The nonproliferative light water thorium technology, also known as RTF (Radkowsky thorium fuel), provides a new approach to light water reactor core design. An RTF core is completely nonproliferative for all practical purposes, provides major reductions in radwaste, reduces fuel cycle cost and consumption of natural uranium, does not require soluble boron control during operation, and is once-through (i.e., does not require reprocessing). The core is made up of multiple seed-blanket units with uranium-zirconium alloy in the seed regions and thorium oxide with ~10% uranium oxide in the blanket regions. A key advantage is that an RTF core has exactly the same control drives and support plates. An RTF core with plutonium substituted for uranium is also optimum for incinerating either weapons- or reactor-grade plutonium, burning at three times the rate obtainable with mixed oxide (MOX). Use of MOX also requires considerable core modifications and produces 60% new plutonium, while RTF core produces none.