ML19329E139
| ML19329E139 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 11/24/1967 |
| From: | ARKANSAS POWER & LIGHT CO. |
| To: | |
| References | |
| NUDOCS 8005300719 | |
| Download: ML19329E139 (36) | |
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TABLE OF CONTENTS Section Page 6 ENGINEERED SAFEGUARDS 6-1 6.1 EMERGENCY INJECTION 5-1 6.1.1 DESIGN BASES 6-1 6.
1.2 DESCRIPTION
6-2 6.1.3 DESIGN EVALUATION 6-3 a l3 6.1. 3.1- Failure Analysis 6-5 6.1.3.2 Emergency Injection Response 6-5 6.1.3.3 Special Features 6-6
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6.1.3.4 Check Valve Leakage - Core Flooding System 6-6 6.1.4 TESTS AND INSPECTIONS 6-7 6.2 REACTOR BUILDING ATMOSPHERE COOLING AND WASHING 6-13 l3 6.2.1 DESIGN BASES 6-13 6.
2.2 DESCRIPTION
. 6-13 6.2.3 DESIGN EVALUATION 6-14 6.2.3.1 Failure Analysis 6-15 6.2.3.2 Reactor Building Cooling Response 6-18 6.2.3.3 Special Features 6-18 6.2.4 TESTS ATD INSPECTIONS 6-18a 17 6.3 ENGINEERED SAFEGUARDS LEAKAGE AND RADIATION CONSIDERATIONS 6-19 6.
3.1 INTRODUCTION
6-19 6.3.2
SUMMARY
OF POSTACCIDENT RECIRCULATION AND LEAKAGE CONSIDERATIONS 6-19 6.3.3 LEAKAGE ASSUMPTIONS 6-20 6.3.4 DESIGN BASIS LEAKAGE 6-20 6.3.5 LEAKAGE ANALYSIS CONCLUSIONS 6-20 6-1 65 3-4-16 Supplement No.17
LIST CF TABLES Table No. Title Pg 6-1 Core Flooding System Performance and Equipment Data 6-h 6-2 Single Failure Analysis-Emergency Injection 8 6-3' Emergency Injection Equipment Performance Testing 6-12 64 Reactor Building Cooling Unit Performance and Equipment Data 6-13 6-5 ' Reactor Building Spray System Performance and Equipment Data 6-14 6-6 Single Failure Analysis-Reactor Building Atmosphere Cooling and Washing 6-16 3 6-7 Leakage Quantities to Auxiliary Building Atmosphere 6-21 i
6-11
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66 5-3-68 Supplement No. 3 ,
1 LIST OF FIGURES (At rear of Section)
- Figure No. Title 6-1 Emergency Injection Safeguards 6-2 Makeup Pump Characteristics 6-3 Decay Heat Removal Pump Characteristics 6-4 Decay Heat Removal Cooler Characteristics 6 Reactor Building At=csphere Cooling Safeguards 6-6 Reactor Building Cooler Characteristics 6-7 Reactor Building Spray Pump Characteristics 4
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6-111
6 ENGINEERED SAFEGUARDS Engineered safeguards are provided to fulfill four functions in the un- 3 likely event of a serious loss-of-coolant accident:
- a. Protect the fuel cladding,
- b. Insure reactor building integrity.
- c. Reduce the driving force for buildin6 leakage,
- d. Remove Fission products from the reactor building 3 atmosphere.
Emergency injection of coolant to the reactor coolant system satisfies the first function above, while building atmosphere cooling satisfies the lat-ter three functions. Each of these operations is perfomed by two or more systems which, in addition, employ multiple components to insure operability.
All equipment requiring electrical power for operation is supplied by the emergency electrical power sources as described in 8.2 3 The engineered safeguards include a core flooding system, hi8 h pressure in-jection equipment, the decay heat removal system, the reactor building cool-ing system, and the reactor building spray system. Figures 6-1 and 6-5 show the operation of these systems in the engineered safeguards mode, together with associated instrumentation and piping.
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Applicable codes and standards for design, fabrication, and testing of com-ponents used as safeguards are listed in the introduction to Section 9, and seismic requirements are given in Section 2. The cafety analysis presented in Section 14 demonstrates the perfomance of installed equipment in relation to functional objectives with assumed failures.
The engineered safeguards functions noted above are accomplished with the post-accident use of equipnent serving normal functions. The design approach is based on the belief that regular use of equipment provides the best pos-sible means for monitoring equignent availability and conditions. Because some of the equipment used serves a nomal function, the need for periodic testing is minimized. In cases where the ec,uipment is used for emergencies only, the systems have been designed to pemit meaningful periodic tests.
Additional descriptive information and design details on equipment used for nomal operation are presented in Section 9 This Section 6 vill present design bases for safeguards protection, equipment operational descriptions, design evaluation of equignent, failure analysis, and a preliminary opera-tional testing program for systems used as engineered safeguards.
6.1 EMERGENCY INJECTION 6.1.1 DESIGN BASES The principal design basis for emergency injection is as follows:
' 6-1 5-3-68 i Supplement No. 3
Emergency core injection is provided to prevent clad melting for the entire spectrum of reactor coolant system failures r3 ranging from the smallest leak to the complete severance of the largest reactor coolant pipe.
