Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Thorium utilization in PWRs. Neutronics studies

Abstract

The main existing reactors can accept thorium fuel without fundamental modification. The aim of the study reported here and limited to PWRs is to bring neutron results up to date by using the CEA's most recent calculation codes, APOLLO 2, CRONOS 2 and PEPIN/DARWIN, associated with the last database, i.e. JEF 2.2. The study involves a 900 MW(e) PWR under three-batch core management and with annual cycles. Four types of fuel, U or Pu with a thorium carrier in the form of mixed oxides were examined. The thorium fuels produce few minor actinides and possess better conversion factors, i.e. unloaded fissile nuclei/loaded fissile nuclei, than the uranium fuels. The 233U-232Th fuel consumes only 12 kg/TWcentre doth of uranium (85 kg/TWcentre doth of 235U in a conventional uranium fuel). The Pu-232Th fuel offers excellent plutonium consumption potential (114 kg/TWcentre doth) and produces a significant quantity (46 kg/TWcentre doth) of uranium rich in 233U (92%), the most effective isotope in a thermal spectrum. The kinetic and control parameters are acceptable. In open cycles, the radiotoxicity levels of unloaded thorium-fuels are lower than those of conventional uranium or MOX fuels up to 10⁴ years of storage. The development of this cycle will require extensive R and D work and investment. However, a great part of the work has already been done: reprocessing by the THOREX process, remote control and shielding in the MOX industry, irradiations (Indian Point, Elk River, Shippingport etc.). Today's need to eliminate strategic materials such as High Enriched Uranium and Plutonium could launch the industrial implementation of a new fuel cycle to complement the uranium cycle.

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Reference:

Proceedings of three IAEA meetings held in Vienna in 1997, 1998 and 1999

International Atomic Energy Agency, Vienna (Austria)

IAEA-TECDOC--1319, pp:185-197