INDIAN RESEARCH REACTORS The importance of nuclear energy as a sustainable energy resource for India was recognized at the very inception of the atomic energy programme five decades ago. A three stage nuclear power programme, to meet the country’s specific requirement was chalked out with Natural Uranium fuelled Pressurized Heavy Water Reactors in the first stage followed by Fast Breeder Reactors utilizing Plutonium based fuels in the second stage and with the advanced nuclear power systems utilizing the large available resources of Thorium in the third stage. In the development of nuclear technology in any country, Research Reactors play a central and key role. They contribute towards development of essential infrastructure for research and development and also the trained human resources. Research reactors are also extensively used in the field of neutron beam research, production of radioisotopes for application in the fields of medicine, agriculture, food preservation and industry, neutron radiography and neutron activation analysis. To gainfully exploit all the nuclear energy options it was essential to develop the research reactors to cater to all the three stages of the power programme. Apsara a 1 MWt swimming pool type research reactor designed and built with totally indigenous effort attained criticality on August 4, 1956. Cirus, a 40 MWt tank type heavy water moderated and light water cooled reactor was commissioned in 1960. In early 1961 a zero energy critical facility named Zerlina (Zero Energy Reactor for Lattice Investigations and New Assemblies) was built, for studying various lattice parameters of natural Uranium fuelled, heavy water moderated reactors. Dhruva a 100 MWt tank type heavy water moderated and cooled reactor was commissioned in 1985 , to fulfill the growing needs of Indian Nuclear Programme. In pursuing the development of the three-stage nuclear program, another critical facility was built in 1972 named PURNIMA (Plutonium Reactor for Neutron Investigations in Multiplying Assemblies). This facility was used for the physics study of plutonium fuelled fast reactors (PFR). As a part of studies with U 233 fuel, a 30 kW research reactor called KAMINI (KAlpakkam MINI) using U 233 as fuel was commissioned at IGCAR Kalpakkam near Chennai. Incidentally Kamini is the only operating reactor in the world with U 233 fuel. Fast Breeder Test Reactor at Kalpakkam commissioned in 1985, provides an essential base for R&D aspects related to the second stage power programme. One of the major utilization areas of the research reactors has been neutron beam research using a variety of neutron spectrometers, several of which have been built in-house. In more recent times, a guide tube facility comprising of two neutron guides has been commissioned at Dhruva. A multi-instrument beam line experimental set-up has been installed in Dhruva under the aegis of the Inter-University Consortium for Department of Atomic Energy Facilities. This will enable further enhancement of the utilization of this National Facility by the academic institutions in the country. In addition to neutron beam research, the other research areas covered include Neutron Activation Analysis, Neutron Radiography, Irradiation testing of research reactor and power reactor fuels and structural materials, Experimental Reactor Physics and Shielding experiments. A good example of research reactor utilization is the conduct of a series of intricate experiments recently in Apsara for optimization of the in-core shielding for the intermediate sodium heat-exchanger for the 500 MWe Prototype Fast Breeder Reactor. Radioisotope production in the Indian research reactors has increased several folds over the years to keep pace with the requirements of isotopes in a variety of areas in medical, industrial and agricultural applications. Construction of the new Multi Purpose Research Reactor (MPRR) is expected to fulfill the growing isotope demand beyond the year 2010. India has regularly participated in several IAEA activities connected with research reactors. These include preparation of safety documents, co-ordinated Research Programmes, training of IAEA fellows and providing services of experts. During the last 4 years, under the IAEA-RCA projects, the "Regional Seminar on Ageing Management of Research Reactors and Project Review Meeting" and the "workshop on In-Service Inspection of Research Reactors" were hosted during December, 2000 and January 2002 respectively. Participants from India attended all the group activities under the projects RAS/4/19 and RAS/4/020 and lecturers from India were also provided in the Training Courses/Workshop under these projects. In the meeting on "Sharing of Research Reactor Resources" held in Bangkok during March 2001, India offered to train scientists and engineers from the countries in the region through the one-year Orientation Training Course conducted by the Bhabha Atomic Research Centre on an annual basis. India has also offered to participate in the proposed programme of back-up supply of radioisotopes in the region. The Department of Atomic Energy of India has recently entered into a Memorandum of Understanding with the IAEA to further strengthen the Training Programmes for IAEA sponsored personnel in India with the Bhabha Atomic Research Centre as the nodal agency. |
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Sectional plan of Apsara
Apsara , attained criticality on August 4, 1956. The reactor uses enriched uranium in the form of uranium-aluminium alloy plates clad in aluminium as the fuel and demineralized water as the coolant and moderator. The power regulation and shut down of the reactor is achieved with the help of four cadmium control rods. Sectional elevation of Apsara The entire reactor is housed in a pool of demineralised water that serves as a moderator, coolant and reflector. a concrete wall surrounds the metal lined pool and the combination of water and concrete wall provides good shielding against the radiation emanating from the core. Apsara has got certain special features such as movable core enabling reactor operation at different positions in the pool with appropriate experimental facilities built at each location. The rated power of the reactor is 1 M w with a maximum neutron flux of 1 x 10 13 neutrons/cm 2/s. Apsara is mainly utilized to carry out studies in the field of neutron physics, fission physics, biological studies and irradiation research. Study of the two -phase flow conditions of coolant through natural circulation boiling water loop of the advanced heavy water reactor was carried out using neutron radiography in Apsara.
