ML19319E133
| ML19319E133 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/18/1975 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| References | |
| NUDOCS 8003310639 | |
| Download: ML19319E133 (2) | |
Text
.
5
, 4 m %mo fy Q.. nn p
.c
(
SACnAMtNTO MUNICIPAL UTiUTY DisTnlCT O 6201 S Stn.et, Box 15830 Sacramento, Cal'fornia 95813; (916) 452 3?11 t
April 18, 1975 7*
h
- f.
k; si
?
Director i
-i Division of Reactor Licensing I
U.S. Nuclear Regulatory Commission Washington, D. C.
20545 i
i Operating License DPR-54 3-Docket No. 50-312
, Unusual Event 75-2
[.,
f
Dear Sir:
As defined by Technical Specifications " Appendix B," Section
-)
5.6.2.C, we are reporting the following Unusual Event as UE-75-2.
?
4' During normal operation at Rancho Seco, chlorine is injected-h-
into the Circulation Water System to control algae. The additions are at high concentration to " shock" the organisms affixed to. the main condenser i
and to increase the total circulating water system to approximately 1.0 ppm chlorine, The programmed-injection starts automatically twice a day at 0900 arid 2i00 asid tierisiisioi.es ot 1030 orid 2230. The sequence innoives 1/2 5
hour injection into one-half of the main condenser,1/2 hour
- to the Plant Cooling Water System (part of the Circulating Water System), and 1/2 hour into the second half of the condenser. When the system is operating I'
at. power the chlorine is removed from the warm water when sprayed through, the cooling towers.
On April 7,1975, the reactor was shut down and the automatic
'{.'k chlorine injection was terminated by putting the system in manual mode.
The circulating water system is kept at low chlorine levels by controlled 3
injections manually. An addition of chlerine on April 7 consisted Qf a 30-minute injection at a rate of 1.38 Lb/ min. A check that afternoon 9'
showed 1.95 ppm in the Circulating Water System and 0.1 ppm at the plant 2
effluent. The dilution flow in the plant effluent was increased to assure k
control.of the effluent chlorine within the limit of 0.2 ppm.
. !l However, on April 8,1975, the dilution flow was secured at 0130
)
and a sample that morning indicated 0.4 opm chlorine in the plant effluent.
i Dilution flow was re-established and blowdown from the Circulating Water i;
System was terminated. The chlorine at the plant effluent decreased to undetectable at 1150 that day and thereafter remained below the
)
l specification limit.
i
[~p
.y b333 00s
- i 8
i,txar08l90f/
u.
n ectaic s,5 m m m.c mt m
.a c..m in m t
4 4
- a. m pat
- Director, Division of. Reactor Licensing April 18, 1975 A check at the chlorinator station indicated that the controls were put in automatic during the April 7,1975 injection and remained in
-this mode for two cycles. The automatic injection added much more chlorine to the system than originally requested. This explained the high chlorine concentration in the Circulating Water System and plant effluent. The system was turned to "off" position shortly after measuring high chlorine in the effluent the morning of April 8.
To prevent reoccurrence of this event, the operating proced'ures will be modified to include the following.
!I (1) During shutdowns the chlorinator will be secured by putting the system in "canual".
I (2) Chlorination during shutdowns will be done in " manual" mode only.
~
(3) Chlorination during shutdowns will be done only as requested by the Radiation-Chemistry Group.
In addition to the above changes, the Generation Engineering Group will evaluate the feasibility of installing an on-line chlorine monitor in the plant effluent monitoring system.
We feel ~ that if the above conditions are put into effect, the safety of the environment will be assured and a reoccurrence of this event will be prevented.
Y Respectfully,
.. %n=a l
J. J. Mattimoe Assistant General Manager and Chief Engineer-cc:
R. H. Engelken, Region V i
]
i e
r i
t.
f t
f
..o
=_ _,.. _
-.