The UK Royal Navy is planning to replace a dangerous type of reactor, the PWR2 installed on its existing nuclear submarines, with a safer the PWR3 option.
The replacement has become essential as the reactors are potentially lethal and could lead to multiple fatalities among submarine crews whilst also failing to meet modern safety standards.
The PWR2, which shares similar features of the nuclear reactors involved in the Japan Fukushima Dai Ichi disaster, are used in the four Trident submarines as well as six Trafalgar Class and seven Astute Class submarines.
The PWR3, unlike the PWR2, uses passive cooling, making it less dependent on back-up power with additional methods of injecting coolant into a reactor.
The safer reactor is currently used in modern US nuclear submarines and the replacement would cost the UK Ministry of Defence a further £261m, according to the Guardian.