41-172.1 Nuclear Power - Magnetrol International

INDUSTRY
APPLICATIONS
SERIES
A Guide to Level Instrumentation for the Nuclear Power Industry
2
For a discussion of the major
applications in conventional
steam turbine power generation
see the Magnetrol® PowerGen
Applications brochure.
L E V E L A P P L I C AT I O N S
These applications utilize level instruments for process
control. A separate alarm using a different technology
often serves as a back-up for spill detection.
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PAGE
Emergency Coolant Tanks . . . . . . . . . . . . . . . . . . .3
SCRAM Discharge Volume Tank . . . . . . . . . . . . . .3
Steam Generator . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Containment & Drainage Sumps . . . . . . . . . . . . . .4
Spent Fuel Pool . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Feedwater Heaters and Storage . . . . . . . . . . . . . .5
Diesel Fuel Storage . . . . . . . . . . . . . . . . . . . . . . . . .6
Lubrication Oil Storage . . . . . . . . . . . . . . . . . . . . . .6
Liquid Waste Storage . . . . . . . . . . . . . . . . . . . . . . .7
Cooling Tower Intake & Basin Levels . . . . . . . . . .7
STEAM TURBINE
POWER GENERATION
UNITS
Generator
Turbines
10
9
REACTOR
CONTAINMENT
STRUCTURES
8
6
7
The Pressurized Water
Reactor (PWR) and the
Boiling Water Reactor (BWR)
schematics shown below
represent the world’s two
most common forms of
nuclear power generation.
4
To Turbines
Low
Pressure
6
Pressurizer
1
High
Pressure
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3
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5
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5
1
3
EMERGENCY COOLANT TANKS
Coolant Tank
Application: The Emergency Core Cooling
System (ECCS) supplies cooling water to the
reactor during an interruption of the reactor’s normal cooling system. Upwards of 250,000 gallons
of emergency make-up water is drawn from
Refueling Water Storage Tanks (RWST) during the
injection phase and from a containment sump
during the second recirculation phase.
I N S T R U M E N TAT I O N
Challenges: Level control of Refueling Water
Storage Tanks is essential for emergency cooling
operations. Low levels in these tanks can trigger
actuation of pumps which bring additional coolant
from accumulators, deaerators, de-mineralized
water tanks, and treated condensate tanks. The
ECCS can be tripped by an indication of coolant
pressure loss or by low level of reactor coolant.
2
Point Level:
Models A10 or
B10 DisplacerActuated
Switches
Continuous Level:
Eclipse® Model 705
Guided Wave Radar
Transmitter or
Pulsar® Model R95
Pulse Burst Radar
Transmitter
Visual Indication:
Atlas™ or Aurora®
Magnetic Level
Indicators can be
supplied with
switches or
transmitters
SCRAM DISCHARGE VOLUME TANKS
SCRAM Tanks
I N S T R U M E N TAT I O N
Application: A SCRAM is a rapid shutdown of a
nuclear reactor whereby control rods are inserted between the fuel rods in the reactor core to
discontinue the fission reaction. The SCRAM is
actuated manually by an operator or automatically when parameters are exceeded. When control rods are inserted, radioactive coolant is displaced by the rods and routed to a storage tank.
This “hot” coolant is later processed and routed
back to the recirculation system.
Challenges: Level instrumentation in the
Discharge Volume Tank is an important control in
the Reactor Protection System (RPS). The level
controls must be approved for radioactive service in a steam environment. Conventional float
switches are frequently specified as they meet
these requirements with high reliability.
Point Level:
Model B40 FloatActuated External
Cage Switch
Continuous Level:
E3 Modulevel®
Displacer
Transmitter
(remote version
only)
Visual Indication:
Atlas™ Magnetic
Level Indicator
4
3
STEAM GENERATOR
Steam Generators
Application: Primary coolant circulating in a PWR
is heated under extremely high pressures to prevent boiling. The heated coolant enters two or more
boilers called Steam Generators (SG) and boils the
secondary loop coolant in a heat transfer process
accomplished without mixing the fluids together.
The coolant turns to steam which drives the turbine-generator.
Challenges: 30% of emergency PWR shutdowns
are attributable to SG level control problems.
Controls balance feedwater to steam flow under all
operating conditions. High-high levels can trip the
turbine. Abnormally low levels can actuate emergency feedwater or a reactor shutdown.
