ML19345G122
| ML19345G122 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 02/01/1974 |
| From: | Searls F PACIFIC GAS & ELECTRIC CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| 1059, NUDOCS 8103020615 | |
| Download: ML19345G122 (2) | |
Text
~.,
fogulblory Docket "";
PACIFIC GAS AND ELECTR,IC C O M PANY bM'jlf 77 BEALE STR F R A N CISCO, C ALIFO R NI A 94106.(415) 781-4211 I
e A.
P R E o r R e c x T. s E A R L S
=Q w.es asa.
Fqb,ruarfgl 1974
,';f.lg{gll,
,,o...m..,........u....t
.s o H N C. MORR 8SSE Y
(/
b p
(Q a _e... e,
s... a
=.\\
r
=..... =.., _,..
.dJl Lq
_) 4 w,u...
..o..
q, Ip) 1
,t,,.%..,", g h,3j
- .:;,w
[-
g
..;g,...n..
-,ui
.so-~.
n g
om..........
s ALu
....u.
m......
-O
~W.
N f-
.-.-.-6s.=.
u a 6 eo<w a. u ae.n u on 4C
.\\
k
[.8 g % P
.. 4
..... '1".*ll.'.
,, hs 4
.-imi,a.c..=s.s E
.n s..
&T"**.'.* '.* M Mr. J. F. O' Leary
'((
'::'-".l t.O
Director, Directorate of Licensing m $rm O
"it E"'"-
Office of Regulation N
,),
3.5 E,I."",7;.f.
U. S. Atomic Energy Commission d.
Washington, D. C. 20545
~
I':::rt;O."=::
Re:
Docket No. 50-133 License No. DPR-7
Dear Mr. O' Leary:
Pursuant to Section IX.H.2.b. (2) of the Humboldt Bay Power Plant Unit No. 3 Technical Specifications, we are hereby notifying you of a malfunction of the suppression chamber vacuum relief line automatic isolation valve.
The malfunction occurred at 2210 on January 2, 1974 when the valve closed at a drywell pressure below its set pressure due to the malfunction of its initiating pressure switch, dPS 665.
At the time of the malfunc-tion, the Unit was operating normally at 209 MWt, 62 MWe.
The pressure switch is a Mercoid model CP, bellows operated, magnetic mercury switch, with a pressure rating of 80 psig and a range of 0--60 ~ inches of water.
When it was disas-sembled on the morning of January 3, 1974, the return spring was found to be exerting no pres'sure on the magnet arm, allowing the arm to swing freely and not follow the bellows movement.
The spring was replaced, and the pressure switch was tested satis-factorily.
The suppression chamber vacuum relief isolation valve.
was re-opened and the vacuum relief line reported normal at 1532 on January 3, 1974.
Technical Specification Sections III.B.10.b, Pressure Suppression Containment, and III.B.10.a, Power Operation require that the suppression chamber vacuum relief isolation valve be open during power operation except on high drywell pressure.
In considering the containment status, the closure of this valve was in the safe direction because it is designed to shut on increasing P00R ORIGINAL s
g S/63ORDbaIC
-4
I..
Mr. J. F. O' Leary 2
February 1,1974 drywell pressure, loss of control air, or loss of electrical power.
The closure of the isolation valve during power operation removes the protection against suppression chamber liner damage due to excessive vacuum.
However, since the suppression chamber is normally pressurized to 10 inches of water during power operation, a vacuum is not expected to occur under any operating or accident conditions relating to power operation.
Therefore, the failure of the pressure switch and resulting isolation of the suppression chamber vacuum breakers did not result in degradation of the pressure suppression system or of plant safety.
Very truly yours, f
f
/
l i
l l
l l
l l
I
.