ML12146A367
| ML12146A367 | |
| Person / Time | |
|---|---|
| Issue date: | 05/25/2012 |
| From: | NRC/OI, NRC/OIG |
| To: | |
| References | |
| Download: ML12146A367 (51) | |
Text
OI/OIG SEMINAR March 2010 1
Boiling Water Reactors
Objectives:
- 1. Become familiar with boiling water reactor basic theory of operations 2
reactor basic theory of operations
- 2. Become familiar with basic accident sequences
z Boiling Water Reactors (35) z Pressurized Water Reactors (69) 3
Boiling water reactor basics:
- 1. Light water cooled and moderated
- 2. Designed for boiling in the reactor vessel 3 D i
d t k
ll t
l t i 4
- 3. Designed to keep all reactor coolant in the containment building when warranted
- 4. Produced by General Electric
Boiling water reactor basic operation 5
The major components of any BWR are:
REACTOR VESSEL AND INTERNALS REACTIVITY CONTROL SYSTEMS 6
SEMI-CONVENTIONAL STEAM PLANT EMERGENCY CORE COOLING SYSTEMS PRESSURE SUPPRESSION CONTAINMENT
REACTOR VESSEL AND INTERNALS Feedwater Steam 7
Core Feedwater
REACTOR VESSEL 8
CORE SHROUD Core 9
REACTOR CORE (FUEL) 10 About 100 tons of fuel in the core
REACTOR CORE (FUEL) 11 Neutrons striking certain uranium and plutonium atoms causes them to become unstable. They split, or fission, releasing energy, slighting more than two neutrons and two fission products (smaller atoms).
In a reactor at power, the freed neutrons cause more fissions in a nuclear chain reaction.
PRIMARY & SECONDARY CONTAINMENT It is the radioactivity from fission products rather than from fresh fuel that can be hazardous to workers and the public.
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REACTOR CORE (FUEL) 177 in 660 lbs Active Fuel Length 13 144 inches
Plenum Spring Fuel Rod Fuel Pellet REACTOR CORE (FUEL) 14
Removed Looking Down 15
STEAM SEPARATOR & STEAM DRYER Water vapor leaving the reactor core passes through holes in the shroud head into the steam separator. The vertical tubes force the flow to spin, with water droplets returned to the 16 topside of the shroud head and steam sent along to the steam dryer.
The steam dryer forces the flow along an S-shaped route, again separating water droplets from steam. Dry steam leaves the vessel while the water drains back to the annulus.
REACTIVITY CONTROL SYSTEMS
- CONTROL RODS 9 NORMAL INSERTION AND WITHDRAWAL 9 RAPID INSERTION (SCRAM)
RECIRCULATION FLOW 17
- RECIRCULATION FLOW 9 NORMAL POWER INCREASES/DECREASES 9 RAPID POWER REDUCTIONS
- STANDBY LIQUID CONTROL 9 EMERGENCY SHUT DOWN
Control rod drive mechanisms apply water pressure to one side of a hydraulic piston and vent water from the opposite side of the piston to move control rod(s).
- NORMAL INSERTION AND WITHDRAWAL d
d l
l d
b d
CONTROL RODS 18 An individual control rod can be moved in 6-inch increments or full length in 48 seconds
- RAPID INSERTION (SCRAM)
All control rods inserted in 3 to 5 seconds
CONTROL RODS 19
CONTROL RODS 20
CONTROL RODS Cutaway Fuel Bundles 21 Top of Control Rod
CONTROL RODS 22 Control rods contain boron, which acts like neutron glue.
Inserting a control rod soaks up free neutrons, slowing the nuclear chain reaction.
CONTROL RODS Normal insertion: Valves open for a single control rod to admit water to the bottom of the DRIVE PISTON and vent water from above it. About 260 pounds differential pressure move the control rod into the reactor core.
Normal withdrawal: Valves open for a single control rod to admit water to th t
f th DRIVE PISTON d
23 the top of the DRIVE PISTON and vent water from below it. About 260 pounds differential pressure move the rod out of the reactor core.
Scram: Valves open for all control rods to admit water to the bottom of the DRIVE PISTON and vent water from above it. About 1,200 pounds differential pressure moves the rods into the reactor core.
STANDBY LIQUID CONTROL If the control rods fail to shut down the 24 reactor, the operators can manually start pump(s) to inject boron in liquid form into the reactor vessel.
RECIRCULATION FLOW Two motor-driven pumps draw water from the reactor vessel and return it through jet pumps located between the shroud and the reactor 25 shroud and the reactor vessel wall. High velocity water in the jet pump nozzles pulls water from the annulus. The combination of drive and driven flow passes through the reactor core.
RECIRCULATION FLOW Jet Pump Nozzle High velocity drive flow from recirculation pumps pulls flow from annulus 26 region to force about 3 times as much flow through reactor core.
RECIRCULATION FLOW Varying the flow rate through the reactor core affects the formation of steam bubbles (voids) and thereby the power level. Increasing the flow rate sweeps bubbles away faster, increasing the reactor power level.
27 Operators can change the reactor power level from about 40% to 100% rated output by regulating the recirculation flow rate.
When conditions warrant pump or core protection, the recirculation pumps output will be automatically reduced, rapidly dropping the reactor power level.
RECIRCULATION FLOW 28
Semi-Conventional Steam Plant Because steam is radioactive, gas pulled from condenser is treated before release.
