ML20004E985
| ML20004E985 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry, Sequoyah  |
| Issue date: | 05/26/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-81-03, IEB-81-3, NUDOCS 8106160299 | |
| Download: ML20004E985 (15) | |
Text
. l 400 Chestnut Street Tower II May 26, 1981 i....,b.
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Mr. James P. O'Reilly, Director Office of Inspection and Enforeement U.S. Nuclear Regulatory Comission Region II - Suite 3100 101 Marietta Street Atlanta, Georgia 30303
Dear Mr. O'Reilly:
OFFICE OF INSPECTION AND MEURCEME21T BULLEIIN 81-03-RII:JP0 50-259, -260,
-296 - BROWNS FERRY NUCLEAR PLANT. 50-327, -328 - SEQUOYAH NUCLEAR PLANT In responw to your letter dated April 10, 1981, Enclosures 1 and 2 are action item responses required of holders of operating licenses (OL) for IE Bulletin 81-03: Flow Blockage of Cooling Water to Safety System Components by Corbicula sp. (Asiatic Clam) and Mvtilus sp. (Mussel). is a response to items 1 through 5 for th'e Browns Ferry Nuclear Plant. Enclosure 2 is a response to items 1 through 5 for the Sequoyah Nuclear Plant. Sequoyah's unit 2 is considered licensed for purposes of responding to IE Bulletin 81-03 action itetts. If you have any questions, please call Ralph Shell at FTS 857-3260.
To the best of my knowledge, I declare the statements contained herein are couplete and true.
Very truly yours, j
TE2iNESSEE VALLEY AUTHORITY l
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L. M. Mills, Manager Nuclear Regulation and Safety Enclosures cc: Mr. Victor Stcllo, Director (Enclosures)
Office of Inspection and Enforcement y
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U.S. Nuclear Regulatory Comission
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Enclosuro 1
RESPONSE
NRC IE BULLETIN NO. 81-03 RII:JPO BROWNS FERRY NUCLEAR PLANT ITEM NO. 1 Determine whether Corbicula sp. or Mytilus sp. is present in the vicinity of the station (local environment) in either the source or receiving inter body. If the results of current field monitoring programs provide reasonable evidence that neither of these species is present in the local environment, no fbrther action is necessar/ except for items 4 and 5 in this section for holders of operating licenses.
RESPONSE
Asiatic clams w{rs first manifested as a nuisance in plant raw water systems in 1974.
Even though their presence in the local environment was known, there was no formal monitoring program in effect at that time. An investigation in October 1974 revealed how severe the problem was. An apparent loss of condenser efficiency on units 1 and 2 revealed,a geavy infestation of clams on the tubesheets of several wa te rboxes.
Later, in December 1974, a leaking heat exchanger on 1B recirculation pump MG set drive gtor was disassembled and found to be partially plugged with clams.
All waterboxes and the intake conduits were drained and several hundred pounds of clams were removed. A program was initiated to cigan the waterboxes and intake conduits annually or thienever necessary.
ITP! NO. 2 If it is unknown whether either of these species is present in the local environment or is confirmed that either is p:*esent, determine whether fire protection or safety-related systems that directly circulate water from the station source or receiving water body are fouled by clams or mussels or debris consisting of their shells. An acceptable method of confirming the absence of organism or shell debris consists of opening and visually examining a representative sample of components in potentially affected safety systems and a sa=ple of locations in potentially affected
2 fire protection systems. The sample shall have included a distribution of components with supply and retura piping of various diameters which exist in the potentially affected systems. This inspection shall have been conducted since the last clan or mussel spawning season or within the 9-month period preceding the date of this bulletin. If the absence of organisms or shell debris has been confirmed by such an inspection or another method which the licensee shall describe in the response (subject to NRC evaluation and acceptance), no further action is necessarf except for items 4 and 5 of actions applicable to holder.s of an operating license.
RESPONSE
The testing and inspections described below are in coupliance with the inspection intervals specified by NRC in the bulletin.