Emergency core cooling includes pumped injection and the core flooding tanks. Pumped injection is sub- 3 divided in such a way that there are two separate and independent strings, each including both high pressura and low pressure coolant injection and each capable of providing 100 percent of the necessary core injec-tion with the core clooding tanks. The core flooding tanks are passive components which are needed for only a short period of time after the accident, there-by assuring 100 percent availability when needed.
High pressure injection 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 low 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 conser-vatively sized to limit the temperature 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 associated instrumentation.
Emergency injection fluid, pumped to the reactor coolant system during safeguards operations, is supplied in each case from the borated water necessary to fill the fuel transfer canal during refueling operations and is connected to the injection pump suction headers by two lines, one connected to the high pressure injection pumps, and one connected to the decay heat removal pumps. Additional coolant for emergency injection supply is contained in core flooding tanks which inject coolant without fluid pumping as described later in this section.
3 Emergency injection into the reactor coolant system vill be initiated in the event of (a) an abnormally low reactor coolant system pressure of 1,800 psi during power operation or (b) a reactor building pressure of 10 psig during power operation. The low pressure signals will automatically increase high pressure injection flow to the reactor coolant system with the following changes in the operating mode of the makeup and purification system described in Section 9:
(a) Two makeup pumps will be in operation (b) the stop valves in each injection supply line to the makeup and decay heat pumps vill open, and (c) the injection valve in lh each of four injection lines vill open. Emergency high pressure injection vill continue until reactor coolant system. pressure has dropped to the point where code flooding tanks begin emergency injection. The flow characteristic curves for each makeup pump are given in Figure 6-2.
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6-5-68 h9 6-2 Supplement No. 4
The core flooding system is composed oi o flooding tanks, each directly.
connected to a reactor vessel nozzle by r. line containing two check valves and one stop (isolation) valve; the .qstem provides for automatic flooding injection with initiation of flow when the reactor coolant system pressure reaches approximately 600 psi. This injection provision does not require any electrical power, automatic switching, or operator action to insure sup-ply of emergency coolant to the reactor vessel. Operator action is required only during reactor cooldown, at which time the stop valves in the core flooding lines are closed to contain the contents of the core flooding tanks.
The combined coolant content of the two flooding tanks is sufficient to re-cover the core hot spot assuming no liquid is contained in the reactor ves-sel, while the gas overpressure and flooding line sizes are sufficient to insure core reflooding within approximately 25 sec. after the largest pipe rupture has occurred.
The dccay heat removal system (described in Section 9) is nomally maintained on standby during power operation and provides supplemental core flooding flow through the two core flooding lines after the reactor coolant system pressure reaches 135 psi. Emergency operation of this system vill be ini-tiated by a reactor coolant system pressure of 200 psi or by a reactor 3 building pressure of 10 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 flow into the reactor vessel at a vessel pres-sure of 100 psi.
Iov pressure injection, with supply from the borated water storage tank, using the decay heat pumps vill continue until a low level signal is received from the tank (39 min at a combined low pressure injection and reactor build-ing spray flow of 9,000 gpm). At this time, the operator vill open the va'ves controlling suction from the reactor building sump, and recirculation of cool-ant from the sump to the reactor vessel vill begin. The decay heat coolers will cool the recirculated flow, thus removing heat from the reactor building fluid and preventing further reactor building accumulation of decay heat generated by the core.
The decay heat removal pumps are located at an elevation below the reactor building sump with dual suction lines routed outside the reactor building to the pumps. In the event one suction line is unavailable for recirculation, the lines have been sized so that one line vill be capable of handling the total pctential recirculation flow of one 3,000-gpm decay heat removal pump and one 1,500-gpm reactor building spray pump. The NPSH available has been conservatively calculated to be greater than the NPSH requirement of the decay heat removal pumps and the reactor building spray pumps.
The calculations for available NPSH at the reactor building spray pump and the decay heat removal pump suctions will include a safety margin over and above the requirements of these pumps. The calculations will assume conser-vatively that minimum water levels exist in the borated water storage tank and in the reactor building, and that air pressure in the reactor building is 1 psi below normal atmospheric pressure. Final pipe sizes vill be adjusted
' to provide a safe NPSH margin for either pump operating mode.
6-3 5-3-68 Supplement No. 3
The heat transfer capability of each decay heat cooler as a function of -
recirculated ' water temperature is illustrated in Figure 64. The heat I transfer . capability at the saturation temperature corresponding to reactor building pressure is in excess of the heat generation rate of the core fol-loving storage tank injection.
Design data for core flooding system components are given in Table 6-1.
Design _ data for other emergency injection components are given in Section 9 except for those shown in Figures 6-2, 6-3, and 64.
6.1 3 DESIGN EVA MATION In establishing the required components for the emergency injection the fol-loving factors were considered:
- a. The probability of a major reactor coolant system failure is very lov.
