It has emerged during routine maintenance work on two of the UK’s six remainingTrafalgar-class attack submarines – Turbulent and Tireless – that equipment that blocked hull valves , used during during earlier maintenance to test hull pressure for leaks – was not removed after the tests. The purpose of the valves is to allow an build up of excess pressure in the ship’s nuclear reactor, to vent. Obviously, with the blocks left in place, venting is impossible and excess pressure could then lead to radioactive water bursting into the manned areas of the ship.

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