Apsara-Interior view of reactor hall Testing of the indigenously developed self powered neutron detectors and evaluation of the composite shield materials for use in future reactors etc are also carried out in Apsara.
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CIRUS
In order to augment the scope of neutron beam research and radioisotope production, another reactor was built in 1960, under the Colombo plan. 40 MW CIRUS reactor attained criticality on July 10, 1960 and attained full power on October 16, 1963. Natural uranium rods clad with finned aluminium tubes constitutes the fuel assembly. Cirus reactor uses heavy water as the moderator and light water as the coolant. The main reactor vessel is a cylindrical aluminium tank with around 200 vertical calandria tubes arranged in a hexagonal array for housing fuel assemblies, shut off rods (Boron carbide), isotope irradiation tray rods and an engineering test loop for fuel and material testing.
Cirus-Sectional elevation
Two concentric rings of graphite blocks around the reactor vessel to form reflectors to get maximum neutron economy. Cirus reactor is being extensively used for experimental research in solid-state physics, fission physics, neutron physics, radiochemistry and radiation chemistry, isotope production, reactor engineering, metallurgy, test irradiation of fuel, studies on the structural integrity of various reactor components and materials and also in providing training to personnel for operation and maintenance of power reactors. Detailed ageing assessment of Cirus was carried out during mid-nineties. Based on the assessment, refurbishment of the reactor was undertaken wherein some safety upgrades were also incorporated. The major refurbishment activities include;
- Strengthening of central shaft and cupola joints of the emergency water reservoir (ball tank) for shut down cooling of the core, by additional reinforcement with steel plates and epoxy grouting to make it a monolithic structure to meet safe shut down earth quake (SSE) qualification criteria as per present standards and Repairs to Ball Tank.
- Refurbishment of Non-isolatable segments of underground (4 meter below grade) carbon steel Primary Coolant Pipelines.
- Replacement of Failed Fuel Detection System.
- Remote Installation of Split Sealing Clamps on the Helium Line Flange Joints between reactor vessel and cover gas system piping
- Detailed inspection and metallurgical studies towards re-qualification of reactor vessel.
- Rectification of leak from the weld joint of coolant inlet line to the upper aluminum thermal shield by installation of hollow plug using remote handling techniques.
- Physical separation of Ball tank make up pumps, a safety related equipment, to guard against common cause failures.
- Design, installation & commissioning of an improved iodine removal system with combined HEPA and activated charcoal cum filters.
- Detailed studies and theoretical analysis towards assessing the thermal safety of the Graphite reflectors
- In-house design and installation of an automatic ground fault detection for the 125V DC power supply system.
- Repair/replacement of plant equipment based on performance review, availability of spares & obsolescence.