- b. The fraction of a given component lifetime for which the com-ponent is unavailable because of maintenance is estimated to be a mall part of lifetime. On this basis, it is estimated that the probability of a major reactor coolant system acci-dent occurring while a protective
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/l 6-3 a 5-3-68 Supplement No. ?
' compon:nt is out for maintenance is two orders of m gnitude below the low basic accident probability.
- c. The equipment downtime for maintenance in a well-operated plant often can be scheduled during reactor shutdown periods. When maintenance of an engineered safeguard component is required during operation, the periodic test frequency of the remaining equipment can be in-creased to insure availability, 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 needed.
That is, equipment reliability is improved by using it for other than emergency functions. .
Three makeup pumps are installed: one is normally operating, one can be down for maintenance, and one is required for engineered safeguards.
Table 6-1 Core Flooding System Performance and Equipment Data Cere Flooding Tanks (*)
Number 2
, Design Pressure, psig 700 Normal Pressure, psig 600 Design Temperature, F 300 Operation Temperature, F 110 Total Volume, ft3/ tank 1,h10 Normal Water Volume, ft3/ tank 9h0 Material of Construction Carbon Steel- SS Clad 3 Check Valves Number per Flooding Line 2 Size, in, 14 Materinl- SS Design Pressure, psig 2,500 Design Temperature, F 650 Isolation (Stop) Valves Number per Flooding Line 1
_ Size, in.
Material lh SS Design Pressure, psig 2,500 Design Temperature, F 650
(*) .
Designed to ASME Section III, Class C.
I 7g 6h 5-3-68 Sugglement No. 3
Table 6-1.- (Cont'd)
Piping Number of Flooding Lines 2 Size, in, lh Material SS Design Pressure, psig 2,500 Design Temperature, F 650 6.1.3.1 Failure Analysis The single failure analysis presented in Table 6-2 is based on the assumption 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 actuating the emergency injection systems or as a secondary accident effect. All credible failures were analyzed. For example, the analysis includes malfunctions or
- failures such as electrical circuit or motor failures, stuck check valves, etc.
It was considered incredible that valves would change to the opposite position by accident if they were in the required position when the accident occurred.
In general, failures of the type assumed in this analysis should be unlikely, because a program of periodic testing and service rotation of standby equipment will be incorporated in the plant operating procedures.
The single failure analysis (Table 6-2) and the dynamic postaccident performance analysis (Section 14) of the engineered safeguards considered capacity reduction as a result of equipment being out for maintenance, or as a result of a failure to start or operate properly. This amounts to adding another factor of conserva-tism to the analyses because good operating practice requires repairing equip-ment as quickly as possible. Plant maintenance activities will be scheduled so that the required capacity of the engineered safeguards systems will always be available in the event of an accident.
The adequacy of equipment sizes is demonstrated by the postaccident performance analysis described in Section 14, which also discusses the consequences of achieving less than the maximum injection ficws. There is sufficient redundancy 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 The emergency high-pressure injection valves are designed to open witnin 10 sec.
One makeup pump is normally in operation, and the pipe lines are filled with coolant. The four high-pressure injection lines contain thermal sleeves at their connections into the reactor coolant piping to prevent overstressing of the pipe juncture owing to the 90 F water being injected into these high temperature lines.
The equipment normally operating is handling 125 F water, and hence will exper-ience no thermal shock when 90 F water is introduced.
Injection response of the core flooding system is dependent upon the rate of re-ddction of reactor coolant system pressure. For a maximum hypothetical rupture,
'the core flooding system is capable of reflooding the core to the hot spot within a safe period after a rupture has occurred.
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6-5 .
. /J t 2-8-68 1 -
Emergency low pre cura ' injection by th2 d: cry h It removal system will be deli-vered within 25 see after the sreactor coolant system reaches the actuating pres-sure of 200 psig. Tais anticipated delay time consists of these intervals: ,s
- a. Total instrumentation lag -- =:1 see
.b. Emergency power source start -- <15 sec
- c. Pump motor startup (from the time the pump motor line circuit breaker closes until the pump attains full speed) -- 2510 sec
- d. Injection valve operating time -- < 10 sec
- e. Borated water storage tank outlet valves -- < 10 see Total (only b and c are additive) : 25 sec 6.1.3.3 Special Features The core flooding nozzles (Figure 3-61) will be specially designed to insure that they will safely take the differential temperatures imposed by the acci-dent condition. Special attention also will be given to the ability of the injection lines to absorb the expansion resulting from the recirculating water temperature.
For mest 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 wall are not subject '
to missile damage because there are no credible sources of missiles in that area. To afford further missile protection, a high-pressure injection line connects to each reactor coolant inlet pipe, and the two core flooding nozzles are located on opposite sides of the reactor vessel.
All water used for emergency injection fluid will be maintained at a minimum concentration of 2,270 ppm of boron. The temperature, pressure, and level of these tanks will be displayed in the control room, the alarms will sound when any condition is outside the normal limits. The water will be periodically 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 will have no adverse effect on reactor operation.
