Towards sustainable, secure and safe energy future: Leveraging opportunities with Thorium Anil Kakodkar

Growing economic empowerment of a larger part of world population and little carbon space available necessitates a quick shift to non-fossil energy sources.

Climate Change Stabilization Scenarios Source: IPCC (2007), Table 5.1, p. 67 If total primary energy consumption doubles by 2050, 85% of energy must be supplied by clean technologies in order to attain a 70% GHG cut from 2000 levels. Source: WNA Nuclear Century Outlook Source IEO2013 We do not know how close we are to the tipping point. However we need to act now to secure survival of our future generations.

What we should do? Business as usual approach is unlikely to work Apart from electricity we need energy in fluid form derived through non-fossil means This would need high temperature capability Since time is running out we need to explore what can be done by reconfiguration of available technologies even as we develop new technologies

GREATER SHARE FOR NUCLEAR IN ELECTRICITY SUPPLY REPLACE FOSSIL HYDRO- CARBON IN A PROGRESSIVE MANNER RECYCLE CARBON- DIOXIDE DERIVE MOST OF PRIMARY ENERGY THROUGH SOLAR & NUCLEAR Sustainable development of energy sector Transition to Fossil Carbon Free Energy Cycle Fossil Energy Resources Nuclear Energy Resources Hydrogen ENERGY CARRIERS (In storage or transportation) Electricity Fluid fuels (hydro- carbons/ hydrogen) Biomass WASTE CO2 H2O Other oxides and products Nuclear Recycle Sustainable Waste Management Strategies CO 2 Sun Urgent need to reduce use of fossil carbon in a progressive manner chemical reactor CO2 CH 4 Fluid Hydro carbons Electricity Carbon/ Hydrocarbons Other recycle modes

In spite of such strong motivation, what has slowed the growth of nuclear power?  Irrational fear of radiation caused by LNT logic  Potential for large scale displacement of people following a severe accident  Panic potential following a terrorist action  Unresolved spent fuel disposal & constraints on recycle  Regulatory delays

Evidence of threshold Crosses show the mortality of Chernobyl firefighters (curve is for rats). The numbers show the number who died/total in each dose range. Colorado,USA has a population over 5 millions residents. According to LNT model Colorado should have an excess of 200 cancer deaths per year but has a rate less than the national average.. Ramasar,Iran, residents receive a yearly dose of between mSv. This is several time higher than radiation level at Chernobyl and Fukushima exclusion zone. People living in Ramsar have no adverse health effect, but live longer and healthier lives.. We also know that China, Norway, Sweden, Brazil and India have similar areas where radiation level is many times higher than 2.4 mSv/yr world average. In spite of evidence for no health consequences below a threshold, mindset driven by LNT logic has caused irrational fears in public mind with regard to potential accident impact in public domain. This has led us to a situation where significant off-site impact in a severe accident is no longer acceptable.

Can we eliminate serious impact in public domain with technology available as of now?

Advanced Heavy Water Reactor (AHWR) is an innovative configuration that should nearly eliminate impact in public domain using available technologies. The design enables use of a range of fuel types including LEU, U-Pu, Th-Pu, LEU-Th and 233 U-Th in full core AHWR Fuel assembly Bottom Tie Plate Top Tie Plate Water Tube Displacer Rod Fuel Pin Major design objectives Several passive features grace period > 3 days No radiological impact in public domain Passive shutdown system to address insider threat scenarios. Design life of 100 years. Easily replaceable coolant channels. Significant fraction of Energy from Thorium

AHWR300-LEU provides a robust design against external as well as internal threats, including insider malevolent acts. Reactor Block Components AHWR 300-LEU is a simple 300 MWe system fuelled with LEU-Thorium fuel, has advanced passive safety features, high degree of operator forgiving characteristics, no adverse impact in public domain, high proliferation resistance and inherent security strength. Peak clad temperature hardly rises even in with extreme postulate of complete station blackout and simultaneous failure of both primary and secondary systems.

ThO 2 has better physical, chemical and nuclear properties to enable better safety > Higher thermal conductivity and lower co-efficient of thermal expansion compared to UO 2. Melting point 3500 o C as against 2800 o C for UO 2. > Favourable reactivity coefficients > Fission product release rate one order of magnitude lower than that of UO 2. > Relatively inert. Does not oxidise unlike UO 2 which oxidizes easily to U 3 O 8 and UO 3. Does not react with water. Lower fuel temperatures Less fission gas release Better dimensional stability Stable reactor performance Good stability under long-term storage Ref. case LEULEU+Th Pu(RG)+D.U. Pu(RG)+Th U(WG)+Th Pu(WG)+Th For a Typical PHWR LEU

12 PSA calculations for AHWR indicate practically zero probability of a serious impact in public domain Plant familiarization & identification of design aspects important to severe accident PSA level-1 : Identification of significant events with large contribution to CDF Level-2 : Source Term (within Containment) Evaluation through Analysis Release from Containment Level-3 : Atmospheric Dispersion With Consequence Analysis Level-1, 2 & 3 PSA activity block diagram Variation of dose with frequency exceedence (Acceptable thyroid dose for a child is 500 mSv) Iso-Dose for thyroid -200% RIH + wired shutdown system unavailable (Wind condition in January on western Indian side) Contribution to CDF SWS: Service Water System APWS: Active Process Water System ECCS HDRBRK: ECCS Header Break LLOCA: Large Break LOCA MSLBOB: Main Steam Line Break Outside Containment SWS 63% SLOCA 15% 1 mSv0.1 Sv1.0 Sv10 Sv

How can we address issues related to long term waste (legacy as well as new arising), proliferation concerns and realisation of full potential of nuclear energy?

