MoD pressed for transparency after ‘Category A’ nuclear incident at Faslane

“(Faslane, Scotland – August 14, 2025) – The Ministry of Defence (MoD) is facing calls to reveal what happened during a “Category A” nuclear safety incident at HM Naval Base Clyde earlier this year, as newly published figures confirm that the incident took place between January 1 and April 22, 2025. The base, commonly known as Faslane, is home to the Royal Navy’s Vanguard-class submarines armed with Trident missiles and the UK’s Astute-class attack boats.

What has been confirmed so far

A Sky News report, citing MoD disclosures, said that a Category A incident was recorded at Faslane in the period up to April 22. The MoD described all incidents during this period as “low safety significance”, adding that there was no risk to the public and no radiological impact on the environment. The department responsible for national security and operational sensitivity The citation did not provide specific details of the Category A incident.

• Her Majesty’s Naval Base, Clyde, located primarily at Faslane on Gare Loch, is one of three operating bases for the Royal Navy in the United Kingdom. It is the headquarters of the Navy in Scotland and is best known as the home of Britain’s nuclear weapons in the form of nuclear submarines armed with Trident missiles. (David Dixon/Wikimedia)

Classification: What does “Category A” mean?

In the MoD’s Nuclear Site Event Reports (NSERs), Category A refers to the most serious class of incident and is included in the public-content summary of an incident in the environment. is. Defined as an event with a real or high probability of a radioactive release. Independent naval analysts note that the MoD has not said whether there was any contamination in this case; officials also indicated that, under the international INES scale, recent UK naval incidents have been assessed at the lowest level (Level 1).

Number of incidents at Faslane and Coolport

From 22 April 2024 to 22 April 2025, 1 Category A, 5 Category B, 29 Category C and 71 Category D incidents were recorded at Faslane. 13 Category C and 34 Category D incidents were recorded at nearby RNAD Coolport – a warhead storage and loading facility – in the same period, according to ministerial responses referenced by Sky. The MoD said no personnel or members of the public were harmed.

What officials and politicians are saying In a written response quoted by Sky News, Defence Secretary John Healy said the reported incidents were “classified as of low safety significance”, and were at Level 1 out of 7 significant safety incidents, according to the INES guidelines. The MoD added: “These “incidents posed no risk to the public and there was no radiological impact on the environment.” Scottish National Party leaders, including deputy leader Keith Brown, described the incident as “deeply concerning” and urged full transparency into what happened at Faslane.

Further investigation into recent reference

The revelation follows separate reports of a historic discharge of radioactive water** from a pipework failure into Loch Long from the nearby Coulport site last week, which Scotland’s environment regulator said was “not of any regulatory concern” but nevertheless exposed long-standing maintenance challenges. That series of episodes has intensified political and public attention to nuclear safety practices.

• **HMS Vengeance, the Royal Navy’s fourth and final Vanguard-class submarine, returns to HMNB Clyde after completing operational sea training in Scottish exercise areas. The ship carries Trident ballistic missiles, which form a key element of the UK’s nuclear deterrent.
  *(Tam McDonald/Wikimedia)*

Background: Previous serious incidents

Campaign groups and investigators have documented previous serious incidents at HMNB Clyde, including the 2023 Category A incidents and the barge-related spill in the River Clyde in 2008, stressing that such incidents are rare, but not unprecedented.

Analysis: Risk, assurance and transparency gaps

The MoD’s position – that the incident was of low safety significance with no radiological impact – is consistent with a conservative nuclear safety regime where near misses, equipment anomalies or procedural defects are recorded at low INES levels yet trigger the highest internal categories if the potential for a release exists. From a safety-culture perspective, that’s reassuring: reporting and learning from failures, big and small, is the reason why critical systems remain secure.

However, the ambiguity surrounding Category A disclosures outside the time limit breeds distrust, particularly in Scotland where public sentiment is opposed to nuclear weapons and where recent maintenance disclosures at Coulport have undermined trust. The tension is structural: operational security limits what can be disclosed, but credibility depends on sufficient detail demonstrating that causes, corrective actions and lessons learned have been objectively, resourcefully and independently verified. A practical solution would be a revised incident summary that outlines the initial cause, corrective actions and whether the incident was a near miss, a technical fault or involved an administrative/procedural breach.

• The 600-metre shiplift at HM Naval Base Clyde, located next to the Vanguard-class submarine jetty, is capable of lifting vessels weighing up to 28,000 tonnes for maintenance and inspection. (Greg Morse/Wikimedia)

What to look out for next

• Official summary: Is the Ministry of Defence publishing a summary of the Category A incident (with sensitive elements removed), including root cause and remedial action.
• Regulatory reporting: Any references to upcoming stakeholder or safety group reports for Faslane/Coolport covering the first half of 2025.
• Infrastructure investment signals: Evidence of accelerated maintenance or replacement programs at Clyde sites, particularly for older utilities and control systems, highlighted in recent reporting.”

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