A navy nuclear submarine reactor is very different from the nuclear power plants used to generate electricity on land. Naval reactors are designed to be compact so that they can fit inside the hull of a submarine. The reactor is used to heat water, which turns to steam and powers the submarine’s turbines.

In addition to being more powerful than traditional steam turbine propulsion systems on power to weight ratio, pressurized water reactors are more efficient.


A pressurized water reactor can run at higher speeds for longer periods of time than a conventional water reactor and not damage the engine. Pressure vessels have a lower failure rate than steam turbines, with a single major failure occurring about every 10,000 cycles. But there are inherent risks to wildlife and sailors crewing such vessels. Not to mention the cost of decommissioning and storing the radioactive waste. Much of which ends up at the bottom of the ocean, sometimes by design, as when Brazil deliberately scuttled the aircraft carrier Sao Paulo in the Atlantic in February 2023. Russia is worse, sinking nuclear submarines in the Kara and Norwegian seas.




The alternative to nuclear power, hydrogen powered steam turbines are held to be too bulky, though ideal as replacements to coal fired steam driven energy generation. Hydrogen-Fired Steam Generation is a pending technology capable of driving megawatt-scale steam-turbine generator sets in commercial power plants, generating steam directly from the combustion of a fuel-mix composed of hydrogen and oxygen gases in stoichiometric proportion The intense heat generated is used to vaporize the water-flow necessary to drive the turbine, creating electricity as it turns the generator set. A brief overview of the technology, and the history of its development can be found here.

The only product of combustion is pure, virgin water, used directly in powering the turbine. There is no smokestack required, as there are no emissions of any kind, toxic or otherwise. In a typical Rankine Cycle power plant, the combustion of hydrogen-oxygen fuel-mix adds approximately 20% of the total water flow to the system on each pass.

While fuel-cell technology holds promise as a component in an energy storage and retrieval system for use in automobiles, homes and even some small business operations, its efficacy in a gigawatt-scale power plant is questionable at this time. Hydrogen-fired steam generation is the only technology available worldwide, capable of generating gigawatt-scale electric power from energy stored in the form of hydrogen and oxygen gases.

Steam turbines typically last between 20 and 30 years, whereas pressurized water reactor typically last between 30 and 50 years. Pressure-sensitive water reactors have a number of disadvantages in addition to needing a lot of water to operate. It is especially difficult for submarines, which must dive continuously underwater. Despite these disadvantages, pressurized water reactor (PWR) nuclear power plants continue to be the most common type of reactor around the world. They are also the most common type of nuclear power plant used in commercial power plants, as well as being used in almost all large naval nuclear missile vessels.


Because nuclear power is typically produced in relatively small quantities, the majority of their power comes from highly enriched uranium (>20% U-235, originally 95%, but with an increasingly likely 97% in recent US submarine models), as well as 25% of some western vessels, 20% in the first and second. This is highly classified information.

If you know how much fuel is required and can estimate the heat transfer area of the reactor, you should be able to provide a good idea of its power. Most of this material has a confidentiality or nondisclosure agreement in place. They can tell you about the general science behind everything, but they can’t go into specifics about fuel loading, enrichment, or material properties, without revealing performance statistics, though this can be reverse engineered by calculating drag and rated top speed.

The Rolls-Royce 'Pressurised Water Reactor' (PWR) series has powered the Royal Navy's nuclear submarines since the Valiant class, commissioned in 1966.

The United Kingdom's first nuclear-powered submarine HMS Dreadnought was commissioned in 1963 powered by a Westinghouse S5W reactor, provided to Britain under the 1958 US-UK Mutual Defence Agreement.


The first British naval reactor was the PWR1. It was based on a core and reactor assembly of purely British design. The reactor first went critical in 1965, four years later than planned. Technology transfers under the US-UK Mutual Defence Agreement eventually made Rolls-Royce entirely self-sufficient in reactor design in exchange for a "considerable amount" of information regarding submarine design and quietening techniques being passed on to the United States.

