ML19319C277
| ML19319C277 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/01/1969 |
| From: | TOLEDO EDISON CO. |
| To: | |
| References | |
| NUDOCS 8002110759 | |
| Download: ML19319C277 (36) | |
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,_,. TABLE OF CONTENTS Section M
6 ENGINEERED SAFETY FEATURES 6-1 6.1 EMERGENCY CORE COOLING SYSTEM 6-2 6.1.1 DESIGN BASES 6-2 6.
1.2 DESCRIPTION
~ 6-2 6.1.3 DESIGN EVALUATION 6-4 6.1.3.1 Failure Analysis 6-5 6.1.3.2 Emergency Injection Response 6-6 -
6.1.3.3 Special Features 6-10 6.1.3.h' Check Valve Leakage - Core Flooding System 64 6.1.h TEST AND INSPECTIONS 6-11 6.2 CONTAliNENT ATMOSPHERE COOLING SYSTEMS 6-13 6.2.1 DESIGN BAbIS 6-13 6.2.2 SPRAY SYSTEM 6-13 6.2.2.1 Description 6-13 6.2.2.2 Design Evaluation 6-14 6.2.2.3 Tests and Inspections 6-14 6.2.3 CONTAINMENT AIR RECIRCULATION COOLERS 6-15 6.2 3.1 Description 6-15
. 6.2.3.2 Design Ev duation 6-16 6.2.3.3 Tests and Inspec to: 6-17 6.2.h FAILURE ANALYSIS 6-17 j 6.3 EMERGENCY VENTILATION SYSTEM 6-20 l 7 I6
.'3.l' DESIGN BASIS 6-20 6.3.2. SYSTEM DESCRIPTION 6-20 I. .
6-1 Amendment No.T
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Section h e 6.3.3 DESIGN EVALUATION 6-20 l 6.3.h TESTS AND INSPECTION e 21 i 6.3 5 FAILURE ANALYSIS 6-21 T l6.3.6 PRESSURE IN ANNULAR SPACE VERSUS TIME AFTER LOCA 6.21 4 4 4 1 . i i i t i - t 1 0101 s Amendment No,'7 6 D-B , LIST OF TABLES \ Table Page
/-l High Pressure Injection System Equipment Data 6h C-2 Core Flooding System Performt ace and Equipment Data 6-5 G-3 Single Failure Analysis-Emergency Injection 6-7 6-4 Emergency Injection Equipment Performance Testing 6-11 6-5 Containment Spray System Performance and Equipment 6-14 Data 6-6 Containment Air Recirculation Unit Performance and Equipment Data 6-16 .
6-7 Single Failure Analysis-Containment Atmosphere Cooling Systems 6-18 6-8 Single Failure Analysis-Shield Building and Penetration Room Ventilation and Filtration Systems 6-22 3 0102 6-iii Amendment No. 3
D-B l LIST OF FIGURES (At Rear of Section) Figure No. 6-1 Emergency Injection Cafety Features 3l 6 .2 High Pressure Injection Pump Characteristics 6-3 Decay Heat Pump Characteristics - ! 6-4 Decay Heat Cooler Characteristics 6-5 Containment Spray System
- 6-6 Containment Cooling Water System :
6-7 Containment Cooling and ventilation System l i l
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l i 0103 U l Amendment No. 3 g 6-iv. ( - 1 0 ;.
D-B 6 ENGINEERED SAFE'IY FEATURES , ( Engineered safety features are provided to fulfill three functions in the un- 8 likely event of a serious loss-of-coolant accident:
- a. Protect the fuel cladding.
- b. Ensure containment vessel integrity 6
- c. Reduce the driving force for containment leakage.
(DELETED) l3 Emergency injection of coolant to the reactor coolant system satisfies the first function above, while containment vessel atmosphere cooling satisfies the !6 latter two functions. Each of these operations is performed by two or more sys-tems which, in addition, emplo,r multiple components to ensure operability. All equipment requiring electrical power for operation is supplied by the e=ergency
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electrical power sources as describe.d in 8.2.3. The engineered safety feltures include core flooding tanks, high pressure cool-ant injection, low pressure coolant injection, the containment vessel cooling system, and the containment vessel spray system. The emergency core cooling sys-tem (ECCS) includes the core flooding tanks, high pressure coolant injection,
'and low pressure coolant injection. Figure 6-1 shows the operation of the ECCS in the engineered safety features mode, together with associated instru-mentation and piping.
