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British Fleet Submarines (SSN)

The SSN (Ship Submersible Nuclear), or Fleet Submarines contribute to peace and security by providing a conventional deterrence to anyone or nation that may pose a threat to world stability. They combine qualities of stealth, endurance and flexibility. These characteristics afford the SSN an unparalleled freedom to operate world-wide, SSNs can act independently or in support of a surface ship task group and or land operations. The SSNs of the Swiftsure and Trafalgar Class are extremely sophisticated, deep diving, high-speed submarines, capable of fulfilling a range of maritime military tasks undreamed of by the strategists of previous generations.

Submarines contribute to peace and security by providing a conventional deterrent to anyone or any nation that may pose a threat to world stability. They combine qualities of stealth, endurance and flexibility. These characteristics afford the submarine an unparalleled freedom to operate world-wide, acting independently or in support of a surface shipor land operations. Modern nuclear submarines can travel at speeds in excess of 25 miles per hour (40 kilometers per hour) and can maintain this speed indefinitely, so allowing the submarine the ability to go anywhere in the world quickly and quietly. Submarines can dive to depths in excess of 250 meters. The actual depth is classified information. Nuclear submarines are able to produce their own indefinite supply of air, water and power for driving the submarine forward. Its only limitation for staying submerged is the amount of food on board, or if they sustain a major defect.

The Tomahawk Land Attack Cruise Missile (TLAM) is in service and was fired from HMS SPLENDID in the Kosovo conflict in 1999. This weapon allows the SSN to influence the land battle by posing a threat in the period prior to hostilities and, after hostilities commence, the use of highly accurate and lethal warhead against important targets which may otherwise be relatively invulnerable.

Arguably the most important role of the submarine, the SSN has an unrivalled capability to seek out and destroy other submarines that may pose a threat to any friendly force. The SSN also has a well-proven capability to detect and attack surface forces. The spearfish torpedo can be used against other submarines or surface ships. This capabilities can be used when the SSN is acting independently or in support of a task force. The SSN is used to great effect when the submarine is deployed in advance of friendly forces in order to reduce the flexibility of an opposition force by denying the use of an area or region. This is known as regional sea denial.

The ability to approach close to oppositions forces and monitor their operations and movements whilst remaining undetected is a classic capability of the submarine. This surveillance can include underwater photography, sometimes of surface warships, who will almost certainly be unaware of the submarine's presence.

Using modern video technology or digital photography a submarine, able to approach a coastline in shallow water, can make a significant contribution to the intelligence collection effort prior to any subsequent maritime or land action.

In a pressurized water nuclear reactor, nuclear heat from uranium oxide fuel elements heats water to 300 degrees centigrade. In order to localise the radioactivity, this 'primary' water is pumped through steel tubes so as to heat 'secondary' water in boilers so that steam is generated which drives turbines. Steel is prone to cracking both in manufacture and throughout the working life of highly stressed steel components like the reactor pressure vessel (RPV). All except one of the British 'hunter killer' nuclear submarines, which use pressurized water nuclear power for their propulsion, were in the news because of the need for repairs of serious cracks in their pipework. During operation an enormous amount of energy is stored in the 'primary' hot water. If the RPV ever became weakened sufficiently for it to burst while working then the most dreadful accident would ensue.

Submarine reactors work on the same principles as the larger ones used on land in nuclear power stations. However submarine reactors are built-in, sealed units that contain enough uranium fuel rods to last for ten years or more. The longer period a fuel rod is in a reactor, the more radioactive it becomes. Thus the core of a submarine reactor that is close to refit/replacement date will be extremely radioactive.

In April 2009 a report revealed that Britain's submarine fleet had been hit by a series of safety breaches involving repeated leaks of radioactive waste into the Firth of Clyde and broken pipes and waste tanks at its home base at Faslane. The discharges into the Gareloch had no measurable or quantifiable environmental consequences. There has never been a significant accidental discharge of radioactive material to the environment from a Royal Navy nuclear submarine in the Clyde. A total of more than 40 radioactive leaks have acknowledged at HM Naval Base Clyde at Faslane, near Glasgow, the home port for British nuclear-powered and nuclear-armed submarines, over the last three decades. At least eight liquid radioactive leaks into the sea loch over the past 10 years from radioactive waste storage facilities were made public on 27 April 2009 following an investigation carried out by Channel Four News. The worst breaches include three leaks of radioactive coolant from nuclear submarines in 2004, 2007 and 2008 into the Firth of Clyde.

Safety is a top priority for submarines. The submarine is designed and operated to ensure that the crew, the public, and the environment are protected from the risks of radiation. The ship is designed with "shielding" around the reactor to reduce radiation levels. Radiation levels are very low, so much so that a submariner gets less radiation at sea than a person on a beach receiving radiation from the sun and other natural sources.

Conventionally powered submarines were disposed of either by selling them to other friendly nations or byscrapping. Nuclear powered submarines are disposed of by taking them to a port where there are facilities to remove all the equipment that can be re-used. After the removal of all non-essential equipment, the submarine is monitored to ensure that the nuclear power plant is still safe and that there are no harmful emissions. This monitoring will continue until it is decided that the nuclear fuel is safe tobe removed and disposed of safely.

The records of fire incidents onboard UK nuclear submarines are not held centrally prior to 1 January 1987. Since this date the Royal Navy records provide the following information: 213 small scale fires, that are categorised as a localised fire such as a minor electrical fault creating smoke dealt with quickly and effectively using minimal onboard resources; 21 medium scale fires that were generally categorised as a localised fire such as a failure of mechanical equipment creating smoke and flame requiring use of significant onboard resources; Three fires occurred while the submarines involved were in naval bases, requiring both ship and external resources.

The Royal Navy has no records of collisions between nuclear powered submarines and other submarines and naval vessels, other than the incident involving HMS Vanguard and the French submarine Le Triomphant. The full list of incidents of collisions and groundings involving Royal Navy nuclear powered submarines for which the Royal Navy holds records is as follows:

  1. HMS Astute grounded off the Isle of Skye in October 2010.
  2. HMS Torbay grounded in the Eastern Mediterranean in April 2009.
  3. HMS Vanguard collided with FS Le Triomphant in February 2009.
  4. HMS Superb grounding in the Red Sea in May 2008.
  5. HMS Tireless struck an iceberg while on Arctic Patrol in May 2003.
  6. HMS Trafalgar grounded on Fladda-chuain in November 2002.
  7. HMS Triumph grounded in November 2000.
  8. HMS Victorious grounded, while surfaced, on Skelmorlie Bank in November 2000.
  9. HMS Trenchant grounded off the coast of Australia in July 1997.
  10. HMS Repulse grounded in the North Channel in July 1996.
  11. HMS Trafalgar grounded off the Isle of Skye in July 1996.
  12. HMS Valliant grounded in the North Norwegian Sea in March 1991.
  13. HMS Trenchant snagged the fishing vessel Antares in the Arran Trench in November 1990.
  14. HMS Spartan grounded west of Scotland in October 1989.
  15. HMS Sceptre snagged the fishing vessel Scotia in November 1989.
  16. HMS Conqueror collided with the yacht Dalriada off the Northern Irish coast in July 1988.

All the vessels, apart from HMS Superb, which was decommissioned in October 2008, were repaired and returned to service. The older nuclear-powered submarines of the Valiant / Churchill classes were prematurely withdrawn from service as a result of serious cracking in the primary cooling circuits of their nuclear reactors. The Swiftsure class have similar power plants and experienced similar problems. One, HMS Swiftsure, has been decommissioned for this reason.

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Page last modified: 22-10-2016 16:11:01 ZULU