India's Prototype Fast Thorium Breeder Reactor (PFTBR) - the 200-tonne safety vessel being lowered into the reactor vault at the Madras Atomic Power Station (MAPS) located at Kalpakkam about 80 kilometres (50 mi) south of Chennai, India
INTRODUCTION
“Safe enough for our back yard”
Electricity is a predominant input for the economic development of any country. In spite of the impressive strides in increasing overall installed capacity in the India, the country is still facing power shortages. Options available for commercial electricity generation are hydro, thermal, nuclear and renewable sources. In the energy planning of the country, a judicious mix of hydro, thermal, nuclear and renewable is an important aspect. Diversified energy resource-base is essential to meet electricity requirements and to ensure long-term energy security. With the limited resources of coal and oil available in India and the growing global concerns of greenhouse gases generated by fossil fuel fired stations, in the medium and long-term perspective nuclear power is designated to play a vital role. For a trillion dollar plus economy, like India, increase in the nuclear generation capacity is rational and an inevitable approach as it is environmentally benign, commercially viable and ensures the energy security of the country.
Current Scenario
Post Obama’s visit to India and the clearing of the nuclear deal between India and the US, a great amount of buzz has been generated on this issue. However, the focus has thus far been on using Uranium as a source of nuclear fuel and India getting access to this source of fuel besides the nuclear reactors.
A Sample of Thorium
A couple of years back when the nuclear deal was first proposed during the UPA government’s stint in power, scientists in India vehemently opposed placing its fast breeder reactor technology under the preview of international nuclear watch dogs and pressed for focusing on Thorium based Fast Breeder Reactor technology for the future.
However, the previous UPA government followed an unwritten policy of severely downsizing both the Fast Breeder Reactor (FBT) as well as the thorium-based technology program, thereby making India dependent on foreign countries for advanced nuclear technology, this is claimed by many key scientists on condition of anonymity.
Until 2005, Indian was at the forefront of thorium based research. It is also by far the most committed nation as far as the use of thorium fuel is concerned, and no other country has done as much neutron physics work on thorium as India. The country published about twice the number of papers on thorium as its nearest competitors during each of the years from 2002 to 2006.
Bhabha Atomic Research Centre (BARC) had the highest number of publications in the thorium area, across all research institutions in the world during the period 1982-2004. During this same period, India ranks an overall second behind the United States in the research output on Thorium. Analysis shows that majority of the authors involved in thorium research publications appear to be from India.
Illustration of a Molten salt Reactor
Research and development of thorium-based nuclear reactors, primarily the Liquid fluoride thorium reactor, (LFTR), MSR design, has been or is now being done in the U.S., U.K.,Germany, Brazil, India, China, France, the Czech Republic, Japan, Russia, Canada, Israel and the Netherlands.
According to Siegfried Hecker, a former director (1986–1997) of the Los Alamos National Laboratory in the U.S., "India has the most technically ambitious and innovative nuclear energy program in the world. The extent and functionality of its nuclear experimental facilities is matched only by Russia and is far ahead of the United States".
Back to circa 2015, India is back to counting on foreign suppliers for expensive Uranium fuel and reactors. And this is certainly the wrong direction taken by the policy makers on account of these following vital facts:
Thorium offers a form of energy that is stable, abundant, inexpensive, powerful, safe, continuous, domestically-sourced, non-polluting during both extraction and consumption, transportable, and for which India has at least a thousand-year reserve.
India's Research on Prototype Fast Thorium Breeder Reactor (PFTBR)
At present, there are no internal fertile blankets or fissile breeding zones in power reactors operating in the world. Thorium-based fuels and fuel cycles have been used in the past and are being developed in a few countries but are yet to be commercialized. However, BARC's Prototype Fast Thorium Breeder Reactor (PFTBR) is claimed to be the first design that truly exploits the concept of "breeding" in a reactor that uses thorium. The handful of Fast Breeder Reactors (FBRs) in the world today - including the one India is building in Kalpakkam near Chennai, use plutonium as fuel. These breeders have to wait until enough plutonium to be accumulated through reprocessing of spent fuel discharged by thermal power reactors that run on Uranium. In February 2014, BARC presented its latest design for a "next-generation nuclear reactor" that will burn thorium as its fuel. The target date to commission the system is envisioned for 2016 and it would be a completely automated design which means it would not require any operator to run the reactor for more than two months. The commissioning of PFTBR would make India the most advanced country in thorium research. The concept has won praise from nuclear experts elsewhere. According to former BARC Director P.K. Iyengar, this new design is one way of utilizing thorium and circumventing the delays in building plutonium for India's FBRs. (Text based on reports from Times of India, Circa 2007)
Switching from Uranium to Thorium
India has chalked out a three-stage program to reduce its reliance on imported uranium seeks to make more substantial use of thorium, of which India holds 25% of the world’s total reserves. Although Th-232 is not fissile, it will absorb slow neutrons to produce fissile U-233 when placed in a reactor. (See the sidebar "Now you’re cooking with Thorium" in "Developing the next generation of reactors," POWER, April 2008.) A thorium-powered reactor would be based on a closed fuel cycle.