Applicable codes and standards for design, fabrication, and testing of compo-nents used as safety features are listed in the introduction to Section 9, and seismic requirements are given in Section 2 The safety analysis presented in Section 14 demonstrates the performance of installed equipment in relation to functional objectives with assumed failures. Some of the engineered safety features functions noted above are accomplished l3 with:the post-accident use of equipment serving normal functions. The design approach is based on the belief that regular use of equipment provides the best possible means for monitoring equipment availability and conditions. Be-cause some of the equipment used serves a normal function, the need for periodic testing is minimized. In cases where the equipment is used for er.argencies only, the systems have been designed to permit meaningful periodic tests. Ad-ditional descriptive information and design details on equipment used for nor-mal operation are presented in Section 9. Section 6 will present design bases for safety features protection, equipment operational descriptions, de-sign evaluation of equipment, failure analysis, and a preliminary operational testing program for systems used as engineered safety features. t 0104 6-1 s Amendment No. 8 E# ., k e
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D-B 6.1 EMERGENCY CORE COOLING SYSTEM ' 6.1.1 DESIGN BASES The principal design basis for the emergency core cooling system is as follows:
" Emergency core injection is provided to limit the temperature transient below that of the clad melting point so that fuel geometry is maintained to provide core cooling capability.
This equipment has been conserystively sized to limit the tem-perature transient to 2300 F or less since temperatures in excess of this value promote a faster zirconium water reaction rate and the termination of the transient near the melting point would be difficult to demonstrate." The capability of. the ECCS equipment to terminate the temperature transient and to maintain core geometry are the basic design objectives. These would be , accomplished if the temperature were terminated before the melting point of - the clad was reached. However, the rate of temperature rise due to metal-water reacticn is very rapid as the melting point is approached and, as a re-sult, exact temperature limitations at these higher values would be difficult to justify. Under these conditions the design has included a safety factor to limit the temperature transient to 2300 F until additional information be-comes available to substantiate the cooling required to permit a higher tempera-ture limit. Emergency core cooling includes pumped injection and the core flooding tanks. 3l Pumped injection comprises two syste=s,the high pressure injection system and the decay heat removal system. The core flooding tanks are passive componer.ts which are always ready to provide emergency core cooling during all periods of reactor criticality. 3l High pressure Ppetion is provided to prevent uncovering of the core for small coolant piping leaks at high pressure and to delay uncovering of the core for intermediate-sized leaks. The core flooding system and the decay heat removal system (which provides 1cw pressure injection) are provided to recover the core at intermediate-to-low pressures so as to maintain core integrity during leaks ( ranging from intermediate to the largest size. This equipment has been con-servatively sized to limit the te=perature transient to a clad temperature of 2,300 F or less. 6.1. 2 DESCRIPTION Figure 6-1 is the schematic flow diagram for the emergency injection and asso-ciated instrumentation. Emergency injection fluid is supplied frcm the borated water storage tarA. This tank contains the volume of borated water necessary to fill the re-3l fueling canal during refueling operations and is connected to the injection pump suction headers. Additional coolant for emergency injection supply is contained in core flooding tanks which inject coolant without fluid pumping. Amendment No. 3 6-2 '0105
D-B Emergency injection into the reactor coolant system will be initiated in the
, - - event of (a) an abnormally low reactor coolant system pressure of 1,500 psig
! or (b) a centainment pressure of 4 psig during pcVer operation. Either of these' signals will automatically initiate high pressure injection flow to the reactor coolant system. The two high pressure injection pumps will start and the in' ction valve in each of four injection lines will open. Emergency high pressure injection will continue until terminated by the operator. The flow characteristic curves for each high pressure injection pu=p aregiven in Figure 6-2. Table 6-1 gives performance and equipment data for the high pressure injection system. 3 The core ficoding system is composed of two flooding tanks which are pressur-ized with N2, each directly connected to a reactor vessel nozzle by a line con-taining two check valves and one stop valve. The system provides for automatic floodin; injection when the reactor coolant system pressure reaches approxi-mately 600 psig. This injection provision does not require any electrical power, automatic switching, or operator action to insure supply of emergency coolant to the reactor vessel. Operator action is required only during reactor cooldcun, at which time the stop valves in the core flooding lines, which are open during normal operation, are closed to contain the contents of the core flooding tanks. The combined coolant content of the two ficoding tanks is cufficient to recover the core hot spot, assuming that no liquid remains in the reactor vessel at the time injection begins. The gas overpressure in the core ficoding tanks, along with the size of the flooding lines, is sufficient to insure core reflooding within about 25 seconds after the largest pipe rupture has occurred. The decay heat removal system (described in