Who might buy it?
Astute Submarines built for the Royal Navy cost in excess of £1 billion. Presumably and export version will cost more. Very few navies have this kind of money to chuck around. However growing powers like Brazil and India may represent a market.
If India purchased even a handful of these vessels it would be able to dominate the Indian Ocean. These boats are far more capable than anything the Russians, Chinese and Pakistani could offer in response.
Brazil has sought help from France and Russia as part of it's indigenous SSN program. At present the Brazilians claim the boat will not run on highly enriched Uranium. This will limit the boats power and will mean that it will be required to return to port every 5 years to refuel.
Australia is looking to acquire 12 submarines for a project cost of AUD 38 billion. These boats are to be conventional but with the capability of an SSN. At present the Australian government has ruled out an SSN to fit the bill however the capability they require seems very difficult with a SSK. As navy's such as China and India begin to deploy SSN's public opinion in Australia may shift more towards accepting nuclear submarines. AUD 38 billion would definitely cover a purchase of 12 Astute's.
Can we sell it?
International treaties do not prohibit the sale of SSN's between countries, nor the transfer of the technology it's self. For instance the US gave the UK Nuclear reactor technology in the 1950's. Russian has given technology in the past to China and supports current Chinese efforts to acquire modern SSN's. Russia is also supporting India and Brazil in their efforts to aquire SSN's.
(under the U.N. Arms Register and the Wassenaar Arrangement) are remarkably permissive, essentially allowing countries to make their own decisions on exports of diesel and even nuclear-powered submarines, with the only stipulation that they “declare” sales of larger submarines or those equipped with certain types of longer-range missiles. But no actual, international limitations exist.
The US participated heavily in the building of Astute unlike previous British SSN's. This was largely down to the fact that we had not built a nuclear boat in nearly 10 years and much of the design skill had been lost. Astute may be covered in the Technology transfer treaty we are trying to get the US to ratify at present. However for the moment the US has not ratified it and will likley not do so for several more years if ever. One thing would be clear though. The US would be unhappy about sales and would certainly refuse to cooperate with us in future on SSN design.
The main legal issue that would arise would actually be with the fuel for the boats. We could sell the boats and even the reactors however British and American submarines require nuclear fuel enriched to a level of above 90%. It's illegal for any state other than the 5 recognised nuclear weapons states to have uranium enriched to this level under the non proliferation treaty. However India is not a signatory to this treaty and obviously has the ability to enrich uranium for it's nuclear weapons. Brazil while maintaining it's not enriching uranium for its own SSN program is refusing to play ball with the IAEA so we can assume they probably have the ability to make there own HEU fuel. Australia has no uranium enrichment capability and will likely not pursue one.
Would we want to sell Astute?
The advantages of selling Astute would be two fold. It would represent a massive export industry for the UK. It would allow us to maintain our submarine industry well into the future when the Royal Navy is likley to begin building an astute replacement in the 2020's.
The US gave the UK SSN technology because it realised that on it's own it could not build enough boats to counter the Soviet Navy. Selling Our allies SSN's might allow us to better counter countries such as China in the future.
The disadvantages would be numerous. SSN's like Astute represent the pinnacle of human technology. With out platforms as good as these any potential adversary would find it immensely difficult to fight us. We have learned in the past during conflicts such as the Falklands and Iraq that a country who is our Allie today may not be in future and we have often found our own weapons being used against us in future conflicts.
It will take India, Brazil and even China decades to catch up with the US and UK in the field of SSN technology. Selling them these boast allows them to catch up over night. While they would buy the first generation from us you could bet that in 10 years time they would be building there own after ripping off our technology.
While India and Brazil may be able to enrich there own fuel it would be wrong for us to encourage proliferation. Even if technically it was not illegal.
However there is still one option available. Australia has the same treaty with the US as the UK does in relation to technology transfer. We can always be sure that in any future conflict Australia will be on our side our neutral so we are unlikely to find this technology used against us. It would help the RIMPAC nations counter the increasing threat of Chinese SSN's. The main issue we would face is the HEU fuel needed for the reactors. However we could easily come up with a compromise where by the Reactors themselves were owned by the Royal Navy and run and maintained by RN officers. This would also mean that Aussie boast would have to return to the UK for refueling and maintenance would would help us offset much of our costs for our own Astutes.
The other obstacle to over come is Australian public opinion. At present the Australian public is very anti nuclear. However the requirements that Australia has for a future SSN will be near on impossible to provide with an SSK. Australian public opinion may change if they begin to feel threatened by Chinese SSN's and Indonesians SSK's in waters they have previously considered to be Australian. If Australia does change there mind about SSN's we should be ready to help out.