ML20035C272
| ML20035C272 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 04/02/1993 |
| From: | Fox J GENERAL ELECTRIC CO. |
| To: | Poslusny C Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9304060426 | |
| Download: ML20035C272 (6) | |
Text
'e GENuclear Energy cenew ormr cocvun 775 Ce:v Awwe Sr.b5n CA %125 April 2,1993 Docket No. STN 52-001 Chet Poslusny, Senior Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of the Nuclear Reactor Regulation
Subject:
Submittal Supporting Accelerated ABWR Review Schedule - DFSER Confirmatory Item 6.2.51 and 6.2.S-2 and Open Item 203-10
Dear Chet:
Enclosed are SSAR markups addressing DFSER Confirmatory Items 6.2.5-1 and 6.2.5-2 and Open Item 203-10.
v Please provide a copy of this transmittal to Gene Gou.
Sincerely, YM Jack Fox Advanced Reactor Programs cc: Bill Fitzsimmons (GE)
Norman Fletcher (DOE)
Bernie Genetti (GE) e 060043 i
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Standard Plant REV C (16) The primary containment purge system will required, through a pathway from the wetwell aid in the long term post-accident cleanup airspace to the stack. The pathway is solated operation. The primary containment during normal operation with two ruptur disks.
atmosphere will be purged through the SGTS to the outside environment. Nitrogen makeup The following modes of operation are provided:
will be available during the purging operation.
(1) Startup - Inerting. Liquid nitrogen is vaporized with steam or electric heaters to (17) Tbc system is also designed to release a temperature greater than 20 F and is 0
containment pressure before uncontrolled injected into the wetwell and the drywell.
containment failure could occur.
The nitrogen will be mixed with the primary containment atmosphere by the drywell 6.2.5.2 System Design coolers in the drywell and, if necessary, by the sprays in the wetwell.
6.2.5.2.1 General usea T _ 6. R.4 2,/
A (2) Normal - Maintenance of Inert Condition. A
~The ACS provides control over hydrogen and]
nitrogen makeup system automatically sup-oxycen generated following a LOCAfin an inerted plies nitrogen to the wetwell and upper containment, mixing of any hydrogen generated is drywell to maintain a ;, lightly positive not required. Any oxygen evolution from pressure in the drywell and wetwell to pre-radiolysis is very slow such that natural clude air leakage from the secondary to the convection and molecular diffusion is sufficient primary containment. An increase in con-to provide mixing. Spray operation will provide tainment pressure is controlled by venting further assurance that the drywell or werwellis through the drywell bleed line.
l uniformly mixed. The vste consists of the following features:
'e (3) Shutdown - Deinerting. Air is provided to n/JER T 6,2,5,2-2 the drywell and wetwell by the primary (1) Atmospheric mixing is achieved by natural containment HVAC purge supply fan. Exhaust processes. Mixing will be enhanced by is through the drywell exhaust lines and gg operation of the containment sprays, which wetwell to the plant vent, through the HVAC are used to control pressure in the primary or SGTS, as required.
lAU'I containment.
f us rR T (,,2. 5, 2 -3 g,(4) Overpressure Protection. If the wetwell (2) flTe pumary containment nitrogen purgg pressure increases to about 5.6 2
establishes and maintains an oxygen -
kg/cm g, the rupture disks will open.
i deficient atmosphere (13.5 volume percent)
The overall containment pressure decreases in the primary containment during normalj as venting continues. Later, the operators operatioV can close the two 350A air-operated butterfly valves to re-establish (3) The redundant oxygen analyzer system (CAMS) containment isolation as required.
measures oxygen in the drywell and suppression chamber. Oxygen concentration The following interfaces with other systems are displayed in the main control room. are provided:
Description of safety-related display instrumentation for containment monitoring (1) Residual Heat Removal System (RHR-Ell).
is provided in Chapter 7.
Electrical The RHR provides post-accident suppression requirements for equipment associated with pool cooling as necessary following heat the combustible gas control system are in dumps to the pool, including the exothermic accordance with the appropriate IEEE heat of reaction released by the design standards as referenced in Chapter 7.
basis metal-water reaction. This heat of reaction is very small and has no real In addition, the ACS provides overpressure affect on pool temperature or RHR heat protection to relieve containment pressure, as exchanger sizing. The wetwell spray 6.2-33 Ammendment 17 r
as !
6 sam.c_:ver CNFM 6 2.5-l p2&
g ggsgnr 4 2.5.%~~l The FCS and ACS are systems designed to control the environment within the primary containment.
The FCS provides control over hydrogen and oxygen generated following a LOCA.
IM5ER T 4.2.5. 2-2 (1)
The FCS has two recombiners installed in the secondary containment.