Emergency Eculpment Cooling Water (EECW) System inadequate cooling teter flow.{ the EECW system have frequently indicated Past flow verification tests o To date, these flow inadequacies have report (TR's).ge licensee event reports (LER's), and numerous trouble resulted in fi Subsequent investigations have revealed large amounts of clamy, mud, and debris plugging tubesheets and restricting flow in pi~ ping Raw Cooling Water (RCW) System.
Similarly, scheduled maintenance activities on other nonsafety-related heat exchangers and coolers supplied gy the RCW system have revealed large accunulations of mud and clams.
High Pressure Fire Protection (HPFP) System l
l Scheduled inspections and flushing of the HPFP system always yield l
small amounts of mud and clams, but the severe flow restriction and l
pluggage problems experienced during the igitial inspections and I
flushings are now practically nonexistent Residual Heat Removal Service Water (RHRSW) System The RHRSW system, unlike the EECW system, is a higt -volume, high-velocity l
system that does not operate continuously. These operating conditions are not conducive to clam survival.
In addition, water used in the RHRSW system is first strained by rotating screens that effectively remove any-thing larger than 1/8 of an inch in diameter. Any clams or debris passing through the screens also pass through the RHR heat exchangers.
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. ITEM NO. 3 If clams, aussels or shells were found in potentially affected systems or their absence was not confirmed by action in item 2 above, measure the flow rates through individual components in potentially affected systems to confirm adequate flow rates i.e., flow blockage or degradation to an unacceptably low flow rate has not occurred. To be acceptable for this determination, these measurements shall have been made within six months of the date of this bulletin using calibrated flow instruments.
Differ-ential pressure (DP) measurements between supply and return lines for an individual component and DP or flow measurewnts for parallel connected individual coolers of conponents are not acce.ptable if flow blockage or degradation could cause the observed DP or be masked in parallel flow paths.
Other methods may be used which give conclusive evidence that flow blockage or degrudation to unacceptable low flow rates has not occurred. If another method is used, the basis of its acceptance for this determination shall be included in the response to this bulletin.
If the above flow rates cannot be measured or indicate significant flow degradation, potentially affected systems shall be inspected according to item 2 above or by an acceptable alternative method and cleaned as nec essary. This action shall be taken within the time period prescribed for submittal of the report to NRC.
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RESPONSE
EEC'4 System l
Because of the flow restriction problems with the EEC'4 system, th e frequency of the flow verification test, Mechanical Results Instruction, MRI-303, has been increased from semiannually to quarterly. All EEC'4 components passed the most recent test performed on February 7, 1981.10 The next scheduled test was in progress when this response was prepared.
HPFP System Cleanliness of the HPFP system is assured by the performance of Mechanical Maintenance Instruction, WI-122, and SI 4.ll. A.l. f.a.
WI-122 is performed once per month and effectively flushes all major HPFP loops.
Every third month, MMI-122 requires that all in-line strainers be cleaned and yielded an insignificant amount of clams and debris.hin March 1981 after the monthly flush. The strainers were last cleane j
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. Surveillance Instmotion, SI 4.ll.A.1.f.a is performed quarterly and flushes all loops, all deluge systems and all fire hose stations. The spring 1981 performance of SI 4.11. A.l.f.a was completed on April 28, all cogonents yielding clear water with no pluggage or flow restriction.3 3 RHRSW System Each RHR heat exchanger is cleaned once every two years. There has not been a significant accuculation of clama or debris removed from any RHR heat exchanger. In addition, monthly flow rate testing of RHRF4 pumps in accordance with ASME Section XI has indicated no fouling of the RHR heat exchangers.
ITEM NO.'4 Describe methods either in use or planned (including implementation date) for preventing and detecting fbture flow blockage or degradation due to clams, or mussels, or shell debris. Include the following information in this description:
a.
Evaluation of the potential for intmsion of the organism into these systems due to low water level and high velocities in the intake structure expected during worst case conditions.
Evaluation of effectiveness of prevention and d)tection methods used b.
in the past or present or planned for fbture use.
RESPONSE
Recently, attention was focused on the intake structure forebay. On Dec ember 12, 1980, TVA divers at the request of plant management, inspected the forebg and found a heavy concentration of clams in various stages of maturity.
