Patent Number: 
Section: claims

1. A fuel bundle for use in a channel type heterogeneous reactor core of a heavy water reactor, the fuel bundle comprising:a filled central displacement tube; anda plurality of thorium based fuel pins surrounding the filled central displacement tube,wherein the plurality of thorium based fuel pins are arranged in a single ring around the filled central displacement tube. 2. The fuel bundle of claim 1, wherein the filled central displacement tube is filled with ZrO2, MgO, BeO, graphite or stagnant D2O coolant. 3. The fuel bundle of claim 1, wherein there are 21 radially positioned thorium based fuel pins surrounding the filled central displacement tube. 4. The fuel bundle of claim 1, wherein there are 35 radially positioned thorium based fuel pins surrounding the filled central displacement tube. 5. The fuel bundle of claim 1, wherein the fuel bundle is a seed fuel bundle and the plurality of thorium based fuel pins comprises a homogeneous mixture of (PuO2+ThO2) with a PuO2 content of 3% or higher. 6. The fuel bundle of claim 1, wherein the fuel bundle is a seed fuel bundle and the plurality of thorium based fuel pins comprises a homogeneous mixture of (UO2 +ThO2) with a UO2 content of 35% or higher. 7. The fuel bundle of claim 1, wherein the fuel bundle is a blanket fuel bundle and the plurality of thorium based fuel pins comprises a homogeneous mixture of (PuO2+ThO2) with a PuO2 content of 2% or less. 8. The fuel bundle of claim 1, wherein the fuel bundle is a blanket fuel bundle and the plurality of thorium based fuel pins comprises a homogeneous mixture of (UO2+ThO2) with a UO2 content of 30% or less. 9. A method of using a thorium based fuel comprising:placing the fuel bundle of claim 1 in a channel type heterogenous reactor core of a heavy water reactor; andconducting a burnup of the thorium based fuel. 10. The fuel bundle of claim 1, wherein the filled central displacement tube is filled with stagnant D2O coolant. 11. A fuel bundle for use in a channel type heterogeneous reactor core of a heavy water reactor, the fuel bundle comprising:a filled central displacement tube; anda plurality of thorium based fuel pins surrounding the filled central displacement tube,wherein all of the plurality of thorium based fuel pins have an identical composition, andwherein the plurality of thorium based fuel pins are arranged in a single ring around the filled central displacement tube. 12. The fuel bundle of claim 11, wherein the filled central displacement tube is filled with stagnant D2O coolant.