The recombiners process the combustible gases drawn from the primary containment drywell.
(2)
The FCS is activated when a LOCA occurs.
The oxygen and hydrogen remaining in the recombiners after having been processed are transmitted to the suppression pool.
The ACS provides for inerting the primary containment during normal or on-line operation.
This system is not designed as an on-line containment purging system.
The ACS exhaust line isolation valves are closed when ABWR is on-line.
The nitrogen supply lines, compensating for leakage, provide a continuous flow of nitrogen to the containment.
If a LOCA signal is received by the ACS the nitrogen supply valves close.
Nitrogen purge from the containment occurs at SAvfdown.
"f'r ;rn gurging is accomplished as the containment exhaust isolation valves are opened and the nitrogen supply valves are closed.
Nitrogen is replaced by air in'the containment (See Item (3) Shutdown - Deinerting below in this Subsection).
The system has the following features:
IMSERT 6.1.F.2-3 l(2) The ACS primary containment nitrogen makeup maintains an oxygen-deficient atmosphere (s3.5 volume percent) in the primary containment during normal operation.
~
YS cNFr! & *L ci-l - P1 M 3 nassarn Standard Pfart am a 1i 9A.$ Reactor Building Ventilation System 9A3.1.2 System Description d
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The reactor buildmg HVAC system is composed The reactor building secondary containment of the following subsystems:
HVAC system P&ID is showFFigure 9.4-3. The i
system flow rates are given in Table 9.4-3, and the
.j (1) Secondary Containment HVAC System system component descriptions are given in Figure 9.4-3. The HVAC system is a once-through type.
i (2) Essendal Equipment HVAC System (14)
Outdoor air if filtered, tempered and delivered to the secondary containment. The supply air system.
(3) Non-Essential Equipment HVAC System (8) consists of a medium grade filter, a heating coil, a cooling coil, and three 50% supply fans located in the (4) Essential Electrical Equipment HVAC System turbine building.- Two are normally operating and
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(3) the other is on standby. The supply fan furnished conditioned air through ductwork and registers to (5) Essential Diesel Generator HVAC System (3) the equipment rooms and passages. The exhaust air-i conf 48nment" c/teer/;Ag system pulls the air from the rooms through (6)MrvwcH PurrJ2 Supply / Exhaust System t ductwork, filters and monitors the air for radioactivity and exhausts out the plant stack. fyJERT j
(7) Mainsteam/Feedwater Tunnel HVAC System q,yg/,Q 9A3.1.3 Safety Evaluation j
(8) Reactor Internal Pump Control Panel Room Operation of the secondary containment HVAC -
9A3.1 Secondary Containment HVAC System system is not a prerequisite to assurance of either of l
the following:
9.43.1.1 Design Bases (1) integrity of the reactor coolant pressure -
9A3.1.1.1 Safety Design Bases boundary, or The secondary conrMnment HVAC system has no (2). capability to safely shut down the reactor and safety-related function as defined in Section 3.2.
to maintain a safe shutdown condition.
Failure of the system does not compromise any safety-related equipment or component and does not However, the system does incorporate features prevent safe reactor shutdown. Provisions are incor-that provide reliability over the full range of normal ~
porated to minimize release of radioactive plant operation. The following signals automatically
=
I substances to atmosphere and to prevent operator isolate the secondary containment HVAC system:
exposure.
(1) secondary containment high radiation signal, i
9A3.1.1.2 Power Generation Design Bases (2) refueling floor high radiation signal, The secondary containment HVAC system is de-
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signed to provide an environment with controlled (3) drywell pressure high signal, temperature and airflow patterns to insure both the comfort and safety of plant personnel and the integ-(4) reactor water levellow signal, and l
rity of equipment and components.
(5) secondary containment HVAC supply / exhaust f
The secondary containment is maintained at a neg-fans stop.
ative pressure with respect to atmosphere.
On a smoke alarm in a division of the secondary -
The system design is based on outdoor summer containment HVAC system, the HVAC system shall j
conditions of 115 F, outdoor winter conditions of be put into smoke removal mode. To remse smoke
-40 F. Space temperature is maintained as specified from the secondary containment, the standby exhaust l
in Appendix 31.
and supply fans are started to provide an increase in j
air flow through the secondary containment. The l
resear 9ll. SiI.I.2-9.4-2c
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. the 'sh4down mode, o4 cpyttion in M c.AcS on 4 1 N-i
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RM C Sandard Plant elevation which would be covered by post-LOCA the same time and made from the same sheet flooding for unloading the fuel.
to provide uniformity of relief pressure.
