Early reports on Plymouth local radio on 13 October said that the nuclear powered hunter/killer submarine HMS TRENCHANT S91(Trafalgar Class) had ‘broken down’ off the coast of Portugal. First reports said there had been a problem with the propulsion unit (reactor) and that the crew (110) had been taken off the submarine while checks were carried out. It was not clear if the submarine was submerged or on the surface when the incident occurred.
A later report said the submarine was off Lisbon when the problem was detected, that the reactor was not running at the time and that most of the crew (130 this time) were on shore leave when the problem occurred. A report in the evening news confirmed that a small amount of ‘steam’ had escaped from the reactors cooling system which had been contained. It did not say if the steam was from the primary or secondary system. There was reported to be no radiological hazard and a team of engineers had been sent out from Devonport Naval Base (home port to the Second Submarine Squadron).
This is the second coolant failure incident in the last 12 months. In November 1997, HMS TURBULENT limped back to Devonport with a suspected coolant escape. All 130 and several dockyard workers were tested for radioactive contamination. HMS TRENCHANT was reported out on patrol on 3rd September 1998.
TRENCHANT returned to Devonport under its own power on 20 October.