Measurement accuracy is challenged by thermal
reverse effects known as “shrink and swell” and by
static pressure effects.
I N S T R U M E N TAT I O N
Point Level:
4
Series 3 Floatactuated External
Cage Level
Switch; or B40
Float-Actuated
Level Switch
Continuous Level:
E3 MODULEVEL
Displacer
Transmitter or
ECLIPSE Model 705
Radar Transmitter
Visual Indication:
ATLAS or AURORA
Magnetic Level
Indicators can be
supplied with
switches or
transmitters
CONTAINMENT & DRAINAGE SUMPS
Application: A plant has many low-lying drainage
reservoirs known as sumps. Small sumps include
pump enclosures and tank rupture basins that
contain leakage. The reactor’s large, containment
sump is an essential reservoir of the ECCS whose
function is to continuously circulate coolant
through the reactor once all coolant storage tanks
are depleted.
I N S T R U M E N TAT I O N
Challenges: Small sumps are monitored for leak
detection with simple, float-operated level switches designed for bracket mounting in floor level
sumps or troughs. These switches detect leaks or
spills from pumps, valves, vessels, and pipelines.
Levels of the large containment sump, or ECCS
sump, are monitored during the recirculation
phase of residual heat removal when the reactor’s
primary coolant system is down.
Point Level:
Models A10 or B10
Displacer-Actuated
Switches
Continuous Level:
ECLIPSE Model 705
Guided Wave Radar
with Single Rod
Probe (remote
version only)
Visual Indication:
ATLAS Magnetic
Level Indicator
5
5
SPENT FUEL POOL
Spent Fuel Pool
Application: One-third of the total fuel load of a
reactor is removed from the core every 12 to 18
months and replaced with fresh fuel. Spent fuel rods
generate intense heat and high radiation and are
stored underwater in pools with depths of 20 to 40
feet. The water cools the fuel and provides radiation
shielding. Spent fuel is later sent for reprocessing or
dry cask storage.
I N S T R U M E N TAT I O N
Challenges: Without cooling, the spent fuel pool
water will heat up and boil. Exposed fuel assemblies
will overheat, melt or combust. Pool level is tightly
controlled and water is continuously cooled by recirculation to heat exchangers and then back to the
pool to resume cooling. High and low level alarms
as well as redundant continuous level indication are
typically required.
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Point Level:
Models A10 or B10
Displacer-Actuated
Switches
Continuous Level:
PULSAR Model RX5
Radar Transmitter
Visual Indication:
Not applicable
FEEDWATER HEATERS AND STORAGE
Feedwater Tank
Application: Low and High Pressure Feedwater
Heaters use extraction steam from the turbine to
pre-heat feedwater destined for steam generation.
The primary water sources for the heaters are the
Condensers and Condensate Storage Tank. The
Emergency Service Water System or the Ultimate
Heat Sink (usually a river or lake) provides back-up
feedwater to the SGs in the event of an interruption
in the primary feedwater system.
I N S T R U M E N TAT I O N
Challenges: Redundant control loops manage
feedwater heater level to prevent liquid from rising
into the extraction steam; keep tubes in the condensing zone immersed; keep the drain cooler
flooded, and optimize heater performance. The
primary and back-up feedwater sources are
typically equipped with level switches for valve
actuation and alarms.
Point Level:
Series 3 FloatActuated External
Cage Level
Switch; or B40
Float-Actuated
Level Switch
Continuous Level:
E3 MODULEVEL
Displacer
Transmitter or
ECLIPSE Model 705
Radar Transmitter:
Visual Indication:
ATLAS or AURORA
Magnetic Level
Indicators can be
supplied with
switches or
transmitters
6
7
DIESEL FUEL STORAGE TANKS
Diesel Storage Tanks
Application: Diesel-powered engine-generator
sets provide emergency power to operate critical
nuclear plant systems in the event of a loss of station service power. The main diesel fuel storage
tank provides a fuel capacity for one to seven days
of full-load generator operation. The main storage
tank is connected to an indoor day tank holding
less than 1,000 gallons.
I N S T R U M E N TAT I O N
Challenges: Main storage tanks typically require a
fuel level indicator with a remote indication transmitter. Sensors actuating electrical pumps connected to the main tank continuously monitor day
tank fuel level. Day tank high-level alarms can lock
out supply pumps until a system reset. Low levels
and critical low-levels actuate alarms and the system will display the low-level conditions.
