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A new era of nuclear energy is emerging through innovative nuclear reactors that are to satisfy the new philosophies and criteria that are being developed by the INPRO program of the International Atomic Energy Agency (IAEA). It is establishing a new paradigm in relation to nuclear energy. The future reactors should meet the new standards in respect to safety, economy, non-proliferation, nuclear waste, and environmental impact. The fixed bed nuclear reactor (FBNR) is a small nuclear reactor that meets all the requirements. It is an inherently safe and passively cooled reactor that is fool proof against nuclear proliferation. It is simple in design and economic. It can serve in a dual purpose plant to produce simultaneously both electricity and desalinated water, thus making it especially suitable to the needs of the Middle-East Countries. FBNR is being developed with the support of the IAEA under its program of small reactors without on-site refueling. The reactor uses the pressurized water reactor technology. It fulfills the objectives of design simplicity, inherent and passive safety, economy, standardization, shop fabrication, easy transportability, and high availability. The inherent safety characteristic of the reactor dispenses with the need for containment; however, a simple underground containment is envisaged for the reactor in order to reduce any adverse visual impact.

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SUMMARYSpent nuclear fuel out of conventional light water reactors contains significant amount of even plutonium isotopes, so called reactor grade plutonium. Excellent neutron economy of Canada deuterium uranium (CANDU) reactors can further burn reactor grade plutonium, which has been used as a booster fissile fuel material in form of mixed ThO 2 /PuO 2 fuel in a CANDU fuel bundle in order to assure reactor criticality. The paper investigates incineration of nuclear waste and the prospects of exploitation of rich world thorium reserves in CANDU reactors.In the present work, the criticality calculations have been performed with 3-D geometrical modeling of a CANDU reactor, where the structure of all fuel rods and bundles is represented individually. In the course of time calculations, nuclear transformation and radioactive decay of all actinide elements as well as fission products are considered.Four different fuel compositions have been selected for investigations: ① 95% thoria (ThO 2 ) + 5% PuO 2 , ② 90% ThO 2 + 10% PuO 2 , ③ 85% ThO 2 + 15% PuO 2 and ④ 80% ThO 2 + 20% PuO 2 . The latter is used for the purpose of denaturing the new 233 U fuel with 238 U. The behavior of the criticality k ∞ and the burnup values of the reactor have been pursued by full power operation for~10 years.Among the investigated four modes, 90% ThO 2 + 10% PuO 2 seems a reasonable choice. This mixed fuel would continue make possible extensive exploitation of thorium resources with respect to reactor criticality. Reactor will run with the same fuel charge for~7 years and allow a fuel burnup~55 GWd/t.