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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.
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
CO2
Sun
Urgent need to reduce use of fossil carbon in a progressive manner
chemical reactor
CO2
CH4 FluidHydro carbons
Electricity
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 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 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 233U-Th in full core
AHWR Fuel assemblyAHWR 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.
ThO2 has better physical, chemical and nuclear properties to enable better safety
> 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.
• Lower fuel temperatures• Less fission gas release• Better dimensional stability• Stable reactor performance• Good stability under long-term
storage
800 1200 1600
2
3
4
5
6
Therm
al C
onductivity (
W/m
K)
Temperature (K)
ThO2, BARC
ThO2, INEEL
ThO2, Bakker
UO2
Ref. case
LEULEU+Th
Pu(RG)+D.U.
Pu(RG)+ThU(WG)+ThPu(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
Plant familiarization & identification of design aspects important to severe accident
PSA level-1 : Identification of significant events with large contribution to CDF
PSA level-1 : Identification of significant events with large contribution to CDF
Level-2 : Source Term (within Containment) Evaluation through Analysis
Level-2 : Source Term (within Containment) Evaluation through Analysis
Release from Containment Release from Containment
Level-3 : Atmospheric Dispersion With Consequence Analysis
Level-3 : Atmospheric Dispersion With Consequence Analysis
Level-1, 2 & 3 PSA activity block diagramLevel-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
SWS63%
SLOCA15%
10-3 10-2 10-1 100
10-14
10-13
10-12
10-11
10-10
Fre
qu
ency
of
Exc
eed
ence
Thyroid Dose (Sv) at 0.5 Km
1 mSv 0.1 Sv 1.0 Sv 10 Sv
10-
14
10-
13
10-
12
10-
11
10-
10
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-LEUprovides betterutilisation ofnatural uranium,as a result ofa significantfraction of theEnergy being extracted from fission of 233U,converted in-situfrom the thoriumfertile host. LEU-Thorium fuel can lead to
better/comparable utilisation of mined Uranium
238Pu 3.50 %
239Pu 51.87
%
240Pu 23.81
%
241Pu 12.91
%
242Pu 7.91 %
9.54 %
41.65
%
21.14
%
13.96
%
13.70
%232U 0.00 %
233U 0.00 %
234U 0.00 %
235U 0.82 %
236U 0.59 %
238U 98.59 %
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 238Pu content which causes heat generation & Uranium in spent fuel contains significant 232U 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 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.
0 20 40 60 80 1000
20
40
60
80
Discharge fuel
Initial fuel
Fiss
ile p
luto
nium
con
tent
in th
e fu
el (
kg/te
)
Discharge burnup (GWd/te)
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
0 20 40 60 80 100 1200
1000
2000
3000
4000
5000
6000
0
2
4
6
8
10
12
14
16
Burn up GWd/te
23
2U
con
cen
trati
on in
pp
m
23
3U
con
cen
trati
on
(g/k
g o
f H
M)
233U
232U
0 20 40 60 80 100 1200
1000
2000
3000
4000
5000
6000
1
10
100
1000
Burn up GWd/te
23
2U
con
cen
trati
on in
pp
m
Exp
osu
re t
ime (
hr)
to a
cquir
e
LD5
0 at
1 m
for
8.4
kg 23
3U
232U
Exposure time for lethal dose
Lethal dose: LD 50/30( =5 Gy) for 8.4 kg Sphere of 233U one year after reprocessing, at 1 m distance
Detectability of 233U (contaminated with 232U) 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
ReactorsFor ex. AHWR
LEU Thorium fuel
Reprocess Spent Fuel Fast
Reactor
Recycle
ThoriumReactorsFor ex. Acc. Driven MSR
Recycle
Thorium
Thorium
Uranium
MOX
LEU-Thorium
233UThorium
Thorium
For growth in nuclear
generation beyond thermal reactor
potential
Present deploymentOf 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