Fabrication Services

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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Core reactor components

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.

Reactivity mechanisms


The bellows assembly is designed to seal the annular space between the pressure tube and the calandria tube in a CANDU reactor.

Generally the bellows allows for some expansion in each channel while maintaining channel integrity. The bellows allows axial motion of the channels and also supports the torque of the end fitting from the feeder pipe. The bellows material is typically Inconel.

Closure Plugs

Closure plugs are removable units used to seal each end of the fuel channel. This enables access for refuelling by the fueling machine.

The steel closure plug is held in place by lugs that fit into slots on the inside diameter of the end fitting body. The closure plug is sealed by a metal face seal.

Custom Precision Seamless Tube Sizes

CFM specializes in the cold work fabrication (pilgering) of custom seamless Zircaloy tubing. Sizes range from 0.250” (7mm) OD to 2.000” (50mm) outside diameter. The wall thickness can be as low as 0.010" (0.25mm).

Standard tolerances as low as 0.0005” (0.02mm) are common. Higher precision is available upon request.

Drive Mechanism (Gearbox)

We manufacture drive mechanisms which are mounted above the reactor, on the reactivity mechanism deck. It is used to drop and hoist rods into the core. In the case of a shutoff drive mechanism unit, the clutch will release the shutoff rod for very rapid insertion into the core to stop the reaction.

Other drive mechanisms can be utilized for control rods or absorber rods. In this case, the gearbox is slightly different as finer motion controls are required.


Small flasks are used as shielding to protect workers from increased radiation as the cobalt adjuster rods are removed from the reactor. The flask is inserted during the rod removal operation and then it is removed after the cobalt adjuster assembly is extracted.

The flasks that CFM manufactures are made of either a depleted uranium or tungsten metal material.

Guide Tubes

The guide tubes are used in a vertical stationary configuration to allow rapid insertion of shutoff rods or adjuster rods. We manufacture guide tubes in two configurations; one with numerous holes or one without holes. In the configuration with holes, approximately 35% of the metal is removed. This minimizes the amount of neutron absorption by the amount of Zircaloy in core. It also precludes voids occurring in the moderator heavy water.

Other guide tubes are manufactured for the neutron flux detector assemblies for protection of the detector from water ingress.

Ion Chambers

The ion chamber unit consists of the ion chamber housing, access tubes and vault wall penetration assembly, shield plugs, ion chamber instruments and cables, and the shutter assembly.

Ion chambers measure the reactor power. They are mounted on the outside of the calandria vessel. The output of the ion chamber is used for reactor control at low power levels. They also give a rate of change of reactor power, which is a shutdown system trip parameter.

Latch Assembly

The latch assembly is a small device located in each fuel channel at the downstream end of the fuel channel.
The purpose of the latch assembly is to prevent the fuel from traveling or moving down the channel. The water flow through each channel exerts a tremendous pressure on each fuel bundle.

Liner Tubes

Liner tubes are used in each fuel channel to guide the fuel and shield plug into the channel. Each fuel channel has two liner tubes. Typically, 410 stainless steel is used as liner tube material.

Perforations in the liner tube provide for a large flow area so that the coolant pressure drop over the liner tube is as small as possible.

Pyle National Connectors for Flux Detectors

The pyle national connector is a device to provide a sealed connection from the flux detector head to another bulkhead. A number of different connector configurations are available, depending upon our customers’ unique application. Differing configurations ensure that SDS1 and SDS2 connectors cannot be incorrectly installed.

Shield Plugs

Shield plugs are installed on every CANDU fuel channel to minimize neutron leakage from the fuel channel. In the case of a downstream to water flow shield plug, the plug also provides axial support to the column of fuel bundles.


Vertical thimbles extend from the top of the calandria up through the reactivity mechanism deck. They enclose the moderator and its cover gas while being immersed in the vault shield water. Metal bellows are welded to the deck penetrations to maintain a seal between the vault shield water and the reactivity mechanism deck. The bellows also permit free vertical movement to accommodate thermal expansion.