The valves will be specified to meet the tightness requirements of MSS-SP-61,
" Hydraulic Testing of Steel Valves."(*) For these valves, this amounts to a
(*)
MSS - Manufacturers' Standardization Society.
6-6 7 2-8-68 Amendment No. l'
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maximum permissible leakage of 140.cc/hr per valve. Two valves in series are pro-1 vided in each core flooding line; hence, leakage should be ,below this value.
Leahageacrossthesecheckvalvescanhavethreeeffects: (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 dilution of the borated water in the core flooding tank. Leakage at the rate mentioned above causes insignificant. changes in any of these parameters. A leakage of 1h0 cc/hr causes level increase in the tank of less than 1 in./mo. The associated temper-ature and pressure increase is correspondingly lovl If it were assuned 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 would be approximately 2 in./ day. A 2-in. level change vill re-sult in a pressure increase of approximately 10 psi. With redundant tempera-ture, pressure, and level indicators and alarms vailable to' monitor the core flooding tank conditions, the most significant effect on reactor operaticns is expected to be a more frequent sampling of tank boric acid concentration.
To insure that no temperature increase vill 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 vill be left uninsulated to promote convective losses to the -
building atmosphere.
In summary, reactor operation may continue with no adverse effects coincident with check valve leakage. Maximum permissible limits on core flooding tank
[ parameters (level, temperature, and boron. concentration) vill be established to
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insure compliance with the core protection criteria and final safety analyses.
6.1.4 TEST AND INSPECTIONS '
. M All active components, as listed in Table 6-3, of the emergency injection sys-tems vill be tested periodically to demonstrate system readiness. In addition, normally operating components will be inspected for leaks from pump reals,. valve packing, flanged joints, and safety valves.
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' Table 6-2 Single Failure Analysis-Emergency Injection ..r compcnent Malfunction Comments and Consequences A. 'High Pressure Injection ,
- 1. Stop-check valve at . Valve remains.open. When the tank is empty, tank prea'sure 17 makeup tank outlet. would be less than the high-pressure injection pump suction pressure (with borated water storage tank on the line),
, thus preventing the release of hydrogen y from the tank to the pump suction line.
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- 2. Power operated valve Fails to open. Similar valve in other safeguard string in engineered safeguard will deliver required flow to redundant-suction header connected engineered safeguard pumps.
to borated water storage m tank. .
b Makeup pump. out for maintenance. Two pumps will still be available. Only 3.
- one pump is required for engineered 4
safeguards. *
. 4. Makeup pump. Fails (stops). Other makeup pump delivers required flow.
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- 5. Makeup pump isolation Left inadvertently See Item A4 above. Valves will normally 0% valve. closed. be left open since the check valve in each pump discharge will prevent back-h .l- Operating procedures will call ti;'A .
flow.
B for pump isolation valves to be closed
% only for maintenance. ,
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Table 6-2 (Cont'd)
Component Malfunction Comments and Consequences
- 6. Makeup pump discharge check Sticks closed. This is considered incredible since valve. the pump discharge pressure of 2,700 psi at no flow would tend to open even a very tightly stuck check disc.
- 7. Pressurizer level control Fails to close. No consequences, a valve.
A sj 8. Seal injection control valve. Fails to close. Injection flow through this line
'sJ would be small compared to the flow through the two injection lines due to the high flow resis-tance of the reactor coolant. pump seals.
os 9. Power operated valve in Fails to open.. Flow from one pump will go through y, high-pressure. injection the alternate line. Other pump will line.. operate as normal.
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- 10. Check valve in injection - Sticks closed. .
See comment on Item A-6 above.
line (inside reactor. build-ing).
11 Injection line inside reactor Rupture. Flow rate indicators in the four building.
injection lines would indicate.the
- gross difference in flow rates.
Check valve in the injection line would prevent additional loss of s7 coolant from the reactor. The line ,
is protected from missiles by reac-
$ j[ ( tor coolant system shielding.
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Table 6-2 (Cont'd)
Component ,
Malfunction Coments and Consequences
- 12. Manual normally closed Inadvertently left open. No significant consequences. A small 17
valve from decay heat percentage of LP injection flow will coolers to makeup pumps. be bypassed to HP suction.
13 Manual nomally closed Stuck closed and cannot Similar valve in other makeup pianp N valve from decay heat be opened. string will 'leliver required flow. *17 CD coolers to makeup pumps. '.
14 1 Double manual valves Inadvertently left open. Not credible that both valves will connecting pump lines. inadvertently be left open.
[ B. Core Flooding System O
- 1. Flooding line check valve. Sticks closed. This is considered incredible based' on the valve size and opening pressure
. = applied.
C. Decay Heat Removal System
- 1. Check valve at reactor Sticks closed. . This is considered incredible since ':
vessel. these valves will be used periodically during decay heat : emova, and the opening force will be approximately enu 5,000 pounds.
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- 2. Power-operated injection Fails to open. Second injection line will deliver Ml ts .
valve. required flow,
, 3 Safety valve. Stuck open. Ioss of injection flow is small since ,
,o valve is small. ,
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Table 6-2 (Cont'd) l%
Component Malfunction Comments and Consequences ,
4.. Decay heat cooler. Isolation valve left closed. Other heat exchanger will take required injection flow and remove required heat.
