thorium fuel cycle development in india

thorium fuel cycle development in India

The long term - goal of India‘s nuclear program has been to develop an advanced heavy water thorium cycle. The first stage of this employs the PHWRs fuelled by natural uranium, and light water reactors to produce plutonium.

Stage 2 uses fast neutrons reactors burning the plutonium to breed U-233 from thorium. The blanket around core will have uranium as well as thorium so that further plutonium ( ideally fissile PU ) is produced as well as the U-233.

Then stage 3 Advanced Heavy Water Reactors (AHWR) burn U-233 from stage 2 and this plutonium with thorium getting about two thirds of their power from the thorium.

On 2002 the regulatory authority issued approval to start BHAVINI. It is expected to be operating in 2012, fuelled with uranium -plutonium oxide ( the reactor-grade PU being from existing PHWRs ). It will have a blanket with thorium and uranium to breed fissile  U-233 and plutonium respectively. This will take India’s ambitious thorium program to stage 2, and set the scene for eventual full utilization of country’s abundant thorium to fuel reactors. Six more such 500 Mwe fast reactors have been  announced for construction four of them by 2020.

So far  about one tonne of thorium oxide fuel has been irradiated experimentally in PHWR reactors and has reprocessed and some of this has been reprocessed , according to BARC. A reprocessing centre for thorium fuel is being set up at Kalpakkam .

Design is largely complete for first 300 Mwe  AHWR, which was intended to be built in the 11th plan period to 2012, though no site has yet  been announced. It will have vertical pressure tubes in which light water coolant under high pressure will boil, circulation being by convection. A large heat sink-“ Gravity driven water pool “ -with 7000 cubic meters of water is near the top of reactor building. In April 2008 an AHWR critical facility was commissioned at BARC “ to conduct a wide range of experiments, to help validate the reactor physics of AHWR through  computer codes and in generating nuclear data about materials,  such as thorium-uranium 233 based fuels, which have not been extensively used in the fast.”  it has all components of AHWRs core including fuel and moderator and can be  operated in different  modes with various kinds of fuel in different configurations.

In 2009 the AEC announced some features of Mwe AHWR. It is mainly thorium fuelled reactor with several advanced passive safety features to enable meeting next generation safety requirements such as three days grace period for operator response, elimination of need for exclusion zone beyond plant boundary, 100 year design life, and high level of fault tolerance. The advanced safety characteristics have been verified in a series of experiments carried out  in series of experiments carried  out in full-scale test facilities. Also per unit of energy produced in current generation light water reactors. Importantly ,a high level of radio activity in the fissile and fertile materials recovered from used fuel of AHWR, and their isotopic  composition, preludes the use of these materials for nuclear weapons . In mid 2010 a pre licensing safety appraisal had been completed by AERB and site selection was in progress. The AHWR can be configured to accept a range of fuel types including enriched U, U-PUMOX , Th-PU MOX and U-233- Th MOX in full core.

At the same time AEC announced LEU version for AHWR. This will be use low-enriched uranium plus thorium as fuel, dispensing with plutonium input. About 39%  of power will come from thorium ( via in Situ  conversion to U-233,  C+ two thirds in AHWR)  and burn up will be 64 Gwd / t.  Uranium enrichment level will be 19.75%  giving 4.21% average fissile  content of U-th fuel. While designed closed fuel cycle, this not required . Plutonium production will be less than light water reactors, and fissile proportion will be less and the PU-238 portion three times as high, giving inherent  proliferation resistance. The design is intended for overseas sales and AEC says that “ the reactor is manageable with modest industrial infrastructure within reach of developing countries.