| needed for the third stage of the Indian
nuclear programme. AHWR has several innovative design
features, including passive safety systems, making it
a front-runner among the recent international initiatives
for the development of innovative nuclear energy systems.
Continued technological developments, facilitated by the
experience with the construction and operation of the
AHWR, should be pursued to further enhance the safety
and economics of Indian advanced water cooled thermal
reactor systems, and thorium based fuel cycles.
It was proposed to optimize project gestation period
by meticulously detailing the design using IT aided
design processes and project management techniques,
advancing pre-project activities and ordering of long-delivery
components well in advance.
Several recommendations were made for technological
improvements aimed at improving availability of existing
and future power plants. These included using predictive
maintenance techniques for fault diagnosis, using fuel
efficient reactor physics and control algorithms, implementing
fuzzy logic control in reactor regulation and protection
systems for eliminating operator intervention during
reactor start-up and shut-down, conducting on-power
inspection of coolant channels using fuelling machines
in PHWRs. Recommendations were also made for ageing
management and life extension5 programmes of the existing
reactors.
Fuel Cycle
The growth of nuclear power in India envisaged in the
previous section is possible provided robust technologies
are developed for both the front end and the back end
of the fuel cycle with a matching time frame. Presently,
the known uranium reserves in India are modest and uranium
production needs to be augmented manifold to realize
the planned growth of PHWRs. Considering the low grade
of uranium ore, low tonnage of some deposits, difficult
terrain of some of the locations having rich deposits
and strata bound uranium deposit associated with dolostone
in the southern part of
| 5 For more details on this
aspect, see the sub-topic ‘sensors, detectors
and NDT’. |
Cuddapah basin of AndhraPradesh, it is challenging
to speedily augment uranium production. Atomic Minerals
Directorate for Exploration and Research (AMD) has identified
as many as 14 Middle Proterozoic basins in India, which
can host un-confirmity-type deposits. Such deposits
are of high grade, have large tonnage deposits and are
concealed without any surface manifestation. Since such
deposits are elongated and narrow, advanced drilling
rigs with deviation control mechanism have to be deployed
to prove such deposits. Exploration needs to be stepped
up to locate new deposits including those concealed
deep in the earth.
|
Potential high grade uranium
targets proterozoic basins of India |
There is a persisting need for developing techniques
for economic and efficient extraction of uranium from
lean sources and it should be done by research groups
jointly with UCIL. Uranium extraction from phosphoric
acid could be used to augment uranium supply. Monazite
sand is another resource of uranium and IREL could examine
recovering uranium by acid leaching followed by solvent
extraction. Sea water can be an important source of
uranium on a long-term basis and R&D for recovery
of uranium from sea water should be systematically pursued.
To make fuel fabrication economical and eco-friendly,
Nuclear Fuel Complex (NFC) has to implement robust manufacturing
technologies to minimize
the process steps and rejections, leading to a decrease
in cycle times, effluents and power consumption. Automated
inspection using laser metrology, machine vision systems
etc., should be employed to enhance fuel quality, minimize
manpower and lead to defect-free manufacturing which would
save cost significantly6 . Alternate processes such as
sol-gel process, which are ideal for remote fabrication,
need to be developed to a level of maturity. Microwave
technology will immensely help fuel fabrication and recycle
steps minimizing liquid waste. A unified alloy for all
thermal reactor components will greatly reduce the cost.
Specifications for fuel and other components should be
reviewed to reduce manufacturing cost without sacrificing
fuel performance. Improved austenitic stainless steels
for claddings and advanced ferritic steels for wrappers
with close tolerances on composition, microstructure and
dimensions, with minimum rejects will economize power
through FBRs and can be addressed by networking the expertise
of Indira Gandhi Centre for Atomic Research (IGCAR), Mishra
Dhatu Nigam (MIDHANI), Indian Institute of Technology
(IIT), Bombay and NFC. Rapid growth of fast reactors
is possible only through the deployment of metal alloy
fuels with high breeding ratio. It is necessary to launch
urgently a large programme for studying irradiation
behaviour of metal alloy fuels to generate the database
necessary for physics design, development of technology
for fabrication, characterization and pyro-electrochemical
processing.