- Replacement of kilometers of old piping, cable & process instrument tubing as necessary
 Desalination unit attached to CIRUS On completion of the refurbishment activities and re-commissioning of various systems, Cirus reactor was made critical on 30 th October, 2002 and rededicated to the nation by the Hon’ble Prime Minister of India. After repairs to seepage from Ball Tank, the reactor operation was resumed during October, 2003 and power was raised in steps, with safety review at every stage and necessary safety precautions, to design power level of 40 MW during November, 2004. Maximum ever achieved availability factor (94.78%) and capacity factor (90.82%) for a month for the reactor was during December 2004. Utilization of various sample irradiation facilities of the reactor has commenced. Installation of experimental set up by the researchers at the beam tube locations, which were dismantled during refurbishing, are being installed. During the refurbishing outage, a Desalination Unit of 30 ton/day capacity, based on Low temperature Vacuum Evaporation process has been integrated with the primary coolant system of the reactor towards demonstration program of utilization of waste heat from nuclear reactor. During 2004, the unit was commissioned and it could deliver the rated output with reactor operating at full power. The potable water produced by the unit is passed through a mixed bed ion exchange cartridge and is utilized to augment the capacity of demineralized water make up plant at Cirus.
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Zerlina was commissioned in January 14, 1961. The design, fabrication, installation and commissioning of this reactor was carried out using indigenous resources. The reactor core was fuelled with natural uranium using heavy water as the moderator. This tank type reactor was exclusively used for reactor physics experiments and also for the nuclear reactor lattice studies for pressurized heavy water reactors. This reactor was decommissioned in April 1983.
India has gained sufficient expertise in fast breeder reactor technology through the setting up and operation of plutonium-239/Uranium-233 fuelled experimental reactors Purnima I, II and III. These experimental reactors were of immense help in providing operational experience for Indian Nuclear Power program Stage II and III using plutonium-239, Uranium-233 and Thorium-232 fuels.
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Purnima I – The first plutonium fuelled experimental fast reactor became operational in May 1972. Studies on the fast neutron physics as well as features of small reactors with different fuel and reflector configurations were carried out using Purnima I. Purnima II used uranium 233 in the form of uranyl nitrate solution as the fuel and this reactor is unique for both the fuel and the moderator are in the same phase –viz. liquid phase. Uranium-233 as uranyl nitrate in solution is the fuel while the aqueous part of the solution functioned as the moderator. Purnima II attained criticality with 440 gm of uranium-233 fuel making it the smallest critical mass facility. The core of the reactor was surrounded with beryllium oxide as the neutron reflector serving to sustain the nuclear chain reaction. This reactor was helpful in understanding the operational feasibility of U-233 fuelled reactors and also for carrying out neutron radiography experiments. Purnima I and II were de commissioned after the realization of their purpose. Purnima III used U-233-Aluminium alloy and attained criticality in November 1990. Purnima III core later became the core for the 30 kWt KAMINI set up for neutron radiography studies at IGCAR Kalpakkam, Chennai.
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Dhruva is the next in the series of thermal research reactors built in India in order to augment the production of radioisotopes and to carry out certain reactor engineering experiments and production of high specific activity radioisotopes that was not possible with the neutron flux available in the CIRUS reactor. This reactor was designed, developed, constructed and commissioned by Indian scientists and engineers exclusively by making use of indigenous technical know how. The maximum neutron flux available in Dhruva is 1.8 x 10 14 n/cm 2/s. Dhruva uses metallic uranium fuel and heavy water as moderator and coolant. The main reactor vessel is made of stainless steel with 146 positions available for the fuel rods, cadmium shut off rods, isotope irradiation facilities and experimental loops. The reactor vessel is housed inside a water filled stainless steel lined concrete vault. Dhruva reactor is widely used in neutron beam research studies involving material science and nuclear fission processes.
A number of beam holes are provided in Dhruva reactor in order to facilitate research using neutron beams. Mirror guides are employed in Dhruva to transport neutron beams to an adjacent laboratory to carry out low radiation background experiments. Dhruva has in-pile-loop facilities in the form of vertical tubes for carrying out fuel/material test irradiations under simulated conditions of pressure, temperature and flow conditions prevailing inside the power reactors.