Arrangements have been made to remove the clam from the forebay and the dredging eperation is currently in progress.g' g If the clam population in the forebay were left undisturbed and a high velocity / low water level situation occurred, we wculd experience severe fouling in the condenser water boxes. The fire pump strainers (if the HPFP pumps were operating), the RCW strainers and the EECW/RHRF4 strainers would suffer some mild fouling initially, but because of their continuous backwashing features would soon be clear of debris.
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. Even though such an occurrence is possible, it apperrs 'ver/ reacte especially since the clam population in the foreba) is being removed.
A program of periodic forebay inspections for clam propogation has been e stab lished.
The plant's National Pollutant Discharge Elimination System (NPDES) permit allows two (2) 21-day chlorination cycles for clam control per year. The actual dates of the chlorination periods var / but always occur during the late spring and again during late fall. The spring 1981 chlorination cycle is scheduled to begin about June 1.
Inforal comunications with know-ledgeable TVA personnel help to optimize the timing of the chlorination so that it coincides with the spawning of the clams in this vicinity.
Due to the uncontrollable " natural" variables that govern the spawning season, and the limited duration and importance of the chlorination cycle, these informal comunications will be formalized into SI 4.ll. A.l.f.b before June 1.
A recent examination into the flow prglems experienced on unit 2 EEC'4 system revealed a biofculing problem.
A permanent sodium hypochlorite system is currently under construction and is expected to be completed sometime in 1982. Provisions have been made to chlorinate the EEC'4 system on a temporar basis until the permanent sodium hypochlorite.nystem is c omple ted. Tie-in connections are expected to be installed by May 28*,
1981, and the chlorination of the EEC'4 system should begin around June 1, 1981.
As a direct response of I.E. Circular 78-13, the comon pit for our 12 l
RHR service water pumps was inspected by divers. An extensive accamulation of clams and ::ud was found and removed. A periedic program for inspecting /
cleaning this pit was established.
During a subsequent inspection of the pit, only a small accumalation of debris was found. Following the dredging of the intake forebay this spring, the pit will be inspected and cleaned, if necessarf, to fbether minimize clam intrusion problems.
The above programs are in addition to those described in the response to item number 3 l
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ITEM NO. 5 Describe the actions taken in items 1 through 3 above and include the following information:
a.
Applicable portions of the environmental monitoring program including last sample date and results.
b.
Components and systems affected.
c.
Extent of fouling, if any existed.
d.
How and when fouling was discovered.
e.
Corrective and preventive actions.
RESPONSE
The information requested by item number 5 is adequately addressed in our response to items 1 through 3 above.
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F_OOTNOTE REFERENCES 1.
Memorandum from B. G. Isom, Supervisor, Limnology Section, EDB, Muscle Shoals ; to W. W. Barnes, Q11ef, Environmental Biology Branch, EDB, Mascle Shoals ; titled, " Nuisance Concentration of Asiatic Clams at the Browns Ferrf Nuclear Plant," dated October 25, 1974.
2.
Ib id.
3 Minutes of Nuclear Safety Review Boani Meeting No. 33, held Febmary 19-20, 1975; Attachment 1; titled, " Power Production Exprience With Asiatic Clams - Corbicula."
4.
Ib id.
5.
Browns Ferry Nuclear Plant Mechanical Results Instruction No. 303,
" Emergency Equipment Cooling Water System Quarterly Flow Verification; Test Results."
6.
Memorandum from J. G. Dewease, Assistant Director of Nuclear Power
( Op era tions), to H. L. Aben:rombie, P.lant Manager, Browns Ferry Nuclear
- Plant, dated October 29, 1980, titled, " Browns Ferrf Nuclear Plant -
. Cooling Water Flow Blockage To Components Served By Emergency Equipment
~' Cooling Water (EECW) - Mee fag Minutes" ( ARMS L22 801015 800).
7.
Memorandum from J. G. Dewease, Assistant Director of Nuclear Power (Opera tions) to H. L. Abercrombie, Plant Manager, Browns Ferrf Nuclear Plant dated January 30, 1981, titled, " Inspection of Heat Exchangers and Analysis of Samples Removed From the Emergency Equipment Cooling Water (EECW) System At Browns Ferry Nuclear Plant"' ( ARMS L26 810119 8 49 ).
