An Ontario nuclear reactor was just shut down for good at the close of 2024, the second such reactor to be taken offline at the Pickering Nuclear Generating Station in the late months of the year as the massive plant gears up to close in the near future.

Ontario Power Generation (OPG) confirmed the removal of Pickering's Unit 4 from service with a post on social media on December 31, marking the fourth of eight reactors to be taken offline in the plant's gradual closure.

In the post shared by OPG, Pickering Mayor Kevin Ashe congratulated plant workers for over 50 years of safe operation of what the local politician referred to as Pickering's "nucular" (which, I must stress, is not a real word) Generating Station.

The brief clip also includes congratulatory messages from Pickering Board of Trade Executive Director Alli Leetham, Ontario Minister of Energy and Electrification Stephen Lecce, and local MP Peter Bethlenfalvy.

As the year comes to a close and Pickering Unit 4 is removed from service, we extend our gratitude to the thousands of workers who have contributed to its legacy since 1973. For decades, it has played a vital role delivering safe, reliable, and low-carbon electricity for Ontario. pic.twitter.com/ndCPGHe1Mh

— Ontario Power Gen (@opg) December 31, 2024

Unit 4 began construction back on May 1, 1968, over a year before the first moon landing, and would go online on June 17, 1973 — just months after the first-ever cellular telephone call was made.

These 500 MWe reactors, collectively known as Pickering A, used home-grown CANDU technology that was a major innovation in the mid-20th century, a design that was widely exported and helped bring nuclear energy to nations across the globe.

However, technology ages quickly, and these reactors were never meant to last more than a couple of generations.

All four units were laid up in the mid-1990s, with units 2 and 3 later retired and the remaining two units refurbished and restored in the early 2000s. This bought Pickering A another couple of decades, but the clock ran out in the final months of 2024.

Unit 4 was officially taken offline at 12 p.m. on December 31, 2024, marking the last of four units of Pickering A to cease power generation. Unit 1 was removed from service months earlier at 11 p.m. on October 1, 2024.

The remaining four units at Pickering B will stay in operation for another two years following approval by the Canadian Nuclear Safety Commission (CNSC) of OPG's request for a licence amendment to operate Pickering's Units 5 to 8 to Dec. 31, 2026.