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User: How many accidents has the Pickering Nuclear Generating Station in Pickering, Ont had?

How many accidents has the Pickering Nuclear Generating Station in Pickering, Ont had?

Assistant: Good question.

Good question. There’s no simple “number of accidents,” but a few major incidents at Pickering Nuclear Generating Station (Pickering, ON) are well-documented:

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So that’s at least 7-8 significant incidents (depending on how you define “accident”).

If you mean all reportable “events” (including minor ones), regulatory reports might list many more. Do you want a full historical list?

User: How many of these put humans, animals or fish at risk?

How many of these put humans, animals or fish at risk?

Assistant: Good question.

Good question. Based on documented incidents, at least a few of them posed some potential risk to humans, animals, or the environment (including fish), though in many cases the risk was assessed as very low. Here are some key ones:

Incidents that posed (or could have posed) risk:

1. 1992 – Heavy water / tritium leak - According to a Senate report, there was a leak from a heat exchanger that released 2,300 trillion becquerels of tritium into Lake Ontario. SenCanada - Tritium is radioactive, and because it was released into the lake, there is a potential risk to aquatic life and possibly to humans. Clean Air Alliance - Environmental groups note that tritiated water “is absorbed by… animals.” Clean Air Alliance
2. 1994 – Loss-of-coolant accident - On December 10, 1994, a pipe break caused a major loss of coolant (185 tonnes of heavy water), and the emergency core cooling system had to be used. SenCanada - According to the Canadian Nuclear Safety / Senate report, this was serious, though there’s no clear documentation of a large-scale release of highly dangerous radionuclides to harm the public. Canada - Workers were involved in clean-up, so there was direct human exposure risk in that context. SenCanada
3. 1996 – Tritium leak - In April 1996, there was a leak that released 50 trillion becquerels of tritium into Lake Ontario, per the Senate report. SenCanada - As with the 1992 leak, this presents a risk to the aquatic environment (fish, etc.) because tritiated water is biologically active. Clean Air Alliance
4. 2011 – Demineralized water leak - 73,000 litres of demineralized water (with trace tritium) leaked into Lake Ontario due to a failed pump seal. CityNews Toronto - However, officials (Ontario Power Generation and the Canadian Nuclear Safety Commission) stated that the radiological risk was “negligible” for both human health and the environment. CityNews Toronto - The tritium concentration in the leaked water was very low compared to regulatory limits. Global News

Incidents that did not (or likely did not) pose significant external risk:

• 1983 (pressure tube rupture): Although there was a loss-of-coolant, no radioactive material was released from containment, so no public or environmental release. Canada
• 1988 (operator error, fuel damage): According to sources, radioactive iodine contaminated the cooling system and was “vented … over weeks,” but the exact level of release to the environment and corresponding risk is not clear in publicly cited summaries. Pembina Institute
• 1990 (power shifts / flux tilt): This was a reactor control issue; not clearly associated with a radioactive release to the environment. Pembina Institute
• 2020 false alarm: On January 12, 2020, an emergency alert was sent in error, but there was no abnormal release of radioactivity, and authorities stated there was “no danger to the public or environment.” CityNews Toronto

Summary

• Number of incidents with environmental / ecological risk: At least 2–3 (1992 tritium leak, 1994 coolant accident, 1996 tritium leak) had meaningful potential for risk to humans / fish / environment.
• Severity / real risk: In many cases, regulators judged the actual risk to be very low or “negligible”, especially for human health in the 2011 leak. CityNews Toronto

If you like, I can check all the reported “events” (including minor ones) from regulatory archives and estimate how many of them posed an actual risk to public health or the environment — do you want me to do that?