ML20010F882

Final Deficiency Rept Re River Silt Deposited in Intake Flume of Svc Water Pump Structure.Silt Monitoring & Removal Will Be Implemented as Outlined in Encl App J to FSAR

ML20010F882
Person / Time
Site:	Zimmer
Issue date:	08/28/1981
From:	Borgmann E CINCINNATI GAS & ELECTRIC CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
10CFR-050.55E, 10CFR-50.55E, QA-1470, NUDOCS 8109150074
Download: ML20010F882 (13)

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THE CINCINNATI GAS & ELECTRIC COMPANY t1t - '

etNCINN ATI OHIO 4 5201 A '

28, 1981 E. A. BORGMAN N twion vict PRES 6 DENT fi I N J

• U. S. Nuclear D , atory Commission

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• Q ,

Region III ,

E1 SEP 141981 m. -9 799 Roosevelt Road .d u sensas e.ma m sa E

' esau m me Glen Ellyn, Illinois 60137 ,

b.\ 8 Attention: Mr. J. G. Keppler g Director y

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RE: WM. H. ZIMMER NUCLEAR POWER STATION UNIT 1 - SERVICE WATE*t INTAKC FLUME 50.55(c) FILE M-12, W.O. #57300-957, i JOB E-5590 Gentlemen:

On .Tuly 23, 1979, we submitted our letter QA-ll68, canceling a 10CFR50.55(e) condition, M-12. This situation involved river silt deposited J.a the intake flume of our Service Water Pump Structure.

As requested by Mr. Paul Barrett of the NRC in his July 1, 1981, telephone conversation with Mr. Harlan Sager Of the Cincinnati Gas & Electric Company, Quality Assurance Dept.,

a copy of Cincinnati Gas & Electric Company plans for silt monitoring and removal as outlined in Appendix J of our FSAR are attached.

We trust that the above <ill be found acceptable as a final report under the requirements of 10CFR50.55(e).

Very truly yours, THE CINCINNATI GAS & ELECTRIC COMPANY By

• E. A. BORGMANN SENIOR VICE-PRESIDENT EAB/FKP/ejc Attachment cc: NRC Resident Inspector #/ ,

Attn: F. T. Daniels NRC Director, Office of Inspection & Er.forcenn t

"--* agt n D.C. 20555 0109150074 810828 PDR ADOCK 05000358 *EP W 19@

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TPS-1 REVISION 69 DECEMBER 1980 J.8 SILT SITUATION J.8 ; Source of Siltation The sediment in the flume is the result of runoff in the Ohio River drainage basin. Ihe Ohio River drainage basin consists of parts of Ohio, Pennsyl-vania, New York, West Virginia, Maryland, Virginia, North Carolina, and Kentucky. As previously discussed, a significant buildup of silt occurred in the intake flume and pump bay during plant construction. During this period, water velocities in the fiume were lower than normal because caly 1/2 to 1/3 normal plant service water flow was being pumped through the system.

The Ohio River carries heavy loads of suspended sediment during floods.

The suspended sediment consists of clay, silt, and fine sand. The material requires a long detention time for the sediment to deposit; there fore ,

a major part of the suspended sediment should not deposit in the fiume during normal operation of .w plant but will be carried through the pumps back into the river or the cooling tower basin. Some of the larger diameter particles of sediment will settle in the fiume and service water pump bay. The intake and service water pump structure (SWPS) will require manitoring and periodic dredging. This is normally considered a part of maintenance and operations of a power plant. 69 The Wm. H. Zimmer Nuclear Power Stacion is located on ;&e right bank of the Ohio River, 0.3 mile downstream from Moscow, Ohio c at river mile 443. The Captain Anthony Meldalh Dam is 7 miles upstream from Zimmer.

Zimmer is in the Markland Dam pool and the dam is 88 miles downstream from Zimmer.

The service water pump structure consists of a concrete caisson sitting on rock. The intake flume is a steel sheetpile structure with the piles driven tu rock. The intake flume is approximately 150 feet loag and 30 feet wide and is angled downriver at 45 to prevent barge impact.

The flume has three levels of braces at elevations 458 f t 11\ in.,

473 ft 5b in., and 506 ft 5 in. The top of the sheetpile walls i at elevation 510 ft 0 in. The flume has a concrete alab at the bottom at elevation 437 ft 0 in. A floating trash boom will be located at the entrance of the flume to preven: large floating objects from entering the flume. A bar grill is Ic.ated at the entrance to the SWPS to prevent smaller objects from entering the pump day (see Figure J.2-1).