Neutron beam experiments set up inside Dhruva India has gained more than 150 reactor years of operational experience in the safe operation and maintenance of research reactors as per the International standards. The important safety features provided in the research reactors include the capability of fast shut down of the reactor, continuous removal of the decay heat from the reactor core even in the shut down state. Cirus and Dhruva are provided with containment buildings to limit the radiation release to the environment in an unlikely event of an accident. The constant and continuous monitoring of neutron flux level, coolant flow and the core temperature are carried out and any adverse variation in any of these parameters will automatically generate a “trip signal” that will de-energise the magnetic clutches holding the shut-off-rods thereby shutting down of the reactor within 3 seconds. The plant operation crew is adequately trained in radiological safety aspects and regular refresher programs are conducted to update their information about the latest techniques and procedures in reactor safety aspects. Periodic inspection and performance audits of the reactor machineries and related instruments are taken up and appropriate preventive maintenance carried out with no compromise on safety of the reactors.
Towards utilization of the abundant resources of Thorium a new reactor concept with Thorium fuel cycle is being developed. To optimize and confirm the physics design parameters of such an Advanced Heavy Water Reactor (AHWR) a ‘Critical Facility’ for lattice investigations is under construction at BARC. This facility is expected to become critical by December 2005. The Critical Facility is a tank type, heavy water moderated reactor with natural uranium metal clusters. The reactor is designed for a nominal fission power of 100 Watts and an average flux of 10 8 n/cm 2/sec. For AHWR core experiments, the central 9 natural uranium metal clusters will be replaced by AHWR fuel consisting of (Th-Pu) O2 and (Th-U 233) O 2 - MOX clusters.
India has also launched a scaling-up programme for the presently operating 235 MWe PHWR designs to higher power level of 540 MWe and 700 MWe. For accurately estimating the physics design data, experiments would be conducted in the critical facility. Hence, the core size is made large enough to conduct experiments with all 37-pin natural uranium oxide clusters. The critical facility is ideally suited to carry out experiments to study the loosely coupled cores, such as 540 MWe and 700 MWe PHWR.
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RESEARCH REACTOR UTILIZATION
CIRUS has been provided with the following experimental and irradiation Facilities
- Pressurized Water Loop – 400 kW, 2000 psig & 300 0C for irradiation testing of nuclear fuels, activity transport studies etc.
- Pneumatic Carrier Facility – Designed for pneumatically transporting the sample to the reactor for short term irradiation.
- Thermal Column Facility – Provides thermalised neutrons by replacing concrete shielding with graphite blocks in specified zones around reactor.
- 25 beam tubes and experimental holes
Dhruva has been provided with the following experimental and irradiation facilities
- Beam Tubes
- 100 mm dia tangential and radial beam tubes - Four each
- Two 300 mm dia radial beam tubes
- Two through tubes of 100 mm dia beam tubes
- One 300 mm dia cold neutron source beam tube
- One 300 mm dia for installation of hot source beam tube
- 2 dedicated positions for isotope production and any lattice position can be used for installation of additional irradiation assemblies
- Pneumatic Carrier Facility – A short term irradiation facility for NAA
- 2 MW Pressurized Water Loop – operating at 100 kg/cm2 & 290 0C for irradiation testing of nuclear fuels
- Two Creep and Corrosion testing positions
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Neutron Beam Tube Research
Apsara, Cirus and Dhruva reactors are extensively used in the frontier areas of neutron beam research. Complete expertise has been developed in the area of neutron beam research in crystallography, magnetic scattering, and inelastic scattering which has yielded information on structures of amino acids, ferrites, magnetic alloys, high temperature super conductors, intermetallic compounds like Zr2Ni for Hydrogen absorbing properties and other systems exhibiting phase transitions. Lattice dynamical studies of metals and complex ionic systems have been carried out. Small angle neutron scattering(SANS) were undertaken to study nano-composites, soft matter (gel, colloids, polymers), ferro fluids, micellar formation using variety of surfactants including multi-head group surfactants, etc . Several instruments like Single crystal diffractometer, powder diffractometers, high-Q diffractometer, polarization analysis spectrometer, have been developed and a time-of-flight quasielastic spectrometer spin-echo spectrometer and ultra small angle instrument will be installed soon
Fuel Irradiation studies
Towards development of Mixed Oxide (MOX) fuel, UO2-PuO2 fuel pins were test irradiated for stipulated burn up in Pressurized Water Loop (PWL) of Cirus reactor. Various design and manufacturing parameters were assessed through these tests. Towards utilization of Thoria based fuel in PHWRs, an experimental assembly containing ThO2-PuO2 fuel pellets was successfully irradiated to a burn up of more than 15000 MWD/Te in PWL. Irradiation of intentionally defected fuel pin was carried out for Activity transport studies. These studies have contributed significantly to the development of Nat U oxide and Nat U-Pu MOX fuels for power reactors.
