Products & Services: Core Reactor Components

Cameco Fuel Manufacturing (CFM) fabricates a wide variety of highly specialized mechanisms used in pressurized light and heavy water reactor components for utility customers around the globe.

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Calandria Tubes & Calandria Spools

Calandria tubes are a unique pressure vessel, seam-welded tube designed specifically for the Candu reactor. The calandria tube acts as a secondary pressure containment device in the unlikely event of a pressure tube failure. The calandria tube is considered part of the fuel channel and also adds a degree of structural rigidity to the core.

CFM has manufactured virtually every calandria tube for Candu reactors world-wide.

The calandria tube spools are short versions of the calandria tube. These are generally used for testing and validation purposes. The two ends of the spool are exactly representative of the ends on a full length calandria tube.

Fuel Channel Annulus Spacers (Garter Springs)

The fuel channel annulus spacer is specific to the design of the Candu reactor. This spring wound coil is used to separate the outside diameter of the pressure tube from the inside diameter of the calandria tube. The coil is loosely wound to allow for the flow of gas through the annulus.

A zircaloy tracer wire is strung through the spring which is used to locate the position of the spring along the fuel channel. Once in the core, the location of the spring must be periodically verified.

Guide Tube Assemblies

The guide tube assembly is manufactured from a tubular zircaloy in-core guide tube and stainless steel out of core section called the guide tube extension.

Guide tubes are tensioned by coil springs at the bottom of the tube which act on couplings attached to the locators.

Liquid Injection Shutdown System
(LISS) & LISS Nozzles

The liquid injection shutdown system (LISS) is part of safety shutdown system 2 (SDS2) in the Candu reactor. The LISS provides for a rapid injection of gadolinium nitrate solution by helium displacement. This liquid solution is injected from an external poison tank into the heavy water in the calandria vessel.

Many in core components are manufactured to ASME Pressure vessel code standards and precise technical specifications.

Liquid Zone Control Assemblies

The liquid zone control absorbers are the primary devices for controlling reactivity within the Candu reactor during normal operation.

Six liquid zone control assemblies are positioned vertically throughout the core. In total, there are 14 chambers within the six liquid zone controls (LZC). Some LZC have three chambers while others have two.

The principle for reactivity control is the balancing of helium and light water within tubes welded vertically in the LZC. The LZC are built to ASME Pressure Vessel Code standards and precise technical specifications.

Neutron Flux Detector Assemblies

The neutron flux detector assembly is used to measure the neutron flux density in various regions throughout the core. This assembly can be up to 15 metres long depending on configuration. A connector (shown in the photo) is also available to take the low amperage signal from the neutron flux detector.

During the last 25 years, CFM has manufactured over 2,000 flux detector assemblies for a wide variety of reactors around the globe.

Shut-off, Control & Adjuster Assemblies

Shutoff rods are manufactured to meticulous quality standards as they are an important part of safety shutdown systems. They are manufactured with a precise amount of cadmium and stainless steel. Control rods themselves form part of the reactor operating system. Finer control of the reactor operation is ensured by control rods. Adjuster absorber rods (21 in a Candu 6 reactor) are used for flux shaping, both radially and axially. The adjuster is made of stainless steel.

Complete assemblies for shut-off, control and adjusters are available for Candu operators.