Section 9) is normally maintained on standby during power operation and provides supplemental core flooding ficw through the two core flooding lines after the reactor coolant system pressure reaches approximately 135 psi. Emergency operation of this system will be initiated by a reactor coolant system pressure of 200 psi or by a containment pressure of 4 psig during any accident. The flow characteristics of each decay heat pump for injection are shown in Figure 6-3; each pump is designed to deliver 3,000 gpm flew into the reactor vessel at a vessel pressure of 100 psi. Lov pressure injection, with supply from the borated water storage tank, will con-tinue until a low level signal is received from the tank. At this time, the valves controlling suction frcs the containment vessel emergency sump will open l. 8 automatically and recirculation of coolant from the sump to the reactor vessel vill begir as described in Section T.2.2.2. The decay heat coolers will cool the recirculated flow, thus removing heet from the containment fluid and preventing further containment accumulation of decay heat generated by the ccre. The decay heat removal pumps and containment spray pumps are located at an ele-vation below the containment vessel emergency sump with dual suction lines routed l8 outside the containment to the pumps. The lines have been sized so that each will be capable of handling the total potential recirculation flow of one 3,000- ~ gpm decay heat removal pump, and one 1,300'-gpm containment spray pump. 0106 6-3 Amendment No. 8 t 4
D-B The calculations for available NPSH at the containment spray m and the decay heat removal pu=p suctions will include a safety margin over and above the requirements of these ms. The calculations will assume conservatively that minimum water levels exist in the borated water storage tank and in the 3l containment. Final pipe si::es will be adjusted to provide a su,fe NPSH margin for either pump operating mode. The heat transfer capability of each decay heat cooler as a function of recir-culated water temperature is illustrated in Figure 6 h. The heat transfer capability at the. saturated temperature corresponding to containment vessel pressure is in excess of the heat generation rate of the enre following stor-age tank injection. Design data for core flooding system components are given in Table 6-2 De-sign data for other emergency injection components are given in Section 9 ex-cept for those shown in Figures 6-2, 6-3, and 6 h. Table 6-1 High Pressure Injection System Equipment Data - High Pressure Injection Pump Quantity 2 Type Centrifugal 3 Rated Capacity, gpm 500 Rated Head, ft at sp gr = 1 2600 Rated Motor Horsepower 700 D Pe ure, psig 2 00 Design Temperature, F 300 - 6.1. 3 DESIGT EVALUATION In establishing the required components for the ECCS, four factors were con-sidered:
- a. The probability of a major reactor coolant system failure is very low,
- b. The fraction of a given component lifetime for which the component is unavailable because of maintenance is estimated to be a small part of lifetime. On this basis, it is estimated that the probability of a major reactor coolant system accident occurring while a protective component is out tr maintenance is several orders of magnitude below the low basic accident probability,
- c. The equipment downtime for maintenance in a well-operated station
, often can be scheduled during reactor shutdown periods. When main-tenance of an engineered safety features component is required dur- )
ing operation, the periodic test frequency of the remaining equipment can be increased to ensure availability. 1 3 Amendment No. 3 6-4 j _ 0107
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- d. Where the systems are designed to operate normally or where meaning-ful periodic tests can be performed, there is also a low probability that the required emergency action would not be performed when need-ed; that is, equipment readiness is improved by using it for other than emergency functions.
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7 D-B Table 6-2 l3 Core Flooding System Performance and Eculpment Data Core Floeding Tanks Number 2 Design Pressure, psig 700 Normal Pressure, psig 600 Design Temperature, F 300 OperationTempergture,F 110 Total Volume, ft / tank 1 410 1 3 Ucrmal Water Volume, ft / tank 950 Material of Construction Carbon Steel, SS-lined Code ASME Sec. III-C Check Valves Number per Flooding Line 2 Size, in. 14 Material SS Design Pressure, psig 2,500 Design Temperature, F 650 (Nearest Reactor) - 300 (Nearest Tank) Code ANSI B16.5 l3 Isolation (Stop) Valves Number per Flooding Line 1 Size, in. 14 Material SS Design Pressure, psig 2,500 Design Temperature, F 300 Code ' ANSI 316.5 l3 Piping Number of Flooding Lines 2 Size, in. 14 Material SS Design Pressure, psig 2,500 (Reactor to Isolation Valve) 700 (Isolation Valve to Tank) Design Temperature, F 650 (Reactor to First Check Valve) 300 (First Check Valve to Tank) Code ANSI 331.7 l3 6.1.3,1 Failure Analysis The single failure analysis presented in Table 6-3 is based on the assu=ption ! 3 that a major loss-of-coolant accident had occurred. It was then assumed that an additional malfunction or failure occurred either in the process of actu- ' ating the emergency injection systems or as a secondary accident effect. All credible failures were analyzed. For exa=plet the analysis includes malfunc-tions or failures such as electrical circuit or motor failures, stuck check valves, etc. It was considered incredible that valves would change to the op- ; posite position by accident if they were in the required position when the ac-cident occurred. In general, failures of the type assumed in this analysis l e rf, o-5 Amendment No. 3 0103 i
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'should be unlikely because a program of periodic testing and service rotation of standby equipment will be incorporated in the station operating procedures.
