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This module covers the following areas pertaining to instrumentation and
control.
• Pressure
• Flow
• Level
• Temperature
• Neutron Flux
• Control
At the end of training the participants will be able to:
Pressure
• explain the basic working principle of pressure measuring devices,
bourdon tube, bellows, diaphragm, capsule, strain gauge,
capacitance capsule;
• explain the basic operation of a differential pressure transmitter;
• explain the effects of operating environment (pressure,
temperature, humidity) on pressure detectors;
• state the effect of the following failures or abnormalities:
over-pressuring a differential pressure cell or bourdon tube;
diaphragm failure in a differential pressure cell;
blocked or leaking sensing lines; and
loss of loop electrical power.
Flow
• explain how devices generate a differential pressure signal: orifice,
venturi, flow nozzle, elbow, pitot tube, annubar;
• explain how each of the following will affect the indicated flow
signal from each of the above devices:
change in process fluid temperature;
change in process fluid pressure; and
erosion.
• identify the primary device, three-valve manifold and flow;
transmitter in a flow measurement installation;
• state the relationship between fluid flow and output signal in a
flow control loop with a square root extractor;
• describe the operation of density compensating flow detectors;
• explain why density compensation is required in some flow
measurements;
• state the effect on the flow measurement in process with
abnormalities: Vapour formation in the throat, clogging if throat by
foreign material, Leaks in HI or LO pressure sensing lines;
Note
Science and Reactor Fundamentals – Instrumentation & Control 4
CNSC Technical Training Group
Revision 1 – January 2003
Level
• explain how a level signal is derived for: an open vessel, a
closed vessel with dry reference leg, a closed vessel with wet
reference leg;
• explain how a DP cell can be damaged from over pressure if it
is not isolated correctly;
• explain how a bubbler derives level signal for an open and
closed tank;
• explain the need for zero suppression and zero elevation in level
measurement installations;
• describe the effects of varying liquid temperature or pressure on
level indication from a differential pressure transmitter;
• explain how errors are introduced into the DP cell signal by
abnormalities: leaking sensing lines, dirt or debris in the sensing
lines;
Temperature
• explain the principle of operation of temperature detectors: RTD,
thermocouple, bimetallic strip & pressure cylinders;
• state the advantages and disadvantages of RTDs and
thermocouples
• state the effect on the indicated temperature for failures, open
circuit and short circuit;
Flux
• state the reactor power control range for different neutron sensors
and explain why overlap is required: Start-up instrumentation, Ion
Chambers, In Core detectors;
• explain how a neutron flux signal is derived in a BF3 proportional
counter;
• explain the reasons for start-up instrumentation burn-out;
• explain how a neutron flux signal is derived in an ion chamber;
• state the basic principles of operation of a fission chamber
radiation detector;
• state and explain methods of gamma discrimination for neutron ion
chambers;
• explain how the external factors affect the accuracy of the ion
chamber’s neutron flux measurement: Low moderator level, Loss
of high voltage power supply, Shutdown of the reactor;
• describe the construction and explain the basic operating principle
of in-core neutron detectors;
• explain reactor conditions factors can affect the accuracy of the incore
detector neutron flux measurement: Fuelling or reactivity
device movement nearby, Start-up of the reactor, long-term
exposure to neutron flux, Moderator poison (shielding);