Valves will be closed only for mainte- l nance of heat exchanger.
- 5. Decay heat cooler. Massive rupture. Not credible. During normal decay heat removal operation, heat exchanger will NJ , be exposed to higher pressure and approx-imately the same temperature as the post-accident temperature,and presaure.
- 6. Decay heat cooler. Out for maintenance. Remaining heat exchanger will take re- !
, quired injection flow. j b 7. Decay heat pump isola- .Left closed. Remaining pump will deliver required tion valve. injection flow.
- 8. Decay heat pump discharge Sticks closed. See comment on Item C-1 above, check valve.
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- 9. Decay heat pump. Fails to start. -
Remaining pump will deliver required injection flow.
- 10. Check valve in Sticks closed. Alternate line will permit required
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17 suction header connected
- mm to borated water storage
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h'N gO 11. Power operated valve Fails to open. Two lines and valves are provided. One 171 g permitting suction from will provide the required flow, reactor building sump. -
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Table 6-2 (Cont'd)
Component Malfunction Comments and Consequences
- 12. Reactor building sump outlet' Becomes clogged.
pipe. Clogging of a single line does not impair function because of the dual
- sump line arrangement,'the size of '
the lines, and the sump design. The 1 two recirculation lines take suction from the different portions of the C%3 sump. A grating vill be provided over C) the sump, and additional heavy duty ,
strainers vill be provided.
- 13. Dual manual valves connect- Inadvertently left open. Not credible that both valves will' be in- 3 ing outlet of decay heat coolers. advertently left open because of admin-os istrative controls. .<
h 14. Power-operated valves per- Inadvertently and prema-a mitting suction from reac- The high pressure injection pumps vould '
turely opened after LOCA.
tor building sump. continue drawing from the storage tank., .
The decay heat removal and reactor build- 1
, ing spray pumps would take suction from .; ,
the sur.p. The hot sump water vould be i cooled in the decay heat removal coolers before the L.P. injection. The hot sump - ,
, water would however, cause a drop in the '
reactor building spray cooling efficiency.
The reactor building emergency coolers ,
would continue to operate at 100% capacity '
and would more than adequately compensate .
for the loss of spray cooling efficiency. As .)
soon as the building pressure drops below the i un vi borated storage tank static pressure, the pumps - E!'
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vould resume taking suction from the storage tank.
H 5 \ The consequences of this operator error would
[ \ depend on the reactor building pressure at 6-y 1 the time the valve was opened. ~i
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If the building pressure were below the static pressure at the borated water storage tank, Q t, ~]v )
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' Ccanponent - Malfunction Comments and Consequences the pumps would continue to take' suction from the storage tank and there would be some flow l3-
, from the storage tank into the. sump. However, since this water will become available when recirculation begins, there are no resultant' consequences.
CO. If the building pressure is greater than N
the static pressure of the' storage tank at the time of the valve opening, the flow of borated water from the storage tank would be cut off by the closing of the check valve in the borated water suction line.
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Table 6-3 I. .
Emergency Injection Equipment Performance Testing Makeup Pumps One pump is operating continuously.' The other two will be periodically tested.
High Pressure Injection The remotely operated stop valve in each Line Valves line will be opened partially one at a time. The flow devices will indicate flow through the lines.
Mtheup Pump Suction Valves The makeup tank water level will be raised to equalize the pressure exerted by the storage tank and the borated water storage tank. The valves will then be opened indi-vidually and closed.
Decay Heat Pumps In addition to use for shutdown cooling, these pumps will be tested singly by open-ing the borated water storage tank outlet valves and the bypasses 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 in-jection lines and back to the tank.
( Borated Water Storage Tank 'Tae operational readiness of these valves Outlet Valves will be established in completing the pump operational test discussed above. During this test, each of the valves will be test-ed separately for flow.
Low Pressure Injection With pumps shut down and borated water Valves .
storage tank outlet valves closed, these valves will be opened and reclosed by oper-ator action.
Valve for Suction From With pumps shut down and borated water Sump storage tank outlet valves closed, these valves will be opened and reclosed by oper-a'or action.
Valves in Core Flooding Valves can be operated during each shutdown
' Injection Lines to determine performance. Isolation valves will be closed to contain water in core flooding tanks during shutdown.
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6-12 2-8-68 Amendment No. 1
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.6. 2 , REACTOR BUILDING ATMOSPHERE COOLING AND WASHDIG 6.2.1 DESIGN BASES .
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Emergency building atmosphere cooling and washing is provided to limit pos't-accident building pressures to design values and reduce the post-accident level of fission products in the building atmosphere.
Reactor building air recirculation and cooling units, backed up by reactor building sprays, are used for emergency atmosphere cooling. Chemical ad-ditives contained in the building sprays are used to reduce post-accident fission product concentrations in the building atmosphere.
6.
2.2 DESCRIPTION
The schematic flow diagram of the emergency reactor building atmosphere cool-ing and associated instrumentation is given in Figure 6-5.
