ML20084U063
| ML20084U063 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 08/31/1973 |
| From: | SARGENT & LUNDY, INC. |
| To: | COMMONWEALTH EDISON CO. |
| Shared Package | |
| ML20084U060 | List: |
| References | |
| 33, NUDOCS 8306270039 | |
| Download: ML20084U063 (45) | |
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O o DRESDEN STATION SPECIAL REPORT NO. 33 Final Flood Protection Measures (Permanent Flood Protection of the containment Cooling Service Water Pumps and Diesel Generator Cooling Water Pumps) - Dresden Units 2 and 3 AEC Dockets 50-237 50-249 Commonwealth Edison Company August, 1973 i r306270039 730820 PDR ADOCK 05000237PDR P i
CARGENT Q LUNDY r
.,, s2' 1
' ENGIN LE RO ,
.s V J TABLE OF CONTENTS ;
1.0 Introduction 2.0 Design Details 2.1 Iso'lation of the Condenser Pit from the Condensate Pump Room 2.1,1 Determination of Maximum Flood Level 2.1.2 Design Modification of Condenser Pit 2.1.3 Testing 2.2 Separation of the Containment Cooling Service Water Pumps 2.2.1 Determination of Maximum Flood Level 2.2.2 Design Modifications 2.2.3 Testing 2.3 Protection of the Diesel Generator Cooling Water Pumps 2.3.1 Determination of Maximum Flood Level 2.3.2 Design Modifications 2 3.3 Testing 3.0 Safety Evaluation 4.0 Conclusion
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, .) CARGENT & LUNDY t
, ENGINEERO ,4 5
a c ucaso LIST OF FIGURES Fig. No.
- 1. Layout CCSW Flood Protection, Elevation 46956" - Unit 2 lA. Layout CCSW Flood Protection, Elevation 495'0" - Unit 2
- 2. Layout CCSW Flood Protection, Elevation 469'6" - Unit 3 2A, Layout CCSW Flood Protection, Elevation 495'0" Unit 3
- 3. Section CCSW Flood Protection j
- 4. Vault Wall Section Details 5 Vault Wall Section Details
- 6. Ventilation Cover Plate
- 7. Multi-Cable Transit Seal '
- 8. Multi-Cable Transit Seal - Detail
- 9. ' Bed Plate Drains - Diagram * '
10 Vault Cooler Scheme
- 11. Watertight Seal Detail Test (Multi-Cable Transit)
- 12. Submersible Pump - Detail O
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- 1. 0 - Introduction On June 7, 1972, while the quad-Cities - Unit 1 was in the cold shutdown condition, an operator was performing maintenance and scheduled modification on the circulating water system when the air was vented from the hydraulic system on one of the 120" circulating water butterfly valves at the condenser. The resultant sudden butterfly valve closure caused a water hammer in the system. The water hammer effect led to a failure of a rubber expansion joint in the 120" circulating water line and the subsequent flo.oding of the condenser pit (where the expansion joint is located) and the condensate pump room.
t The water flowed from the condenser pit to the condensate, pump room by way of a doorway and two large ventilation openings betwean the two areas. The water roso to a height of approx-i inately 16 feet in the condensate pump room and flooded all the pumps in that room some of which are Class I safety related equipment normally required to bring the unit to a cold shutdown. As the plant was already in the cold shutdown l condition this damage did not present a problem for plant safety or operation. Plans were implemented immediately to remove the water and place the equipment back into service. O _j .
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, CARGENT Q LUNDY ENGINEERS CHICA10 As a result of this flooding at luad-Cities Station, modifi-cations will be made both at the Quad-Cities Station and at
- the Dresden Station. The remainder of this report discusses those modifications to be made at the Dresden Station.
3 Basically three design modifications will be made at Dresden:
- 1. The paths that flood water could follow from the condenser f
pit to the condensate pump room will be permanently sealed. This isolates the condenser pit and prevents any source of flood water in the condenser pit from becoming a source of flood water to the condensate pump room (floor elevation 469'6") and consequently to the containment cooling service water pumps (CCSW) located one floor above the . 3 condensate pump room (at floor elevation 495'o").
- 2. Two of the four containment cooling service water pumps (i.e., the B and C pumps) per unit will be enclosed in a watertight vault, These vaults are designed to ensure that a postulated rupture in the containment cooling service water system will not result in loss of all four
, pumps due to flooding. {- 1 1 i
e- . CARGENT & LUNDY ENGINEERO CHICAGO
- 3. The diesel generator cooling water pumps, which are located in the crib house pit, will be replaced with special submersible type pumps and motor drives. In the event that the crib house pit is flooded the pumps can operate while submerged.