The reactor fuel was highly enriched uranium (HEU) enriched to between 93% and 97%. Each nuclear core had a life of about 10 years, so had to be refueled about twice during the lifetime of a submarine.

Rolls-Royce Marine Power Operations at Derby was the centre for design and manufacture of the UK's submarine reactors, and remains so today. The Ministry of Defence's Vulcan Nuclear Reactor Testing Establishment (NRTE), at Dounreay, tested each reactor core design prior to its installation in nuclear submarines.


The PWR2 was developed for the Vanguard-class Trident missile submarines and is a development of the PWR1. The first PWR2 reactor was completed in 1985 with testing beginning in August 1987 at the Vulcan Naval Reactor Test Establishment.

The reactor fuel is highly enriched uranium (HEU) enriched to between 93% and 97%. The latest PWR2 reactor core design is "Core H", which has a life of about 30 years removing the need for refueling, allowing a submarine to avoid two reactor refits in its service life. HMS Vanguard was fitted with the new core during its refit, followed by her three sister boats. The Astute-class submarines have this full-life core installed. As they were developed for SSBNs, the reactors are considerably larger than those of then-current British fleet submarines. The diameter of then-forthcoming Astute-class hulls was therefore increased to accommodate the PWR2.

A safety assessment of the PWR2 design by the Defence Nuclear Safety Regulator in November 2009 was released under a Freedom of Information request in March 2011. The regulator identified two major areas where UK practice fell significantly short of comparable good practice: loss-of-coolant accident and control of submarine depth following emergency reactor shutdown. The regulator concluded that PWR2 was "potentially vulnerable to a structural failure of the primary circuit", which was a failure mode with significant safety hazards to crew and the public.

In January 2012 radiation was detected in the PWR2 test reactor's coolant water, caused by a microscopic breach in fuel cladding. This discovery led to HMS Vanguard being refueled early and contingency measures being applied to other Vanguard and Astute-class submarines, at a cost of £270 million. This was not revealed to the public until 2014.

In February 2013, the Ministry of Defence (MoD) awarded Rolls-Royce a £800 million ten year "foundation" contract to "deliver and maintain" the reactors of the Astute-class and the Vanguard-class replacement the Successor. In February 2019, the MoD awarded Rolls-Royce a £235 million three year contract for Nuclear Propulsion Lifetime Management for the Trafalgar, Vanguard and Astute classes.


Three propulsion options were considered for the replacement of the Vanguard-class, the Successor: PWR2, PWR2b (derivative with improved performance) and PWR3. PWR3 was a new system "based on a US design but using UK reactor technology". The Royal Institution of Naval Architects reported that it was likely that the UK was given access to the US Navy S9G reactor design used in their Virginia-class submarines. The PWR3 was a simpler and safer design with a longer life and lower maintenance requirements than the PWR2 variants and cost roughly the same as the PWR2b. The PWR3 has 30% fewer parts compared to the PWR2.

In March 2011, Defence Secretary Liam Fox said the PWR3 was the preferred option "because those reactors give us a better safety outlook". In May 2011, the Ministry of Defence announced that PWR3 had been selected for the Successor (later named the Dreadnought-class in 2016). The PWR3 cost about £50 million more per boat to purchase and operate compared to PWR2 designs. This is offset by the PWR3's longer life over the 25-year life PWR2 designs. The PWR3 does not require reactor core prototype tests; instead computational modelling is used. Consequently, the Vulcan Nuclear Reactor Testing Establishment operated by Rolls-Royce closed in 2015.

In June 2012, the MoD awarded Rolls-Royce a £600 million contract to produce reactors for the Dreadnought-class and also for the final boat of the Astute-class HMS Agincourt. The MoD also awarded Rolls-Royce £600 to refurbish their Rolls-Royce Marine Power Operations reactor core manufacturing plant at Derby to manufacture the PWR3 and to extend the plant's operational life to 2056. In January 2020, the National Audit Office reported that the construction of the plant was five years behind schedule and was now forecast to be in service in 2026.