Th's normal pool elevation of the Ohio River is 455 f t 0 in. The 1937 modified flood of record is elevation 508 ft 6 in. The design maximum probable flood is at elevation 546 ft 0 in. (see Figure J.8-1).

The service water pump structure has four service water pumps, two on each side, located at elevation 435 ft 0 in. The two cooling tower makeup pumps are also located at this elevation. There ace four traveling screens in this area.

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The intake fiume was constructed in 1976. A temporary sheetpile cut-off wall was installed at the entrance to the flume and the top of the J.8-1

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ZPS-1 REVISION 69 DECEMBER 1980 cut-off wall is at elevation 463 ft 0 in. The flume was dewatered and the C.~

concrete slab at elevation 437 ft 0 in, w s placed in mid-September of 1976.

This was the beginning of the sediment deposition in the intake flume whenever the river exceeded elevation 463 f t. The concrete plugs that held water out of the service water pump structure were removed on Feb-ruary 16, 1978. This was the beginning of sadiment deposition in the service water pump structure pump bay. Two pieces of the sheetpile cutoff wall were lifted up in March 1978 to ensure flow of river water to the fiume when the river was below elevation 463 f t. The balance of the sheetpile cutoff wall was removed in September 1979. One service water pump, with a capacity of 12,500 gpm, has been pumping water inter-mittently from the service water pump structure since March 1978.

The siltation was' discovered in April 1979 as part of a pump field test investigation. The depth of the sediment was approximately 12 feet at the mid point of the fiume. The sediment tapered to an approximate 5-foot depth at the service water pump structure and at the river end of the flume. The coaraer material and fine sand was deposited at the river end of the intake fiume. The finer material, with longer detention times, was carried further into the flume and into the service water pump structure. The very fine sedimentation material wes pumped through the 69 system and back into the river. This is documented in the Harza Engineer-ing Company Report attached hereto as Attachment J1.

The Harza Engineering Company was retained in May 1979 to investigate the siltation and estimate future sedimentation rates. The siltation

() estimates were based on two river sampling surveys. The survey at low water was conducted in June 1979 and the survey at high water in March 15d0. The March 1980 survey consisted of obtaining suspended sediment sampics and bed material samples above and below Meldahl Dam and the Zimmer intake flume. No appreciable difference in suspended sediment above or below Meldahl Dam or the Zimmer intake flume was observed.

Tha final Harza Report for a flume diecharge of 31,000 gpm predicts an annual sedimentation rate in the intake flume under average annual flow conditions of 12.8 feet and 16.6 feet under 25 year annual flow con-ditions. The corresponding sedimentation rates in the service water pump structure would be 6.8 feet and 8.7 feet, res pe c tive ly. The corres-ponding maximum monthly sedimentation ratec in the intake flume would be 2.2 feet and 2.4 feet, res pective ly. Twenty-five year annual flow con-ditions and 40 year annual flow conditions would be 2.2 feet, 2.4 feet ,

and 3.8 feet, res pective ly. The corresponding sedimentation rates in the service water pump structure would be 1.2 feet, 1.3 feet , and 2.0 feet. The sedimentation in the intake fiume during a 100 year flood would be 4.2 feet and 4.4 feet for a 200-year flood. The corresponding sedimentation rates in the service water pump structure for ine 100-year ficod and 200-year flood would be 2.2 feet and 2.3 feet, res pec t ive ly . Approzimately 75%

of the annual sedimentatien will be deposited in the December-May time frame. The largest sedimentation buildup would be expected in the month of March.

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P J.8-2

I,.__ . , . . _ _ . - - _ _ _ . . -__ . . . _ - .- - ._ -r ZPS-1 REVISION 69 .

DECEMBER 1980 wr '

J.8.2 Silt Prevention After consideration of the quantity of silt expected to accumulate annually, a permanent continuous monitoring system was developed. This monitoring system makes use of five ultrasonic transducers located in strategic locations in the intake fluma and pump bay (see Figures J.8-2 and J.8-3).

Similar devices are now in use throughout the pisnt to measure sludge levels in tanks. Although there are five transducers, only four indicators will be used. Due to the difficulty in reaching the transducers in the pump bay, redundant transducers will be installed for maintenance.

However, only one indicator vill be used at a time. The monitoring panel will 'ae located in the service water pump structure. Alarms will sound in the main control room as well as locally. Installation of this system is proceeding and successful operation will be demonstrated prior to fuel load.