The complete design details of these three modifications are discussed in the following section. e M [
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N CARSENT Q LUNDY ENOINECMO
,- t (MICAto 2.0 Design Details 2.1 _ Isolation of the Condenser Pit from the Condensate Pump
_ Room 1 2.1.1 _ Determination of Maximum Flood Level There are three possible sources of flood water 4 in the condenser pit. They are: Case 1 A break in an expansion joint (as happened at the Quad-Cities Station) after which I the circulating water pumps continued to fill the condenser pit until they are shut off. Case 2. A break in an expansion joint after which the circulating water pumps are shut off, but the condenser pit is ' flooded by backflow from the river, i Case 3. A failure of the hotwell. x The maximum flood level inside the condenser pit from'the above sourcos is the 508:o" elevation (2780" above the condenser. pit floor elevation 481'0"). . This maximum flood level was arrived at in the following manner: - l '
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- 2.1.1.1 In Case 1 above the expansion joint ^ break was analyzed for the wors't condLtion in which the entire expansion joint material is blown out leaving a 6" circumferential gap around the pipe for water to escape.
In order to calculate t'he maximum flow of water from the break it was assumed that the gap would act as an orifice of area equal to the area of the gap. Using the circulating water pump head and system , friction loss curves, it was calculated 1 that a maximum of 250,000 gpm could be pumped through the oper.ing in the pipe. If this 250,000 gpm were allowed to con-tinue being pumped the condenser pit would be filled to the 517'0". elevation (ground level) in approximately 1 5 , , minu te s . At this point, the water would begin to flow throughout the 517'0" elevation of the turbine cavity- and the ~ , plant. In order to prevent this occurrence,,a system of level switches
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. will-be installed in the condenser-pit a
to indicate and control flooding of the condenser area. The following switches
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CARGENT O LUNDY , ( '. cNGINECRO ( cwicAso will be installed: Level Function
- a. 180" (1 switch) Alarm on main control '
room panel "Hi Water Condenser Pit"
- b. 3'0" (1 switch)' Alarm on main control room panel "Hi Cire.
Water Condenser Pit"
- c. Bio" (2 redun- Alarm on main control dant switches) room panel and circ.
water pump trip Level (a) indicates water in the condenser pit from either the hotwell or the circu-lating water system. Level (b) is above the hotwell capacity and indicates a probable circulating water failure. At the level (b) alarm the operator in the control room shall manually trip the circulating water pumps for the 'affected unit thereby preventing the flooding to continue due to operation of the pumps. Should.the switches at level (a) and (b) fail or the operator fail to trip the circulating water pumps on' alarm at level (b), the actuation of.either level switch l I
. ' . ,_ CdRGENT O LUNDY ,
e . ENGINEERO s CHICASO at level (c) shall trip the circulating water pumps automatically and alarm in the control r,oom. These redundant level switches at level (c) will be designed and installed to IEEE 279, " criteria for Nuclear Power Plant Protection Systems." As the circulating water pumps are tripped, either manually or automatically at level (c) of 5'0", the maximum water level reached in the condenser pit due to pumping will be at the 491'0" elevation (10' above condenser pit floor elevation 481'o", 5' plus an additional 5' attributed to pump coast down). 2.1.1.2 Once the circulating water pumps have been shut off the condenser pit will continue to fill up due to' backflow from the river. Theoretically, this backflow will continue until the level inside'the condenser pit is equal to the devation of the river. Then
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the maximum theoretical flood elevation in the condenser pit is 508'o"-(maximum
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historical flood level).
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For design purposes, the maximum flood elevation contributible to backflow was taken as 508: 0". 2.1.1.3 The hotwell contains 10,200 cubic feet of water at its normal overflow level. Should the hotwell rupture (catastmphi~ cally) this water would be dumped into the condenser pit (as this happens, loss of condenser vacuum will trip the turbine and the bypass valves so that flow to the condenser will cease). The maximum flood level due to this water would be approximately 3 feet to the 484to" elevation. 2.1.1.4 In reviewing paragraphs 2.1.1.1 - 2.1.1.3 it can be seen that if any one or all three of the above cases occur, the maxi-mum flood level in'the' condenser pit wiil be be 508'0". Therefore, in the design modification to isolate the condenser pit from the condensate pump room a maximum flood to the 508'o" elevation in the c,ondencer pit was used. This overall height of 27.05 (elevations 508 o" less
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' 481'0") was used, plus 10% margin to come up with a maximum flood depth of 30 feet.
2.1.2 _ Design Modification of Condenser Pit During a postulated flooding incident, water would pass from the condenser pit to the condensate pump room through two vent openings, a doorway, pipe penetrations, and several floor and equipment drains. The following modifications will be made to isolate the condenser pit from the condensate pump-room in the event of a flood to the 508'0" elevation: 2.1.2.1 Yne two ventilation openings between the condenser pit and the condensate pump pit will be permanently sealed by means of a 1" s teel plate to which 8" channels will be attached on the upper side for support (see Fig. 1, 2 and 6 ) . This entire assembly will be anchored.into-the concrete with 1/2" diameter cinch - I anchors on 6" centers on all four sides.