Horizontal thimbles extend from the shield wall through the vault wall to the calandria nozzles. These, too, are sealed by metallic bellows.

In-stock Zircaloy metals

Small Quantities of Zircaloy Bar | Rod | Sheet | Tube

CFM always has small quantities of Zircaloy available from stock. All material will have certificates and traceability as it is nuclear grade.

The stock varies from time to time due to availability but if you urgently need small quantities of Zircaloy we will likely have it. Several different Zircaloy grades are available:

  • ASTM R60804; Zircaloy4, nuclear grade.
  • ASTM R60802; Zircaloy2, nuclear grade.
  • ASTM R60904; Zr2.5Nb, nuclear grade.
  • ASTM R60702; non-nuclear grade.

Other services

Complete Non-Destructive Testing Services

CFM employs a variety of non-destructive testing processes to ensure the quality and integrity of our critical pressure vessel components

We perform ultrasonic testing, liquid penetrant testing and radiography on our specialized equipment and can plan, design and perform eddy current testing. We also custom design, build and commission non-destructive testing equipment for clients’ on-site use.

Custom Fabrication - Isotope Transportation Packaging

CFM custom fabricates Co60 isotope transportation packages.

After an extended stay in-reactor, cobalt 60 (Co60) is artificially produced by neutron activation of Co59. Once it is rendered highly active, Co60 is difficult to transport due to the high level of gamma radiation emitted. For this reason, a highly shielded transportation package is required.

We manufacture two types of customized cobalt isotope transport packages licensed by both the Canadian Nuclear Safety Commission (CNSC) and the US Nuclear Regulatory Commission (NRC).

Co60 is used mainly for sterilization of medical equipment and as a radiation source for medical radiotherapy, industrial radiography, pest insect sterilization as well as food and blood irradiation.

Custom Fabrications - Reactivity Drive Mechanisms

Drive mechanisms are typically used to drop devices into the reactor and retract them from the core. These mechanisms include shut-off rods, or other types of reactivity control devices such as control rods, adjuster absorber rods and cobalt adjuster rods. These devices consist of a radiation prepared servo drive motor, an electromagnetic clutch, a sheave winding system and a damper mechanism.

During regular operation of the reactor, the electro-magnetic clutch is engaged, holding the reactivity mechanisms in position either fully or partially retracted. When activated or during a power loss to the nuclear generating station, the electromagnetic clutch disengages and the reactivity rods are fired into the reactor for a complete shut-down. The damper mechanism allows the rods to decelerate as they reach their final resting position in the reactor.

Associated with drive mechanisms, we also produce sensors used in defining the position of the various control or shut-off rods when fully retracted. These are known as rod-ready indicators.

Oxide Coating Services

Zircaloy is relatively mid-range in terms of hardness and other mechanical properties. To increase abrasion resistance and strength, CFM can provide surface oxide treatment to various grades of nuclear Zircaloy.

The zirconium oxide depth and thickness can vary to meet precise design specifications. The zirconium oxide surface provides an extremely hard and abrasion resistant surface.

Pickling & Passivation

A solution of hydrofluoric acid is used to pickle Zircaloy components. Site specific or overall dimensional control can be achieved by either preferential pickling or overall pickling. Depending upon the amount of metal to be removed, the type of acid bath may be altered. Pickling can also be used for inside surface conditioning of longer length tubing.

Passivation is used to make the metal more "inert." Different acid baths are used to achieve passivation of Zircaloy components.


Several different polishing techniques are available, depending upon the technical specifications required by the customer. Typically, the outside diameter will be polished to provide either a specified surface condition or a dimensional requirement. Lengths of tube and bar between one to six metres can be polished on the outside diameter. Shorter lengths can be inside diameter polished.

Seam Welded Precision Tubing

CFM can perform axial and radial welds in tubes up to seven metres long, with outside diameters ranging from 88 mm to 180 mm. Tubes are usually robotically welded, followed by an X-ray or ultrasonic inspection of the weld and tube itself. Liquid penetrant testing can also be performed.