TXX-3352, Forwards Response to IE Bulletin 81-03, Flow Blockage of Cooling Water to Safety Sys Components by Corbicula Sp (Asiatic Clam) & Mytilus Sp (Mussel). No Clams Found.Mussel Not Evident
| ML20010G238 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 06/26/1981 |
| From: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-81-03, IEB-81-3, TXX-3352, NUDOCS 8109150470 | |
| Download: ML20010G238 (5) | |
Text
. - - _ -
TEXAS UTil.ITIES CEN1%\\ TING COMPANY Log # TXX-3352 exn navas wwsn.nauu.wxas mm File # 10115 aghfd ~,$b;;'
June 26, 1981 3
J Mr. Karl V. Seyfrit, Director U. S. Nuclear Regulatory Commission Region IV RIV 611 Ryan Plaza Drive, Suite 1000 Docket Nos. 50 465/IE Bulletin 81-03 Arlington, Texas 76012 50-446/IE Bulletin 81-03 SUMECT: COMANCHE PEAK STEAM ELECTRIC STATTON i
1981-83 2300 MW INSTALLATION
]
Dear Mr. Seyfrit:
In reference to IE Bulletin 81-03, dated April 10, 1981 we provide the enclosed response.
Sincerely, f
/
R. J. Gary
/
RJG: tis Enclosura:
Response to IE Bulletin 81-03 A 9' N, f cc:
U. S. Nuclear regulatory Commission
/ 02
'4 Office of Inspection and Enforcement C
S/v Division of Reactor Opgrations Inspec p:
/I 3 g
{)k Washington, D.C.
205b m
k> ;>..?j/
.5!
~
&sj
- > r
/
lY
-fG t!
s I t i
8109150470 810626 PDR ADOCK 05000445 O
l Response to IE Bulletin 81 03
" Flow Blockage of Cooling Water to Safety System Components by Corbicula (Asiatic Clam) and Mytilas (Mussel)"
Response to Action Items for holders of Construction Permits.
Inspection Results 1
Squaw Creek Reservoir and tbs Safe Shutdown Inpoundment at CPSES are coneidored fresh water bodies for the purpose of this bulletin, therefsre, the inspection conducted as a result of bulletin 81-03 was for Corcibula or Asian Clam. This inspection was conducted as a supplemental non-routine effort, since it is not required as part of the current environmen.a1 monitoring program.
The inspection began by selecting several areas considered to have a likely habitat for the clams. Areas in both Squaw Creek Reservoir and the Safe Shutdown Impoundment were sampled. Areas sampled contained shallow bottom sediments. The inspection was performed by an inde-pendent consultant under contract to TUCCo during the period of May 12, 1981 to May 15, 1981. The inspection performed found no clams present in any of the areas sampled. This would indicate that if 1
Corbicula are present in either Squaw Creek Reserv0ir (SCR) or the Safe Shutdown Impoundment (SSI), their population is currently too small for detection and therefore do not constitute any problems at this time.
TUGCo does consider, however that the Corbicula population could at some time in the future grow to possibly significant numbers which could create potential problems. Based on previous experience with cooling reservoirs within the North Central Texas area, the period required for Corbicula to establish a significant population may take as long as ten years after impoundment of the resarvoir. As an example, the Texas Power and Light DeCordova Bend Station on Lake Granbury, wh.ich was ispounded in 1968, has or.ly recently (within the past 2 years) experienced any Corbicula infestations. Vi fully expect this phenomena to exist in SCR and the SSI as well. This will allow ample time for more research and the development of more effective treatment methods.
For this reason TUGCo feels it inappropriate to commit to a specific I
treatment method at this time. TUCCo has, however, discuesed possible alternatives currently available, and whick vill be evaluated for application at CPSFS on a selective basirs This discussion is included in the treatmenr/ prevention section of ou response.
~
r l
As stated above, TUGCo has concluded that Corbicula are not present in dete-table numbers, and are therefore not a problem at this time. As a result, inspections of systems and components supplied water from the SSI and currently filled were not required to be inspected. The safety related systems and components supplied water from the SSI are listed below.
Affected Systems 1.
Service Water System Individual Components a.
Component Cooling W,tter
(
Heat Exchangers I
b.
]
Heat Exchangers l
c.
Safety Injection Pump Lube Oil Coolers d.