8
Point Level:
Continuous Level:
ECLIPSE Model 705
Guided Wave Radar,
PULSAR Model RX5
Radar Transmitter,
or Jupiter®
Magnetostrictive
Level Transmitter
Models A10 or
B10 DisplacerActuated Switches
or Echotel® Model
961 Ultrasonic
Switch
Visual Indication:
ATLAS or AURORA
Magnetic Level
Indicators can be
supplied with
switches or
transmitters
LUBRICATION OIL STORAGE
Lube Oil Tanks
Application: Nuclear plants operate many
machines that require lubrication. Lubricants
prevent damage caused by excessive friction and
prolong equipment life. Oil is stored in stainless
steel and carbon steel tanks. A generator gearbox
lube oil system may have a reservoir with a capacity of 3,000 gallons and a turbine oil system may
have a capacity of 150 gallons.
I N S T R U M E N TAT I O N
Challenges: Level monitoring of oil reservoirs will
ensure the proper functioning of pumps, gearboxes, drives, compressors, materials handling equipment, generators and turbines. Temperature shifts
in oil reservoirs affect media density that excludes
some technologies, such as dP devices. Because
ISO cleanliness levels increase oil change
frequency, controls should be easy to remove.
Point Level:
ECHOTEL
Model 961
Ultrasonic Switch
or Tuffy® II FloatActuated Switch
Continuous Level:
ECLIPSE Model 705
Guided Wave Radar
or PULSAR Model
RX5 Radar
Transmitter
Visual Indication:
ATLAS or AURORA
Magnetic Level
Indicators can be
supplied with
switches or
transmitters
9
7
LIQUID WASTE STORAGE
Liquid Waste Storage Tanks
Application: Waste liquids from sumps, radioactive
leakage collectors, the Reactor Cooling System
(RCS), and allied systems are collected, stored and
processed. Inactive wastes are discharged or
reused; active wastes are collected for processing.
Radioactive liquids can provide make-up to the
RCS, the ECCS, and the spent fuel storage pool.
I N S T R U M E N TAT I O N
Challenges: Waste liquids are collected and stored
in large single- and double-walled tanks designed
to suit radioactivity levels. Tanks are monitored for
activity levels and their contents are processed,
released or reused. Tank level instruments,
frequently of redundant design, indicate inventory
levels and protect against overfilling or underfilling
that cavitates pumps. Prevention of tank overfilling.
10
Point Level:
Continuous Level:
Models A10 or B10
Displacer-Actuated
Switches
Not applicable due to
possible radioactivity
Visual Indication:
ATLAS or AURORA
Magnetic Level
Indicators can be
supplied with
switches or
transmitters
COOLING TOWER INTAKE & BASIN LEVELS
Cooling Tower Water Pumps
Application: The hyperbolic cooling tower releasing clouds of water vapor is the iconic image of
nuclear power. Warm water from the condenser is
pumped to the natural draft cooling tower, distributed to remove waste heat to the ambient atmosphere through evaporation, and collected in a basin
prior to being recycled back to the condenser.
I N S T R U M E N TAT I O N
Challenges: The cooling tower’s intake structure,
typically a vertical wet pit, requires level sensing
and pump control. Water basin level controls
maintain level through the addition of make-up
water and are frequently configured with high and
low level alarms.
Point Level:
ECHOTEL
Model 961
Ultrasonic Switch
Continuous Level:
ECLIPSE Model 705
Guided Wave Radar,
or PULSAR Model RX5
Radar Transmitter or
ECHOTEL Model 355
Non-Contact
Ultrasonic Transmitter
Flow & Pump
Protection:
Thermatel® Model
TD1/TD2 Switch
AN INDUSTRY GUIDE TO LEVEL MEASUREMENT AND CONTROL FROM MAGNETROL
Other industry and special application brochures from MAGNETROL include:
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Chemical
Crude Oil Processing
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Food & Beverage
Interface Level Measurement
Life Science
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Modular Skid Systems
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Petroleum Refining
Power Generation
Pulp & Paper Mills
Renewable Energy
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Tank Overfill Prevention
Understanding Safety Integrity Level (SIL)
Water & Wastewater
PLEASE NOTE: The instruments recommended in these brochures are based on field experience with
similar applications and are included as a general guide to level and flow control selection. Because
all applications differ, however, customers should determine suitability for their own purposes.
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Bulletin: 41-172.1 • Effective: March 2009