Because traditional silt removal devices could not be used in the pump bay area, a system of spray nozzles was designed. These nozzlas (shown in Figures J.8-4 and J.8-5) use the cooling tower makeup pumps for their water source. The objective is to keep the silt in suspension to prevent deposition. It is anticipated this spray piping will be operated periodically as needed to resuspend any sediment that may 69 have settled since the last jetting period. The silt that is resuspended vill be pumped through the service water system in the normal flow paths.

The pump vendor has been contacted and no severe wear problems are expected due ts this higher concentraticn of silt. This piping will be installed (h and opercting in the fall of 1980 and any adverse effects on the pumps will be discovered prior te fuel load. Any occurrence of deterioration or accelerated wear should be discovered with the vibration monitors to be added to the pumps and by the monthly inservice inspection (performance) checks (ribration, flow, pressure, temperature, and speed).

Although this piping is not essential, it is designed to withstand a seismic event without causing damage to an essential component.

When this silt accumulation was discovered, there was between 5 and 12 feet of sediment in the intake ilume and pump strucutre. Several methods were used to remove the sediment. The initial cleanout of the pump structure was by divers and pumps. This cleanout was accomplished by a diver using a small jetting punp to loosen large accumulations of silt and then using a larger centrifugal pump like a vacuum cleaner to pump the resuspended oilt out of the fiume. The initial cleanout of the intake fiume was accomplished primarily by the use of a clamshell bucket. The silt was put directly into a truck and transported to the settling basin located approximately 1/2 mile north of the plant. The initial silt remaining after the clamshell operation in the intake flume was removed by divers using a method similar to the method used to clean the pump bay.

Subsequent long-rerm cleanout of the pump bay should not be required.

Operation of the spray header piping will not allow the silt to accumulate.

Subsequent cicanout of the intake fiume could be accomplished using

{]} several different types of devices. The first type is an airlift type device shown pictoriall, in Figure J.8-6 and schematically in Figure J.8-7.

J.8-3 *

fM" T _ _._ M ..

ZPs-1 REVISION 73 MAY 1981

( The device works by sequentially applying vacuum and high pressure air to three separ;te chambers. As vacuum is applied, the chamber fills with a high density slurry. When the chamber is full, air pressure is applied and the slurry is discharged. This device would be supported by a portable crane and moved to various locations within the flume until I the fiume was clear. ) This device has been demonstrated in the fiume.

Other types of pumpiEg devices are unde- investigation and will be demon-strated during the next flood season. Each device currently under investi-gation would use an intermediate pumping station loc.ted at the top of the fiume walls (see Figure J.8-8) to serve several purposes. The intermediate pumping station would allow mixing of the high density slurry with clean water for dilution, if necessary. It would also serve as a hoaster station so the slurry could be pumped the 1/2 mile north of the plant to the settling basin (see Figure J.8-9). During construction, the settling basin has served as a borrow pit for fill, as required, and will be use' as a settling basin for cooling tower blowdown and demineralizer backwash dacing plant operation. The set ling basin has a volume of approximately 1000 acre-feet. A distance of approximately 1200 feet from input to overflow will allow for approximately 40 days detention time. This basin has already been approved and discharges to the river (if any) will be in accordance with the NPDES permit. It is not anticipated that this basin will have any discharge to the Ohi 69 River for 5 to 7 years and possibly longer if the sffects of groundwater seepage and evaporation are included.

4

/ The intermediate pumping station which is normally located at the top of the intake flume will be moved to higher elevations if the river should approach the 510 f t " Top of Flume" elevation. It will be returned to the top of the fiume after the river has receded sufficiently to permit. During such periods when the pump has been removed, intake flume 73 cleanout operations will not occur.

A second backup pump will be available and stored so as to be protected from the 546 ft elevation maximum probable flood. This second pump may be used during periods of maintenance on the " normal" pump.

Thus, several methods have already demonstrated their capability to remove silt. The bigge s t sa fety factor involved is the time available to remove the silt before it becomes a problem. Figure J.8-10 shows the relative pertinent elevations. Given that the spray nozzles will keep the pump bay, travelling screen, sad bar grille areaa clear, then all that is needed is to be ensured that the silt will not accumulate such that, a low river elevaticn would allow the sitt to act as a dam. It is anticipated that the sitt level at which cleaning operations begin will be below this level.

