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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.
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Growing economic empowerment of a larger part of world population and little carbon space available necessitates a quick shift to non-fossil energy sources.
Source: IPCC (2007), Table 5.1, p. 67
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.
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
Sustainable development of energy sector
Greater share for nuclear in electricity supplyreplace fossil hydro- carbon in a progressive manner recycle carbon- dioxidederive most of primary energy through solar & nuclear
Other recycle modes
Sustainable Waste Management Strategies
Urgent need to reduce use of fossil carbon in a progressive manner
LNT model Colorado should have an
excess of 200 cancer deaths per year
but has a rate less than the national
. Ramasar ,Iran, residents receive a
yearly dose of between 100-260 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
. We also know that China , Norway,
Sweden, Brazil and India have similar
areaswhere radiation level is many
times higher than 2.4 mSv/yr world
Crosses show the mortality of Chernobyl firefighters (curve is for rats).The numbers show the number who died/total in each dose range.
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.
Top Tie Plate
Bottom Tie Plate
Major design objectives
The design enables use of a range of fuel types including LEU, U-Pu , Th-Pu , LEU-Th and 233U-Th in full core
AHWR Fuel assembly
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.
Reactor Block Components
AHWR300-LEU provides a robust design against external as well as internal threats, including insider malevolent acts.
> Higher thermal conductivity and lower co-efficient of thermal expansion compared to UO2. Melting point 3500o C as against 2800o C for UO2.
> Favourable reactivity coefficients
> Fission product release rate one order of magnitude lower than that of UO2.
> Relatively inert. Does not oxidise unlike UO2 which oxidizes easily to U3O8 and UO3. Does not react with water.
For a Typical PHWR
Plant familiarization & identification of design aspects important to severe accident
Level-3 : Atmospheric Dispersion With Consequence Analysis
Release from Containment
PSA level-1 : Identification of significant events with large contribution to CDF
Level-2 : Source Term (within
Containment) Evaluation through Analysis
Level-1, 2 & 3 PSA activity block diagram
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
Contribution to CDF
Iso-Dose for thyroid -200% RIH + wired shutdown system unavailable (Wind condition in January on western Indian side)
Variation of dose with frequency exceedence
(Acceptable thyroid dose for a child is 500 mSv)
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?
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 U235 as fissile material
as a result of
fraction of the
Energy being extracted from fission of 233U,
from the thorium
LEU-Thorium fuel can lead to better/comparable utilisation of mined Uranium
Disposal of used Uranium remains an unresolved issue
Uranium-based fuel: Neutron absorption in 238U 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.Thorium, an excellent host for disposal of excess plutonium
Plutonium destruction in thorium-plutonium fuel in PHWR
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 outThorium is a logical choice for fuel cycle in both present and future systems
232U concentration in ppm
233U concentration (g/kg of HM)
232U concentration in ppm
Exposure time (hr) to acquire LD50 at 1 m for 8.4 kg 233U
Exposure time for lethal dose
Burn up GWd/te
Burn up GWd/te
Case of Pu-RG+Thoria in AHWR
Lethal dose: LD 50/30( =5 Gy) for 8.4 kg Sphere of 233U one year after reprocessing, at 1 m distance
-Bruno Pellaud, Former Deputy Director General,IAEA
Of nuclear power
Reprocess Spent Fuel
For growth in nuclear
generation beyond thermal reactor potential
LEU Thorium fuel
Nuclear power with greater proliferation resistance
For ex. AHWR
For ex. Acc. Driven MSR
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 riskThorium 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