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- SARGENY Q LUNDY -
. ENGINEEC2D
' C*CA88 The ventilation closures have been analyzed and found acceptable to withstand a 30' head of water in addition to a 0.12 r, (DBE earthquake load value) vertical accelera-tion as applied to the mass of water.
Because of the small mass of the plate, the horizontal seismic forces are negligible. The plate and structural members providing these closures undergo stresses which do not exceed 1-1/3 times the working allow-able stresses for the materials. 2.1.2.2 The doorway between the condenser pit and the condensate pump room will be sealed by a watertight door.' The wa'tertight door will be designed
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to withstand a 30.' head of water plus the effects of a 0.'18 g (DBE earthquake load
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value) horizontal seismic occurrence (this includes the " sloshing effect" of the 308 head of water as analyzed using TID-7024, Nuclear Reactors and Earthquakes.
,Because of the small mass of the door the vertical seismic forces are negligible.
The door materials undergo stresses which j do not exceed 1 1/3 times the working allowable stresses of the materials.
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' CARGENT es LUNDY 4 . - '
s ENGINEERO emexso
. I 2.1.2.3 The piping and electrical penetrations between the condenser pit and the con-densate pump room will be permanently sealed with concrete, RTV silicone sealant, or rubber boot type seals (designed-by Brand Industrial Services) to prevent leakage between the condenser pit and the condensate pump room in the event of a flood. These seals will be designed for the maximum flood condition in relation to the elevation where each is located.
2.1.2.4 The wall between the condenser pit and-the condensate pump room (approximately Column "E" on Figs. 1 and 2) provides a watertight seal with the addition of the seals specified in paragraphs 2.1.2.2 and 2.1.2.3 above. This wall has been analyzed and found ' capable of withstand-ing a head of 30' of water acting on the condenser side of the wall plus the effects of a 0.18g horizontal and a 0.12 g vertical seismic occurrence (this includes " sloshing" as in paragraph 2.1.2.2). The construction e
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- CARGENT C: LUNDY I' ENGINEERO _\
emcaso . l of the existing' wall is more than adequate to contain the water pressure and the effects of the seismic occurrence with stresses in the concrete and reinforcing steel not exceeding 1 1/3 times the allow-able working stresses. l It is recognized that the flooding of the condenser pit is an additional load onto the foundation of the structure The added weight is more than adequately j supported directly on the founding rock , through the concrete mat on which the structure rests. 2.1.2 5 The floor and equipment drains which run 1 from the condenser pit to the. sumps in the condensate pump room will be~perman-ently sealed or sealed with removable 4 plugs where periodic drainage is necessary. The seals and plugs are designed to with-stand the maximum flood level. 2.1.2.6 , Included in the design modifications are- , the level switches as discussed in para-graph 2.3.1.1. -
i . CARGENT & LUNDY
. ENGINEERS CH8CA10 2.1.3 Testing 2.1.3.1 There will be no testing required for the bulkhead door or' penetration seals in the condenser pit wall. These seals will be designed for maximum flood level therefore no catastrophic failure of the seals will occur. Testing the seals would only assure that no small leaks are present. Since the CCSU pumps are located on the floor approximately 255 above the condensate pump room, small leakage flow will in no way endanger the CCSW pumps. Therefore, testing of the seals would be an unnecessary expense without any benefit to plant safety.
l 2.1.3.2 The IEEE-279 design switches discussed in paragraph 2.1.1.1 will be testable with i the plant in operation. 2.2. Separation of the Containment Cooling Service Water Pumps 2.2.1 Determination of Maximum Flood Level
. LIA193>Jtr1319%LaAr ENGINEERD e CMCAto S
J V 1 1 There are three other possible sources of flood l water in the condensate pump room. They aire:
- 1. The three contaminated condensate storage tanks.
- 2. The condenser hotwell and condensate piping to the condensate pumps.
- 3. The CCSW system piping to the CCSW pumps.