3 The single failure analysis (Table 6-3) and the dynamic post accident perfor-mance analysis (Section 14) of the engineered safety features considered capacity reduction as a result of equipment being out for maintenance, or as a result of a failure to start or operate properly. Station maintenance activities will be scheduled so that the required capacity of the engineered safety sys-tems will always be available in the event of an accident. The adequacy of equipment sizes is demonstrated by the post accident perfor-mance analysis described in Section 14, which also discusses the consequences of achieving less than the maximum injection flows. There is sufficient redun-dancy in the emergency injection systems to preclude the possibility of any single credible failure leading to core melting. 6.1. 3. 2 Emergency Injection Response 8 3 The emergency high pressure injection valves are designed to open within 10
- s. The four high pressure injection lines contain thermal sleeves at their connections into the reactor coolant piping to prevent overstressing of the pipe juncture when 90 F water is injected into these high temperature lines during emergency operations.
Injection response of the core flooding system is dependent upon the rate of reduction of reactor coolant system pressure. For a maximum hypothetical rup-ture, the core flooding system is capable of reflooding the core to the hot spot within a safe period after a rupture has occurred. Emergency low pressure injection by the decay heat removal system will be de-livered within 25 s after the reactor coolant system reaches the actuating pressure of 200 psig. This anticipated delay time consists of these inter-vals:
- a. Total instrumentation lag %1s
- b. Emergency power source start <15 s
- c. Pump motor startup % 10 s
- d. Injection valve opening time <10 s
- e. Borated water storage tank outlet valves < 10 s Total (only b and e are additive) %25 s
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n C Amendment No. 8 6-6 O , GO ]
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~ Table 6-3 l3 Single Failure Analysis-Emergency Injecti. .
Component Malfunction Comments A. High Pressure Injection
- 1. Remote-operated suction Fails to open. Similar valve in other high pressure injec-valve from borated water tion pump string will deliver requirea 3 1 storage tank. flow.
(Deleted) 3 2 High Pressure Injection Fails (stops). Other pump delivers required flow. Pump l3 3 High Pressure Injection Sticks closed. This is considered incredible since the Pump discharge check high pump discharge pressure at no flow 7' valve, would tend to open even a very tightly 3 e,
~4 stuck check disc. Es (Deleted)
CD FA 3 Fa M. Remote-operated isola- Fails to open. Flow from one pump will go through the 13 tion valve in high-pressure alternate line. Other pump will oper-injection line. ate as normal. E . a - B o W D
Table 6-3 (Cont'd) l3 Component Milfbnction Co@aents k @ 5. Injection line inside Rupture. Flow rate indicators in the four in- l3 l/ containment vessel. jection lines would indicate the gross @ difference in flow rates. Check valve " in the injection line would prevent y additional loss of coolant from the reactor. The lines are protected from " missiles by reactor coolant system shielding.
- 6. Valve from decay heat coolers to high pressure Inadvertently left open. No significant consequences. A small percentage of LP injection flow will be l3l1
(~ injection pump suction line. bypassed to IIP suction. B. Core Flooding System
- 1. Flooding line check Sticks closed. This is not considered credible based m valve, on the valve size and the opening pres- ts
/n sure applied, d, C. Decay IIeat Removal System
- 1. Check valve at reactor Sticks closed. This is not considered credible, since vessel, these valves will be used periodically during decay heat removal, and the opening force will be approximately 5,000 pounds.
- 2. Remote-operated in- Fails to open. Second injectica lin: hl1 deliver re-jection valve, quired flow.
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Table 6-3 (Cont'd) 13 Component Malfunction Comments i 3 Decay Heat Pump. Faila to start. Remaining pump will deliver required , injection flow.
-4.
, Check valve at borated Sticks closed. Alternate line will permit required -
water storage tank out- flow, let. 5 Remote -operated valve Fails to open. Two lines and valves are provided. One permitting suction will provide required flow. These from containment valves are not 1,eeded until 30 to vessel emergency swmp 50 min. after start of accident. l8
- 6. Containment vessel Becomes clogged. Clogging of a single line does not im- 1 emergency sump outlet pair function because of the dual sump l8 as pipe. line arrangement, the size of the lines, d) and-the sump design. The two recircula- 7 tion lines take suction from the different portions of the sump. A grating will be provided over the sump, and additional heavy duty strainers will be provided.