8.
Inspection of plant boilermakers cooler cleaning logbook and conversations with boilermaker foreman.
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Inspection of past performances of SI 4.11. A.1.f. ; " Flushing of the High Pressure Fire Protection System," perioa covering 1977 to present and conversations with pipefitter foreman.
10. Mechanical Results Instruction No. 303, "Ehergency Equipment Cooling Water System Quarterly Flow Verification," dated February 7,1981.
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Mechanical Maintenance Instmotion 122, formally Operating Instmetion 26 and Surteillance Instruction 4.ll. A.l.f.a, dated March and April respec tively.
12. Memorandum from H. L. Abercrombie, Plant Manager, Browns Ferr/ Nuclear Plant, to J. G. Dewease, Assistant Director of Nuclear Power (Op era tions), titled, " Clam Population in the Forabay - Browns Ferry Nuclear Plant," dated December 15,1980 (ARMS L52 801215 994).
13 Memorandum from J. G. Dewease, Assistant Director of Nuclear Power (Opera tions), to H. L. Abercrombie, Plant Manager, Browns Ferr/ Nuclear Plant, titled, " Clam Population in the Forebay - Browns Ferry Nuclear Plant," dated Febmar/ 13,1981 ( ARMS L29 810204 965).
14. Special Test No.199, titled " Dredging of Intake Forebay for Clams -
Unit Common," dated May 1,1981.
15. Memorandum from J. G. Dewease, Assistant Director of Nuclear Power
( Op era tions), to H. L. Abemrombie, Plant Manager, " Browns Ferr/
Nuclear Plant, titled, " Browns Ferry Nuclear Plant Chlorinat1on Emergency Equipant Cooling Water (EECW) System," dated Januar/ 21, 1981 ( ARMS L29 810115 925).
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Enclocura 2
Response
NRC IE Bulletin No. 81-03 RII:JP0 Sequoyah Nuclear Plant Item No. 1 Determine whether Corbicula sp. or Mytilus sp. is present in the vicin-icy of the station (local environment) in either the source or receiving water body.
If the results of current field monitoring programs provide reasonable evidence that neither of these species is present in the local environment, no further action is necessary except for items 4 and 5 in this section for holders of operating licenses.
Response
Corbicula sp. (Asiatic Clams) is present in the vicinity of Sequoyah Nuclear Plant. The Asiatic Clam population density in the Chickamauga Lake (Sequoyah's raw water supply) was determined by a November 1980 survey to be 91.3 clams per square meter. Therefore, Sequoyah has a
" moderate" level of Asiatic Clam infestation in the vicinity of the plant ("moder, ate" being defined as less than 100 clams per square meter of rivar bottom).
Item No. 2 If it is unknown'whether either of,these species is present in the local environment or is confirmed that either is present, determine whether fire protection or safety-related systems that directly circulate water from the station source or receiving water body are fouled by clams or mussels or debris consisting of their shells. An acceptable method of confirming the absence of organisms or shell debris consists of l
opening and visually examining a representative sample of components in potentially affected safety systems and a sample of locations in potentially affected fire protection systems. The sample shall have included a distribution of components with supply and return piping of various diameters which exist in the potentially affected systems.
This inspection shall have been conducted since the last clam or mussel spawning season or within the nine month period preceding the date of this bulletin.
If the absence of organisms or shell debris has been con-firmed by such an inspection or another method which the licensee shall describe in the response (subject to NRC evaluation and acceptance),
no further action is necessary except for items 4 and 5 of actions appli-cable to holders of an operating license.
Response
The fire protection (FP) and essential raw cooling water (ERCW) systems l
l are the only safety-related systems that circulate raw water at Sequoyah.
These two systems are not fouled by class or debris consisting of their shells.
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_2 Visual Inspections to Detect Asiatic Clam Fouling a.
The tube side of the component cooling water heat exchanger circu-lates ERCW. The unit one heat exchanger was opened in May 1980 and inspected and the absence of clams and their shells confirmed.
The unit two heat exchanger was opened in July 1980 with the same results.