, Emergency and nomal cooling are performed with the same basic units. Each unit contains nomal and emergency cooling coils and a single speed fan.
During normal plant operation, chilled water from the plant main water chillers is circulated through the nomal cooling coils. For emergency cooling, all rejected units to will operate the service under post-accident water system. conditions Each of these units, can remove with60the heat being Btu /hr x 10 under peak reactor building temperature conditions. Figure 6-6 shows the heat exchange characteristics versus building ambient conditions for these units.
The design data for the cooling units are shown in Table 6-4.
,17 )
Table 6-4 Reactor Building Cooling Unit Perfomance and Equipment Data (Capacities are on a per unit basis)
- Emergency Nomal No. Installed 4 4 No. Required 4 3 Type Coil Finned Tube Peak Heat Load, Btu /hr Finnedpbe 60 x 10 J.15 x 10D 17 Fan Capacity, cfm 30,000 30,000.
Reactor Building Atmosphere Inlet Conditions Temperature, F 286 110 .
Steam Partial Pressure, psia 54 --
Air Partial Pressure, psia 20 T Total Pressure, psig 59 Atmospheric Cooling Water Flow, gpn 1,200 130 Cooling Water Inlet Temperature, F 85 50 Cooling Water Outlet Temperature, F. 185 68 Simultaneously with the air recirculation cooling, reactor building sprays are supplied with water by two pumps which take suction on the borated water stor-8J7 6-13 -
5-4-70 Supplement No. 17
age tank until this coolant source is exhausted. The sodium thiosulfate
' chemical additive required for the reactor building sprays is supplied from a storage tank connected by dual lines containing power operated and stop-check valves to the suction of the spray pumps. Sufficient sodium thiosulfate is injected into the borated water to create a 1 wt % concentration in the reactor building water inventory. Sodium hydroxide in a quantity sufficient 17 to achieve a reactor building water inventory pH of 9 5 is injected into the borated water flowing through the engineered safeguards suction headers from a storage tank provided with dual discharge lines containing power-operated valves and step-check valves. After the supply from the-borated water storage tank is exhausted, the spray pumps take suction from the reactor building sump recirculation line. .This continued spraying serves to reduce the reactor building atmosphere to the temperature of the reactor building sump.
Design data for the reactor building spray system components are given in Table 6-5, and the flow characteristics of the reactor building spray pumps are given in Figure 6-7. Design data for components of the reactor building cooling and decay heat removal systems used in this phase of engineered safe-guards operation are given in Section 9 and supplemented by Figures 6-3, 6-4, 6-6, and 6-7 of this Section.
Table 6-5 Reactor Building Spray System Performance and Equipment Data (Capacities are on a per unit basis.)
Reactor Building Spray Pumps Number 2 Flow, gpm 1,500 Developed Head at Rated Flow, Ft. 430 Motor Horsepower, hp 250 Material SS Design Pressure, psi 300 Design Temperature, F 300 Sodium Thiosulfate Tank Number- 1 Volume, Ft 3 2,700 Material SS Design Pressure, psi 50 Design Temperature, F 150
' Sodium Thiosulfate Concentration, wt % 30 Sodium Hydroxide Tank Number 1 Volume, Ft 3. 1,728 17
. Material CS Design Pressure, psi 50 Design Temperature, F 150 Sodium Hydroxide Concentration, wt % 20 Spray Header Number 2 Spray Nozzles per Header 96 (1/
6-14. .-
5-4-70 Supplement No. 17
r-6.2 3 DESIGN EVALUATION This function of cooling the reactor building atmosphere is fulfilled by either of the two methods described above, and redundancy of equipment with-in both methods will provide for protection of building integrity. The reactor building sprays through duplication, basic washing concept, and chemical additive will serve to reduce fission product levels in the build-ing atmosphere.
For the first 30-40 min. following the maximum blowdown loss-of-coolant accident, i.e., during the time that the reactor building spray pumps take their suction from the borated water storage tank, this system provides more than 100 per cent of the heat removal capacity of the reactor building cooling system.
'Ihe reactor building spray system design is based on the spray water being raised to the temperature of the reactor building in falling through the steam-air mixture within the building.
Detailed evaluation of system performance is presented in Sec-tion 14. Each of the following equipment arrangements will provide sufficient heat removal capability to maintain the post-accident reactor building pressure below the design value:
- a. Reactor building spray system.
- b. All emergency units in the reactor building cooling ,
system.
- c. Two emergency cooling units and the reactor building spray system at one-half capacity.
The reactor building spray system shares the suction line from the borated water storage tank and the tank itself with the high and low pressure in-jection safeguards.
6.231 Failure Analysis A single failure analysis has been made on all active components of the systems used to show that the failure of any single active component will not prevent fulfilling of the design functions. This analysis is shown in Table 6-6. Assumptions 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 performance of these safeguards are presented in Section~ 14 under analysis of post-accident conditions.
6-15 5-4-70 Supplement No. 17 85
(
Tablo 6-6 Single Failure Analysis-Reacto$ Building Atmosphere Cooling and Washing
.~ .