The first stage consists of setting up pressurized heavy water reactors (PHWRs). Already 17 PHWRs with an installed capacity of 4,000 MW are in operation, and five reactors with an installed capacity of 2,660 MW are under construction. "The choice of PHWRs in the first stage is driven by the fact that in PHWRs, on account of the use of heavy water as moderator and on-power refueling, more neutrons are available to convert U-238 to Pu than in the case of Light Water Reactors (LWRs)," Anil Kakodkar, chair of India’s Atomic Energy Commission, said at a public lecture in Bangalore last year.
The second phase will start with the deployment of domestically designed fast breeder reactors (FBRs) fueled with mixed oxide, and then — when all "necessary technologies" have been developed and demonstrated — metallic fuel – based FBRs, Kakodkar said. These are expected to convert uranium – 238 into plutonium, increasing power generation to 300 GW for about 70 years.
The third stage will involve the gradual transition to thorium-based systems, likely through an advanced heavy water reactor (AHWR) being developed at the Mumbai-based Bhabha Atomic Research Center (BARC). The uranium-233 required for third-stage breeder reactors will be obtained by the irradiation of thorium in PHWRs and FBRs. "Studies indicate that once the FBR capacity reaches about 200 GW, thorium-based fuel can be introduced progressively in the FBRs to initiate the third stage, where U-233 bred in these reactors is to be used in the thorium-based reactors," Kakodkar said.
Construction of a 500-MWe prototype FBR — the first in India — is already in full swing at Kalpakkam, Tamil Nadu (Figure 10). All research and developmental work by the Indira Gandhi Centre for Atomic Research (IGCAR) has been completed on the R35 billion ($680 million) reactor. The project, a joint venture between Bharatiya Nabhikiya Vidyut Nigam, the Nuclear Power Corp. of India, and the IGCAR (which are all federal enterprises) — is expected to begin generating power sometime in 2010.
Types of thorium-based reactors
There are seven types of reactors that can be designed to use thorium as a nuclear fuel. The first five of these have all entered into operational service at some point. The last two are still conceptual, although currently in development by many countries:
- Heavy water reactors (PHWRs)
- High-temperature gas-cooled reactors (HTRs)
- Boiling (light) water reactors (BWRs)
- Pressurized (Light) water reactors (PWRs)
- Fast neutron reactors (FNRs)
- Molten salt reactors (MSRs, LFTRs)
Thorium is Stable (fertile, not fissile)
- Half life of 1.39x1010 years
- Stable in natural state
- Can be handled with care in solid form. Shavings or powder can self-combust in air.
- For energy purposes, we will be dealing with thorium as a liquid fluoride.
Thorium is Powerful
Thorium, by itself, is virtually non-radioactive. It must be bombarded by neutrons to jump-start it. The fissionable result is 233U, which gives off 198 MeV or 82.0 TJ/kg.
Per nucleus fission, the thorium fuel cycle is virtually as powerful as that of uranium.
Thorium is Abundant
- More common in the earth's crust than gold, mercury, tungsten, and tin.
- More plentiful than uranium by 3.73 times.
- Can be found in uranium mine tailings and coal power plant ash piles
- India has 319,000 tons of Thorium
Liquid Fluoride Thorium Reactor (LFTR)
- Allow for continuous feed for higher fuel utilization
- Simplify chemical separation
- Provides self-regulation, i.e. higher temperature expands liquid which dilutes concentration, which lowers neutron absorption and fission, which lowers temperature
- Make xenon gas removal easy, thereby maintaining high efficiency
- Can process today's nuclear waste materials
Fluorides
- Chemically stable
- Combine with fission products and transuranics
- High temperature operation brings high efficiency
- No water cooling, control rods, or elaboratecontainment facility needed
- Salt plug safety mechanism
- Very high percentage of a single isotope leads to single isotope fission, thereby a smaller set of fission products/waste.