2.2.1.1 The three contaminated condensate storage
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tanks hold a combined storage of 700,000 gallons of water. Of this 700,000 gallons, 520,000 gallons could flow into the condensate pump room upon failure of contaminated condensate line-in the room (180,000 gallons is held for the HPCI and LPCI systems). 2.2.1.2 The hotwell and condensate piping to'the condensate pumps contain approximately 85,000 gallons of water. In the event of a postulated condensate line break this volume of water would flow into the conden-sate pump room. At the time of the pipe break the condenser would lose its vacuum, and consequently, the turbine would trip and the main s. team bypass valves would trip closed essentially stopping any additional flow into the condenser. Therefore, the
. volume available to flood the condensate m
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CARGENT O LUNDY o o
. E N GIN E E RS i
The floor area of each condensate pump room is approximately 3,465 sq.ft. (free floor area minus pump base plates). Therefore, the 605,000 gallons (520,000 plus 85,000 gallons equals 80,872 cu.ft.) available vould flood the condensate pump room to a height of 23.3 feet. (This is a conservative estimate as the pump base plate dimensions were projected upward and subtracted from the total volume available as en estimate of the volume of the pumps and piping that would be under water). 2.2.1.3 The other~possible source of flooding in the condensate pump room is a postulated
- rupture in the CCSW system piping. If such a postulated accident occurred outside the CCSW vault, water would backflow from the river and fill the condensate pump room
, and CCSW pump room until water reached river level of 508'0".
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- OARGENT & LUNDY
. ENGINEERS
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. CHICAMD . 2.2.1.4 Likewise, a postulated CCSW pipe rupture inside the CCSW vault will result in water
- backflowing and filling the CCSW vault to
- river level of 508'0" (13'0" above the vault floor elevation 495'o").
2.2.1.5 In reviewing paragraphs 2.2.1.1 - 2.2.1.4 it can be seen that if any one of the above cases occurs, the maximum flood level , will be 508:o". Therefore, in the design modification to protect the. CCSW pumps a t maximum flood to the 508'o" elevation was used. This height of 13' (elevations 508'o" less 495'o") was used as the maxi-mum CCSW flood depth. i 242.2 Design Modifications of CCSW Putnp Room 2.2.2.1 Each unit at the Dresden Station has four containment cooling service water pumps, any two of which will provide the required , containment cooling. Each unit will have two of the above pumps in an isolat'ed vault.- The pumps are enclosed 'in the i following manner, using Un it 2 as an i
CARGENT & LUNDY
.) ENGINEERS o . . -
o example (See Fig. lA): Containment Cooling l Service Water pumps 2B-1501-44 and 20-1501-44 are in a vault. Unit 3 pumps are enclosed in a like manner (See Fig. 2A). 2.2.2.2 The following piping will remain in the vaults because of the complexity of its '. removal and its necessity to the operation of the CCSW pumps: Hypochlorite Injection Piping Service W' a ter Injection Piping Two ventilation Ducts Penetrations for all of the above piping through the watertight vaults will be properly sealed as discussed in paragraph 2.2.2 5. 2.2.2.3 Each of the vaults will be constructed by building a new flood protection wall around the B End C CCSW pumps in each unit. These new walls are keyed into the existing walls and slabs and ' anchored with drilled in anchors (see Figs. lA, 2A, 3, 4 &-5).
~~ . . , s CARGENT & LUNDY
- ENGINEERS CHACAOO The walls are designed and will be con-structed to withstand a 13' head (see paragraph 2.2.1 5, Determination of Maxi-mum Flood Level) of water on either side of the wall in addition to the combined
. horizontal effect -of a 0.18 g (DBE earth-quake loading) seismic occurrence, vertical effect of a 0.12 g (DBE earthquake loading) seismic occurrence and including a sloshing effect of the water per Nuclear Reactors and Earthauakes TID-7024.
The walls are capable of withstanding the above mentioned combined loads with stresses not exceeding 1 1/3 times the allowable working stresses for the materials. Stresses in these reinforced walls are such that no cracking is expected to occur which would cause flooding of the pump vaults. 2.2.2.4 Access into the pump vaults will be by means of either watertight, steel, bulkhead or submarine type doors. 2Thehe. V. - doors will be designed and constructed to the same flood and seismic criteria as the walls. .
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* ~ CARGENT Q LUNDY rNGINEEMO - (~')
, , onoso v 2.2.2.5 Pipe penetrations through the vault walls Will be sealed with grout cement.
Electrical cables supplying power to the CCSW pumps will be sealed in the vault walls using a Nelson-Multi-Cable Transit fitting (see Figs. 9 and 10). The fitting consists of a box frame which is cast into the vault wall. Inside this frame are rubber blocks which. are pre-cut to accept the exact cables that are routed through the opening. Tne rubber blocks are then compressed within the frame to form a seal. These seals are designed to withstand a head of 50' of water. Small conduit penetrations are sealed with grout cement in a manner similar to the pipes discussed above. Junction boxes connected to conduit which penetrates the vault walls 'will be sealed with - RTV (silicone rubber sealant) to prevent leakage into the vaults. k
CARGENT CiLUNDY ENGINEERO {m
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4 1 4 2.2.2.6 Electrical instrumentation, controls and other components which are susceptible l to water damdge will be located
, at an elevation above the flood elevation i
of 508 o". _ 2.2.2 7 There are provisions for two types of j drains from the flood protection vaults: (1) floor drainage and (2) equipment
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drainage via the containment cooling service 1 . water pump bed plate drains. i Floor drainage of each vault is accomplished through a carbon steel pipe which penetrates 1 the new vault wall. When open this pipe will drain the vault floor to a floor drain outside the vault. Under normal conditions the pipe will be closed off,by' ! a standard, screwed pipe cap good for 125 . psi. When it is desired that the vault ! floor be drained, the cap is removed manually. Equipment drainage from the vaults will. l , be via the CCSW pump bed plate drains (see Fig.11) . The following equipment in the vault will drain to the above bed plates: .
f- CAP.'J ENT C LUNDY -
* .
