Advanced Heavy Water Reactor
Encyclopedia
The Advanced Heavy Water Reactor (AHWR) is the latest Indian design for a next generation nuclear reactor that will burn thorium
in its fuel core. It is slated to form the third stage in India's 3 stage fuel cycle plan. Thorium is an element that is 3 times more abundant globally than uranium. As all mined thorium is potentially usable to breed reactor fuel (in contrast with approximately 0.7% of natural uranium being usable as reactor fuel, some 40 times the amount of energy per unit mass might theoretically be available from thorium.)
The proposed design of the AHWR is that of a heavy water moderated nuclear power reactor that will be the next generation of the PHWR type. It is now being developed at Bhabha Atomic Research Centre
(BARC), in Mumbai
, India and aims to meet the objectives of using thorium fuel cycle
s for commercial power generation. The AHWR is a vertical pressure tube type reactor cooled by boiling light water under natural circulation. A unique feature of this design is a large tank of water on top of the primary containment vessel, called the Gravity Driven Water Pool (GDWP). This reservoir is designed to perform several passive safety functions.
The reactor design incorporates advanced technologies, together with several proven positive features of Indian Pressurised Heavy Water Reactors (PHWRs). These features include pressure tube type design, low pressure moderator, on-power refueling, diverse fast acting shut-down systems, and availability of a large low temperature heat sink around the reactor core. The AHWR incorporates several passive safety features. These include: Core heat removal through natural circulation; direct injection of Emergency Core Coolant System (ECCS) water in fuel; and the availability of a large inventory of borated water in overhead Gravity Driven Water Pool (GDWP) to facilitate sustenance of core decay heat removal. The Emergency Core Cooling System (ECCS) injection and containment cooling can act (SCRAM
) without invoking any active systems or operator action.
The reactor physics design is tuned to maximise the use of thorium based fuel, by achieving a slightly negative void coefficient
. Fulfilling these requirements has been possible through the use of PuO2-ThO2 MOX, and ThO2-233UO2 MOX
in different pins of the same fuel cluster, and the use of a heterogeneous moderator
consisting of amorphous carbon
(in the fuel bundles) and heavy water
in 80%-20% volume ratio. The core configuration lends itself to considerable flexibility and several feasible solutions, including those not requiring the use of amorphous carbon based reflectors, are possible without any changes in reactor structure.
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
in its fuel core. It is slated to form the third stage in India's 3 stage fuel cycle plan. Thorium is an element that is 3 times more abundant globally than uranium. As all mined thorium is potentially usable to breed reactor fuel (in contrast with approximately 0.7% of natural uranium being usable as reactor fuel, some 40 times the amount of energy per unit mass might theoretically be available from thorium.)
The proposed design of the AHWR is that of a heavy water moderated nuclear power reactor that will be the next generation of the PHWR type. It is now being developed at Bhabha Atomic Research Centre
Bhabha Atomic Research Centre
The Bhabha Atomic Research Centre is India's primary nuclear research facility based in Mumbai. It has a number of nuclear reactors, all of which are used for India's nuclear power and research programme.- History :...
(BARC), in Mumbai
Mumbai
Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...
, India and aims to meet the objectives of using thorium fuel cycle
Thorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
s for commercial power generation. The AHWR is a vertical pressure tube type reactor cooled by boiling light water under natural circulation. A unique feature of this design is a large tank of water on top of the primary containment vessel, called the Gravity Driven Water Pool (GDWP). This reservoir is designed to perform several passive safety functions.
The reactor design incorporates advanced technologies, together with several proven positive features of Indian Pressurised Heavy Water Reactors (PHWRs). These features include pressure tube type design, low pressure moderator, on-power refueling, diverse fast acting shut-down systems, and availability of a large low temperature heat sink around the reactor core. The AHWR incorporates several passive safety features. These include: Core heat removal through natural circulation; direct injection of Emergency Core Coolant System (ECCS) water in fuel; and the availability of a large inventory of borated water in overhead Gravity Driven Water Pool (GDWP) to facilitate sustenance of core decay heat removal. The Emergency Core Cooling System (ECCS) injection and containment cooling can act (SCRAM
Scram
A scram or SCRAM is an emergency shutdown of a nuclear reactor – though the term has been extended to cover shutdowns of other complex operations, such as server farms and even large model railroads...
) without invoking any active systems or operator action.
The reactor physics design is tuned to maximise the use of thorium based fuel, by achieving a slightly negative void coefficient
Void coefficient
In nuclear engineering, the void coefficient is a number that can be used to estimate how much the reactivity of a nuclear reactor changes as voids form in the reactor moderator or coolant...
. Fulfilling these requirements has been possible through the use of PuO2-ThO2 MOX, and ThO2-233UO2 MOX
Mox
MOX might be a name or acronym for:*Malaysian Oxygen Berhad - A Malaysian company that is specializes in providing total gas solutions.*Mixed Oxide Fuel, from nuclear reprocessing*An alien race in the TimeSplitters 2 video game, the Mox...
in different pins of the same fuel cluster, and the use of a heterogeneous moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
consisting of amorphous carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
(in the fuel bundles) and heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...
in 80%-20% volume ratio. The core configuration lends itself to considerable flexibility and several feasible solutions, including those not requiring the use of amorphous carbon based reflectors, are possible without any changes in reactor structure.
See also
- Advanced CANDU ReactorAdvanced CANDU ReactorThe Advanced CANDU Reactor is a Generation III+ nuclear reactor design and is a further development of existing CANDU reactors designed by Atomic Energy of Canada Limited. The ACR is a light-water-cooled reactor that incorporates features of both Pressurised Heavy Water Reactors and Advanced...
- Breeder reactorBreeder reactorA breeder reactor is a nuclear reactor capable of generating more fissile material than it consumes because its neutron economy is high enough to breed fissile from fertile material like uranium-238 or thorium-232. Breeders were at first considered superior because of their superior fuel economy...
- Generation IV reactorGeneration IV reactorGeneration IV reactors are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030...
- Pressurised Heavy Water Reactor
- Thorium fuel cycleThorium fuel cycleThe thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...