Component -
' Malfunction -
Comments and Consequences
- 1. . Reactor building spray nozzles. Clogged. Large number of nozzles (96 on each of * '
17';
two headers) renders clogging of signi- .
ficant number of nozzles as incredible.
- 2. Reactor building spray header. Rupture. This is considered incredible due to low operating pressure differential.
- 3. Check valve in spray header line. Sticks closed. This is considered incredible due to ff( large opening force available at pump shutoff head.
- 4. Motor-operated valve in spray Fails to open. Second header delivers 50 per cent flow.
header line.
os E. 5 Spray pump isolation valve. Left closed. Flow and cooling capacity reduced to 50
, per cent of design. In combination with emergency coolers,150 per cent of total design requirement is still provided.
- 6. Reactor building sprey pump. Fails to start. '
Flow and cooling capadity reduced to 50 per cent of design. In combination with emergency coolers,150 per cent of total pyn design requirement is still provided, e er
{hh 7. Reactor building cooling unit fan. Stops. Emergency cooling by the other operating g -
units with supplemental cooling by the g sprays.
$ 8. Reactor building cooling unit. Rupture of cooling The tubes are designed for 200 psi and
[, coil. 300 F which exceeds maximum operating 4.
I conditions. Tubes are protected against
, credible missiles. Hence, rupture is not considered credible.
i
i-Table 6-6 (Cont'd) domponent ' '
Malfunction *
'Coments and Consequences
'9 Reactor building cooling Rupture of casing and/or Consideration will be given during ducts.
unit. detailed design to the dynamic forces .
resulting from.the pressure buildup during s postaccident situation. The '
units will also be inspectable and protected against credible missiles.
Cooling with these units will be sup-
.s plemented by the sprays.
( 10. Reactor building' cooling units.
. Rupture of system piping.
~
Rupture is not considered credible since all piping is Schedule l+0, per-mitting an allowable working pressure of at least 500 psi at 650 F for all sizes. Piping is inspectable and pro-p '
tected from missiles. Maximum actual y . internal pressure will be less than .
200 psi at temperatures below 300 F.
- 11. pneumatically onerated valve Sticks closed. Second water supply valve serves two of at_ inlet penetration. the four cooling units (50% of the required emergency cooling capacity). 17
, In combination with sprays,150 percent
% of total design requirement is still
,g y provided.
'd 1 -
. {i$ 12. Fneumatically operated valve Fails to open. Comments for Item 11 apply.
g at outlet penetration e
g 13. Power-operated valve at Fails to open. Valve in line connected to redundant spray 17 sodium thiosulfate headers will permit. flow to sprays y storage tank outlet. on 50 percent capacity redundant spray .
-4 header.
s
\
6.2.3.2 R actor Building Cooling Rasponsa Air recirculation is establish through the chined water coils during normal 17 operation through three of the four building ventilation units. Under accident conditions the chilled water coils are bypassed and air is recirculated through ,
the service water coils in all four ventilation units. This action is initiated when the reactor building pressure increases to !+ psi. Cooling continues until the building pressure reaches near-atmospheric, and the decay heat removal system is placed into emergency service, recirculating and cooling fluid from the reactor building sump. -
The reactor building spray system will likewise be activiated by a single para-meter signal. Two of three signals signifying high reactor building pressure will start both of the reactor building spray pumps, open the reactor building spray inlet valves, and open the suction valves from the borated water storage tank. The system components may also be actuated by operator action from the control room for performance testing.
The total time to delivery of reactor building sprays is approximately 1 min after building pressure reaches 10 psi. i 6.2 3 3 Special Features The casing design for the ventilation units win be of a conventional nature ;
unless additional analysis shows the possibility of pressure wave collapse. ;
In that event, quick, inward-opening hinged doors, or other protective features, will be incorporated into the design to maintain postaccident operability. The ;
ventilation units are located outside the concrete shield for the reactor vessel, steam generators, and reactor coolant pumps at an elevation above the water level in the bottom of the reactor buildihg at postaccident conditions. In this '
location, the systems in the reactor building are protected from credible mis- '
ailes and from flooding during postaccident operations. Also, this location 4 provides shielding so that the design radiation dose level allows for mainte-nance, iepair, and inspections to be performed during power operation. See 11.2.1.1, Radiation Protection Design Bases.
The design of the Reactor Building cooling units is different from any other 17 application. The units will be approximately 9' vide by 16' long by n' high.
Four units are required. Each unit will consist of one roughing filter of the renewable media type, one set of chined water cooling coils to be used for normal cooling, one set of service water cooling coils to be used for emergency cooling, followed by a vane axial type fan. The fan will be mounted vertically on top of the unit. A relief damper will be provided on top of the unit between the chined water coils and the service water coils. The '
relief damper will be a counter balanced type that will open at a preset pressure differential. The damper win open in case of a pressure increase in ;
the Reactor Building thereby permitting the internal pressure in the unit to -
equalize with the external pressure. The unit however win be designed to 4 withstand 60 psia external pressure with the damper closed. The damper will -
also allow the saturated air in the Reactor Building to by-pass the filter and the chilled water cooling coils and to go through only the service water cooling coils. The decrease h precoure drop due to the by-passing of the filter and chilled water coolhg coils will permit the fan in the unit to handle the necessary quantity of air for cooling purposes at the same speed / as
' required for nomal operation, thereby precluding the necessity of two speed -
motors with their necessary additional controls and wiring.