- ENGINEERO
, CHICAGO
- 1. CCSW pumps
- 2. Vault coolers for each of the above pumps j
Each bed plate drain enters the floor slab where.it is tied into other bed plate drain 4 piping which runs through the slab to the equipment drain sump (located outside the vaults) (See Fig. 9 ).
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As a means of preventing backflow from outside the vaults in the event of a flood, a check valve and an air operated valve are installed in each bed plate drain line above the point where it enters the floor slab. The check valve is a 2" Crn.ne swing check No. 34 designed for 125 psic service. The air operated valve is a Fisher control valve designed for a 15 psi differential pressure. The control valve will be in the normally open position in the energizad condition and will close upon any one of the following:
- 1. Loss ~of air or power 2.
< 'High level in the equipment drain sump (signalling a possible flood)
- 3. High level in the vault 1
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, CARGENT & LUNDY ENGINEERO e
CMICAGO , 4 Closure of the control valve on high water level in the vault is affected by use of a level switch set at a. water level of 6" inside the vault. Upon actuation of the switch, it will close the control valve and alarm in the control room to notify the operator of trouble in the vault. The 1 operator will also be aware of problems in the condensate pump room if the high level , alarm on the equipment drain sump is not terminated'in a reasonable amount of time. It must be pointed out that these alarms provide information to the operator but that operator action upon the above alarms is not a necessity since the automatic provisions provide adequate protection. 2.2.2.8 In order to prevent the CCSW pump motors from overheating two vault coolers are supplied for each pump. The vault coolers are designed to maintain the vault at a maximum 105'F temperature during operation of a respective pump and provide humidification.
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- cmeme For example, if CCSW pump 2B-1901-44.
starts, its coolers' also start and maintain. the vault at lo5*F by removing heat supplied by the pump motor of 2B-1501-44 If, at the same time pump 2B-1501-44 is in operation, CCSW punp 2C-1501-44 starts, its coolers will also start and compensate for the added heat supplied to the vault by the 20 pump motor keeping the vault at loS*F. Each of the coolers is supplied with cool-ing water from its respective pump's dis.- charge line (see Fig. 10). After the water has been passed through the cooler it returns to its respective pump's suction line. In this way the vault coolers are supplied with cooling 9ater totally inside the vault. The cooling water quantity needed for each cooler is approximately 1% to.5% of the design flow of the pumps so that the recircula-tion of this small amount of heated water will not affect pump or cooler operation. .
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(V) CAn:ENT Q LUNDY ENOINEERG CHICAG O The cooling water piping and vault coolers are designed and constructed for seismic Class I conditions. The coolers are similar in design and construction to
- coolers which have been specified and installed at the Zion Station (Docket No.
50-295). The coolers are manufactured by The Buffalo Forge Company. Electrical supply to the fan motors of the vault coolers is supplied in the same manner and off the same bus as that of their respective pumps, thereby upholding the Class I' integrity of these systems and assuring cooler operation concurrent with pump operation. 2.2.3 Testing The watertight bulkhead door and the penetration seals for cables penetrating the vault walls and ceilings will be designed to withstand the maxi-mum flood conditions. However, in order to assure that their installation is adequate for maximum flood conditions a method of testing each seal has been devised.
CARGENT & LUNDY ENGINEERG
,. . CHicAto l 2.2.3.1 In order to test the watertight doors, a test frame will be installed on the conden-ser side of the condenser pit wall door and both sides of the CCSW vault door.
At the time of the test ( reinforced rubber diaphrams as manufactured by the Goodyear Tire and Rubber Company will
, be clamped into test frames.
