On his recent visit to France, India’s chief of naval staff, Admiral Sunil Lanba, was given a detailed presentation by his French hosts on the Barracuda-class, its latest nuclear-powered attack submarine (SSN), the first of which is expected to be commissioned next year into the French navy. This assumes importance for a number of reasons. India plans to make six SSNs apart from nuclear-powered ballistic missile submarines (SSBNs), the first of which—INS Arihant—is operational and the next in class, INS Aridhaman, has been launched recently. India is also looking to make conventional diesel-electric submarines (SSKs) under project P75I after the current programme to make six French Scorpène submarines, being constructed at Mazagon Docks.

This is where the potential of exploring the Barracuda lies. The French are developing two versions of the Barracuda—nuclear-powered for its navy and diesel electric for Australia, after winning a $50 billion contract for 12 boats named Shortfin Barracuda. As India is looking to make both conventional and nuclear attack submarines, the design commonality offered by the Barracuda will help keep construction, operational, maintenance and training costs low.

The Barracuda is designed with pump-jet propulsion instead of the conventional propeller, which will make the submarine quieter than propeller-driven ones. The pump-jet-propelled submarines are also faster and easily manoeuvrable. The conventional version of the Barracuda will have a vertical launch system to launch cruise missiles, a requirement for India’s P75I.

What is, however, more interesting is that India has asked France if it will be willing to help with the nuclear reactor technology. The French appear to be inclined. There is no law prohibiting cooperation on naval nuclear reactors (NNRs) which allowed India to lease the Russian Akula class nuclear attack submarine which is currently in operation with the Indian Navy.

If India is indeed seriously looking at the French NNR, it will mark a move from the highly enriched uranium (HEU) core that powers the Arihant-class SSBN to the low-enriched uranium (LEU) core that powers the French nuclear submarines. India uses 40% HEU while France uses 5-7% LEU for its Rubis-class SSN, Triomphant-class SSBN and aircraft carrier Charles de Gaulle.

The reactor on INS Arihant produces about 83MW of power to propel the over 6,000-tonne submarine. However, a more powerful reactor will be required for future SSBNs, which will be substantially larger than the Arihant. The French K-15 reactor produces 150MW that propels the 12,000-tonne Triomphant-class submarine with 16 vertical launch tubes to launch the M51 submarine-launched ballistic missiles, similar to what India plans in boats succeeding the Arihant. The reactor on the Barracuda will be based on K-15, with suitable power adjustments.

Incidentally, India is also considering the use of nuclear propulsion for its future aircraft carriers. However, it is unlikely that the next one to be constructed will have nuclear propulsion considering the lack of an adequately powered nuclear reactor that is sufficiently miniaturized. France uses two K-15 reactors on its aircraft carrier.

India’s consideration of a shift to LEU reactors may be influenced by disarmament negotiations. The Fissile Material Cut-off Treaty (FMCT) particularly aims to ban production of HEU, which is uranium with over 20% enrichment, to stop nuclear weapons proliferation. India is committed to negotiate the treaty which has been stalled for the moment by Pakistan’s veto. If the FMCT comes into effect, it will prohibit the production of HEU that is used in India’s NNR, affecting its strategic requirements.

While the treaty doesn’t appear to be coming into force anytime soon, India might be looking to make its nuclear submarines future-proof by adopting LEU reactors. The adoption of LEU will save India the cost of expanding its HEU production facilities and leave the current stockpile and production capacity for making nuclear weapons to ensure minimum credible deterrence till the FMCT comes into force. The US, which uses a HEU core, has been mulling a shift to LEU to further its non-proliferation goals although it has sufficient stockpile of HEU for its navy.

The use of LEU has its challenges, especially the larger size of the core. France has been successful in sufficiently miniaturizing the LEU core. While the 93% HEU cores of US and UK submarines don’t require refuelling, LEU cores need to be refuelled at least twice in their lifetime. France has developed a fuel mix that gives a reasonably long core life of 7-10 years before refuelling. In fact, INS Arihant will also need refuelling in a process that will require cutting open the submarine hull and welding it back after refuelling. The process will take two to three years, affecting the availability of a critical strategic asset. France, on the other hand, uses secure hatches above the reactor which allows refuelling to take place in a matter of weeks, leading to greater availability.

France is India’s strategic partner and is regarded as a reliable supplier of weapons. India can look to France to provide consultancy on both conventional and nuclear attack submarines derived from the Barracuda project and acquire design and technologies to make LEU cores for its nuclear submarines. A sufficiently well-powered LEU core can also propel India’s future aircraft carriers.

Yusuf Unjhawala is the editor of Defence Forum India and a commentator on defence and strategic affairs.

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