A “category A” nuclear safety incident occurred at Faslane naval base earlier this year, the Ministry of Defence (MoD) has confirmed.
Category A incidents are where there is judged to have been “actual or high potential for radioactive release to the environment”.
The MoD said it is unable to release further detail about the event for security reasons, but stressed it posed “no risk to the public and did not result in any radiological impact to the environment”.
Defence Secretary John Healey described it as being of “low safety significance”.
Officially known as HMNB Clyde, Faslane in Argyll and Bute is home to the Royal Navy’s flotilla of nuclear submarines.
Figures made public through a response to a written parliamentary question in May show the incident was one of 28 “nuclear site events” recorded at the facility between January 1 and April 22, 2025.
Of the other 27 incidents, two were graded category B, seven as category C, 13 as category D and 5 as “below scale”.
Last year there were 119 incidents recorded at the base.
In her written answer, UK defence procurement minister Maria Eagle said nuclear site event reports were raised to “foster a robust safety culture that learns from experience, whether that is of equipment failures, human error, procedural failings, documentation shortcomings or near-misses”.
A Ministry of Defence spokesperson said: “We place the upmost importance on handling radioactive substances safely and securely.
“Nuclear site event reports demonstrate our robust safety culture and commitment to learn from experience.
“The incidents posed no risk to the public and did not result in any radiological impact to the environment. It is factually incorrect to suggest otherwise.
“Our Government backs our nuclear deterrent as the ultimate guarantor of our national security.”
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