Reactor safety figures for Navy’s Astute class submarines published

Nuclear reactors on board the Royal Navy's Astute class submarines have been involved in over twenty safety-related events over the last year, according to official figures released by the Ministry of Defence (MoD).

MoD's internal Defence Nuclear Safety Regulator (DNSR) has been formally notified of 69 nuclear safety incidents involving nuclear reactor plant that have taken place on board the submarines – the most up-to-date in the Navy's fleet – over the past four years.  21 of these incidents were recorded between 6 January 2015 and 6 January 2016 – the largest number for any single year within the four year period.

12 such incidents took place over the equivalent period for 2014-15; 20 in 2013-14; and 16 in 2012-13.  The figures cover events that took place both while submarines were at sea or docked at a shore-based berth.  Events with nuclear safety implications which did not involve submarine reactor plant, and non-nuclear health and safety incidents, are not included.

The information has been published by MoD in response to a request made under the Freedom of Information Act by a member of the public (available to download at the bottom of this article).

The figures relate to incidents reported as Naval Reactor Plant (NRP) 'events' or 'near misses'.  An NRP event is defined as “any occurrence that has, or could have, led to a reduction in nuclear or radiation safety or that provides and opportunity for Operator Experience Feedback (OEF)”.  A near miss is defined as “any occurrence that could have led to an NRP event, or that provides an opportunity for OEF”.

According to the response from MoD, all of the events were at the lowest level of severity on the International Nuclear and Radiological Event Scale (INES), corresponding to a level 0 rating (below scale / no safety significance).  As a result, no further action was taken by DNSR to follow up any incident.

The number of events recorded covers incidents for Astute class submarines that are both in build and in commission.  As the Astute class construction programme is still under way, the number of submarines is increasing, with a subsequent increase in related activities and operations which MoD suggests may be responsible for an increasing trend in nuclear safety events.


Download the full response from MoD here:


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