88 fup ment No.17 i L
The spray headers of the reactor building spray system are located outside and above'the reactor and steam generator. concrete shield. During operation, a shield also provides missile protection for the area immediately above the reactor vessel. The spray headers are therefore protected frc= missiles originating within the shield. The spray pumps are located outside the reactor building and are thus available for operative. checks during plant operation.
. 6. 2. I+ TESTS AND INSPECTIONS Active components of the ventilation units will normally be in service.
Valving on the cooling coils can be periodically cycled, thus placing the coils into service periodically during operation. .
The active components of the reactor building spray system will be tested on a regular schedular as follows:
Q, ' ~
6-18a 5 !+-70
. Supplement No.17
Reactor Building These pumps vill be tested singly by opening the valves in Spray Pumps the test line and the borated water storage tank outlet valves. Each pump in turn vill be started by plant opera-tor action and checked for flow establishment to each of the spray headers. Flow will also be tested through each of the borated water storage tank outlet valves by operating these valves.
Borated Water These valves vill be tested in performing the pump test Storage Tank listed above.
Outlet Valves Reactor Building With the pumps shut down and the borated water storage tank Spray Injection outlet valves closed, these valves vill each be opened and Valves closed by operator action.
Reactor Building Under the conditions specified for the previous test, and Spray No::les with the reactor building spray valves closed, low pressure air vill be blown through the test connections.
6.3 ENGINEERED SAFEGUARDS LEAKAGE AND RADIATION CONSIDERATIONS 6.3 1 INTRODUCTION The use of normally operating equipment for engineered safeguards functions and the location of some of this equipment outside the reactor building require that consideration be given to direct radiation levels after fission products have accumulated in these systems with leakage from these systems. Although the engineered safeguards equipment is designed for control room operation fol-loving an accident, long-term postaccident operation could necessitate manual operation of certain valves.
The shielding for components of the Engineered Safeguards is designed to provide
, protection for personnel to perform all operations necessary for mitigation of the accident within acceptable dose limits in the event of an MHA.
6.3.2
SUMMARY
OF POSTACCIDENT RECIRCULATION AND LEAKAGE CONSIDERATIONS Following a loss-of-coolant accident and exhaustion of the horated water storage tank, reactor building su=p recirculation to the reactor vessel and the reactor building sprays is initiated.
While the reactor auxiliary systems involved in the recirculation complex are closed to the auxiliary building atmosphere, leakage is possible through compo-nent flanges , seals , instrumentation, and valves.
The leakage sources considered are:
- a. Valves.
(1) Disc' leakage when valve is on recirculation complex boundary. ,
(, (2) Stem leakage.
'I 0 6_1,
- b. Flanges.
- c. Pump stuffing boxes.
While leakage rates have been assumed for these sources, maintenance and periodic testing of these systems vill preclude all but a small percentage of the assumed amounts. With the exception of the boundary valve dises, all of the potential leakage paths may be examined during periodic tests or normal operation. The boundary valve disc leakage is retained in the other closed systems and there-fore vill not be released to the auxiliary building.
While valve stem leakage has been assumed for all valves , the manual valves in the recirculation complex are backseating.
6.3.3 LEAKAGE ASSbMPTIONS Source Quantities 1
- a. Valves - Process (1) Disc leakage 10 cc/hr/in. of nominal disc diameter.
(2) Stem leakage 1 drop /ntin 'e (3) Bonnet flange 10 drops / min
- c. Flangee 10 drops / min
- d. Pump Stuffine Boxes 50 drops / min
' For the analysis, it was assumed that the water leaving the reactor building was less than 200 F vhen recirculation occurs.
6.3.h DESIGN BASIS LEAKAGE The design basis leakage quantities derived from these assu=ptions for postacci-dent ' sump recirculation are tabulated in Table 6-7, 6.3.5 LEAKAGE ANALYSIS CONCLUSIONS It may be concluded from this analysis (in conjunction with the MHA discussion and analysis in lb.2.2.h.h) that leakage from Engineered Safeguards equipment outside the reactor building does not pose a public safety problem.
6-20 \
Table 6-7 Leakage Quantities to Auxiliary Building Atmosphere No. Of Per Source Total Leakage Source SlurcEs Drop / Min ec/hr
- a. Pumn Seals Decay heat pumps 2 50 300 Spray pumps 2 50 300
- b. Flanges (a) 11b 10 3,320
- c. Process Valves 35 1 105
- d. Instrumentation Valves 25 1 75
- e. Valve Seats at Boundaries 11 (b) 750 Total h,850 3 (a) Assumes process and boundary valves, and process components are flanged.
(b) Assumes 10 cc/hr/in of nominal disc diameter.
6-21 5-3-68 Supplement No._3 J
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