Nuclear Icebreaker Reactor – At the Heart of Arihant Class Submarines

 

Recently, India won a deal to build 4 non-nuclear icebreaker ships estimated to be worth over Rs 6,000 crores for Russia. Russia’s state-owned nuclear energy company ROSATOM will seek “favorable and capable yards” in India to construct the ships to support its Northern Sea Route (NSR) development plan in the face of sanctions imposed by the USA and other countries.

This brings to notice the nuclear icebreakers operated by Russia, the only nation to do so in the world. So why are we talking about nuclear icebreakers? It is because of the nuclear reactors in them that have been used in the Arihant class SSBNs of the Indian Navy. Many may not be aware that Russia provided the nuclear reactors of its nuclear icebreakers to be developed into reactors for S1/half-boat, S2/Arihant, S3/Arighaat, S4/Aridhaman, and the supposed S4*. Kindly note USA, the Soviet Union/Russia, China, France, and Britain hold nuclear reactor technology very dear to heart, and won’t share it with anyone just like the fighter jet engine technology. Although the main reason to not share the nuclear technologies is them being part of NPT and CTBT.

However, unlike others, Russia has operated nuclear-powered icebreakers since the 1950s. So, when India through BARC requested Russia to provide it with nuclear technology for use in its nuclear-powered submarines, Russia readily provided access to nuclear reactors of the ice breakers. This brings to question, access to which type of nuclear reactor onboard the nuclear ice breaker did Russia provide India.

In all sense and purpose, it is the nuclear reactor aboard the 1^st ever nuclear ice breaker Lenin, an experimental 16,000 tonne, 134-meter-long icebreaker commissioned in 1957 and operated by the Soviet Union/Russia from 1959 to 1989. Since decommissioned, the icebreaker has been converted into a museum ship. The ice breaker Lenin used OK 150 nuclear reactors till 1970 and then OK-900 nuclear reactors till the ice breaker was decommissioned in 1989.  Do note that work on the nuclear reactor by BARC started sometime in 1996 and it went critical onboard the S1/half boat in 2003.

OK 150/OK 900 nuclear reactor specification

The OK-150 reactor (1st generation) and its successor, the OK-900 reactor (2nd generation) are Soviet marine nuclear reactors used to power Russian nuclear-powered icebreaker ships. They are pressurized water reactors (PWRs) that use enriched uranium-235 fuel. The reactor was developed by OKBM.

1. OK-150 specifications

Nuclear Fuel: 5% enriched uranium in the form of ceramic uranium dioxide (UO

2) fuel elements with a cladding. Different cladding materials were used; initially zirconium, and later on, stainless steel as well as a zirconium-niobium alloy were tried.

Fuel load: 75 to 85 kilograms

Power production: 90 megawatts

Distilled water was used for heat transfer and as a moderator. The core was 1.6 m high by 1 m diameter. It consisted of 219 fuel assemblies, totaling 7,704 fuel pins. There was a biological shield made of concrete mixed with metal shavings.

2. OK-900A specifications:

Fuel: 90% enriched uranium in the form of metallic uranium-zirconium alloy fuel elements

Fuel load: 150.7 kg

Power production: 171 megawatts

Three OK-150s were used to power the Soviet icebreaker Lenin at the time of its launch in 1957. Later, after damage caused by nuclear accidents in 1965 and 1967, these were removed and replaced with two OK-900s.

BARC’s Work on S1/half boat Reactor

BARC got a chance to closely observe and study both the OK 150 and OK 900 nuclear reactors. BARC kept the nuclear power generation at 90 MW from OK 150 but enriched the uranium to over 90% from OK 900 and developed its own version of the nuclear reactor and miniaturized the design to fit it inside S1/half boat, a 42-metre (138 ft) section of the submarine's pressure hull that contains the shielding tank with water, reactor, control room, auxiliary control room for monitoring safety parameters. The S1/half boat incidentally is still operational at BARC Kalpakkam. Many may say that S1/half boat or S2/Arihant are powered by 83 MW nuclear reactors only.

Truth is the nuclear reactor for S1/half-boat, S2/Arihant, S3/Arighaat, and S4/Aridhaman, and the supposed S4* is at least 89 MW just 1 MW short of OK 150s specification but only 83 MW has been stated. This may have been a case of understating the actual power (something India does with missile power) to ensure any avoidable issue due to the fact that OK 150 was a nuclear reactor used in nuclear ice breaker but BARC modified it and developed a compact version to fit inside a submarine hull. Also, the loss of 1 MW of power may have been due to miniaturization efforts.

This is evident from the fact that both S2/Arihant and S3/Arighaat are 6000-ton SSBNs but S4/Aridhaman and the supposed S4* both will be 7000-ton SSBN means 1000 tons heavier. This means these 2 submarines will require additional power, but there are no reports as such that the power of S4/Aridhaman, and the supposed S4* has been increased. It means they will have the same power as S2/Arihant, and S3/Arighaat 6000-ton SSBNs. If that happens; it means the S4/Aridhaman, and the supposed S4* will be underpowered. Is that even possible? No, this clearly means that the 7000-ton S4/Aridhaman, and the supposed S4* both are powered by at least an 89 MW nuclear reactor, which also means that S1/half-boat, S2/Arihant, S3/Arighaat all have 89 MW nuclear reactor in reality.

This also means that BARC has reworked the OK-900 nuclear reactor of ice breaker Lenin and modified it to generate 190 MW power and has all the schematics ready to fit that nuclear reactor inside the S5 class/13000-ton SSBN. That same reactor incidentally will also be used in the 6000-ton P75A class SSNs that are still supposedly on the drawing board. It proves that the only true friend that India has in the global scenario is Russia, but unfortunately in its eagerness to please the Western world, India isn’t standing in support of Russia. I just hope this situation changes as soon as possible.