Centrifugal Charging Pump Lube Oil Coolers e.
Containment Spray Pump Bearing Coolers 2,
Fire Protection System l
t l
Planned Insnection/ Detection Methods:
To ensure against Corbicula infestations TUGCo will monitor for their
{
j growth and ctreading.
On a semi-annual basis both SCR and the SSI l
will le sampled in areas with likely Corbicula habitats.
The SSI l
sampling areas will be chosen on the basis cf habitats within close l
proximity to the intake for the Service Water / Fire Protection l
systems.
This will inform us as to not only the presence of Corbicula in the SSI but also whether they are in a position to enter the Service Water or Fire Protection systems. The semi-annual inspections will begin with the past inspection in May. Once Corbicula have been identified in potentially problem causing numbers, this sampling may be fiscontinued.
t,
.= __
l As the Service Water system components are placed in service, TUGCo will begin monitoring of individual component flow rates. All components supplied cooling water from the Service Water system are equipped with flow measuring devices. Using base line data from the initial flow balancing will provide an easy reference for future comparison and detection of flow degradation.
In addition, small strainers on the suction
~ side of the Service Water screen wash pumps can be periodically inspected for clam infestations. This would provide an early warning of clam presence in the system since the strainers filter comparitively small particles.
The Fire Protection system will be monitored by inspecting the discharged water from the periodic flush required by the Technical Specification for clam shells.
These inspection / detection programs will be implemented by procedure.
The above outlined programs will provide pos'itive means of detection of Corbicula since it is a two-fold program.
That is, both the source water to the SSI (SCR) and the SSI itselt' will be inspected for clam presence. As previously stated, past experience with cooling reservoirs in this ar2a shows a considerable amount of time is required for establish-ment of significant Corbicula populations. This will provide further assurance that Corbicula will be discovered prior to any flow blockage problems occuring.
Once a significant population doea become established, flow monitoring of individual components in the Service Water syacea will provide reasonable assurance for intrusion detection.
Since tube size in the supplied heat exchangers varies from " to 3/4" flow blockage would be detected in the smaller heat exchangers prior to a massive blockage occurin~g.
In addition, the strainers at the Service Water screen wach pump sucticn will trap th'e smallest clam shall. Blockage of this strainer would provide the earlies; warning possible of clam intrusion.
Intrusion of clams of sufficient size to block " or larger diameter tubes would require a growinF population to have established itself within the SSI intake structure since the service water screen mesh size is 3/8".
Although the exact velocity of water required to transport a given size clam was not determined, it is expected that the normal velocities in the intake bay to the Service Water and Fire Protection systems would be sufficient to transport a clam of 3/8" to " in size (largest single dimension). This woold mean that i'e the clams existed in the intake bay they would be drawn into the system. Reduction of the SSI water level would only add to the likelihood. Normal level fluctuations from elevation 775 to approximately 770 is a 20% reduction in water level at the' intake bay resulting in a corresponding 30% increase in velocity, assuming the same flow rate.,
- w. - -
W Treatment / Prevention Methods As previously stated in the inspection portion of this response, TUGCo feels it inappropriate to commit to a specific treatment / prevention method (s) at this time. Corbicula have been observed to require a significant period of time to establish themselves in a nee reservoir.
.TUCCo wi l use this interim period to research the best method or l
methods for implementation at CPSES. The sampling of SCR and the SSI for Corbicula growth will provide an ample warning period so that appropriate actions can be implemented.
Secondly, chlorination of the Service Water and Fire Protection intake bay will be conducted as a routine prevention against any form of biofouling.
Although shock chlcrination has a limited effect on adult clams, it is etrective on clam larvae. This would prevent the development of Corbicula within i
systems which are periodically idle, Flowing systems would flush out any larvae or, for that matter, any shells if present less than 1/2" in size since Corbicula are not capable of attaching to surfaces.
Some of the treatment / prevention methods which may be selected for evaluation include the following:
1.
Elimination of sand and silt deposits, if present, from the in-take bay.
These sand deposits are necessary for clam development, and would prevent a large population from becoming established.
2.
Extended chlorination of idle trains, up to a 1 week duration.
I 3.
Use of other proprietary biocides.
4.
Ileat Treatment.
l 1 - - -._
.~.
- ~
-