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D-B 6.1.3.3 Special Features The core flooding nozzles will be specially designed to insure that they will safely take the differential temperatures imposed by the accident condition. Special attention also vill be given to the ability of the injection lines to absorb the expansion resulting from the recirculating water temperature. For most of their routing, the emergency injection lines will be outside the reactor and steam generator shielding, and hence protected from missiles orig-inating within these areas. The portions of the injection lines located be-tween the primary reactor shield and the reactor vessel vall are not subject to v'.sile damage because there are no credible sources of missiles in that area. To afford further assurancc that injection water vill reach the core, 8 la high pressure injection line connects to each reactor coolant inlet pipe, and the two core flooding nozzles are located on opposit.e sides of the reactor vessel. All vater used for emergency injection fluid vill be maintained at a minimum 7 l concentration of 1,800 ppm of boron. The pressure, and level of the core flooding tanks will be displayed in the control room, and alarms will sound when any condition is outside the normal limits. The water will be perioda ically sampled and analyzed to insure proper boron concentration. 6.1.3.4 Check Valve Leakage - Core Flooding System The action that would be taken in the case of check valve leakage would be a function of the magnitude of the leakage. Limited check valve leakage vill have no adverse effect on reactor operation. ' The valves vill be specified to meet th ealing requirements of MSS-SP-61,
" Hydrostatic Testing of Steel Valves. "
- For these valves, this amounts to a maximum permissible leakage of lh0 cc/h per valve. Two valves in series are provided in each core flooding line; hence, leakage should be below this value.
Leakage across these check valves can have three effects: (a) it can cause a temperature increase in the line and core flooding tank, (b) it can cause a level and resultant pressure increase in the tank, and (c) it can cause dilu-tion of the borated water in the core flooding tank. Leakage at the rate men-tiened above causes insignificant changes in any of these parameters. A leak-age of 1h0 cc/h causes a level increase in the tank of less than 1 in./mo. The associated temperature and pressure increase h1 correspondingly lov.
- If it were assumed that the leakage rate is 100 times greater than specified, then there would still be no significant effect on reactor operation since the level change vould be approximately 2 in./ day. A 2-in. level change vill re-7 l sult in a pressure increase of approximately 10 psi. With redundant pressure, and level indicators and alarms available to monitor the core flooding tank
- conditions, the most significant effect Gn reactor operations is
(*) MSS - Manufacturers' Standardization Society.
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Amendment No; g 0114 6-10
D-B expected-to be a more frequent sampling of boric acid concentration in the core flooding tank. c. (. \ To ensure that no temperature increase will occur in the tank, even at higher leakage rates, the portion of the line between the two check valves and the line to the tanks will be left uninsulated to promote convective losses to the containment atmosphere. In summary, reactor operation may continue with no adverse effects coincident with check valve leakage. Mn4mnm permissible limits on core flooding tank parameters (level, temperature, and boron concentration) will be established to ensure compliance with the core protection criteria and final safety analy-ses. 6.1. 4 TEST AND INSPECTIONS All active components of the emergency injection systems, as listed in Table 6 4, will be tested periodically to demonstrate system readiness. In addition, l 3: normally operating components will be inspected for leaks from pump seals,
- valve packing, flanged joints, and safety valves.
Table 6 h l3 Emergency Injection Eculpment Performance Testing High Pressure Injec- Both pumps will be peM.odically tested. l3 tion Pumps I High Pressure Injec- The remotely operated stop valve in each line
. tion Line Valves will be opened partia13,y one at a time. The 3 flow devices will indicate flow through the lines, y Decay Heat Pumps In addition to use for shutdown cooling, these pumps will be tested singly by opening the bo-rated water storage tank outlet valves and the bypass in the borated water storage tank fill line. This will allow water to be pumped from the borated water storage tank through each of the injection lines and back to the tank.
Borated Water Storage The operational readiness of these valves will Tank Outlet Valves be established in completing the pump opera-tional test discussed above. During this test, each of the valves will be tested separately l for flow. l 6-11 Amendment No. 3 ) i .o a <
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D-B Table 6-3 (Cont'd)
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Decay Heat Removal With pumps shut down and borated water storage Injection Line Valves tank outlet valves closed, these valves will be opened and reclosed by operator action. Valve for Suction from With pu=ps shut down and borated water storage Sump tank outlet valves closed, these valves vill be opened and reclosed by operator action. Check Valves in Core Check valves can be tested during each shut-Flooding Injection Lines down to determine operability.
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D-B I 6.2 CONTAINME?IT ATMOSPHERE COOLING SYSTEMS k 6.2.1 DESIGN BASIS The containment cooling system is designed to limit and subsequently reduce the containment vessel pressure in the event of a less-of-coolant accident, and hence reduce the leakage of airborne activity from the containment vessel. Theairrecirculationcoogingsystemhasthesamecoolingcapacityasthespray system, which is 150 x 10 Btu /h. Any of the following combinations of equipment will provide the same heat removal capability:
- a. Two containment spray pumps.
- b. Two air cooling units.
- c. One air cooling unit and one containment spray pump.