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Semi-Conventional Steam Plant Same as fossil-fired steam plant Similar to Unlike 30
PRIMARY & SECONDARY CONTAINMENT 31
MARK II Containment BWR Containments 32 MARK I Containment MARK lll Containment
Mark I Containment Mark I Containment 33
DRYWELL HEAD DRYWELL FLANGE DRYWELL SHEAR LUG SUPPORT DRYWELL SHIELD WALL RADIAL BEAM CORE REACTOR PRESSURE VESSEL 34 RADIAL BEAM JET DEFLECTOR VENT DWFDS DWEDS WATER LEVEL PRESSURE SUPPRESSION CHAMBER MANWAY Figure 6.5-1 Mark Containment VENT HEADER VACCUM BREAKER DOWNCOMER PIPE
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T-Quencher 36 Downcomer HPCI Steam Exhaust
MARK II MARK II Containment Containment 37
REACTOR PEDESTAL DRYWELL HEAD DRYWELL REACTOR VESSEL SACRIFICIAL SHIELD WALL STEEL LINER S /R VALVE TAILPIPE (18)
Pressure Suppression 38 DRYWELL DECK VACUUM BREAKERS (5)
SUPPORT COLUMN (12)
EQUIPMENT HANDLING PLATFORM DOWNCOMER (VENT)
PRESSURE SUPPRESSION CHAMBER WATER LEVEL QUENCHER (18)
REINFORCED CONCRETE Figure 6.5-3 Mark II Containment
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CONTAINMENT SPRAY SHIELD BUILDING CONTAINMENT DRYWELL HEAD FUEL TRANSFER POOL REACTOR VESSEL REACTOR SHIELD 125 TON CRANE W/15 TON AUX HOOK UPPER POOL Pressure Suppression 41 REACTOR SHIELD DRYWELL BOUNDRY DRYWELL FUEL TRANSFER TUBE WEIR WALL S/R VALVE LINE SUPRESSION POOL HORIZONTAL VENT Figure 6.5-5 Mark III Containment
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Mark I (BFNP)
Mark II (LaSalle)
Mark III (Perry)
Drywell Material Steel Concrete Concrete Drywell Thickness (ft)
.17 6
6 Drywell Upper Diameter (ft) 39 31 73 Drywell Lower Diameter (ft) 67 73 73 Drywell Height (ft) 115 91 89 Drywell Free Air Volume (ft33) 159,000 209,300 277,685 Drywell Design Internal Pressure (psig) 56 45 30 Drywell Design External Pressure (psig) 2 5
21 Drywell Deck Design d/p (psid)
N/A 25 N/A Drywell Design Temperature (oF) 281 340 330 Drywell max. Calculated LOCA Pressure (psig) 49.6 34 22.1 Shield above RPV Head Concrete Concrete Water Suppression Chamber (or Containment ) Thickness (ft)
.17 4
.15 Suppression Chamber (or Containment ) Steel Liner N/A
.25 N/A Suppression Chamber (or Containment ) Diameter ft) 111 87 120 44 Suppression Chamber (or Containment ) Height (ft) 31 67 183 Suppression Chamber (or Containment ) Free Air 119,000 164,500 1,141,014 Suppression Pool Volume in Drywell (ft3)
N/A N/A 11,215 Total Suppression Pool Volume (ft33) 135,000 124,000 129,550 Upper Pool Makeup to Suppression Pool (ft33)
N/A N/A 32,830 Suppression Chamber (or Containment) Design Internal Pressure (psig) 56 45 15 Suppression Chamber (or Containment) Design External Pressure (psig) 2 5
0.8 Suppression Chamber (or Containment) Design 281 275 185 Suppression Chamber (or Containment) max. Calculated 27 28 11.31 Suppression Chamber (or Containment) design Leak Rate
(% of vol/Day)
.5
.5
.2 Number of Drywell to Suppression Chamber (or Containment) vents 8
98 120 Total Vent Area (ft3) 286 308 512 Drywell Atmosphere N2 N2 Air 1 ft3 = 7.48 gal
EMERGENCY CORE COOLING SYSTEMS High Pressure ECCS The steam-driven High Pressure Coolant Injection (HPCI) system and Low Pressure ECCS The motor-driven Residua Heat Removal (RHR) and Core Spray (CS) pumps can transfer water from the suppression pool to the reactor vessel 45 (HPCI) system and steam-driven non-ECCS Reactor Core Isolation Cooling (RCIC) system can transfer water from the Condensate Storage Tank to the reactor vessel.
the reactor vessel.
EMERGENCY CORE COOLING SYSTEMS Design, assuming single failure, provides a success path for adequate core cooling.
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EMERGENCY CORE COOLING SYSTEMS View down into reactor vessel 47 with steam dryer and steam separator removed showing spray pattern above reactor core from Core Spray system operation.
DESIGN BASES ACCIDENTS Control rod drop accident (CRDA)
A control rod is uncoupled from its mechanism and sticks fully inserted as the mechanism is fully withdrawn. The uncoupled control rod then falls freely to the fully withdrawn position.
Loss of coolant accident (LOCA)
The largest diameter pipe connected to the vessel ruptures, 48 g
m p p p
allowing cooling water to leak from the vessel at the fastest rate.
Main steam line break accident (MSLBA)
A main steam line break inside primary containment deposits energy into containment at the fastest rate.
Fuel handling accident (FHA)
A spent fuel bundle is dropped in transit and falls freely to strike irradiated fuel bundles in the reactor core (or spent fuel pool).
Accidents MSLBA 49 LOCA
QUESTIONS?
51 QUESTIONS?