI.E.2 and 3) described the methods and rationale which we intended to employ in stabilizing the portion of the ruptured tube which remains in the'"C" Steam 4
Generator.
Westinghouse WCAP-11601 (Proprietary) and WCAP-11602 i
(Non-Proprietary), " North. Anna Unit 1 Steam Generator Tube Rupture and i
Remedial Actions Technical Evaluation," which was submitted on September 23, 1987 describes the process in greater technical detail in Section 4.4.
j Stabilization of the tube is now complete.
The method of stabilization was c
modified from that described in' the referenced reports due to difficulties
)
encountered during installation. These differences are discussed below.
Cold lea stabilization.
When the spear described in Revision 1 was expanded into the seventh Tube Support Plate on the cold leg side, the expanding tool was slightly out of position and ruptured the spear wall over a length of about 1/2 inch.
The crack was mainly axial in nature and occurred near the top of the seventh Tube Support Plate.
After fracture and thermal-hydraulic analyses were conducted, it was decided to install a sleeve inside the spear spanning the distance from the tube remnant to the seventh Tube Support Plate.
This sleeve was approximately 13 inches in length and extended from about 3 inches inside the tube remnant to about 9 inches below the seventh Tube Support Plate.
(See sketch).
The bare hole in the tube sheet (cold leg) was sealed with a welded plug.
Hot Leo Stabilization.
In conjunction with the sleeve installation, the cable stabilizer for hot leg insertion was also installed.
During installation, one of the cable' sections was damaged when the stabilizer jammed on the base plate of the insertion tool.
The damaged stabilizer was removed, the base plate was
- modified, and then a second stabilizer, identical to the first, was successfully installed.
The cable stabilizer extends from the hot leg tube 8710300076 871026 8
PDR ADOCK 05000338 t
g P_
-- -- a
i 4
sheet to approximately 30 past the tangent point at the hot leg U-bend.
The hot leg tube end was sealed with a mechanical plug.
Pluaaina of Neiahborina Tubes.
As described i~n our letter Serial No. 87-474E dated October 26, 1987, the neighboring tubes were preventively plugged.
The method of stabilization, and implementing procedures and changes thereto, have been reviewed by the Station Nuclear Safety and Operating Committee and determined not to involve an unreviewed safety question as defined in 10 CFR 50.59.
If you require any further information, please feel free to call.
Very truly yours, kb W. L. Stewart Attachment l
cc:
U. S. Nuclear Regulatory Commission 101 Marietta Street, N.W.
(
Suite 2900 l
Atlanta, GA 30323 I
Mr. J. L. Caldwell I
NRC Senior Resident Inspector North Anna Power Station i
i
[
\\
l i
I i
J
L 7-- Ex23T!No Tust
(
HYDRAULIC EXPANSION 2.75 (NOM)
(
t3 A
gtgEVE-LIKE TDP PORTION (SLEEVE) l i
-TSP 7 n
M i
l HYDRAULIC EXPANSION v
L.3 J (NOM.)
I 4.co
( aen,)
I r
9:
$\\
d}.
f
__1
,.r'
- w gffy,) h h=
- TSP'S 1 THROUGH 6 20 HYDRAULIC EXPANSION PORTIDN OF i
TUBE REMOVED 6
TUBE-LIKE ECTTDM PORTIDN i
TUBESHEET 3
%Mh6
.......a
% VELD PLUG FIGURE 1
NORTH ANNA No.1 STEAM GENERATDR 'C' TU1E R9C51 U-BEND TUDE REMNANT SPEAR STABILI2ER HYDRAULIC EXPANSION UPPER JDINT/ ROLL EXPANDED LOVER JOINT
_ _ _ _ _ _ _ _ _ - _ -