Nuclear attack submarines HMS Tireless and Turbulent are both reported to have taken to sea with a potentially disastrous defect. Safety valves to release steam in an emergency were sealed off which means of course if there was such an emergency the build up of pressure could have led to a very serious accident and a leak of radioactivity. The valves were sealed for maintenance work but were not removed before the submarines returned to sea. Both submarines were in service for over a year (more than 2 in Turbulent's case) before the problem was detected. Poor discipline at Devonport is blamed. There has now been a shake-up of safety procedures the MOD claim.