~b.
The auxiliary ERCW cooling towers were inspected and showed no ev-idence of clam infestation. These cooling towers stand idle most of the time, thereby incraasing the probability of clam infestation within the towers.
The absence of clams in these towers strongly indicates the absence of clams throughout this system.
c.
Flushouts on the ERCW system were inspected upon receipt of this bulletin and showed no evidence of clams or fouling due to the clams or their shells.
d.
Sections of ERCW piping, consisting of various pipe diameters and flow rates, were removed and inspected from February through April 1981. No fouling by clams or their shells was found.
(Note: this inspection was originated to respond ta NRC's concerns on corrosion of piping passing raw cooling water, buc also served to indicate clam problems if they existed).
The Sequoyah maintenance history records file was researched for e.
any documentation about evidence of clams in the ERCW and FP systems.
No evidence was found that suggests clams have caused any problems or that clams have even been sighead within these systems. Dis-cussions with maintenance personnel (craf tsmen and engineers) also indicate that clams have never been sighted within the FP or ERCW systems. The only reference that could be found regarding clacs was that a "few" were found once in the condenser tube cleaning system (nonsafety-related).
I Flow and Timperature Measurements to Deter L Asiatic Clam Fouling Preoperational testing of Sequoyah's entire ERCW system is nearing a.
completion and will verify adequate flow rates to safety-related equipment.
b.
Annual tests are performed on the centrifugal charging and safety injection pumps that verify a bearing temperature difference (bear-0 ing temperature minus ERCW temperature) of less than 72 F.
An increase in this bearing temperature difference is indicative of l
fouling of the bearing oil cooler.
The unit one centrifugal charg-l ing pumps bearing temperature differences were determined in Feb-ruary 1981 to be less than 720F and they did not show an increase from the preceding test in February 1980. The unit one safety in-l jection pumps bearing temperature differences were determined #.n 0
February 1981 to be less than 72 F.
To date, Sequoyah has not had any major temperature problem with c.
equipment s2rved by ERCW. The absence of any such temperature problems stggests proper system operation. The increased temper-atures on certain components can be used to indicate potential problems.
Item No. 3 If clams, mussels or shells were found in potentially affected systems or their absence was not confirmed by action in item 2 above, measure the flow rates through individual components in potentially affected systems to confirm adequate flow rates i.e., flow blockage or degrada-i tion to an unacceptably icw flow rate has not occurred. To be acceptable for this determination, these measurements shall have been made within six months of the date of this bulletin using calibrated flow instru-ments. Differential praesure (DP) measurements between supply and return lines for an individual component and DP or flow measurements for parallel connected individual coolers or components are not ac-captable if flow blockage or degradation could c9use the observed DF or be masked in parallel flow paths.
Other methods may be used which give conclusive evidence that flow blockage ar degradation to unacceptably low flow rates has not occurred.
If another metnod is used, the basis of its acceptance for this deter-mination shall be included in the response to this bulletin.
If the above flow rates cannot be measured or indicate significant flow degradation, potentially affected systems shall be inspected according to item 2 above or by an acceptable alternative methri and cleaned as t
This action shall be taken within the time period prescribed necessary.
for submittal of the report to NRC.
Resconse
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No re:sponse required since the absence of clams was confirmed in item 2 above.
Item No. 4 Describe methods either in use or planned (ic.cluding implementation date) for preventing and detecting future fica blockage or degradation due to clams or mussels or shell debris.
Include che,following infor-mation in this description:
Evaluation of the potential for intrusion of the organisms into a.
these systems due to low water level and high velocities in the intake structure expected during worst case conditions.
b.
Evaluation of effectiveness of prevention and detection methods used in the past or present or planned for future use.
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Response
Methods for Preventing Fl;w Blockage due to Clams Chlorination is the chiof mechanism for preventing the fouling of a.
service water systems at Sequoyah. The fire protection system (FF) is chlorinated each sprir.g and fall for 20 to 27 days coincident with flushing of the systom. When the new sodium hypochlottte system is operational (expscted this spring), the ERCW system will be con-tinuously chlorinated whenever the river tercerature is above 60 F.
