ABSTRACT
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One of the hallmarks of the heavy water reactor (HWR) is its high neutron economy. High neutron economy is a necessity for utilizing natural uranium fuel, but results in a reactor that has a very high degree of fuel cycle flexibility. This enables a country, or utility, to optimize its nuclear fuel cycle based on its own unique circumstances. Thorium-as an alternative to uranium-has been given some emphasis because thorium burns particularly well in HWRs and has the potential to become an important nuclear fuel, initially regionally but ultimately as a huge additional energy resource as once-through uranium cycles are constrained by availability of low-cost uranium ore. This section is a very brief introduction to HWR fuel cycle technology, which draws heavily on the more extensive treatment provided in an earlier IAEA report (IAEA Tec Report 407 2002).