Two spray pu=ps and three air recirculation coolers are provided. 6.2.2 SPRAY SYSTEM 6.2.2.1 Descriution Removal of heat is acco=plished by directing borated water spray into the containment atmosphere. The system is sized to furnish the required cooling capacity if the air recirculating and cooling system is inoperative. The system consists of two half-capacity pumps, two half-capacity spray headers, isolation valves , and the necessary piping, instrumentation and controls as shcwn on Figure 6-5 The pumps and valves can be operated from the control room. Uponhighcontainmentpressureandemergencyinjectionactuationsignal,thel8 two pumps start, taking suction initially from the borated water storage tank. The containment spray system shares the borated water storage tank and the suction lines frcm the tank with the high and low pressure injection systems. 3 After the water in the borated water storage tank reaches a low level, the spray pump suction is transferred to the containment vessel emergency sump. 6 The containment vessel emergency sump water is cooled by the decay heat removal system as described in 6.1. Pu=p motor power is supplied from normal and standby sor ces with back-up supplied from the emergency diesel generators. Design da:a for the spray system components are given in Table 6-4. Design data for components of the decay heat removal systems used in the recirculation phase are given in , Section 9 and supplemented by Figure 6-1. H l ( @c 0117 6-13 Amendment No. 8
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D-B Table 6 h
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Containment Scray System Performance / and Equipment Data Component Containment Spray Pumps 2 Number 2 Flow, gpm 1,300 Motor Horsepower, hp Approx 250 Material SS Design Temperature, F 300 Spray Headers
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Number 2 2 Spray Droplet Size 4,000 Micron Mean Piping Suction and Discharge SS Spray Headers (Downstres= of Isolation Valves) CS 6.2.2.2 Design Evaluation The system heat removal capacity is based on the spray water reaching thermal equilibrium with the steam-air mixture within the containment vessel. The containment spray system is designed to deliver full flow to the spray nozzles within 35 seconds after the LOCA. The spray pumps are located in separate rooms in the lowest level of the auxiliary building. This insures the availability of 50 percent of the system and also ensures sufficient NPSH to the pumps. 6.2.2.3 Tests and Inseections Components of the containment spray system are tested on a regular schedule as follows: Containment These pumps are tested singly by closing the Spray Pumps spray headers va; es and opening the valves in the test line. Each pump in turn vill be started by operator action and checked for flow to each of the spray headers. This test will also verify flow through each of the borated water storage tank outlet valves. N/ Amendment No. 2 6-lh 0118-
D-B Borated Water These normally open valves are cycled by remote e Storage Tank operator action to insure isolation closure. k Outlet Valves Containment With the pumps shutdown and the normally locked Spray Isolation open block valves upstream closed, these valves Valves are each opened and closed by operator action. Spray Nozzles When the unit is shutdown, air or smoke is blown through the test connections with visual obser-vations of the nozzles. Containment Vessel These valves will each be cycled opened and Emergency Sump Line Valves closed by operator action. 6 6.2.3 CONTAINMENT AIR RECIRCULATION COOLERS 6.2.3.1 Description The LOCA air recirculation cooling system is composed of two out of the three air recirculation units located within the containment vessel. These units are used for both normal and emergency cooling. The normal cooling function is discussed in Section 5.h. Each unit consists of a finned tube cooling coil and a direct driven fan. Cooling water for the air recirculation units is supplied by the service water system. The service water supply line for each cooler has a normally open (' isolation valve. The discharge line for each cooler has a normally closed stop valve and a modulating control valve in parallel with the stop valve. The modulating control valve is operated by a signal from a temperature con-troller in the unit air discharge to provide automatic temperature control for the containment during normal station operation. In the event of a LOCA, the emergency injection actuation signal will open the stop valve in the discharge service water line for full water flow. The containment cooling water system is shown in Figure 6-6. The air recirculation coolers are shown in Figure 6-6 and Figure 6-7 6 /h at design post-The rated capacity of each cooling unit is 75 x 10 Btu accident conditions. The design data for the air recirculation units are shown on Table 6-5 h . 3 s t ..Olis wt'o , 6-15 Amendment No. 6
D-B hble 6-5 Containment Air Recirculation Unit Performance and Equitment Data (Capacities Are for Single Components) Duty Equipment Data LOCA Operation Normal Operation No. of Units Installed 3 3 No. Required 2 2 Peak Heat Load, Btu /h 6 75 x 10 1.00 x 106 Fan Capacity, cfm (Total per Unit) 58,000 '.17,000 Containment Atmosphere Inlet Temperature, F 265 104 Cooling Water Flow, gpm 1600 5h0 - Fan Speed Half Full 6.2.3.2 Design Evaluation In establishing the design of the cooling system, the following factors have been considered:
- a. The air recirculation units are located outside the secondary shield at an elevation above the water level in the bottom of the ccptainnent vessel at post-accident conditions. In this
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location the units are protected against credible missiles and frem being flooded.
