ML20113E044
| ML20113E044 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 01/17/1985 |
| From: | George Alexander COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 9648N, NUDOCS 8501230289 | |
| Download: ML20113E044 (4) | |
Text
.-.
'/ OJ Commonwealth Edison i
[
) One First National Plin, Chicago Illinois
( C
. Address Reply to: Post Othea Box 767
. Chicago, lilinois 60690 s
January 17, 1985 Mr. Harold R. Denton, Director Office of-Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Quad Cities Station Units 1 and 2 Response to Request for Information NRC Docket Nos. 50-254/265 Reference (a):
Request for Information-Nuclear Power Plant Biofouling D. B. Vassallo letter to D. L. Farrar dated November 15, 1984
Dear Mr. Denton:
Reference (a) requested that we provide information concerning the Quad Cities Station program for surveillance and control of aslactic clams in plant water systems.
The attachment to this letter contains our response to those questions.
Please address any additional questions that you or your staff may have concerning our response to this office.
.One original and fifteen copies are being provided for your use.
Very truly yours, u
Greg A exan er Nuclear Licensing Administrator
-Attachment lh, p
.9648N i
\\\\
h M obh4 P
rM o
~
ATTACHMENT The maintenance ' staff at Quad Cities Station is aware of the potential for fouling of plant heat exchangers and components by Asiatic Clams._.This response will address the methods used to detect flow blockage caused by Asiatic Clams and methods used to control accumulation of Asiatic Clams.
There are five systems that use Mississippi. River water for cooling at Quad Cities Station.
These systems are the main condenser circulating water system, the plant-service water system, the Residual heat removal (RHR) service water system the diesel generator cooling water system, and the fire protection system.
The circulating water and service water systems are in continuous operation; while the RHR service water, fire protection, and diesel generator cooling water systems are only run on an as-needed basis, normally abot once per month.
I.. The following described the surveillance and inspections performed to detect flow blockage and fouling of equipment:
A.
The Circulating Water system is monitored for differential pressure.
A high differential pressure is indicitive of flow blockage.
In addition, the efficiency and overall performance of the main condenser are monitored.
A loss of efficiency is indicitive of bio fouling.
B.
Major heat exchangers in the Service Water system are routinely inspected for presence of fouling or flow blockage.. The following is a list of major heat exchangers and' inspection invervals:
l.
Recirculation Motor-Generator Set Oil Coolers (8) -
Once per 3 years 2.
Reactor Building Closed Cooling Water Heat Exchangers
+
(5) - Once per 3 years 3.
Turbine Oil Coolers (4) - Once per operating cycle (18 i
months) 4.
Turbine Building Closed Cooling Water Heat Exchangers L
(4) - Once per 3 years 5.
= Stator Cooling Water Heat Exchangers (4) - Once per 3 years C.-
Flow rate testing of the RHR Service Water System is performed once every 3 months.
This test consists of verifying-that the system flow is~ greater than 3500 gpm J
against a system pressure of 198 psig.
Flow blockage in I
r
,['
. - ;J";
(
, the system would be reflected by degraded
['
. performance.
The performance of these tests is tracked by-the Inservice Testing (IST) program,-and a idrop in system performance'would result in_correctiv'e action, if necessary.
In addition.to this, the heat exchangers are inspected every three years for
~-
evidence of blockage.
D.
The: Diesel Generator Cooling Water-: System provides cooling' water to..the heat exhangersuon the emergency diesel generators.
These heat exchangers are inspected for flow blockage every operating cycle (18 months).- In addition to this, a flow performance test of the systems is conducted. quarterly; with the results tracked:by the IST program.
E.
The following testing is performed to verify that no flow blockages have occurred in the fire protection equipment:
1.
The diesel-driven fire pumps are tested for
^ adequate flow rate every operating' cycle (18 g
. months).
s 2.
Flushing of external fire hydrants is performed twice per year.-
3.
Sprinkler head,. nozzle, and wet pipesfire suppression systems:are inspected once per year.
The above actions'have proved adequate in detecting and clearing accumulations of Asiatic Clams and other biofouling agents'before significant flow blockage of major heat removal' equipment has.
. occurred.
-.II.iThe.following.are the.:ethods used.to control Asiatic Clams in plantSwater:sytems:
A.
1The control' of-biofouling agents in the circulating water
" system. consists of~ periodic: flow-reversals'and treatment withfa biocide.
In addition,-the main condensers are
~ '
cleaned every' operating. cycle'to remove any fouling that.
has accumulated.
q,
-8.
Control?in'the_ Service' Water' System presently: consists of removal'of accumulations during inspections.
The system
.was equiped'to' inject: chlorine dioxide (C10 ); however,.
2
- C102 has proved toHbe an' ineffective blacide..
/ nstallation of a new blacide injection'systm on the-I
' Service Water-System is in progress.
The new systemcwill-
^
i A
m,
- .. cd A '
f
~
. e useJa bromine-based biocide, which is-thought to be more Jeffective'than chlorine.
When this. system is installed,
'it should provide. protection from intrusion of Asiatic LClam-: larvae.
Injections of quantities of biocide
-sufficient.to provide' effective control for adult Asiatic
- Clamscis-not possible because the residual levels would
- farjaxceed the levels allowed by the plant discharge
- permit.
Continuous biocide injection is also not permitted by the plant discharge permit.
LC.
l Control in.the RHR Service Water System consists of 1 removal of accumulated shells during routine inspections.
No. biocide is injected in this system at this time, and no
/
1 ~
plans for biocide injection are being made.
The -Station
. feels that the. risks -of chloride or bromide intrusion into the. reactor coolant through potential heat exchanger tube-
. leaks far outweigh the benefits which would be obtained.
. As "s
.D.=
Control-in the_Deisel Generator Cooling Water. System
. consists.of' cleaning the heat exchangers during
. ' inspection.. The ECCS pump room coolers are also fed tur
.this1 system..-The present design of the coolers does:not permit disassembly and inspection of:the~ cooling' water y
side.. A modification to replace these room coolers-with ones which'can be readily inspected is being 1'
~1nvestigated.
No plans for blocide injection in this'
' system are presently being considered.
Ei
, Control in the Fire Protection System is by. periodic i
flushing of;the system.
Because of the large pipe Jdiameters and' lack of heat exchangers in the system,~no problems due to blockage by Asiatic Clams have.been encountered in~this system.
fi
.I,
t r
4648N i
?
i E
9 I
o
_