- Thorium's high thermal neutron cross section (~90%) implies fewer higher mass actinides.
- Thorium fission products have less neutron absorption leading to significantly greater efficiency.
- Chemically separable on the fly from its fissile material (233U).
- Thorium fluoride has low water solubility.
Current Reactor Safety
- No spent fuel rods. instead molten fuel continuously consumed
- No melt down Instead passive cooling
- No water Instead molten salt for heat transfer and gas turbines for electricity generation
- No high pressure. Instead the reactor runs at high temperature, making the turbines more efficient
- No containment facility
- In the unlikely event of a fuel spill, the fuel turns solid.
- Low water soluble compounds, i.e. no ground water contamination if promptly addressed
- Overheated salt self-corrects itself to lower temperature
- Freeze plug for automatic and/or quick shutdown
- No water for steam explosion
- No O2 or other gases in the system to assist explosions
- Low pressure environment can't explode & spread fuel
- Must add fuel to keep reactor running
- No spent fuel stockpile to maintain/protect
- Radioactivity confined to reactor. chemical separators, 1st heat exchanger, & drain tank
Can Thorium be used directly for a bomb?
Thorium is naturally stable. It is no good for a bomb in its elemental state. It is also stable in fluorides and other compounds.
Could a LFTR reactor be used as a bomb?
If you could somehow overload the reactor, the temperature would rise, the freeze plug would melt, and the fluoride would flow to an external reservoir where it would solidify because the geometry would not support fission. You would need a LFTR like environment to unfreeze it and re-stimulate fission to an extreme
Can one take radioactive material out of a LFTR and use it for a dirty bomb?
Yes, but these materials are extremely hot and giving off gamma rays that, nearby, could disable all electronics and kill a person within 72 hours. To then use this material, you would have to build a special reactor/bomb, a task about half the size of the Manhatten Project.
Will LFTR sites need security?
Yes. Even if only for the waste that must be controlled.
Waste Management comparison – Uranium Vs Thorium
- Mine waste generation - Thorium solid waste advantage for this set of steps: 3667 to 1.
- Operation waste generation - Thorium solid waste advantage: 363 to 1
Reactor Waste Products per GigaWyr
Uranium Fuel Cycle
- 250 tons inc. 1.75 t 235U
- 215 tons of depleted 238U inc. 0.6t 235U waste + 35t enrich U inc. 1.15t 235U
- Yields 33.4t 238U & 0.3t 235U & 1t fission products & 0.3t plutonium
- Products include Pu-238, 239 (50%), 240, 241, 242 and 0.1% Americium, neptunium, curium
Thorium Fuel Cycle
- 1 ton Thorium at start
- 83% of fission products are stable in 10 years
- 17% of fission products are stored for 300-350 years
- Zero thorium at end
- 0.0001 ton of plutonium
- Thorium products need sequestering on the order of 350 years versus 350,000 years for the plutonium products.
LFTR Design Advantages
Built-in passive safety, proven, scaleable, site agile, manufacturable, carbonless, domestically sourced, potential export product, small footprint, transportable, manageable waste, abundant electrical power source, enrichment free, available fuel already, no mineral exploration needed, 1000+ year fuel reserve, can consume existing nuclear waste stockpiles, proliferation resistant, resilient to natural diasters, performance tunable/load following, on/off capable, low-cost fuel, waterless, higher electricity conversion efficiency, centralized quality control.
Resilient to natural disasters could use further explanation. LFTRs are scalable in size. For general utility, the optimal size maybe modules about the size of cargo containers. These are relatively small and coud be built to shake as a unit during an earthquake. The relatively small size reduces the torque along any given axis.
If the LFTR ends up under water, the control electronics will probably burn out. But if all fails, the fuel will solidify as it cools.
LFTR development and production
- Cost of 400MWe LFTR equal to Airbus A380 passenger jet
- LFTR modules can be built in factories
- Both have 400MW gas turbines
- Both are low pressure vessels ~10psi
- Production quantities may be similar. They do one a week
- Purchase price ~$320 million
As you can see from the above statistics, Thorium is the Internet of Energy and can fulfill most of our energy requirement of the future.
