Saturday, November 28, 2009

Indian AHWR300-LEU Features Revealed

A pamphlet from the Bhabha Atomic research center in Mumbai, India offers a detailed description of the AHWR300-LEU reactor now under development. The reactor will feature a complex fuel mix that will include both uranium and thorium.

The development of the AHWR300-LEU has significant implications for the less well developed nations of Asia, Africa and Latin America. Current Indian capital costs for reactors are running per $1.10 per watt of generation capacity. The design of the AHWR300-LEU contains numerous cost saving features. An no doubt the Indian's expect to be able to deliver these reactors to less well developed countries at a cost that will be at an order of magnitude lower than that of renewables. The low cost of the AHWR300-LEU could lead to an energy revolution in energy hungry less well developed countries. At the same time the Indians are paying careful attention to traditional nuclear problems such as safety, proliferation control, and nuclear waste management.

The pamphlet states
AHWR300-LEU possesses several features, which are likely to reduce its capital and operating costs.
* Using heavy water at low pressure reduces potential for leakages
* Recovery of heat generated in the moderator for feed water heating
* Elimination of major components and equipment such as primary coolant
pumps and drive motors, associated control and power supply equipment and
corresponding saving of electrical power required to run these pumps
* Shop assembled coolant channels, with features to enable quick replacement
of pressure tube alone, without affecting other installed channel components
* Inherent advantages of using high pressure boiling water as coolant
* Elimination of steam generators
* Use of high-pressure steam
* Production of 500 m3/day of demineralised water in Multi Effect Desalination
Plant by using steam from LP Turbine (For plants located on the sea coast)
* Hundred year design life of the reactor
* A design objective requiring no exclusion zone beyond plant boundary on
account of its advanced safety features
These features to common themes of Indian reactor design. An emphasis on simplicity, low cost, safety and longevity. The AHWR-300-LEU will produce a modest amount of fresh water in the cooling process, and indeed the production of fresh water is not a major goal of the Indian reactor design at the moment.

The AHWR-300-LEU is designed primarily for export, and it contains a number of idiot proof safety features, such as a fail safe protection features that operate to both prevent and mitigate major reactor accidents. Thus
AHWR300-LEU is provided with a double containment. For containment isolation, a passive system has been provided in AHWR300-LEU. The reactor building air supply and exhaust ducts are shaped in the form of U-bends of sufficient height. In the event of LOCA, the containment pressure acts on the water pool surface and drives water, by swift establishment of syphon, into the U-bends of the ventilation ducts. Water in the U-bends acts as a seal between the containment and the external environment, providing necessary isolation between the two.
The Indians are extraordinarily careful about safety:
Some important safety features of AHWR300-LEU are given below.
• Slightly negative void coefficient of reactivity
• Passive safety systems working on natural laws
• Large heat sink in the form of Gravity Driven Water Pool with an inventory of 7000 m3 of water, located near the top of Reactor Building
• Removal of heat from core by natural circulation
• Injection of cooling water by Emergency Core Cooling System directly
inside the fuel cluster
• Two independent shutdown systems (primary and secondary)
• Passive poison injection in moderator in the event of non-availability of both the primary as well as the secondary shut down system due to failure or malevolent insider action
In addition to three shutdown control systems, a reactor design passive safety feature, called a negative reactivity coefficient will shut down the reactor if it starts to overheat.

Careful attention has been paid to design of the AHWR300-LEU fuel mix in order to prevent nuclear proliferation using spent fuel, and to minimize problems related to the long term storage of spent fuel.

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