ML20056B640
| ML20056B640 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 11/12/1971 |
| From: | Larson C NORTHERN STATES POWER CO. |
| To: | Grier B US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9102070654 | |
| Download: ML20056B640 (1) | |
Text
'i'>% Uk) % i W( -
j j
s i
-1_
ld NORTHERN STATES POWER COMPANY Monticello Maclear Generating Plant 1}
55352
%nticellol., Minnesota T,'r u...=
c ~; y ;
.e.
,, i * :.,'.
.c w '
"o
. u.#
.c,v.
., c 2
- ;; r.f.',,,c..,'",,'. 'jj,..
..:.o.
- .,b'q,-
.,.....a. ;'
r 3
,;, ;. h...p.
l.a. V' -
i '.. J W. 3 "*.......
y' l.
g'
....i,:l.' v !.. [g,..'
. i.:: a
..n.
~ 6. /;9,. :....:#';%,y:..
~ " '
)1 November 12, 1971
.~;.. ' '. '-
.cr.:...
.s.
....h., : '.','.'6
. ' a,b l,. ',", [
,'.I [.L
[,1 l f
.g *; i 2
. i
,.s,...I
~
.g 4
j
.. )..:L W.
7
..;a
.y O;
." : S,?, $ ",
4 Mr. Boyce Grier
'i':f; 0,.,,
Reaion iIl Compt iance Office
' hl ".a f'.
5.
4 799 Roosevelt Road
)
Glen Ellyn, Illinois 60137
.p;f
Dear Mr. Grier:
d.'.7
-. ' '.ab.ui.i.;. a_
On Thursday, November 11,1971 'and Friday, November 12,1971, while performing a regularly scheduled surve'illance test, two main steam line high flow sensors, cPIS 2-1170 and d)lS 2-11@, were discovered to trip above the calibrated setpoint "of 113% steam flow, The switches were found to trip at 137% steam flow and 123% steam flow respectively. The e
-f two failed sensors tronitor flow in separate steam lines and would not have
!j prevented the steam lines from isolating if an actual steam lino flow of-h 113% had been reached.
t j
The reason for the switch failures is not known at this time;
.y however, as a result of.the detected failures, the sixteer, steam line flow sensors will be replaced with the 0-200 psid switches which were formerly.
i used in the protection circuitry. The failed sensors, which have a rance F
of 0-70 psid,were installed on September 1 as replacements for the 0-200 l
L]
psid switches. An investigation of the switch failures is continuing.
4 Your office will be advised of the results"of' the investipation and 4y,i our final resolution of the problem. >
i (j'
Yours very truly,
!.s '..Q' i
i' 44 9
p,
' 'r **
.v',.
c,
(
4 cq C.E. Larson, Plant Superintendent / i y~
(
'.4../
i,
"'s.,
j;q Cc: R.O. Duncanson.
S 1
t i' '3.'
+, '
O,%
CEL/ cat
.s
,+>
.p i ?'.
- p Y1 C. i <.
- o id.
,.1...s sq p ' k..':
~
p;
.. l,jj s bt 9102070654 711112
,o s~
g
. < '.
- A.
"~
n 4;.
[
CF ADOCK 05000263
'.h ed.g CF L.
A
'i i
~
w 9.:
^
h d
-~-,m>
..-. 3 m m
__