Engineering news
Unexpected and unexplained failures in the core of a prototype nuclear reactor on test at Dounreay will result in costly refits to Britain's nuclear submarine fleet.
The test reactor – the same basic design as those used in Vanguard and Asute-class vessels – has been running since 2002. The discovery in January 2012 of radioactivity in the water around the core, believed to have been caused by tiny holes in the cooling jacket, has led to the Ministry of Defence ordering the refuelling of HMS Vanguard, the oldest Vanguard-class submarine in service, at a cost of £120 million.
Defence secretary Philip Hammond said: “We now believe that this is due to a microscopic breach in a small area of the metal cladding that surrounds one fuel element within the core of the reactor. It is not yet clear why this breach has occurred. It may be related to the age of the reactor; it may be a function of the high intensity use to which we have subjected the test reactor; or it may be a random event. We do not yet know.”
Dounreay is on the north coast of Caithness, in the Scottish Highlands. Since the 1950s it has been the site of several nuclear research establishments, including a prototype fast breeder reactor, as well as the test site for submarine reactors. Most of these facilities are now being decommissioned. The site is operated by the United Kingdom Atomic Energy Authority (UKAEA) and has five reactors, three operated by UKAEA and two by the MoD.
According to the MoD, Vanguard was the first in the submarines of her class to be launched. She also carried out the first Trident missile test firing in May 1994, and was also the first of the class to undergo her major mid-life refit, from 2002 to 2004, during which she was fitted with the new Core H reactor core, which was intended to provide the power to see her through the rest of her service life.
Hammond said that the level of radioactivity has been classified as “level 0 – no safety significance”, as measured on the UKAEA's scale, but he added that replacing the core was the “responsible” option and would be done as a precaution from 2015 during Vanguard's next period of scheduled service, which is expected to last for three-and-a-half years.
A decision on whether to refuel the next oldest submarine, HMS Victorious, would not need to be taken until 2018. To ensure that Britain could carry out the task, £150 million would be spent on ensuring the capability existed to refuel existing Vanguard-class submarines, entailing investments at the Devonport Royal Dockyard and the reactor plant at Raynesway.