Material Irradiation studies
Zircaloy calandria tubes manufactured by different routes were test irradiated in Dhruva reactor to study their comparative In-pile growth behaviour. Assessment of radiation induced creep of Zirconium materials has been carried out along with radiation embrittlement studies of various structural materials used in Indian PHWRs. These studies resulted in finalization of manufacturing route for the PHWR pressure tubes and calandria tubes. Studies on pressure vessel steel to measure post irradiation static and dynamic fracture toughness were also carried out.
Radioisotope production
Isotope production programme in the country started in mid fifties after setting up of Apsara. The regular supply of isotope for various uses commenced in early sixties after Cirus became operational. At present the reactors cater to the needs of 1250 user institutions. Preparations of Mo 99 , I 131 , I 125, P 32 , S 35, Cr 51 , Co 60,, Au 198, Br 82 , Ir 192 and other isotope are supplied to industrial, agricultural and medical institutions. Variety of nucleonic gauges for measurement of density, thickness, moisture content, bulk quantity, etc have been developed with wide acceptability in the industry. Variety of techniques developed for study of effluent dispersion in water bodies has been successfully employed. Residence time measurement in chemical reactors, flow patterns in fluidized beds, entrainment and flooding patterns in distillation columns, silt movement studies, etc through radioactive tracer techniques are some of the industrial applications developed and utilized.
Radiation processing including sterilization of medical products, sterilization of agricultural products, and hygienisation of city sewage with isotopes produced in BARC are some of the significant utilization for societal benefits
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Neutron Activation Analysis
NAA used for detection of trace elements in variety of matrices such as geological, biological, archaeological, environmental, high purity materials, nuclear pure materials and forensic samples. This facility is also well utilized for quick characterization of geological samples, study of rare earth elements in monazite sand and U & Th containing minerals and characterisation of ultra high purity silicon and gallium. NAA also has been successfully utilized in the analysis of biological and rock samples such as Basalt , Granite, Zircon, Monazite, Apatite , Limonite , etc and also for determining Chloride content of Zr - 2.5 % Nb material. Another significant area where the NAA could be applied is in the field of forensic investigations.
Neutron Radiography
Neutron radiography has been developed at Apsara and has been well deployed i n the development of reactor fuels. Some of the studies for which this facility has been used include, in the Characterization of U-Pu MOX fuel pins, monitoring of compositional variation of PuO2 in U-Pu MOX fuel pellets inside sealed fuel pins and a assessment of hydriding on Zircaloy-2 pressure tube of Pressurised Heavy Water Reactor s (PHWR s ).
Recently this facility has been utilized to study the flow pattern transition instability in boiling channels of the proposed Advanced Heavy Water Reactor. Apart from finding the applications in the nuclear industry, neutron radiography has also been successfully employed in some of the conventional industries also. Non-Destructive Testing of components used in aerospace e.g. cable cutters and pyrocharges used for satellites are a few to name.
Development & Testing of Nuclear Instrumentation
All the research reactors are utilized for testing and Calibration of ion chambers, B-10 lined proportional counters developed by Indian industries.
Calibration of variety of miniature neutron detectors for in-core applications in the future NPPs of the country is done on a regular basis. Measurement of neutron sensitivity of Cobalt, Platinum, Vanadium SPNDs developed in-house are done in Apsara.
Expertise development
With the large experience in design and operation of the research reactors, expertise could be developed in many of the areas enveloping the research reactors. Following are some of the significant areas to mention
- Core physics and neutronic calculations
- Safety analysis and preparation of various safety documentations
- Ageing management of research reactors
- Reactor chemistry aspects including development of ion-exchanger resins.