- b. All equipment, piping, valves and instrumentation associated with the air recirculation and cooling system is designed to withstand the temperature and pressure transient conditions resulting from a LOC' and the seismic forces resulting from the applicable eart} pake.
- c. The failure of the normal and auxiliary electrical power supply will automatically connect the air racirculation units to the emergency electric power from the diesel generators,
- d. The fans and m'; ors are designed to operate under normal con-ditions at full speed, mid at half speed during'LOCA conditions.
The motors are directly connected to the fan shaft.
'e. Excessive service water flow due to leakage from the coil is annunciated in the control room by high water level in the
- cooler condensate sump.
- f. The components of the system are used during normal operation {
and hence are continuously monitored for availability for post- l accident operation. t w 0 , '. 6-16 0120 >
D-B (~ g. Cooling coils of similar design have been tested successfully under design accident conditions in connection with the Haddam Neck and Palisades Plants. 6.2.3.3 Tests and Inspection The equipment, piping, valves and instrumentation are arranged so that all items can be visually inspected. The air recirculation units and associated piping are located outside the secondary concrete shield around the reactor coolant system loops. Personnel could enter this area of the containment vessel during station operation for emergency inspection and maintenance of this equipment. The service water piping and valves outside the shield build-ing are inspectable at all times. Operational tests and inspections vill be performed prior to initial startup. Periodic testing of the air recirculation units will be as follows:
- a. The normally operating two speed fan motors can be switched ~
from normal (high speed) to emergency (low speed) operation at any time to check emergency operability,
- b. The stop valve in the service water discharge line from each cooler vill be opened and the flow checked.
6.2.4 FAILUtiS ANALYSIS '( A single failure analysis has been made on all active components of the systems
'- to show that the failure of any single component will not prevent fulfilling of the design functions. This analysis is shown in Table 6-7 Assumptions l3 inherent in this analysis are the same as those presented in 6.1.3 in regard to valve functioning, failure types, etc. Results of full and partial per-formance of these safety features are presented in Section 14 under analysis of postaccident conditions.
( _ {s 0121 4; 6-17 Amendment No. 3
' {{ ~ , _. . J U Table 6-7 3
@' Single Failure Analysis Containment Atmosphere Cooling and Washin;;
O Component Malfunction Comments and Consequences
- l. ~ Containment spray nozzles. Clogged. Large number of nozzles on each of two
" headers renders clogging of significant u
number of nozzles as incredible.
- 2. Containment spray header. Rupture. This is considered incredible due to lov operating pressure differential.
- 3. Check valve in spray header line. Sticks closed. This is considered incredible due to large opening force available at pump shutoff head.
l 14 . Motor-operated valve in spray Fails to open. Second header delivers 50 percent flow. header line. Y
$ 5 Spray pump isolation valve. Left closed. Flow and cooling capacity reduced to 50 to percent of design. In combination with emergency coolers, 150 percent of total design requirement is still provided.
- 6. Containment spray pump. Fails to start. Flow and cooling capacity reduced to 50 percent of design. In combination with emergency coolers,150 percent of total design requirement is still provided.
7 Containment cooling unit fan. Stops. Emergency cooling by the other operating units with supplemental cooling by the sprays.
- 8. Containment cooling unit. Rupture of cooling The tubers are designed for 200 psi and
coil. 300 F which exceeds maximum operating .
conditions. Tubes are protected against credible missiles. Hence, rupture is not considered credible. h .
n n
. I Table 6-7 (Cont'd) l 3 Component Malfunction Comments and Consequences 9 Containment air cooling unit. Rupture of casing Consideration will be given during and/or ducts. detailed design to the dynamic forces resulting from the pressure buildup during a postaccident situation. The i units will also be inspectable and pro- ;
tected against credible missiles. Cool- ' ing with these units will be supplemented I by the sprays.
- 10. Containment air cooling units. Rupture of system Rupture is not considered credible since piping. all piping is Schedule 40, permitting an allowable working pressure of at least 500 psi at 650 F for all sizes. Piping e P is inspectable and protected from missiles. $
$ Maximum actual internal pressure will be less than 200 psi at temperatures below 300 F.
