ML20004F600
| ML20004F600 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 05/22/1981 |
| From: | Gilberts D NORTHERN STATES POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-79-26, NUDOCS 8106190190 | |
| Download: ML20004F600 (2) | |
Text
.
g Northem States Power Company 9
J 414 Nicollet Man D.E. Gilberts Minneapoks. Minnesota 55401 s.n or vie. Pr ie.m Telephone (612) 330-6071 Power supply 1
May 22, 1981 7 9 0
9> f dl 4
c' nCULb((*d t Mr. James G. Keppler N
L Director, Region III h.
..,13 IO3I h 'Ig Office of Inspection and Enforcement g u.s.
re,,
U. S. Nuclear Regulatory Ccamission i fj\\,
Og 799 Roosevelt Road
/
f Glen Ellyn, IL 60137
Dear Mr. Keppler:
MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Responge to IE Bulletin No. 79-26, Rev. 1 The destructive examination of Monticello's most highly exposed control blade 'nas been completed, with the following results, in response to IE Bulletin No. 79-26, Revisien 1, Item 4.
A.
The tubes examined were tubes numbers 1, 2, 3, 4, 5, 7, 10, 12, 20 and 21 from wing 1 of control blade MT77R.
(Tube 1 is the outermost tube).
B.
All of the tubes were visually examined, and the tcp approximately one-half of each tube was also eddy-current tested. Through-wall defects were found in tube 1 at the following approximate dis:.ances from the tube top:
4, 4, 5, 9k,11,11 3/4,13k,16, 20, 26, 29 3/4, and 30 inches. No through-wall defects were found in any other tube.
C.
The calculated B-10 depletion (percent) for each tube examined versus elevation is:
Tub e Upper 3' Upper Mid 3' Lower Mid 3' Lower 3' 1
47 37 33 7
2 45 35 32 6
3 43 34 30 6
4 41 32 29 6
5 39 30 27 5
7 36 28 25 5
\\/ %$
10 33 26 23 5
~
12 32 25 22 4
20 25 20 18 3
i 21 24 19 17 3
- 810 a 10o 80 0
J
+
)
e.
Mr. James G. Keppler Page 2 May 22,1981 D.
The only significant loss of B C was found to be in tube 1.
The loss g
front extended from the top end plug down about 33 inches.
E.
The =mv4=um local depletion for tubes having no cracks was found to be 6*.98 percent B-10 depletion, near the top of tube 3.
F.
The maximum local depletion for tubes having no loss o' boron was found to be 67.98 percent B-10 depletion, near the top of e <te 3.
(This is the same as item I because the only tube with a crac 2 also showed a loss of boron.)
If additional information is required, please communicate directly with plant management.
Yours truly, D. E. Gilberts Senior Vice President Power Supply cc:
'[r. C. H. Brown Mr. G. Charnoff Director, Office of Inspection and Enforcement Division of Reacter Operations Inspection U. S. Nuclear Regulatory Commission Washington, D. C.
20555 DEG:nk i
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