At high burn-ups considered achievable today, Thorium requires lower fissile content Performance potential vs fissile topping in PHWR Performance potential vs fissile topping in BWR Performace potential vs fissile topping in PWR Indicative results for a set of case studies with U 235 as fissile material  Better fertile to fissile conversion  Smaller reactivity swing with burn up  Greater energy from in-situ generated fissile material  Better Uranium utilisation

AHWR300-LEU provides better utilisation of natural uranium, as a result of a significant fraction of the Energy being extracted from fission of 233 U, converted in-situ from the thorium fertile host. LEU-Thorium fuel can lead to better/comparable utilisation of mined Uranium

238 Pu3.50% 239 Pu51.87% 240 Pu23.81% 241 Pu12.91% 242 Pu7.91% 9.54% 41.65% 21.14% 13.96% 13.70% 232 U0.00% 233 U0.00% 234 U0.00% 235 U0.82% 236 U0.59% 238 U98.59% Thorium provides an effective answer to safe recycle of spent nuclear fuel. Much lower Plutonium production. Plutonium in spent fuel contains lower fissile fraction, much higher 238 Pu content which causes heat generation & Uranium in spent fuel contains significant 232 U content which leads to hard gamma emitters. The composition of the fresh as well as the spent fuel of AHWR300- LEU makes the fuel cycle inherently proliferation resistant. Uranium in spent fuel contains about 8% fissile isotopes, and hence is suitable for further energy production through reuse in other reactors. Further, it is also possible to reuse the Plutonium from spent fuel in fast reactors. 0.02% 6.51% 1.24% 1.62% 3.27% 87.35%  There is already a large (~200,000 tons) used Uranium fuel inventory. Another 400,000 tons are likely to be generated between now and the year 2030 (as per WNA estimate).  Permanent disposal of used Uranium fuel remains an unresolved issue with unacceptable security and safety risks.  We need to adopt ways to liquidate the spent fuel through recycle. Disposal of used Uranium remains an unresolved issue

Thorium, an excellent host for disposal of excess plutonium Options for plutonium disposition – Uranium-based fuel: Neutron absorption in 238 U generates additional plutonium. – Inert matrix fuel (non-fertile metal alloys containing Pu): Degraded reactor kinetics - only a part of the core can be loaded with such a fuel, reducing the plutonium disposition rate. – Thorium: Enables more effective utilisation of Pu, added initially, while maintaining acceptable performance characteristics. Plutonium destruction in thorium- plutonium fuel in PHWR

Adoption of Thorium fuel cycle paves the way to elimination of long lived waste problem  While AHWR300- LEU enables comparable utilisation of Uranium in a safe manner, issues related to spent fuel disposal can be eventually addressed through recycle of fissile and fertile materials.  Production of MA – lowered with Thorium  MAs : fissionable in fast neutron spectrum.  Difficult power control system of critical reactor due to: - Reduced delayed neutron fraction (factor called  eff ) giving lower safety margin to prompt criticality. - Safety parameters: (1) Doppler coefficient, (2) reactivity temperature coefficient, and (3) void fraction- all would not be benign in TRU incinerating critical fast reactor.

We thus need accelerator driven sub- critical molten salt reactor systems with P&T working in tandem to be developed rather quickly. Growth of nuclear power capacity should however pick up immediately through innovative reconfiguration of existing technologies as time is running out Thorium is a logical choice for fuel cycle in both present and future systems

Burn up GWd/te 232 U concentration in ppm 233 U concentration (g/kg of HM) 233 U 232 U Burn up GWd/te 232 U concentration in ppm Exposure time (hr) to acquireLD 50 at 1 m for 8.4 kg 233 U 232 U Exposure time for lethal dose Lethal dose: LD 50/30( =5 Gy) for 8.4 kg Sphere of 233 U one year after reprocessing, at 1 m distance Detectability of 233 U (contaminated with 232 U) for all the cases, is unquestionable Case of Pu-RG+Thoria in AHWR

21 “IAEA is not concerned with the tenth or the thousandth nuclear device of a country. IAEA is only concerned with the first. -And that will certainly not be based on a thorium fuel cycle” Bruno -Bruno Pellaud, Former Deputy Director General,IAEA

Nuclear power with greater proliferation resistance Enrichment Plant LEU Thermal reactors Safe & Secure Reactors For ex. AHWR LEU Thorium fuel Reprocess Spent Fuel Fast Reactor Recycle Thorium Reactors For ex. Acc. Driven MSR Recycle Thorium Uranium MOX LEU- Thorium 233 U Thorium For growth in nuclear generation beyond thermal reactor potential Present deployment Of nuclear power

To Conclude: Thorium is a good host for efficient and safe utilisation of fissile materials. It can support greater geographical spread of nuclear energy with lower risk Thorium can facilitate resolution of waste management issue and enable realisation of full potential of available Uranium. Fast breeder reactors would however be necessary for growth in nuclear power capacity well beyond thermal reactor potential Fast reactors as well as uranium fuel enrichment and recycle needs to be kept within a more responsible domain

Thank you