- 11. Motor-operated valve at inlet Sticks closed. Two of the ventilation units are in penetration. operation normally. Flow will be period-ically established through the idle line to check the operational capability of the standby unit. Such tests will show if valve is malfunctioning. ;
g ! g 12. Motor-operated valve at outlet Fails to open. Comments for Item 11 apply. N
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D-B 7 l6.3 EMERGENCY VENTILATION SYSTEM
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6.3.1 DESIGN HASIS This system is designed to collect and process potential leakage from the containment vessel to minimize environmental activity levels resulting from all sources of containment leakage. The function of the system is to provide a negative pressure within the Shield Building and Penetration Rooms following a loss-of-coolant-aecident and to reduce airborne fission product leakage to the environment by filtra-tion prior to release of air through the station vent. 6.3.2 SYSTEM DESCRIPTION . The system is shown schematically in Figure 6-7 Equipment consists of two full capacity redundant fan-filter assemblies. Each filter system shall be : 6 made up of two units - the first to contain roughing, HEPA, and charcoal filters in series, and the second, a duplicate set of charcoal filters. The arrangement will allow each set of charcoal filters to be tested separately. Following a loss-of-coolant-accident, a Containment Isolation Signal (CIS) (refer to Section 7.2) will start both fan-filter assemblies. The containment purge equipment, if running, will be shut down by the Containment Isolation Signal, and the purge isolation valves in each line closed. . Air from the , Shield Building and Penetration Ro;ms will be drawn through the filter ) assembly consisting of roughing filters, high efficiency particulate filters - and charcoal filters in series and discharged through the station vent. A pressure controller in the Shield Building vill regulate the modulating dampers at the fan discharge to maintain the set point negative pressure within the Shield Building and Penetration Rooms. The entire system is designed to operate under negative pressure up to the fan discharge. In all cases, the flow from these regions vill exceed the total maximum containment leakage plus the Shield Building in-leakage. Temperature indication and radiation monitors are_provided for operator information. Differential pressure indicators are provided across the filters. The system equipment is fully accessible during all normal station operation for maintenance and performance testing, including replacement of filter elements. 6.3.3 DESIGN EVALUATION 1 4 The system is provided with two redundant full capacity fan-filter assemblies. All equipment will be controlled from the control roan. During normal operation, this system is held on standby. The Containment l Isolation Signal vill actuate the fans. Control room instrumentation vill I monitor operation. The system can be tested during normal operation. The -
,, fans, can be operated on diesel generator power.
s..:: l 0124 . . 1 Amendment No. 7 6-20
D-B 6.3.h TESTS AND INSPECTION This system vill be given a pre-operational test before the station produces power. A check will be made to assure that the filters are sealed to prevent by-passing. The fans, filters and valves may be tested any time during normal station operation for operability and performance. The operation of the radiation and pressure monitors can be checked periodically. A13 equip-ment vill be fabricated and installed to provide visual inspection at any time. 6.3.5 FAILURE ANALYSIS A single failure analysis has been made of all active components of the system to shov that the failure of any single componer.t vill not prevent fulfilling of the design functions. This analysis is shown in Table 6-8. l3 6.3.6 PRESSURE IN ANNULAR SPACE VERSUS TIME AFTER LOCA Figure 6-8 shows the build up of pressure in the e.nnular space after LOCA due to the air temperature rise. The shield building emergency ventilation system fan is started after 45 seconds after LOCA. The negative pressure is established in the annular space in approximately 65 seconds. Following parameters have been used in developing the figure 6-8: Initial Temperature inside containment 120 F annular space 110 F 7 Fan Capacity 8000 cm Film Coefficient, h = 0.19 at1/3 Btu /Hr-F-ft2 Reactor Coolant System Pipe , rupture size lk.1 ft' s
.,y l
0125 6-21 Amendment No. 7
- - - , . . . .-. - - . -. . .~. .
( g.~l' TABLE 6-8 13 g ,(; Single Failure Analysis-Shield Building and g r3 Penetration Room Ventilation and Filtration System ' ct 3
+ Component Malfunction Comments and Consequences w
- 1. Fan Fails to start Other fan provides 100 percent capacity.
- 2. Fan Fails during service Alarm in control room will indicate loss of pressure drop through filter and failed fan vill be isolated by the operator.
- 3. Modulating Damper Fails-to operate Loop with malfunction vill be isolated. -
- 4. Ductwork Leakage Leakage of unfiltered air is inward since ductwork will be maintained at negative p pressure, p N
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l l Emergency Design Conditions 7 Injection Water Flow Per Cooler - 3,000 gym Decay Heat Component Cooling Water Fin Per Cooler - 6,000 gpm Decay Heat Component Cooling Water Inlet Temperature - 95 F 320 300 280 , 260
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. _ 0135 1
A B B R EV I AT I O N S , CIS - CON'T AINMENT ISOL AT lON SIGNAL MOD- MODUL AT ING DAMPER 1 PENETRATION ROOMS ENGINEERED SAFETY FEATURE EQUIP. ROOMS
$ RECIRC. VALVE ROOM C SHIELD BLDC,.
CONTAINM E NT VESSEL i f3 uo I 4 1 .L \ l GD / GEN.
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