6.23.2.5 Pressure Control (6) The rupture disks are capable of withstanding full vacuum in the wetwell (1) in general, during startup, normal, and vapor space without leakage, abnormal operation, the wetwell and drywell pressures is maintained greater than 0 psig (7) The piping material is carbon stgel. The to prevent leakage of air (oxygen) into the design pressure is 10.5 kg/cm g (150 primary containment from secondary psi),, and the design temperature is containment but less than the nominal 2 psig 171 C.
scram set point. Sufficient margin is provided such that normal containment 6.2.5.2.7 Recombiner
~7 temperature and pressure fluctuations do not cause either of the two limits to be reached (1) Two permanently installed safety-related h considering variations in initial recombiners are located in secondary j containment conditions, instrumentation containment. Each recombiner, as shown in g errors, operator and equipment response Figure 6.2-40, takes suction from the l time, and equipment performance.
drywell, passes the process flow through a g heating section, a reactor chamber, and a (2) Nitrogen ngakeup automatically maintains a spray cooler. The gas is returned to the 530 kg/m (0.75 psig) positive pressure wetwell.
to avoid leakage of air from the secondary into the primary containment.
(2) The recombiners are normally initiated on high levels as determined by CAMS (if (3) The dr'ywell bleed sizing is capable of hydrogen is not present, oxygen maintaining the primarg containment pressure concentrations are controlled by nitrogen less than 880 kg/m (1.25 psig) during makeup).
the maximum containment atmospheric heating which could occur during plant startup.
6.2.53 Design Evaluation 6.2.5.2.6 Overpressure Protection The ACS is designed to maintain the containment in an inert condition except for (1) The system is designed to passively relieve nitrogen makeup needed to maintain a positive the wejwell vapor space pressure at 5.6 containment pressure and prevent air (0 )
2 kg/cm g. The system valves are capable leakage from the secondary into the primary of being closed from the main control room containment.
using AC power and pneumatic air.
The primary containment atmosphere will be (2) The vent system is sized so that residual inerted with nitrogen during normal operation of core thermal power in the form of steam can the plant. Oxygen concentration in the primary be passed through the relief piping to the containment will be maintained below 3.5 volume stack.
percent measured on a dry basis.
(3) The initial driving force for pressure Following an accident, hydrogen concentration relief is assumed to be the expected will increase due to the addition of hydrogen pressure setpoint of the rupture disks.
from the specified design-basis metal-water reaction. Hydrogen concentration will also (4) The rupture disks are constructed of increase due to radiolysis. Any increase in stainless steel or a material of similar hydrogen concentration is of lesser concern corrision resistance.
because the containment is inerted. Due to dilution, additional hydrogen moves the (5) A number of rupture disks are procured at operating point of the containment atmosphere farther from the envelope of flammability.
6.2 36 Amendment 26
s Onm69.b2 Py 2 of 2 01'E M 2 0,3 - I O 6.2.5.2.7 Recombiners t
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-(l)
The yCS consists of two permanently installed, iF : M thermal hydrogen recombiners, with associated piping, valves, controls and instrumentation. The recombiner units are located in the secondary containment and controlled from the main control room. Each recombiner, as shown in Figure 6.2-40, removes gas from the drywell, recombines the oxygen with hydrogen, and returns the gas mixture, along with the condensate to the suppression chamber.Each recombiner unit is an integral package consisting of a blower, electic heater, reaction chamber, water spray cooler, a water separator, piping, valves, controls and instrumentation.
(2)
During operation of the system, gas is drawn from the drywell by the blower, and heated. Hydrogen and oxygen in the gas will be recombined into steam in the reaction chamber and condensed in the spray cooler.
The condensate and spray water, along with some of the gas, are returned to the wetwell. The rest of the gas is recycled through the blower. Cooling water required for operation of the system after a LOCA is taken from the RER system. The cooling water is used to cool the water vapor and the residual gases leaving the recombiner prior to returning them to the containment.
(3)
All pressure containing equipment, including piping between components is considered an extension of the containment, and therefore is designed to ASME Section III,-Safety Class 2 requirements. Independent drywell and supression chamber penetrations are provided for the two recombiners. Each penetration has two normally closed isolation valves; one pneumatically operated and one motor operated. The system is designed to meet Seismic Category I requirements. The recombiners are in separate rooms in the secondary containment and are protected from damage by flood, fire, tornadoes and pipe whip.
(4)
Af ter a LOCA, the system is manually _ actuated from the control room when high oxygen levels are indicated by the containment atmospheric monitoring system (CAMS). (If hydrogen is not present, oxygen concentrations are controlled by nitrogen makeup). Operation of either recombiner will provide effective control over the buildup of oxygen generated by radiolysis after a design-basis LOCA. Once placed in operation the system continues to operate until it is manually shut down when an adequate margin below the oxygen concentration design limit is reached.
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