Under the AUKUS pact, the US will share nuclear propulsion technology with Australia the same as it has with the UK since 1958 under the US–UK Mutual Defence Agreement as will the UK. The Royal Australian Navy will acquire at least eight nuclear-powered submarines armed with conventional weapons to be built in Australia. The basic design and key technologies will be decided by the Nuclear-Powered Submarine Task Force an 18-month Department of Defence research project headed by Vice Admiral Jonathan Mead, begun in September 2021 with assistance from the US and UK.


The Nuclear Nonproliferation Treaty allows non-nuclear-weapon states to produce the highly enriched uranium for naval reactor fuel. Nevertheless, the agreement to transfer US or UK nuclear submarine technology including possibly highly enriched uranium has been described as an act of nuclear proliferation, and has been criticised by scholars and politicians. In the Bulletin of the Atomic Scientists, scholar Sébastien Philippe criticised AUKUS and wrote "we can now expect the proliferation of very sensitive military nuclear technology in the coming years, with literally tons of new nuclear materials under loose or no international safeguards." James M. Acton of the Carnegie Endowment for International Peace wrote that "the nonproliferation implications of the AUKUS submarine deal are both negative and serious. For Australia to operate nuclear-powered submarines, it will have to become the first non-nuclear-weapon state to exercise a loophole that allows it to remove nuclear material from the inspection system of the International Atomic Energy Agency. I have no real concerns that Australia will misuse this material itself, but I am concerned that this removal will set a damaging precedent. In the future, would-be proliferators could use naval reactor programs as cover for the development of nuclear weapons."

Australia and Brazil would be the first countries without nuclear weapons to have nuclear-powered submarines. Concerns were raised that this may lead to increased risk of arms proliferation if other countries follow the same approach because it would involve other countries enriching uranium for naval reactors, potentially creating more avenues to develop material needed for nuclear weapons without the safeguards provided by regular inspections. This would not apply in the case of Brazil because the reactor will use low enriched uranium at 7% concentration. 20% is the minimum level required to make a nuclear weapon.

This makes a good argument or taking out Russia and China. To stop them forcing AUKUS pushing forward the technology. It's a tinderbox waiting to ignite. Giving rise to the Terramentals.




Astute class submarine, British Royal Navy







The Astute class of nuclear powered submarine, is a British Royal Navy series of vessels designed and built by BAE systems in the United Kingdom. In this fictional John Storm series of ocean awareness adventures, one of these submarines, SSN Neptune, is stolen and used by climate extremists, called Terramentals, to protest the continued use of fossil fuels. The anti global warming terrorists plan to steal US and Soviet submarines, as part of their agenda to prove the futility of all out thermonuclear annihilation, arming themselves to destroy more oil rigs, in the process.





Alvin DSV - Woods Hole Oceanographic Institution

AUKUS - Trilateral nuclear proliferation submarine pact, Australia, UK, US

HMS Astute 1st of Class BAE Systems

HMS Vanguard- Trident

INS Sindhurakshak - explosion & sinking

Lusitania - Torpedo attack

Nuclear PWR reactors for submarines

Nuclear submarines lost at sea

Predator - Covert submarine hunter/killer

Seawolf - Autonomous wolf pack deployment of Predator mini-subs

SSN Neptune - Astute class nuclear submarines

Torpedoes - UUV anti submarine weapons

U20 - Kapitan Lieutenant Walther Schwieger

U530 & U997 - Kriegsmarine Unterseeboots WWII

U534 - U-Boat sunk near Anholt, Denmark 1945, raised (no gold)

U986 - U-Boat declared missing in 20 April 1944 VIIC

USS Bluefish WWI submarine

USS Bluefish - Nuclear submarine

USS Flying Fish - Nuclear sub

USS Jimmy Carter - Seawolf class fast attack nuclear submarine

USS Nautilus - 1st nuclear submarine & subsea north pole passage

USS Scorpion - Skipjack class submarine 99 crew lost at sea













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In this fictional story, the characters and events are the product of the author's imagination.