Chlorination of the ERCW system up until ncw has been sporadic due to construction interference.
b.
The fire protection hose stations and yard fire hydrants have pra-viously been flushed quarterly. Futura plans are to flush these headers semiannually coincident with chlorination of the systec.
The normal variance in water level at Sequoyah does not increase the c.
probability of clam infestation due to lower water levels or higher velocities. The original ERCW pumps took suction f cm behind the condenser circulation water pumps. The new ERCW pumps are to be fully operational this conth and take suction from the bottom of the Tennessee River ahead of the condenser circulating water pumps.
We plan to continue the visual inspections in the event that the new ERCW pumps produce an increased level of fouling due to clams.
d.
The effectiveness ef chlorination to pr snt clam infestation has been demonstrated.at a number of T7A,p.
2.
Continuous chlorina-tion is the best available eethod of pt..enting infestation and will continue to be utilized at Sequoyah.
Water used in the ERCW system is first strained by rotating screens e.
that effectively remove anything larger than 1/32 of an inch in dia-meter.
Methods for Detecting Flow Blockage Due to Clams See the response under item 2.
The effectiveness of detecting flow blockage due to clam infestation is greatest when a visual inspection of suspected components is performed. Therefore, visual inspections have been and shall be used whenever system operation will permit.
Item No. 5 Describe the actions taken in itens 1 through 3 above and include the following infor=ation:
Applicable portions of the environmental monitoring program including a.
last sa=ple date and results.
b.
Components and systems affected.
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5-c.
Extent of fouling if any existed.
d.
How and when fouling was discovered.
e.
Co'rrective and preventive actions.
Response
The action taken in items 1 through 3 have been dascribed above and in-cludes the systems and components affected. No fouling was discovered and the preventive actions have been described in item 4.
The Sequoyah operational environmental monitoring program does not include sampling or monitoring of flow blockage of cooling water to safety system compo-nents by Corbicula sp. (Asiatic Clam) and Mytilus sp. (Mussel).
Conclusion Presently there is not a clam infestation problem at Sequoyah and the evidence indicates that such a problem will not be evident in the near future.
Prevention of clam fouling in safety-related cooling systems is con-trolled by semiannual chlorination.
Detection of clam fouling is best determined by visual inspections of variods components within the affseted systems when opened for other
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Flow and temperature monitoring can be used in lieu of visual reasons.
inspections if system operation will not permit shutdown and disassembly.
Planned Actions i
l The following items are the actions planned by Sequoyah Nuclear Plant to detect and prevent fouling and infestation of the ERCW and FP sys-tems by clams.
1.
Chlorination The ERCW system will be continuously chiccinated whenever the ERCW temperature rises above 600F.
In addition, the fire protection sys-tem will be chlorinated each fall and spring for about thr:e weeks.
2.
ERCW Piping Inspections l
A surveillance instruction will be i=plemented as part of a corrosion investigation on an annual basis to inspect sections of ERCW piping censisting of various pipe diameters and flow rates. The pipe sec-tions will be visually inspected for evidence of corrosion products, l
and cla= accumulations will also be noted.
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Fire Protection Hydraulic Performance Tests At least once every three years, a test will be conducted to verify that the yard and building hydraulic systems can meet design pres-sure and flow.
4.
Fire Protection System Flushes The fire protection hose stations and yard fire hydrants will be flushed semiannually coincident with the semiannual chlorination of the FP system.
5.
Bearing Temperature Measurements Annual tests will be performed on the centrifugal charging and safety injection pumps to verify a bearing temperature difference of less than 72 F since an increase in this bearing temperature difference is indicative of bearing oil cooler fouling.
6.
"C" CCW Heat Exchanger Inspection The common CCW heat exchanger is s'cheduled to be opened and inspected for clams in mid 1981.
7.
Flow and Temperature Measurements Although visual inspection is the best method for detecting clam infestation, flow and temperature measurements can be used in lieu of visual inspections when system operation does not permit visual inspection.
8.
Visual Inspection of Components Visual inspection of components as they are opend for other reasons will continue.
If clam infestation is noted, consideration of pro-gram adjustments will be made.
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