Actua l va lues will be determined from experience and will be included in 69 a technical specification.

Normally, with the river in pool, there is 18 feet of water over the fiume bottom. During spring run-off , this depth would, of course, be greater.

Starting at river pool (elevation 455 feer), if Markland dam would soinchow

() disappear, the water level could coretically drop to elevation 445 feet

_ leaving 8 teet of water above the ilume bottom. If this loss of the dam is concurrent with the all-time historic low flow of the Ohio River, the

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ZPS-1 REVISION 73 MAY 1981 O

vater level could theoretically drop to elevation 442 feet leaving 5 feet of water over th fiume bottom.

To give some idea of the time required for silt removal, a test was conducted.

One diver was able to clear a 6-foot wide path through 1 to 2 feet of sitt in a 6-hour period.

69 During the postulated drought that would allow the river to drop to elevation 442 feet, practically no silt would accumulate. With the river at pool, with normal rainfall, it would take approximately 7 months te deposit 5 feet of silt (see the Harza Report, Attachment J1). Thus, since normal silt deposition occurs at a slow rate, there is ample time to clean the silt beforc any depth of consequence develops.

Silt deposition occurs more rapidly during the spring runoff. Even during these conditions, approximately 3 months is required to deposit 8 feet

'of silt (see the Harza Report, Attachment J1). Again, ample time is avail-able to cican the silt before any depth of consequence occurs.

The highest siltation rate occurs during the maximum probable flood (elevation 546 feet). During the maximum probable flood, approximately 5.9 feet and 3.0 feet would accumulate in the intake fiume and pump bay, respectively 69 (see the liarza Report, Attachment J1). An accumulation of this amount

)' of silt would be well below the river pool and would not adversely affect the safety performance of the service water system. There would be approx-imately 12 feet of water above the top of the silt when the river returned to pool. Past experience has shown that the pumps are able to meet the flow requirements even with silt 2 feet above the suction pipe. Three feet of silt in the pump bay would still be approximately 2 feet below the top of the suction pipe.

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REVISION 69 MAXIMUM PROBABLE DECEMBER 1980 FLOOD EL. 546'-0"- ?

O EINTAKE FLUME

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1937 (MODIFIED)

' 15 '-0 " "  :

16'-0" FLOOD EL. 508'-6"\ \

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4 SHEET PILING >

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T EL. 458'-Il :/2"%h g _ _

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PIPE EL. 438'-6" ,\ 4 7'EL. 437'-0" 1 I I l"

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CONCRETE SLAB WM. H. ZIMMER NUCLE AR POWE.R ST ATION. UNIT 1 s.,cvv .~.tysis acroar q.

ria .c l FIGURE J.8-1 l INTAKE FLUME (SECTION)

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A SERVICE WATER PUMPS (4) f

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WM. H. ZIMMER NUCLE AR POWER ST ATION, UNIT I OHIO RIVER rmat s rrvy .~.tysis atron, FIGURE J.8-2 LMATION OF TRANSDUCERS

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MAXIMUM PROBABLE 80 FLOOD EL.546'-O"\

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FIGURE J.8-3 LOCATI0fl 0F TRANSDilCERS -

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REVISION 69 DECEMBER 1980 O

(COOLING TWR MAKE-UP WATER PUMPS

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, - . , FsNAL SAFETY AN ALyses REPORT

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REVISION 64 DECEMBER 1980 A A FLOOD OF RECORD b ,T,3 f f," - -

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[ WM. H. ZIMMER NUCLE AR POWER ST ATION. UNIT 1 F4N AL SAFETY ANALYSE 5 REPORT

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FIGURE J.8-5 SILT CONTROL SYSTEM -

SECTION VIEW

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9 REVISION 69 DECEMBER 1980 R//E- VACUL/M SCUR R Y 993cypggg CONTROL VALVES /

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.WM H. ZIMMER NUCLE AR POWER ST ATION, UNIT 1 FINAL SAFETY A N A L v 515 REPORT O

FIGURE J.8-6 RIVER DREDGING DEVICE

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REVISION 69 DECEMBER 1980

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( CHAMBER "A" CHAMBER "B" CHAMBER "C" FILLING FILLED EMPTYING l

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WM. H. ZlMMER NUCLE AR POWER ST ATION. UNIT 1 FIN AL SAFETY AN AL Y SIS REPORT

,U FIGURE J.8-7 l INTAKE FLUME DREDGING DEVICE OPERATING SCHEMATIC