Research and development of the Indian AHWR300-LEU is proceeding at the Baba Atomic Research Centre (BARC) in Mumbai. The Low Enrichment Uranium Advanced Heavy Water Reactor 300 MWe is a Generation III+ reactor with many advanced features. The AHWR300 is being designed for a 100 year life span. An article in the May Issue of Nuclear Engineering International describe AHWR-300 design objectives.
The AHWR-300 features
vertical, pressure-tube type, boiling light water-cooled, and heavy water-moderated reactor. The reactor incorporates a number of passive safety features and is associated with a fuel cycle having reduced environmental impact. AHWR300-LEUpossesses several features that are likely to reduce its capital and operating costs.Several features differentiate the new Indian design with past Indian PHWRs. They include:
• Using heavy water at low pressure reduces potential for leakagesUntil now it was not clear how BARC intended to achieve a hundred year life span for theAHWR given the radiation related metallurgy problems with PHWRs that usually limit their useful life to 25 years. The replacement of pressure tubes in PHWRs is an expensive undertaking, that in Canada can run over one billion dollars per reactor.
• Recovery of heat generated in the moderator for feedwater heating
• Elimination of major components and equipment such as primary coolant pumps and drive motors, associated control and power supply equipment and corresponding savings 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
• 100-year reactor design life
The AHWR-300 features significantly improved natural safety features including natural circulation of coolant waters which will automatically continue to circulate after reactor shutdown. Gravity fed emergency cooling water is another natural safety feature.
These natural or passive safety features mean that the AHWR will be significantly safer than early generations of reactors. For example, core meltdown would appear to virtually impossible in a loss of coolant type accident. Indeed the AHWR-300 is believed to be so safe that no exclusion zone is considered necessary. An exclusion zone is a large area outside the reactor building from which public use is excluded for safety reasons.
The fuel pins contain an average of 20 precent uranium and 80% thorium with the fissionable enriched to 19.75%. Nearly 40% of AHWR-300 power will come from thorium fuel cycle conversion of Th-232 to U-233, a fissionable form of uranium. The relatively low uranium content will produce significantly less nuclear waste than would be the case with conventional Light Water Reactors.
The AHWR, which is scheduled to go into commercial production about 2020 should lower construction and operation related nuclear costs significantly while improving nuclear safety. The AHWR-300 is designed to be paired with Indian Fast Breeders. The fast breeders will produce U-233 which will provide the fissionable fuel for a fleet of AHWR-300. current Indian energy plans call for the building of a large reactor fleet of both fast breeders and AHWRs.
Advanced Indian Fast Breeder Development Plans
Further indications of long term Indian Fast Breeder design plans have also recently emerged. Currently India's Fast Breeder Prototype reactor is under construction and is expected to be completed next year. Four more Indian FBR are expected to be built during this decade, with two more to emerge after 2020. This program makes India the first nation that intends to introduce serially built fast breeder reactors into commercial use. The current generation of fast breeders will use oxide fuels. However, reprocessing oxide fuels from fast breeder reactors is challenging and expensive.
The Indians are highly concerned about keeping the cost of nuclear power competitive, and thus they intend to develop a long range program to build metal fueled fast breeders. Few details about the the metal fueled fast breeder, being developed by Indira Gandhi Centre for Atomic Research (IGCAR) were known until recently. The use of metal fuels will lead to easier fuel reprocessing. The Indian metal fuel fast breeder R&D program appears to be large and complex. The currently in use Fast Breeder Test Reactor will be converted to a metal fuel core. This will be followed by a second 120 MW research fast breeder. Then it appears that a 500MWe commercial fast breeder will be converted to metallic fuel. This will be followed by a 1000 MWe commercial fast breeder reactor, beginning some time in the next decade. All Indian commercial fas breeder reactors are expected to feature both uranium and thorium fuel cycle breeding.
Implications for the United States
The size and complexity of the Indian metal fueled fast breeder R&D program should give pause to any proposed IFR in the United States. The Indian's appear to believe that the development of a commercial metal fueled fast breeder would be a very significant and expensive challenge. Indeed the Indian development program, if paralleled in the United States might run to costs as high as $50 billion. Given such high costs it would be well for American policy makers to carefully weigh their options, before committing to a metal fueled fast breeder program, such as the Integral Fast Reactor. One option might be to throw in with the Indians. Even if the United States paid half of the Indian metal fueled fast reactor R&D costs,
access to Indian FBR technology could turn out to be quite a bargain if the United States chose to develop large numbers of LMFBRs. On the other hand The development of the LFTR could offer many advantages including the potential for low cost manufacture and very rapid scaleability. A molten salt fast breeder is possible, using chloride salt carrier/coolant. Thus before the United States commits to a fast breeder program that is similar to India's, it should carefully research and weigh its options.
These ambitious programs, indicates how serious the Indians are about the completion of their three stage nuclear development program. The also suggest something about the complexity of the planned Indian nuclear fuel system. Whether such a system can and/or should be duplicated in the United States, is an open question. Simpler and lower cost Generation IV nuclear fuel systems seem possible at least in the United States, Western Europe, and other advanced industrialized countries.