Water will then be pumped into the rubber diaphragms to the design pressure of.13' and 30' respectively and held for several minutes to insure a watcrtight seal around the door. 2.2.3.2 In order to test an electrical penetration sealed with the Nelson Multi-Cable Transit fitting an identical fitting is permanently installed on the opposite side of the penetration (see Fig.11). Compressed air is supplied to a test connection on the second fitting and the space between the fitting is pressurized to approximately 15 psig. The outer face /s of Nelson fitting /s is/are then tested for leaks using a soap bubble solution. Any leaks noted can be stopped by a readjustment of the seal. m ____ - _ . _ _ _ _ _ _ - - _ - - _ - _ - - - -
. CARGENT Q LUNDY ENGINEEDO , em:4so 2.2.3.3. No test will be made on the total vault i
walls themselves as the only reliabic t method to do this is to flood either the vault or the condensate pump room, neither i of which is feasible. 2.3 Protection of the Diesel Generator Cooling Water Pumps i i 2.3.1 ~ Determination of Maximum Flood Level f 2.3.1.1 The three diesel generator cooling water pumps are located in the crib house pit I (elevation 490'8"). i There ;s only one source of flood water in the crib house pit. Flood water would j enter the pit if a rubber expansion joint ,i on one of the six circulating water pumps failed. If this occurred and the circulat-ing water pumps continued to run, the crib i house pit would' fill with water and.would be filled to the.517'0" elevation (ground level). At this point, the flood water would spill back to the river.
CARGENT O LUNDY ENGINEEQO s
, e CMICASO -
2.3.1.2 The flood elevation of 517'0" for the diesel generator cooling water pumps yields
- a flood depth of 26'4" (elevations 517'0" less 490'8"), plus a 10% margin to come up with a maximum flood depth of 30 feet.
2.3.2 Design Modifications 2.3.2.1 The three diesel generator cooling water j pumps have been replaced with watertight, 4 submersible " canned" type pumps and motor
. drives, as manufactured by Crane Chempump Division, with capacity and head equal to the original pumps (see Fig. 12).
a j 2.3.2.2. The electrical feed conduit to these pumps is furnished with the replacement pumps and is also of watertight design. The electrical motor control center for those pumps is located at elevation 517'0" in the turbine building and is not susceptible ! , to flood damage as it is above flood. level. 2.3.3 Testing 2 3.3.1 The replacement pumps willLbe factory tested and certified to' operate while submerged
$nder 30 feet of water. ,
The diesel generator system will be given a preoperational test after the cooling water pumps have been
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- CARGENT O LUNDY ENGINCEnD cMicAce i
3.0 Safety Evaluation l j 32 If a rubber expansion Joint ruptures at the Dresden station, j as it did at the Quad-Cities Station, the resultant flood water will be isolated in the condenser pit and no Class 1 j I equipment will be affected. Ibsi,gn modifications have } l I been made to protect flooding of the areas of the plant by the installation of IEEE-279 standard circulating water
) pump trip and by scaling off of the condenser pit. The condenser pit has been analyzed to be able to withstand the maximum flooding condition of all the postulated floods I
combined with the plant design basis earthquake including ~ 4' a sloching effect of the flood water. l ' 3.2 As described in the " Design Details" of this report:
; 1 Two of the four containment cooling service water i
pumps per unit will be enclosed ih a watertight vault which will withstand the maximum flooding (total of all potential floods) of the condensate pum.p room. 4 There is no other Class I equipment in the condon-sate pump room that would be affected by such a flood. 2 The diesel generator cooling water pumps .will be replaced with watertight, submersible type pumps which will withstand the max'imum flooding of the l crib house pit. .There is no other Class I equipment. in'the crib house pit that would be affected by such
. ,_. C ARGENT & LUNDY
, ENGlNCERC 7.
, CHICA&Q 4.0 Conclusion Wnce the design modifications discussed in this report are completed, Class I equipment - the contaiment cooling service water pumps and diesel generator cooling water pumps in particular - will not be degraded.by flooding such as occurred at the Quad-Cities Station or any other" postulated flooding.
Therefore, the containment cooling service water pumps and diesel generator cooling water pumps and associated Class I equipment in both Dresden - Units 2 and 3 will meet all engineering safe guards and seismic Class I criteria to ensure their availability and plant reactor safety. l l
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ATOMIC ENERGY COMMISSION wASWNGTON, D.C. 20545 A 9
%,,' n%e" May 9, 1973 Docket s. 50-10 50-237, an Cor:=onwealth Edison Company ATTN: Mr. L. D. Butterfield, Jr.