|
Bank of centrifugal extractors
developed at IGCAR
|
The challenges foreseen for reprocessing of spent fuel
from PHWRs, FBRs and AHWR are related to enhancing the
capability to process fuels with higher burn-ups, having
plutonium content, with lower waste production and increased
use of remote handling techniques. Separation of uranium-plutonium-thorium
in reprocessing streams is an additional requirement
for AHWRs. Develop
ment of a single cycle flow sheet with high organic loadings
for achieving higher decontamination factors is one of
the important goals for the reprocessing technology. The
flow sheet should also enable partial or total partitioning
of plutonium. Equipment such as rotary dissolver, constant
volume feeders and fluidic devices need to be developed
and validated for their performance. Pyrochemical reprocessing
need to be developed for processing FBR fuels discharged
at high burn-up with short cooling time.
| 6 Robotics and automation
are very important for all the activities of the
fuel cycle and several other programmes such as
maintenance of nuclear reactors. For details, see
the sub-topic ‘robotics and automation’. |
R&D on materials is required to address Zr and
Ta based materials for dissolvers and evaporators, coatings
for electrodes and radiation-resistant polymeric seals
and winding insulations. In-service inspection techniques
need to be developed in order to assess the safety status
and residual life of components as well as take steps
to enhance their life. Enhanced computer codes, based
on thermodynamic modelling, would cover a wider variety
of actinides and fission products. Electrolytic conditioning,
acid killing and partitioning have to be adopted for
reducing waste production. On/off-line monitoring of
all the streams and hulls has to be undertaken to address
issues related to nuclear material accounting as well
as minimize loss of nuclear materials. It is also important
to undertake on priority, indigenous development of
pulsed neutron generators for active neutron assay of
hulls and diamond based detectors for on-line determination
of plutonium in process streams.
|
Rotary semi-continuous
dissolver and constant volume feeders for accurate
metering of crucial streams |
Waste management is a subject that needs sustained
development. It is necessary to induct new technologies
so as to enhance performance and minimize waste, leading
to very low impact on the environment and enhanced safety.
This poses a challenge considering the already low levels
of effluents, which are in the range of 10-3 to 10-4
micro Curie per millilitre (µCi/ml). Adoption
of membrane based technologies such as reverse osmosis,
bio-separations and nano/ultra-filtration techniques
has to be considered to address these challenges. Indigenous
development of membranes, overall process engineering
and retrofitting of these processes and technologies
in the existing plants need to be taken up.
|
Pouring of molten glass
from cold crucible into canister
|
| Annual generation of high level waste (HLW) volumes
will be nearly 700 cubic metres by the year 2011
as against the present volume of 170 cubic metres.
As the programme expands, these volumes will keep
increasing. To handle these increased waste volumes,
adoption of robust vitrification melters with higher
throughputs are necessary with improved off-gas
treatment enhancing the decontamination of volatiles
like ruthenium & cesium.
A long-term strategy for high-level waste management
is to partition the minor actinides and long lived
fission products from HLW. This calls for a multi-step
processing involving the use of suitable solvents.
For reprocessing fast reactor fuels, it is necessary
to take up design and synthesis of selective,
efficient, eco-friendly and radiation-resistant
solvents such as higher tri-alkyl phosphates and
substituted amides, which can permit high actinide
loading without third phase formation.
Overall strategy has to be to ensure that uranium
and plutonium are recovered and recycled, fission
products like 137Cs and 90Sr are recovered and
used for radiation processing7 and as heat source,
short half life fission products are separated
and stored under institutional control, and long
half life fission products and minor actinides
are separated and stored in deep geological repositories
after vitrification.
Demonstration of feasibility and safety of deep
geological disposal is a major challenge ahead.
A national level multidisciplinary programme is
necessary for setting up an underground research
laboratory to develop and demonstrate methodologies
and technologies for a deep geological repository.
R&D activities have to be directed towards
effective & environmentally benign processes
and technologies.