- Development of decontamination techniques
- Probabilistic Safety Assessment
- Development of In-Service Inspection techniques
- Evolving an Integrated management system
- Development of remote tools and techniques
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REACTOR ENGINEERING
BARC provides all the necessary engineering support through its constant R&D efforts for design and operation of power reactors. BARC is equipped with the expertiseandinfrastructure in the form of variety of experimental facilities, test loops etc. which enable long or short term testing of components under simulated conditions and to carry out mechanical component design, thermal hydraulics studies, vibration diagnostics, repair technology and process instrumentation. For testing various components and systems of Pressurised Heavy Water Reactor (PHWR) Facility for Integral System Behavior Experiments (FISBE) has been developed . The loop is a scale down model of Primary Heat Transport System including Emergency Core Cooling System as well as Secondary Heat Removal Circuit of a 220 Mwe Indian Pressurised Heavy Water Reactor and t his facility permits experimental simulation of accident scenarios and operational transients in PHWRs .  Some of the other major experimental facilities include 3 MW Boiling water loop, High Temperature Loop, High Flow Test Facility and Flow Test Facility . Non Intrusive Vibration diagnostic technique (NIVDT) has been developed and successfully implemented for identifying coolant channels having pressure tube-calandria tube contact in PHWRs. Computer codes SCAPCA (static and creep analysis of pressure tube and calandria tube assembly) for creep sag analysis of coolant channels, HYCON (for estimation of hydrogen concentration), Code for hydride blister nucleation and growth (BLIST), CEAL etc. have already been developed and applied for life assessment and estimation of the in use reactor components as well as designing the tools and systems for in-service repair and remote inspection.
 
INGRES Sliver Sample Scrapping Tool
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The research reactor utilities-both thermal neutron and fast neutron-research reactors were immensely used to generate data to optimize the process parameters and design features of the Th-232/U-233 fuelled power reactors. The Design, analysis and engineering development of Advanced Heavy Water Reactor (AHWR) is in its final stage of completion. A natural circulation loop has been designed to study the two- phase natural circulation phenomena as proposed in AHWR and its stability in AHWR.
INTEGRAL TEST LOOP
A zero power critical facility is designed to arrive at the design parameters of AHWR and this critical facility will support three types of cores viz. a reference core consisting of 19 element metallic uranium clusters, a reference core with AHWR fuel clusters replacing nine natural uranium metal clusters and a 500 MWe PHWR core.
Scaled Integral test Loop (ITL) is set up carry out various thermal hydraulic experiments related to AHWR and also facilities are available for carrying out the primary heat transport system (PHT) and passive containment cooling system (PCCS).
Mathematical models of flow pattern under different operating conditions and the corresponding computer codes were worked out as a part of AHWR program. Fuel rod simulator (FRS) is a specially designed component for the thermal hydraulic behavior of reactor fuel elements. AHWR incorporates several advanced safety features such as gravity driven water pool and tail pipe towers ets. The Th-Pu and Th-U 233 oxide fuel cluster for AHWR is developed in BARC.
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Accelerator Driven Subcritical System (ADS)  
Design and development of Accelerator Driven Subcritical System (ADS) for the generation of fissile 233U from fertile 232Th is in progress. High-energy proton beam generates neutrons through spallation reaction in a non-fertile and non-fissile target element such as lead. A sub-critical blanket of 232Th/ 233U further amplifies this external source of neutron and produce energy. This novel system of reactor enhances the 233U production and reduces the technical complexities of geological repositories for storage of long-lived high-level radioactive actinides. BARC has developed a high-energy proton injector and beam optics studies are in progress. Also, a 14 MeV neutron source has been upgraded with a higher ion current source to carry out the experimental studies on sub-critical assemblies. Design optimisation of reactor assembly and associated units are in progress. This technology once operational will provide large-scale utilisation of thorium. A Compact High Temperature Reactor (CHTR) with 100 kW thermal power rating for electricity generation in remote areas not connected to the grid as small unattended power packs and also for the production of alternative transportation fuel such as hydrogen and refinement of low- grade coal and oil deposits to recover fossil fluid fuel is under development at BARC. This reactor is designed essentially on the same lines as the thorium based reactor with a compact core and passive heat removal, power regulation and shut down facilities incorporated. Studies related to heat transfer and fluid flow analyses have been carried out to optimize the size and geometry of the CHTR. |