Nuclear Licensing Administrator Post Of fice Box 767 Chicago, Illinois 60690 Gentlemen: In our evaluation of your response dated October 13, 1972, to our letter dated August 3, 1972, regarding flooding of critical equipment, it has become apparent that additional information is required before we can continue our review. The additional information should provide assurance that the plants do or will meet the guidelines set forth in the enclosed Attachment A. Sc=e infor=ation addressing the guidelines has been included in your October 13, 1972 letter and cay be incorporated by reference where appropriate. If your analysis identifies systems or components that require additional changes in your plant to ccet the guidelines, submit the results of your safety analysis regarding the changes, a description of the required changes (including appropriate drawings and sketches), and schedule for completion of the changes. Where te=porary protective measures are to be taken to protect equipment or systens important to safety, submit your analysis, description, and justification for these measures and your installation and test schedule. Also describe and discuss the status of investigations and codifications reported to be in progress in your October 13, 1972 letter. Your response for temporary protective measures shotJ.d be submitted as soon as practicable but in not more than 30 days. Other information requested above should be submitted within 60 days. It is expected s 1
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Commenwealth Edison Company May 9, 1973 that all required corrections will be performed as expeditiously as is practicable. One signed original and thirty-nine additional copics of your submittals are required. Sincerely, j f/ws y - W Dennis L. Zieta , Chief Operating Reactors Branch #2 Directorate of Licensing
Enclosure:
Attachment A - Guidelines cc w/ enclosure: John W. Rowe, tsquire Isham, Lincoln & Beale Counselors at Law One First National Plaza Chicago, Illinois 60670 Morris Public Library 604 Liberty Street Morris, Illinois 60451
33 x,) V ATTACHMENT A GUIDE 1.INES FOR PROTECTION FROM FLOO_ DING OF EQUIPMENT IMPOR_ TANT TO SAFETY Responses should provide assurance that the plants do or will meet the following guidelines:
- 1. Separation for redundancy - single failures of non-Class I system components or pipes chall not result in loss of a system icportant to safety. Redundant safety equipment shall be separated and protected to assure operability in the event a non-Class I system or component fails.
- 2. Access doors and alar s - watertight barriers for protection from flooding of equipcent icportant to safety shall have all access doors or hatches fitted with reliable switches and circuits that provide an alarm in the control room when the access is open.
- 3. Sealed water passages - passages or piping and other penetrations through walls of a roca containing equip =ent important to safety shall be sealed against water leakage f rom any postulated failure of non-Class I water systers. The seals shall be designed for the SSE, including seis=1cally induced wave action of water inside the affected compartment during the SSE.
- 4. Class I watertight structures - walls, doors, panels, or other co=part=ent closures designed to protect equipment important to safety from da= age due to flooding from a ncn-Class 1 system rupture shall be designed for the SSE, including scismically ,
induced wave action of water inside the affected compartment during the SSE.
- 5. Water level alarms and trips - rooms containing non-Class I system cocponents and pipes whose rupture could result in flood damage to equipment important to safety shall have level alarns and pu=p trips (where necessary) that alarm in the control room and limit flooding to within the design flood volume. Redundancy of switches is required. Critical pu=p (i.e. , high volume flow, such as condenser circulating water pumps) trip circuits should teet IEEE 279 criteria.
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- 6. Class I equipment should be located or protected such that rup ture of a non-Class I system connected to a tower containing water or body of water (river, lake, etc. ) will not result in failure of the equipment from flooding.
- 7. The safety analysis shall consider simultaneous loss of of fsite power with the rupture of a non-Class I system component or pipe.
The responses should include a listing of the non-Class I systems considered in the analysis. These should include at least the following systecs: Firewater Demineralized Water Service water Drains Condensate Heating boiler condensate Feedwater Condenser circillating water Reactor Building Cooling Water Makeup Turbine Building Cooling Water Potable water e f
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(UL Commomvealth Edison Company ONE FIR $T NATIONAL PLAZA Addrest foply to
- C H I C A G O. ILLINOIS POST OFFICE 802 747
- C H I C A G O, ILitNOIS 40490 October'13, 1972 f O. /
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. j .- &g Mr. Donald J. Skovholt 1 E 40-237 Assistant Director for bi 0
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1 Commonwerlth "d' son Corgeny Oresden Nuclear Pouer Stotien Review of "nr!neered unfegunr? 9ys ten Cerirns Octcher 6, 1972 The design or engineered safeguards eystems considering equip-ment submercence has been revieued for the three Dresden Units and three aress of concern
- 1dentified. No nrens of concern were identi-fled on Dresden Unit 1; on Units 243 it was determined that three safeguard systems could be submerged as a recult of failures of equipment which was not dosisned to meet the criteria of Class I seismic construction or failure of a sinple Class I component.
