Twenty workers repairing a Trident nuclear weapons submarine at the Faslane naval base received unplanned doses of radiation because of a “prolonged and repeated failure” by Royal Navy personnel according to formerly unpublished documents obtained by Nuclear Information Service.
The documents, released under the Freedom of Information Act after a two year wait (available to download at the bottom of this article), reveal a number of dangerous 'control of work' failures which took place at HM Naval Base Clyde, home port for the Navy's Vanguard class fleet of Trident submarines, in 2012 and 2013. The Navy has been accused of downplaying the seriousness of the incidents.
In the most serious event twenty workers at the base received unplanned doses of radiation over a sixty hour period because a submarine reactor was undergoing trials at the same time as they were working in a nearby tank. The incident took place because there was a “lack of understanding of the magnitude of the hazards present when operating a reactor” among members of the submarine's crew responsible for nuclear safety.
In other cases submarine personnel failed to issue radiation dosimeters to non-ships staff working on board the submarine; a member of staff inadvertently took a radioactively contaminated item back to his office; and a Babcock employee received a dose of radiation when he inspected the wrong tank on a submarine.
The incidents were first mentioned in the small print of a site report published by the Office for Nuclear Regulation (ONR) in the spring of 2013. ONR took nearly two years to respond to a FOI request from NIS asking for more information, and details about the submarines involved and the exact nature of the operations underway have been redacted from the papers released (available to download at the bottom of this article).
The most significant incident took place in August 2012 when twenty workers received a low dose of ionising radiation when they were working in a tanks close to the submarine reactor at the same time as reactor trials were being conducted.
Despite the scale of the incident and clear evidence of a “lack of compliance” with safety arrangements, ONR decided merely to write to the Navy about the matter, rather than take any meaningful enforcement action.
A joint formal letter from ONR and the Ministry of Defence's Nuclear Safety Regulator was felt to be a “proportionate response, taking account of the work the base had undertaken since the event to address the issues” - even though further incidents relating to access to controlled areas had occurred. During a site inspection there was “insufficient work ongoing in the area visited to draw any firm conclusions on the effectiveness of the naval base arrangements” and further development of safety procedures “would not produce significant improvements”, according to ONR inspectors.
Until now, details of the incident have been successfully downplayed by the Navy. The event was mentioned obliquely in response to a Parliamentary Question asked by Scottish National Party MP Angus Robertson in October 2014, when it was blandly described as an “inadvertent radiation dose received by contractors while conducting submarine tank defect rectification work”. Nevertheless, the event was rated as a Category B nuclear safety event by the Navy, corresponding to unplanned exposure to radiation and a “major failure” in administrative controls or regulatory compliance.
The incident took place on 15-18 August 2012 when staff from the Faslane submarine base were working over a weekend to repair a leaking tank on a submarine that was preparing to set sail. At the same time trials were underway on the submarine's reactor, located near to the tank, and reactor power levels were higher than they would normally have been when such work was taking place. Because of confusion over results of a radiation survey – which had been conducted by a trainee - no controlled access area was set up to prevent workers receiving unplanned radiation doses. An internal Navy investigation report into the incident states that a requirement to complete further radiation surveys “was not met” and there was “a lack of appreciation” of the radiological protection controls which were needed.
Although the team leader for the workers in the tank “specifically queried the controls in place” he was “incorrectly assured” that dose rates within the tank were within acceptable limits. “There was a prolonged and repeated failure of the ships staff to understand and control the radiological hazard that they were creating”, the report says, leading to twenty different workers from the base who entered the tank receiving unplanned radiation doses over a period of around 60 hours. The estimated total dose received by the workers was 1.160 man milliSieverts – fortunately, a relatively low dose.
The report describes a catalogue of errors which led to the incident. The risk assessments for work on the tank did “not list radiation as a specific hazard” and the standing instructions for conducting the job did “not specifically consider radiation hazards”.
There was “no confidence” in the validity of data from a key radiation survey and a “lack of compliance” with an agreement to undertake further surveys. “Poor communication and lack of thought process” between submarine staff responsible for operating the reactor and staff monitoring radiation was a “major concern”. Involvement of the submarine's radiation safety officer in supervising the work was “minimal” as he was elsewhere undertaking his handover with the new medical officer.
The Faslane base Health and Safety department was not informed of the incident until 24 August – a week after it had happened – and the seriousness of the incident “was not relayed to the Duty Health Physics Officer at all”. Submarine staff were not interviewed as part of the subsequent investigation as the submarine had set sail immediately after the investigation commenced.
The investigation concluded that safety control measures “failed to sufficiently highlight the interrelation between the [reactor] trial and the tank work”. Workers in the tank did “not recall their safety briefs”; local safety briefs from the Navy sponsor on board the submarine were “cursory or non-existent”; and the submarine's staff “failed to identify the need to carry out radiation surveys within the tank”. Daily and weekly planning meetings on board the submarine “should have prevented any work progressing” in the tank while the reactor trial was underway, but failed to do so.
The investigation report recommended further training for the submarine's engineering staff which “must include the importance of complying with written procedures and statutory requirements”.
Despite a further recommendation that “consideration be given to reviewing the procedure for granting access into open tanks” on board submarines, and if necessary prohibit entry to tanks, a second incident took place just before Christmas 2013 when a Babcock employee removed grilles from the tank of a submarine in the Faslane shiplift building and “stuck his head inside the tank for a few minutes”. The employee had removed the grilles from the wrong tanks and as a result received an unplanned dose of radiation. The report on the incident – which was not made until 7 January – observes that “there was a human error which caused an unplanned extra exposure” and “a control of work issue in how he came to remove the wrong grilles.
The incidents followed an earlier event which took place in April 2012 at the Explosives Handling Jetty at the Coulport nuclear weapons store, when members of the Navy's Flag Officer Sea Training team were allowed to visit the submarine and enter a radiation exclusion zone without being issued with dosimeters. The submarine's Quartermaster “failed to understand” a requirement to issue dosimeters to all non-ships staff visiting the submarine despite having been given “specific and directed training” in the necessary procedures.
In a further incident revealed in the FOI papers, which took place in February 2013, a sailor working on a submarine returned to his office with a “sponge bung” without having checked it for contamination. The bung was found to have been contaminated with radioactivity and required disposal as active radioactive waste. The sailor was checked for contamination but found to be clear, and his office, his work site on the submarine and the route between the two were also checked and found to be clear.