Development of advanced oxidation processes including
wet air oxidation, photochemical oxidation, supercritical
water oxidation etc. on an industrial scale need
to be initiated and developed. Development of
specific sorbents and
magnetic assisted separations will have a key role
to play in future waste management plants. Recovery
of zirconium from the hulls, though a challenge,
would be highly desirable. Management of waste from
pyro-chemical reprocessing will have to be addressed
in the future. Materials compatible with high corrosive
and high temperature environments encountered during
vitrification need to be identified. In-service
inspection techniques8 for health monitoring of
equipment need to be developed.
| 7 See the sub-topics
‘food and agriculture’, ‘environment
and health’, and ‘urban and rural
waste management’ for use of radioisotopes
for radiation processing. |
In-house (BARC, IGCAR, Heavy Water Board) solvent
synthesis activity and collaboration with academic
institutions for exotic solvents need to be strengthened.
Large-scale synthesis of diamides, glycolamides
(TODGA), SANEX (Selective ActiNide EXtraction
process) solvents or crown ethers has to be taken
up enabling mixer-settler runs by the year 2006
and pilot runs by the year 2010. Pilot plants
using hollow fibre membranes/magnetically assisted
separations can be visualized by the year 2010.
Attempts should be made to evaluate the possibility
of bio-sorption and phyto-sorption of actinides
and long-lived fission products onto microorganisms
and sorbents of plant origin. Ultra-filtration
and reverse osmosis technologies for low level
waste (LLW) and intermediate level waste (ILW)
treatment have to be developed on pilot scale
by the year 2009. Utilization of supercritical
fluids and room temperature ionic liquids need
to be studied on laboratory scale. Fluidized bed
de-nitration can be applied to the waste management
programme by the year 2012.
New Energy Systems
The projections about the energy requirement
beyond five decades and available indigenous energy
resources indicate a large gap between them. Given
the urgent necessity to bridge this future energy
resource-requirement gap and the vast resource
of thorium at hand, it is essential to accelerate
the work on thorium utilization.
| 9 This would call
for development of several technologies in
the area of accelerators, cryogenics, high
power RF and fusion. See the relevant sub-topic. |
However, since thorium is not a fissile material,
it needs to be “bred”. Fast breeder
reactor is one way to breed, but the breeding
rate is not high. Alternate technologies, which
offer shorter doubling time, need to be explored
and developed. The potential technologies under
investigation and possible development are based
on the use of an external non-fission source of
neutrons. The neutrons could be generated either
by a spallation reaction using a high energy proton
accelerator or by fusion reactions involving deuterium/tritium
nuclei9 . While the accelerator driven systems
are aiming for a novel and safe kind of a thorium
burner, the fusion systems like tokamaks are aiming
for a large-scale thorium-to-uranium converter.
Both the programes are being pursued in the DAE
institutions. The present programme of tokamak
research in the country is already geared for
exploiting the recent success of tokamaks, to
design systems with the above objective. Other
fusion systems, like laser or inertial fusion
also need to be explored for the expected neutron
fluence and their extrapolation to multi-mega-joule
sources.
|
Schematic of accelerator
driven sub-critical reactor system for nuclear
energy generation. |
A high temperature heat source would be necessary
for the thermo chemical generation of hydrogen
- the energy carrier of tomorrow. Like electricity,
hydrogen is environmentally benign and has to
be produced from some other fuel. For the development
of high temperature heat source, the nuclear energy
is the most desirable option. The high temperature
reactor system, with the-state-of-the-art passive
inherent safety features, calls for developments
in high temperature materials, fuel (like TRISO
coated particles), heavy liquid metal coolant
and many associated technologies for the different
systems of the reactor.
|
Roadmap for accelerator
driven sub-critical reactor system (ADS)
|
|
Schematic of the
prototype fusion breeder reactor |
There is also a need to develop storage and transportation
systems for hydrogen, which could also be used
for storage of other isotopes of hydrogen. Storage
systems would be needed in very near future as
part of heavy water clean up facilities. Possible
storage technologies include storage in high pressure
vessels, storage as a cryogenic liquid and storage
after fixing as metal hydride in a metal matrix.
All the activities for the design and development
of thorium breeders, high temperature reactors
and production of the radio-isotopes would need
to be backed by the development of advanced computational
capability in reactor physics design supported
by extensive experiments for the generation of
nuclear data especially for the thorium fuel cycle.
|
Compact high temperature
reactor |
|
| |
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