The three Dresden Unit 2&3 standby diesel generator cooling water pumps are located at Elevation h908-6" in the cribhouse (see attached Crawing M-10) . This is 17'-h" below high river water level of 506'-o". If a failure of the circulating w/3, ater pumps or piping in the cribhouse occurred, the three (D-2, D-2 and D-3) diesel generator cooling water pumps would be submerged and inopersble. If a diesel generator cooling water pump or the associated piping should f ail, it would result in submergence of the other two (2) ?t , pumps. The four containment coolinE water punps on each Unit are located in the turbine buildings at Elevation h95'-0 (see attached Drawing M-5). These pumps are above the elevrtion of the condensate pump room (Elevation h64 8-6") and the main condenser pit (Elevation 4818-0"). Although tho containnent cooling service water pumps are well above the lowest elevations in the turbine building, they are below river water level, therefore n failure of the circula ting water system in a anit could result in submergence of the four containment cooling service water pumps for that unit. If failure of a contain-ment cooling service water pump or the associated piping were posta-lated, it could result in submergence of the other three (3) pumps. Redesign of the diesel generator cooling water system and containment cooling service water systems is in progress. The diesel generator cooling water pumps and motor will be replaced with These pumps will equipment designed for submerced nnd dry operetion. be purchased in accordance with the original criteria. The present estimate indicates the now pumps will be delivered by late Februsry 1973 The pumps will be installed as quickly as possible and should be available for testing and service by April 1973 To preclude sub-mergence of the containment cooling service water pumps by circulating water, the main condenser pits will be sealed with Class I watertight access doors and ventilation closures. In addition, instrumentation to alarm water level in the condenser pit and trip the circulating water pumps will be provided as described in our Quad Cities report dated July 10, 1972. We plan to complete these designs the week of October 16, 1972. To preclude loss of all containment cooling water pumps on a unit due to a single f ailure in the containment cooling service water system, we are presently evaluating designs forcomplete We plan to separ-cting the pamps by Class .m % I, watertight barriers. gg
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-o .~. Continued operation of Dresden Units 2&3 is justified pending completion of the above described modification; because in the un-likely event one of the three safeguards systems is inoperable due to submergence, the units will be maintained in a safe condition.
If the three diesel generator ecoling water pumps are submerged making the diesel generator inoperable, the two units een be brought to the cold shutdown condition using normal procedures, equipment and off-site power. In the highly unlikely event the diesel gener-ators are inoperable due to submergence of the cooling water pumps coincident with a total loss of off-site power supplies, the units would scran and reactor cooling would be provided by the isolation cordensers supplied make-up water by the diennl-driven fire protec-tion system punp. If the fcur (h) containment cooling service water pumps on one unit are inoperable due to submergence, the affected unit will be brought to the cold shutdown condition us!ng normal procedures and equipment. If the containment cooling eervice water pumps are in-operable coincident with a loss of off-site pouer, the affected unit will be brought to the cold shutdown condition using normal shutdown cooling equipment pawered by the standby diesel generators. If the containment cooling service water pumps are inoperable co-incident with a loss of the normal shutdown cooling system on the
.affected unit, reactor cooling will be provided by the main conden-ser or the isolation condenser.
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8 Q hA u Mr. Donald J. Skovholt iIc'a f %'3pf,?? :,, g# _,.h.e. [ h/
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Assistant Director for Operating Reactors , // ' Directorate of Licensing / '$ M U.S. Atomic Energy Commission 4 g p, i + Washington, D.C. 20545
Subject:
Review of Dresden Station Facilities-to Resist Floodinci Cacabilities
Dear Mr. Skovholt:
' lour letter of August 3, 1972 requested a review of the Dresden Station facilities to determine its ability to resist flooding. This revicw is in progress and a response will be submitted to you during the week of October 9, 1972.
Very truly yours,
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S s s ,. L. D. Butterfield, Jr. Nuclear Licensing Administrator
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4 il . W ASHINGTON. O.C. 20545 ' August 3, 1972 ' Ncket Nos. 50-10, 50-237, and 50--249_ i, 1 Commonwealth Edison Company '
- ATTN: Mr. L. D. Butterfield, Jr.
Nuclear Licensing Administrator Post Office Box 767 Chicago, Illinois 60690 4 Gentlemen: FLOODING OF CRITICAL EQUIPMENT As a result of a failure of an expansion bellows in the circulating 1 water line at Quad-Cities Unit 1, 'you c::perienced flooding and resultant g degradation of some of the engineered safety features. You have .N reported that interim corrective action has been taken and more per-manent corrective measures are planned at Quad-cities 1 and 2 to prevent recurrence; however, similar action has not been reported for your
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other facilities. \ You are, therefore, requested to review the Dresden station facilities to determine (1) whether failure of any equipment which does not meet the criteria of Class. I seismic construction, particularly the cir-culating water system, could cause flooding sufficient to adversely affect the performance of engineered safety systems and (2) whether
. failure of any equipment could cause flooding such that common mode failure of redundant. safety related equipnent would result. The integrity of barriers to protect critical equipment from flood waters should be .)
assumed only when the barrier meets the seismic requirements for Class I structures. If your review determines that engineered safety features could be so affected, provide your plans and schedule for corrective action together with the justification for continued operation of i Dresden station facilities pending completion of the corrective action. l I r M^
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Commonwealth Edison Company August 3, 1972 i The results of your review are requested within sixty days. This information should be provided with one signed original and thirty-nine i additional copies. Sincerely, A Donald J. ovholt Assistant Director for Operating Reactors Directorate of Licensing cc: John W. Rowe, Esquire Isham, Lincoln & Beale Counselors at Law , One First National Plaza Chicago, Illinois 60670 I t}}