at the Darlington Nuclear Generating Station. An effort to optimize the larger units in a fashion similar to CANDU 6 led to the CANDU 9.

By the early 2000s, sales prospects for the original CANDU designs were dwindling due to the introduction of newer designs from other companies. AECL responded by cancelling CANDU 9 development and moving to the Advanced CANDU reactor (ACR) design. ACR failed to find any buyers; its last