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What is a Subcritical Assembly?

A subcritical assembly is a type of nuclear reactor, but on the opposite end of the spectrum from a larger reactor, such as the current ones used by Ontario Power Generation (OPG) or Bruce Power.

The proposed subcritical assembly will be the only facility of its kind in Canada. 


A subcritical assembly is based on the same principles of nuclear science as larger reactors, but vastly different in its operation in that it cannot generate power or electricity.  The table shows how the subcritical assembly compares to other reactors in Canada.

The subcritical assembly has many distinct design characteristics that makes it very conducive for research, training, and teaching purposes; and is why it is often called a “teaching reactor.” 

In Canada it is referred to as a subcritical assembly and that it is what the Canadian Nuclear Safety Commission, our regulatory body, refers to it as.  It is acknowledged that other areas of the world also refer to it as a subcritical reactor.

Types of Reactors In Canada. OPG and Bruce CANDU Power Reactors are on the high end of the spectrum at over 600 MW.  Towards the opposite end of the spectrum we have the Research Reactors at McMaster, Ecole Polytechnique, Royal Military College, and Canadian Nuclear Laboratories.  These range from 5 megawatts to 0.0001 megawatts.  The proposed subcritical assembly is on the low end at 0 megawatts of power.
Check out our FAQ sect...
Check out our FAQ section for a more detailed description of what is a subcritical assembly
Subcritical Assemblies...
Subcritical Assemblies Around the World